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• COBIRAS: Offering a Continuous Bit Rate Slide to Maximize DASH Streaming Bandwidth Utilization. Seufert, Michael; Spangenberger, Marius; Poignée, Fabian; Wamser, Florian; Robitza, Werner; Timmerer, Christian; Hoßfeld, Tobias. In ACM Transactions on Multimedia Computing, Communications, and Applications. 2024.
  • [ BibTeX ]
  • [ EndNote ]
  @article{info3-article-2024-5, author = {Seufert, Michael and Spangenberger, Marius and Poignée, Fabian and Wamser, Florian and Robitza, Werner and Timmerer, Christian and Hoßfeld, Tobias}, journal = {ACM Transactions on Multimedia Computing, Communications, and Applications}, keywords = {ucn}, month = {07}, title = {COBIRAS: Offering a Continuous Bit Rate Slide to Maximize DASH Streaming Bandwidth Utilization}, year = 2024 }

  %0 Journal Article %1 info3-article-2024-5 %A Seufert, Michael %A Spangenberger, Marius %A Poignée, Fabian %A Wamser, Florian %A Robitza, Werner %A Timmerer, Christian %A Hoßfeld, Tobias %D 2024 %J ACM Transactions on Multimedia Computing, Communications, and Applications %T COBIRAS: Offering a Continuous Bit Rate Slide to Maximize DASH Streaming Bandwidth Utilization
• Machine Learning with Computer Networks: Techniques, Datasets and Models. Afifi, Haitham; Pochaba, Sabrina; Boltres, Andreas; Laniewski, Dominic; Haberer, Janek; Paeleke, Leonard; Poorzare, Reza; Stolpmann, Daniel; Wehner, Nikolas; Redder, Adrian; Samikwa, Eric; Seufert, Michael. In IEEE Access. 2024.
  • [ BibTeX ]
  • [ EndNote ]
  @article{info3-article-2024-2, author = {Afifi, Haitham and Pochaba, Sabrina and Boltres, Andreas and Laniewski, Dominic and Haberer, Janek and Paeleke, Leonard and Poorzare, Reza and Stolpmann, Daniel and Wehner, Nikolas and Redder, Adrian and Samikwa, Eric and Seufert, Michael}, journal = {IEEE Access}, keywords = {sys:hidden:article}, month = {04}, title = {Machine Learning with Computer Networks: Techniques, Datasets and Models}, year = 2024 }

  %0 Journal Article %1 info3-article-2024-2 %A Afifi, Haitham %A Pochaba, Sabrina %A Boltres, Andreas %A Laniewski, Dominic %A Haberer, Janek %A Paeleke, Leonard %A Poorzare, Reza %A Stolpmann, Daniel %A Wehner, Nikolas %A Redder, Adrian %A Samikwa, Eric %A Seufert, Michael %D 2024 %J IEEE Access %T Machine Learning with Computer Networks: Techniques, Datasets and Models
• Marina: Realizing ML-Driven Real-Time Network Traffic Monitoring at Terabit Scale. Seufert, Michael; Dietz, Katharina; Wehner, Nikolas; Geißler, Stefan; Schüler, Joshua; Wolz, Manuel; Hotho, Andreas; Casas, Pedro; Hoßfeld, Tobias; Feldmann, Anja. In Transactions on Network and Service Management (TNSM). 2024.
  • [ BibTeX ]
  • [ EndNote ]
  @article{info3-article-2024-1, author = {Seufert, Michael and Dietz, Katharina and Wehner, Nikolas and Geißler, Stefan and Schüler, Joshua and Wolz, Manuel and Hotho, Andreas and Casas, Pedro and Hoßfeld, Tobias and Feldmann, Anja}, journal = {Transactions on Network and Service Management (TNSM)}, keywords = {ucn}, month = {03}, title = {Marina: Realizing ML-Driven Real-Time Network Traffic Monitoring at Terabit Scale}, year = 2024 }

  %0 Journal Article %1 info3-article-2024-1 %A Seufert, Michael %A Dietz, Katharina %A Wehner, Nikolas %A Geißler, Stefan %A Schüler, Joshua %A Wolz, Manuel %A Hotho, Andreas %A Casas, Pedro %A Hoßfeld, Tobias %A Feldmann, Anja %D 2024 %J Transactions on Network and Service Management (TNSM) %T Marina: Realizing ML-Driven Real-Time Network Traffic Monitoring at Terabit Scale
• Plan the Access? Generic Hardware Independent Energy Consumption and Efficiency Model for Different LoRaWAN Channel Access Approaches. Loh, Frank; Raffeck, Simon; Geißler, Stefan; Hoßfeld, Tobias. In IEEE Internet of Things Journal. 2024.
  • [ BibTeX ]
  • [ EndNote ]
  @article{info3-article-2024-3, author = {Loh, Frank and Raffeck, Simon and Geißler, Stefan and Hoßfeld, Tobias}, journal = {IEEE Internet of Things Journal}, keywords = {sys:hidden:article}, month = {02}, title = {Plan the Access? Generic Hardware Independent Energy Consumption and Efficiency Model for Different LoRaWAN Channel Access Approaches}, year = 2024 }

  %0 Journal Article %1 info3-article-2024-3 %A Loh, Frank %A Raffeck, Simon %A Geißler, Stefan %A Hoßfeld, Tobias %D 2024 %J IEEE Internet of Things Journal %T Plan the Access? Generic Hardware Independent Energy Consumption and Efficiency Model for Different LoRaWAN Channel Access Approaches
• Analysis of Energy Intensity and Generic Energy Efficiency Metrics in Communication Networks: Limits, Practical Applications, and Case Studies. Hossfeld, Tobias; Wunderer, Stefan; Loh, Frank; Schien, Daniel. In IEEE Access, 12, pp. 105527–105549. 2024.
  • [ Abstract ]
  • [ BibTeX ]
  • [ EndNote ]
  Energy intensity is the ratio between energy consumed and data volume over a certain time frame. It is frequently used as a metric to indicate the energy efficiency of communication networks and data centres for the provision of digital services, and as a coefficient to apportion the total energy consumption of a network to a specific service. As energy efficiency becomes more important, energy intensity metrics are increasingly used to estimate the energy costs and benefits of changes in data volumes across networks and data centres. Typically, energy intensity integrates annual accounts of energy consumption and data transmitted. At shorter time scales, this metric is affected by the lack of correlation between transmitted data and energy consumption, which leads in some cases to inappropriate conclusions. In this work, we first review the use of energy efficiency metrics in the literature. Then, we define generic measures for energy efficiency as well as energy intensity. The relationships of those measures are analysed, and we show under which conditions they lead to the same or different results. Practical applications of the measures and their insights are demonstrated when benchmarking systems and when considering the value of the system’s output. Furthermore, the limits and pitfalls of the metrics are analysed, especially considering the energy intensity metric for communication networks.

  @article{10614603, abstract = {Energy intensity is the ratio between energy consumed and data volume over a certain time frame. It is frequently used as a metric to indicate the energy efficiency of communication networks and data centres for the provision of digital services, and as a coefficient to apportion the total energy consumption of a network to a specific service. As energy efficiency becomes more important, energy intensity metrics are increasingly used to estimate the energy costs and benefits of changes in data volumes across networks and data centres. Typically, energy intensity integrates annual accounts of energy consumption and data transmitted. At shorter time scales, this metric is affected by the lack of correlation between transmitted data and energy consumption, which leads in some cases to inappropriate conclusions. In this work, we first review the use of energy efficiency metrics in the literature. Then, we define generic measures for energy efficiency as well as energy intensity. The relationships of those measures are analysed, and we show under which conditions they lead to the same or different results. Practical applications of the measures and their insights are demonstrated when benchmarking systems and when considering the value of the system’s output. Furthermore, the limits and pitfalls of the metrics are analysed, especially considering the energy intensity metric for communication networks.}, author = {Hossfeld, Tobias and Wunderer, Stefan and Loh, Frank and Schien, Daniel}, journal = {IEEE Access}, keywords = {sys:hidden:article}, pages = {105527-105549}, title = {Analysis of Energy Intensity and Generic Energy Efficiency Metrics in Communication Networks: Limits, Practical Applications, and Case Studies}, volume = 12, year = 2024 }

  %0 Journal Article %1 10614603 %A Hossfeld, Tobias %A Wunderer, Stefan %A Loh, Frank %A Schien, Daniel %D 2024 %J IEEE Access %P 105527-105549 %R 10.1109/ACCESS.2024.3435716 %T Analysis of Energy Intensity and Generic Energy Efficiency Metrics in Communication Networks: Limits, Practical Applications, and Case Studies %V 12 %X Energy intensity is the ratio between energy consumed and data volume over a certain time frame. It is frequently used as a metric to indicate the energy efficiency of communication networks and data centres for the provision of digital services, and as a coefficient to apportion the total energy consumption of a network to a specific service. As energy efficiency becomes more important, energy intensity metrics are increasingly used to estimate the energy costs and benefits of changes in data volumes across networks and data centres. Typically, energy intensity integrates annual accounts of energy consumption and data transmitted. At shorter time scales, this metric is affected by the lack of correlation between transmitted data and energy consumption, which leads in some cases to inappropriate conclusions. In this work, we first review the use of energy efficiency metrics in the literature. Then, we define generic measures for energy efficiency as well as energy intensity. The relationships of those measures are analysed, and we show under which conditions they lead to the same or different results. Practical applications of the measures and their insights are demonstrated when benchmarking systems and when considering the value of the system’s output. Furthermore, the limits and pitfalls of the metrics are analysed, especially considering the energy intensity metric for communication networks.
• The Missing Link in Network Intrusion Detection: Taking AI/ML Research Efforts to Users. Dietz, Katharina; Mühlhauser, Michael; Kögel, Jochen; Schwinger, Stephan; Sichermann, Marleen; Seufert, Michael; Herrmann, Dominik; Hoßfeld, Tobias. In IEEE Access. 2024.
  • [ BibTeX ]
  • [ EndNote ]
  @article{info3-article-2024-4, author = {Dietz, Katharina and Mühlhauser, Michael and Kögel, Jochen and Schwinger, Stephan and Sichermann, Marleen and Seufert, Michael and Herrmann, Dominik and Hoßfeld, Tobias}, journal = {IEEE Access}, keywords = {sys:hidden:article}, month = {05}, title = {The Missing Link in Network Intrusion Detection: Taking AI/ML Research Efforts to Users}, year = 2024 }

  %0 Journal Article %1 info3-article-2024-4 %A Dietz, Katharina %A Mühlhauser, Michael %A Kögel, Jochen %A Schwinger, Stephan %A Sichermann, Marleen %A Seufert, Michael %A Herrmann, Dominik %A Hoßfeld, Tobias %D 2024 %J IEEE Access %T The Missing Link in Network Intrusion Detection: Taking AI/ML Research Efforts to Users

• Want more WANs? Comparison of Traditional and GAN-based Generation of Wide Area Network Topologies via Graph and Performance Metrics. Dietz, Katharina; Seufert, Michael; Hoßfeld, Tobias. In Transactions on Network and Service Management (TNSM). 2023.
  • [ BibTeX ]
  • [ EndNote ]
  @article{info3-article-2023-5, author = {Dietz, Katharina and Seufert, Michael and Hoßfeld, Tobias}, journal = {Transactions on Network and Service Management (TNSM)}, keywords = {ucn}, month = {07}, title = {Want more WANs? Comparison of Traditional and GAN-based Generation of Wide Area Network Topologies via Graph and Performance Metrics}, year = 2023 }

  %0 Journal Article %1 info3-article-2023-5 %A Dietz, Katharina %A Seufert, Michael %A Hoßfeld, Tobias %D 2023 %J Transactions on Network and Service Management (TNSM) %T Want more WANs? Comparison of Traditional and GAN-based Generation of Wide Area Network Topologies via Graph and Performance Metrics
• On Profiling, Benchmarking and Behavioral Analysis of SDN Architecture Under DDoS Attacks. Huu Thanh, Nguyen; NgocTuan, Nguyen; AnhKhoa, Dang; CongTuan, Le; TrungKien, Nguyen; XuanDung, Nguyen; QuynhThu, Ngo; Wamser, Florian. In Journal of Network and Systems Management. 2023.
  • [ Abstract ]
  • [ BibTeX ]
  • [ EndNote ]
  • [ Download ]
  Software-Defined Networking (SDN) has attracted much attention from research and industrial communities recently as it is more agile and flexible compared to conventional networking technology in offering new network functions and services. By separating the network control functions from the forwarding devices and placing them in a centralized, softwarized and programmable SDN controller, new network functions and services can be easily added into the network in an on-demand manner. However, the centralized control paradigm and the flow-based forwarding principle make the SDN architecture more fragile and vulnerable to malicious actions, such as cyber hijacking or DDoS attacks. In this paper, we focus on analyzing and evaluating negative impacts of DDoS attacks on the SDN architecture. By performing stress tests, the performance of such common SDN controllers as POX, Ryu and Floodlight under DDoS attacks is benchmarked, along with their impacts on the SDN switch and OpenFlow channel. We also address some new threats and vulnerabilities introduced by the nature of SDN.

  @article{info3-article-2023-1, abstract = {Software-Defined Networking (SDN) has attracted much attention from research and industrial communities recently as it is more agile and flexible compared to conventional networking technology in offering new network functions and services. By separating the network control functions from the forwarding devices and placing them in a centralized, softwarized and programmable SDN controller, new network functions and services can be easily added into the network in an on-demand manner. However, the centralized control paradigm and the flow-based forwarding principle make the SDN architecture more fragile and vulnerable to malicious actions, such as cyber hijacking or DDoS attacks. In this paper, we focus on analyzing and evaluating negative impacts of DDoS attacks on the SDN architecture. By performing stress tests, the performance of such common SDN controllers as POX, Ryu and Floodlight under DDoS attacks is benchmarked, along with their impacts on the SDN switch and OpenFlow channel. We also address some new threats and vulnerabilities introduced by the nature of SDN.}, author = {Huu Thanh, Nguyen and NgocTuan, Nguyen and AnhKhoa, Dang and CongTuan, Le and TrungKien, Nguyen and XuanDung, Nguyen and QuynhThu, Ngo and Wamser, Florian}, journal = {Journal of Network and Systems Management}, keywords = {sys:hidden:article}, month = {03}, title = {On Profiling, Benchmarking and Behavioral Analysis of SDN Architecture Under DDoS Attacks}, year = 2023 }

  %0 Journal Article %1 info3-article-2023-1 %A Huu Thanh, Nguyen %A NgocTuan, Nguyen %A AnhKhoa, Dang %A CongTuan, Le %A TrungKien, Nguyen %A XuanDung, Nguyen %A QuynhThu, Ngo %A Wamser, Florian %D 2023 %J Journal of Network and Systems Management %T On Profiling, Benchmarking and Behavioral Analysis of SDN Architecture Under DDoS Attacks %X Software-Defined Networking (SDN) has attracted much attention from research and industrial communities recently as it is more agile and flexible compared to conventional networking technology in offering new network functions and services. By separating the network control functions from the forwarding devices and placing them in a centralized, softwarized and programmable SDN controller, new network functions and services can be easily added into the network in an on-demand manner. However, the centralized control paradigm and the flow-based forwarding principle make the SDN architecture more fragile and vulnerable to malicious actions, such as cyber hijacking or DDoS attacks. In this paper, we focus on analyzing and evaluating negative impacts of DDoS attacks on the SDN architecture. By performing stress tests, the performance of such common SDN controllers as POX, Ryu and Floodlight under DDoS attacks is benchmarked, along with their impacts on the SDN switch and OpenFlow channel. We also address some new threats and vulnerabilities introduced by the nature of SDN.
• Share and Multiply: Modeling Communication and Generated Traffic in Private WhatsApp Groups. Seufert, Anika; Poignée, Fabian; Seufert, Michael; Hoßfeld, Tobias. In IEEE Access, 11, pp. 25401–25414. 2023.
  • [ Abstract ]
  • [ BibTeX ]
  • [ EndNote ]
  Group-based communication is a highly popular communication paradigm, which is especially prominent in mobile instant messaging (MIM) applications, such as WhatsApp. Chat groups in MIM applications facilitate the sharing of various types of messages (e.g., text, voice, image, video) among a large number of participants. As each message has to be transmitted to every other member of the group, which multiplies the traffic, this has a massive impact on the underlying communication networks. However, most chat groups are private and network operators cannot obtain deep insights into MIM communication via network measurements due to end-to-end encryption. Thus, the generation of traffic is not well understood, given that it depends on sizes of communication groups, speed of communication, and exchanged message types. In this work, we provide a huge data set of 5,956 private WhatsApp chat histories, which contains over 76 million messages from more than 117,000 users. We describe and model the properties of chat groups and users, and the communication within these chat groups, which gives unprecedented insights into private MIM communication. In addition, we conduct exemplary measurements for the most popular message types, which empower the provided models to estimate the traffic over time in a chat group.

  @article{info3-article-2023-2, abstract = {Group-based communication is a highly popular communication paradigm, which is especially prominent in mobile instant messaging (MIM) applications, such as WhatsApp. Chat groups in MIM applications facilitate the sharing of various types of messages (e.g., text, voice, image, video) among a large number of participants. As each message has to be transmitted to every other member of the group, which multiplies the traffic, this has a massive impact on the underlying communication networks. However, most chat groups are private and network operators cannot obtain deep insights into MIM communication via network measurements due to end-to-end encryption. Thus, the generation of traffic is not well understood, given that it depends on sizes of communication groups, speed of communication, and exchanged message types. In this work, we provide a huge data set of 5,956 private WhatsApp chat histories, which contains over 76 million messages from more than 117,000 users. We describe and model the properties of chat groups and users, and the communication within these chat groups, which gives unprecedented insights into private MIM communication. In addition, we conduct exemplary measurements for the most popular message types, which empower the provided models to estimate the traffic over time in a chat group.}, author = {Seufert, Anika and Poignée, Fabian and Seufert, Michael and Hoßfeld, Tobias}, journal = {IEEE Access}, keywords = {ucn}, month = {03}, pages = {25401 - 25414}, title = {Share and Multiply: Modeling Communication and Generated Traffic in Private WhatsApp Groups}, volume = 11, year = 2023 }

  %0 Journal Article %1 info3-article-2023-2 %A Seufert, Anika %A Poignée, Fabian %A Seufert, Michael %A Hoßfeld, Tobias %D 2023 %J IEEE Access %P 25401 - 25414 %T Share and Multiply: Modeling Communication and Generated Traffic in Private WhatsApp Groups %V 11 %X Group-based communication is a highly popular communication paradigm, which is especially prominent in mobile instant messaging (MIM) applications, such as WhatsApp. Chat groups in MIM applications facilitate the sharing of various types of messages (e.g., text, voice, image, video) among a large number of participants. As each message has to be transmitted to every other member of the group, which multiplies the traffic, this has a massive impact on the underlying communication networks. However, most chat groups are private and network operators cannot obtain deep insights into MIM communication via network measurements due to end-to-end encryption. Thus, the generation of traffic is not well understood, given that it depends on sizes of communication groups, speed of communication, and exchanged message types. In this work, we provide a huge data set of 5,956 private WhatsApp chat histories, which contains over 76 million messages from more than 117,000 users. We describe and model the properties of chat groups and users, and the communication within these chat groups, which gives unprecedented insights into private MIM communication. In addition, we conduct exemplary measurements for the most popular message types, which empower the provided models to estimate the traffic over time in a chat group.
• Efficient graph-based gateway placement for large-scale LoRaWAN deployments. Loh, Frank; Mehling, Noah; Geißler, Stefan. In Computer Communications, 204, pp. 11–23. 2023.
  • [ Abstract ]
  • [ BibTeX ]
  • [ EndNote ]
  Low Power Wide Area Networks with Long Range Wide Area Networks (LoRaWANs) as one of their most prominent representatives are promising solutions for future Internet of Things deployments. The technology is characterized by low energy requirements leading to long battery lifetimes. However, the drawbacks are limited throughput rates and the unreliable nature of the LoRa technology. Specifically its random channel access approach leads to significant message collisions and thus, data loss in larger deployments. From a network planning point of view, the reduction of potentially colliding messages at the frequency bands in combination with limiting the transmission duration of messages is a promising approach. For that reason, we present a novel graph-based gateway placement approach. We show that our approach performs similar to state-of-the-art related work in the worst case and reduces the required number of gateways by up to 40% while reducing the collision probability by up to 70%. Furthermore, we overcome the challenge of scalability of our approach when placing gateways in very large networks. By splitting the problem into smaller problem instances by pre-clustering, we can solve arbitrarily large instances efficiently without a significant increase in number of required gateways in real networks.

  @article{info3-article-2023-6, abstract = {Low Power Wide Area Networks with Long Range Wide Area Networks (LoRaWANs) as one of their most prominent representatives are promising solutions for future Internet of Things deployments. The technology is characterized by low energy requirements leading to long battery lifetimes. However, the drawbacks are limited throughput rates and the unreliable nature of the LoRa technology. Specifically its random channel access approach leads to significant message collisions and thus, data loss in larger deployments. From a network planning point of view, the reduction of potentially colliding messages at the frequency bands in combination with limiting the transmission duration of messages is a promising approach. For that reason, we present a novel graph-based gateway placement approach. We show that our approach performs similar to state-of-the-art related work in the worst case and reduces the required number of gateways by up to 40% while reducing the collision probability by up to 70%. Furthermore, we overcome the challenge of scalability of our approach when placing gateways in very large networks. By splitting the problem into smaller problem instances by pre-clustering, we can solve arbitrarily large instances efficiently without a significant increase in number of required gateways in real networks.}, author = {Loh, Frank and Mehling, Noah and Geißler, Stefan}, journal = {Computer Communications}, keywords = {sys:hidden:article}, month = {02}, pages = {11-23}, title = {Efficient graph-based gateway placement for large-scale LoRaWAN deployments}, volume = 204, year = 2023 }

  %0 Journal Article %1 info3-article-2023-6 %A Loh, Frank %A Mehling, Noah %A Geißler, Stefan %D 2023 %J Computer Communications %P 11-23 %T Efficient graph-based gateway placement for large-scale LoRaWAN deployments %V 204 %X Low Power Wide Area Networks with Long Range Wide Area Networks (LoRaWANs) as one of their most prominent representatives are promising solutions for future Internet of Things deployments. The technology is characterized by low energy requirements leading to long battery lifetimes. However, the drawbacks are limited throughput rates and the unreliable nature of the LoRa technology. Specifically its random channel access approach leads to significant message collisions and thus, data loss in larger deployments. From a network planning point of view, the reduction of potentially colliding messages at the frequency bands in combination with limiting the transmission duration of messages is a promising approach. For that reason, we present a novel graph-based gateway placement approach. We show that our approach performs similar to state-of-the-art related work in the worst case and reduces the required number of gateways by up to 40% while reducing the collision probability by up to 70%. Furthermore, we overcome the challenge of scalability of our approach when placing gateways in very large networks. By splitting the problem into smaller problem instances by pre-clustering, we can solve arbitrarily large instances efficiently without a significant increase in number of required gateways in real networks.
• Industrial User Experience Index vs. Quality of Experience Models. Hoßfeld, Tobias; Seufert, Anika; Loh, Frank; Wunderer, Stefan; Davies, John. In IEEE Communications Magazine, 61(1), pp. 98–104. 2023.
  • [ Abstract ]
  • [ BibTeX ]
  • [ EndNote ]
  Network operators have increased interest in understanding and quantifying the user perceived quality of experience (QoE). Appropriate QoE models allow mapping of measurable QoS parameters to QoE metrics like mean opinion scores (MOS) or poor-or-worse (PoW) ratios. Unfortunately, there are no QoE models for all applications available yet, and development and standardization is rather time-consuming. For that reason, industry often implements simple but effective approaches based on expert knowledge to get a user experience index able to deliver high value insights. This index is often defined based on thresholds of measurable QoS parameters to classify the resulting user experience. The question arises whether such a threshold-based user experience index can properly estimate the QoE in a system. We therefore answer in this work whether the user experience index is able to quantify the expected QoE in a system and if other QoE metrics like PoW ratios can be derived. Furthermore, we discuss the interpretation and the limits of the index. As a key contribution, we present a detailed systematic analysis of the threshold-based QoE concept and discuss its usability as QoE estimation methodology for industry.

  @article{info3-article-2023-7, abstract = {Network operators have increased interest in understanding and quantifying the user perceived quality of experience (QoE). Appropriate QoE models allow mapping of measurable QoS parameters to QoE metrics like mean opinion scores (MOS) or poor-or-worse (PoW) ratios. Unfortunately, there are no QoE models for all applications available yet, and development and standardization is rather time-consuming. For that reason, industry often implements simple but effective approaches based on expert knowledge to get a user experience index able to deliver high value insights. This index is often defined based on thresholds of measurable QoS parameters to classify the resulting user experience. The question arises whether such a threshold-based user experience index can properly estimate the QoE in a system. We therefore answer in this work whether the user experience index is able to quantify the expected QoE in a system and if other QoE metrics like PoW ratios can be derived. Furthermore, we discuss the interpretation and the limits of the index. As a key contribution, we present a detailed systematic analysis of the threshold-based QoE concept and discuss its usability as QoE estimation methodology for industry.}, author = {Hoßfeld, Tobias and Seufert, Anika and Loh, Frank and Wunderer, Stefan and Davies, John}, journal = {IEEE Communications Magazine}, keywords = {5gqmon}, month = {01}, number = 1, pages = {98-104}, title = {Industrial User Experience Index vs. Quality of Experience Models}, volume = 61, year = 2023 }

  %0 Journal Article %1 info3-article-2023-7 %A Hoßfeld, Tobias %A Seufert, Anika %A Loh, Frank %A Wunderer, Stefan %A Davies, John %D 2023 %J IEEE Communications Magazine %N 1 %P 98-104 %T Industrial User Experience Index vs. Quality of Experience Models %V 61 %X Network operators have increased interest in understanding and quantifying the user perceived quality of experience (QoE). Appropriate QoE models allow mapping of measurable QoS parameters to QoE metrics like mean opinion scores (MOS) or poor-or-worse (PoW) ratios. Unfortunately, there are no QoE models for all applications available yet, and development and standardization is rather time-consuming. For that reason, industry often implements simple but effective approaches based on expert knowledge to get a user experience index able to deliver high value insights. This index is often defined based on thresholds of measurable QoS parameters to classify the resulting user experience. The question arises whether such a threshold-based user experience index can properly estimate the QoE in a system. We therefore answer in this work whether the user experience index is able to quantify the expected QoE in a system and if other QoE metrics like PoW ratios can be derived. Furthermore, we discuss the interpretation and the limits of the index. As a key contribution, we present a detailed systematic analysis of the threshold-based QoE concept and discuss its usability as QoE estimation methodology for industry.
• Do you Agree? Contrasting Google’s Core Web Vitals and the Impact of Cookie Consent Banners with Actual Web QoE. Wehner, Nikolas; Seufert, Michael; Schatz, Raimund; Hoßfeld, Tobias. In Quality and User Experience. 2023.
  • [ Abstract ]
  • [ BibTeX ]
  • [ EndNote ]
  Providing sophisticated web Quality of Experience (QoE) has become paramount for web service providers and network operators alike. Due to advances in web technologies (HTML5, respon- sive design, etc.), traditional web QoE models focusing mainly on loading times have to be refined and improved. In this work, we relate Google’s Core Web Vitals, a set of metrics for improving user experience, to the loading time aspects of web QoE, and investigate whether the Core Web Vitals and web QoE agree on the perceived experience. To this end, we first perform objective measurements in the web using Google’s Lighthouse. To close the gap be- tween metrics and experience, we complement these objective measurements with subjective assessment by performing multiple crowdsourcing QoE studies. For this purpose, we developed CWeQS, a customized framework to emulate the entire web page loading process, and ask users for their experience while controlling the Core Web Vitals, which is available to the public. To properly configure CWeQS for the planned QoE study and the crowdsourcing setup, we conduct pre-studies, in which we evaluate the importance of the loading strategy of a web page and the impor- tance of the user task. The obtained insights allow us to conduct the desired QoE studies for each of the Core Web Vitals. Furthermore, we assess the impact of cookie consent banners, which have become ubiquitous due to regulatory demands, on the Core Web Vitals and investigate their influence on web QoE. Our results suggest that the Core Web Vitals are much less predictive for web QoE than expected and that page loading times remain the main metric and influence factor in this context. We further observe that unobtrusive and acentric cookie consent banners are preferred by end-users and that addi- tional delays caused by interacting with consent banners in order to agree to or reject cookies should be accounted along with the actual page load time to reduce waiting times and thus to improve web QoE.

  @article{info3-article-2023-3, abstract = {Providing sophisticated web Quality of Experience (QoE) has become paramount for web service providers and network operators alike. Due to advances in web technologies (HTML5, respon- sive design, etc.), traditional web QoE models focusing mainly on loading times have to be refined and improved. In this work, we relate Google’s Core Web Vitals, a set of metrics for improving user experience, to the loading time aspects of web QoE, and investigate whether the Core Web Vitals and web QoE agree on the perceived experience. To this end, we first perform objective measurements in the web using Google’s Lighthouse. To close the gap be- tween metrics and experience, we complement these objective measurements with subjective assessment by performing multiple crowdsourcing QoE studies. For this purpose, we developed CWeQS, a customized framework to emulate the entire web page loading process, and ask users for their experience while controlling the Core Web Vitals, which is available to the public. To properly configure CWeQS for the planned QoE study and the crowdsourcing setup, we conduct pre-studies, in which we evaluate the importance of the loading strategy of a web page and the impor- tance of the user task. The obtained insights allow us to conduct the desired QoE studies for each of the Core Web Vitals. Furthermore, we assess the impact of cookie consent banners, which have become ubiquitous due to regulatory demands, on the Core Web Vitals and investigate their influence on web QoE. Our results suggest that the Core Web Vitals are much less predictive for web QoE than expected and that page loading times remain the main metric and influence factor in this context. We further observe that unobtrusive and acentric cookie consent banners are preferred by end-users and that addi- tional delays caused by interacting with consent banners in order to agree to or reject cookies should be accounted along with the actual page load time to reduce waiting times and thus to improve web QoE.}, author = {Wehner, Nikolas and Seufert, Michael and Schatz, Raimund and Hoßfeld, Tobias}, journal = {Quality and User Experience}, keywords = {ucn}, title = {Do you Agree? Contrasting Google’s Core Web Vitals and the Impact of Cookie Consent Banners with Actual Web QoE}, year = 2023 }

  %0 Journal Article %1 info3-article-2023-3 %A Wehner, Nikolas %A Seufert, Michael %A Schatz, Raimund %A Hoßfeld, Tobias %D 2023 %J Quality and User Experience %T Do you Agree? Contrasting Google’s Core Web Vitals and the Impact of Cookie Consent Banners with Actual Web QoE %X Providing sophisticated web Quality of Experience (QoE) has become paramount for web service providers and network operators alike. Due to advances in web technologies (HTML5, respon- sive design, etc.), traditional web QoE models focusing mainly on loading times have to be refined and improved. In this work, we relate Google’s Core Web Vitals, a set of metrics for improving user experience, to the loading time aspects of web QoE, and investigate whether the Core Web Vitals and web QoE agree on the perceived experience. To this end, we first perform objective measurements in the web using Google’s Lighthouse. To close the gap be- tween metrics and experience, we complement these objective measurements with subjective assessment by performing multiple crowdsourcing QoE studies. For this purpose, we developed CWeQS, a customized framework to emulate the entire web page loading process, and ask users for their experience while controlling the Core Web Vitals, which is available to the public. To properly configure CWeQS for the planned QoE study and the crowdsourcing setup, we conduct pre-studies, in which we evaluate the importance of the loading strategy of a web page and the impor- tance of the user task. The obtained insights allow us to conduct the desired QoE studies for each of the Core Web Vitals. Furthermore, we assess the impact of cookie consent banners, which have become ubiquitous due to regulatory demands, on the Core Web Vitals and investigate their influence on web QoE. Our results suggest that the Core Web Vitals are much less predictive for web QoE than expected and that page loading times remain the main metric and influence factor in this context. We further observe that unobtrusive and acentric cookie consent banners are preferred by end-users and that addi- tional delays caused by interacting with consent banners in order to agree to or reject cookies should be accounted along with the actual page load time to reduce waiting times and thus to improve web QoE.

• Towards LoRaWAN without Data Loss: Studying the Performance of Different Channel Access Approaches. Loh, Frank; Mehling, Noah; Hoßfeld, Tobias. In Sensors. 2022.
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  The Long Range Wide Area Network (LoRaWAN) is one of the fastest growing Internet of Things (IoT) access protocols. It operates in the license free 868 MHz band and gives everyone the possibility to create their own small sensor networks. The drawback of this technology is often unscheduled or random channel access, which leads to message collisions and potential data loss. For that reason, recent literature studies alternative approaches for LoRaWAN channel access. In this work, state-of-the-art random channel access is compared with alternative approaches from the litera- ture by means of collision probability. Furthermore, a time scheduled channel access methodology is presented to completely avoid collisions in LoRaWAN. For this approach, an exhaustive simulation study was conducted and the performance was evaluated with random access cross-traffic. In a general theoretical analysis the limits of the time scheduled approach are discussed to comply with duty cycle regulations in LoRaWAN.

  @article{info3-inproceedings-2022-3, abstract = {The Long Range Wide Area Network (LoRaWAN) is one of the fastest growing Internet of Things (IoT) access protocols. It operates in the license free 868 MHz band and gives everyone the possibility to create their own small sensor networks. The drawback of this technology is often unscheduled or random channel access, which leads to message collisions and potential data loss. For that reason, recent literature studies alternative approaches for LoRaWAN channel access. In this work, state-of-the-art random channel access is compared with alternative approaches from the litera- ture by means of collision probability. Furthermore, a time scheduled channel access methodology is presented to completely avoid collisions in LoRaWAN. For this approach, an exhaustive simulation study was conducted and the performance was evaluated with random access cross-traffic. In a general theoretical analysis the limits of the time scheduled approach are discussed to comply with duty cycle regulations in LoRaWAN.}, author = {Loh, Frank and Mehling, Noah and Hoßfeld, Tobias}, journal = {Sensors}, keywords = {sys:hidden:article}, month = {01}, title = {Towards LoRaWAN without Data Loss: Studying the Performance of Different Channel Access Approaches}, year = 2022 }

  %0 Journal Article %1 info3-inproceedings-2022-3 %A Loh, Frank %A Mehling, Noah %A Hoßfeld, Tobias %D 2022 %J Sensors %T Towards LoRaWAN without Data Loss: Studying the Performance of Different Channel Access Approaches %X The Long Range Wide Area Network (LoRaWAN) is one of the fastest growing Internet of Things (IoT) access protocols. It operates in the license free 868 MHz band and gives everyone the possibility to create their own small sensor networks. The drawback of this technology is often unscheduled or random channel access, which leads to message collisions and potential data loss. For that reason, recent literature studies alternative approaches for LoRaWAN channel access. In this work, state-of-the-art random channel access is compared with alternative approaches from the litera- ture by means of collision probability. Furthermore, a time scheduled channel access methodology is presented to completely avoid collisions in LoRaWAN. For this approach, an exhaustive simulation study was conducted and the performance was evaluated with random access cross-traffic. In a general theoretical analysis the limits of the time scheduled approach are discussed to comply with duty cycle regulations in LoRaWAN.
• An Introduction to Online Video Game QoS and QoE Influencing Factors. Metzger, Florian; Geißler, Stefan; Grigorjew, Alexej; Loh, Frank; Moldovan, Christian; Seufert, Michael; Hoßfeld, Tobias. In IEEE Communications Surveys & Tutorials. 2022.
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  Online video games and cloud gaming are rapidly growing in pervasiveness. Their resource demands can put significant stress on the global communication infrastructure. And network conditions are amongst the chief factors that influence one's enjoyment while playing games. This makes it imperative for video games to be considered for network dimensioning, server placement or protocol development. For that reason, in this work we provide an introduction to the technical aspects of video games in general and of their network aspects in particular. This understanding forms the basis for a rich taxonomy of factors that influence and provide context to a video game's Quality of Service (QoS) and Quality of Experience (QoE). The taxonomy covers influence factors from all aspects involved in a video game, from the subjective player and game influence factors to the system and networking influence factors. Finally, this work gives an overview of conducted and ongoing research as well as future research opportunities while taking into account lessons learned from past approaches.

  @article{info3-article-2022-16, abstract = {Online video games and cloud gaming are rapidly growing in pervasiveness. Their resource demands can put significant stress on the global communication infrastructure. And network conditions are amongst the chief factors that influence one's enjoyment while playing games. This makes it imperative for video games to be considered for network dimensioning, server placement or protocol development. For that reason, in this work we provide an introduction to the technical aspects of video games in general and of their network aspects in particular. This understanding forms the basis for a rich taxonomy of factors that influence and provide context to a video game's Quality of Service (QoS) and Quality of Experience (QoE). The taxonomy covers influence factors from all aspects involved in a video game, from the subjective player and game influence factors to the system and networking influence factors. Finally, this work gives an overview of conducted and ongoing research as well as future research opportunities while taking into account lessons learned from past approaches.}, author = {Metzger, Florian and Geißler, Stefan and Grigorjew, Alexej and Loh, Frank and Moldovan, Christian and Seufert, Michael and Hoßfeld, Tobias}, journal = {IEEE Communications Surveys & Tutorials}, keywords = {sys:hidden:article}, month = {05}, title = {An Introduction to Online Video Game QoS and QoE Influencing Factors}, year = 2022 }

  %0 Journal Article %1 info3-article-2022-16 %A Metzger, Florian %A Geißler, Stefan %A Grigorjew, Alexej %A Loh, Frank %A Moldovan, Christian %A Seufert, Michael %A Hoßfeld, Tobias %D 2022 %J IEEE Communications Surveys & Tutorials %T An Introduction to Online Video Game QoS and QoE Influencing Factors %X Online video games and cloud gaming are rapidly growing in pervasiveness. Their resource demands can put significant stress on the global communication infrastructure. And network conditions are amongst the chief factors that influence one's enjoyment while playing games. This makes it imperative for video games to be considered for network dimensioning, server placement or protocol development. For that reason, in this work we provide an introduction to the technical aspects of video games in general and of their network aspects in particular. This understanding forms the basis for a rich taxonomy of factors that influence and provide context to a video game's Quality of Service (QoS) and Quality of Experience (QoE). The taxonomy covers influence factors from all aspects involved in a video game, from the subjective player and game influence factors to the system and networking influence factors. Finally, this work gives an overview of conducted and ongoing research as well as future research opportunities while taking into account lessons learned from past approaches.
• Pandemic in the Digital Age: Analyzing WhatsApp Communication Behavior before, during, and after the COVID-19 Lockdown. Seufert, Anika; Poignée, Fabian; Hoßfeld, Tobias; Seufert, Michael. In Humanities and Social Sciences Communications, 9(1), pp. 140 (1–9). 2022.
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  The strict restrictions introduced by the COVID-19 lockdowns, which started from March 2020, changed people’s daily lives and habits on many different levels. In this work, we investigate the impact of the lockdown on the communication behavior in the mobile instant messaging application WhatsApp. Our evaluations are based on a large dataset of 2577 private chat histories with 25,378,093 messages from 51,973 users. The analysis of the one-to-one and group conversations confirms that the lockdown severely altered the communication in WhatsApp chats compared to pre-pandemic time ranges. In particular, we observe short-term effects, which caused an increased message frequency in the first lockdown months and a shifted communication activity during the day in March and April 2020. Moreover, we also see long-term effects of the ongoing pandemic situation until February 2021, which indicate a change of communication behavior towards more regular messaging, as well as a persisting change in activity during the day. The results of our work show that even anonymized chat histories can tell us a lot about people’s behavior and especially behavioral changes during the COVID-19 pandemic and thus are of great relevance for behavioral researchers. Furthermore, looking at the pandemic from an Internet provider perspective, these insights can be used during the next pandemic, or if the current COVID-19 situation worsens, to adapt communication networks to the changed usage behavior early on and thus avoid network congestion.

  @article{info3-article-2022-14, abstract = {The strict restrictions introduced by the COVID-19 lockdowns, which started from March 2020, changed people’s daily lives and habits on many different levels. In this work, we investigate the impact of the lockdown on the communication behavior in the mobile instant messaging application WhatsApp. Our evaluations are based on a large dataset of 2577 private chat histories with 25,378,093 messages from 51,973 users. The analysis of the one-to-one and group conversations confirms that the lockdown severely altered the communication in WhatsApp chats compared to pre-pandemic time ranges. In particular, we observe short-term effects, which caused an increased message frequency in the first lockdown months and a shifted communication activity during the day in March and April 2020. Moreover, we also see long-term effects of the ongoing pandemic situation until February 2021, which indicate a change of communication behavior towards more regular messaging, as well as a persisting change in activity during the day. The results of our work show that even anonymized chat histories can tell us a lot about people’s behavior and especially behavioral changes during the COVID-19 pandemic and thus are of great relevance for behavioral researchers. Furthermore, looking at the pandemic from an Internet provider perspective, these insights can be used during the next pandemic, or if the current COVID-19 situation worsens, to adapt communication networks to the changed usage behavior early on and thus avoid network congestion.}, author = {Seufert, Anika and Poignée, Fabian and Hoßfeld, Tobias and Seufert, Michael}, journal = {Humanities and Social Sciences Communications}, keywords = {ucn}, month = {04}, number = 1, pages = {140 (1-9)}, title = {Pandemic in the Digital Age: Analyzing WhatsApp Communication Behavior before, during, and after the COVID-19 Lockdown}, volume = 9, year = 2022 }

  %0 Journal Article %1 info3-article-2022-14 %A Seufert, Anika %A Poignée, Fabian %A Hoßfeld, Tobias %A Seufert, Michael %D 2022 %J Humanities and Social Sciences Communications %N 1 %P 140 (1-9) %T Pandemic in the Digital Age: Analyzing WhatsApp Communication Behavior before, during, and after the COVID-19 Lockdown %V 9 %X The strict restrictions introduced by the COVID-19 lockdowns, which started from March 2020, changed people’s daily lives and habits on many different levels. In this work, we investigate the impact of the lockdown on the communication behavior in the mobile instant messaging application WhatsApp. Our evaluations are based on a large dataset of 2577 private chat histories with 25,378,093 messages from 51,973 users. The analysis of the one-to-one and group conversations confirms that the lockdown severely altered the communication in WhatsApp chats compared to pre-pandemic time ranges. In particular, we observe short-term effects, which caused an increased message frequency in the first lockdown months and a shifted communication activity during the day in March and April 2020. Moreover, we also see long-term effects of the ongoing pandemic situation until February 2021, which indicate a change of communication behavior towards more regular messaging, as well as a persisting change in activity during the day. The results of our work show that even anonymized chat histories can tell us a lot about people’s behavior and especially behavioral changes during the COVID-19 pandemic and thus are of great relevance for behavioral researchers. Furthermore, looking at the pandemic from an Internet provider perspective, these insights can be used during the next pandemic, or if the current COVID-19 situation worsens, to adapt communication networks to the changed usage behavior early on and thus avoid network congestion.
• YouTube Dataset on Mobile Streaming for Internet Traffic Modeling and Streaming Analysis. Loh, Frank; Wamser, Florian; Poignée, Fabian; Geißler, Stefan; Hoßfeld, Tobias. In Nature, Scientific Data. 2022.
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  Around 4.9 billion Internet users worldwide watch billions of hours of online video every day. As a result, streaming is by far the predominant type of traffic in communication networks. According to Google statistics, three out of five video views come from mobile devices. Thus, in view of the continuous technological advances in end devices and increasing mobile use, datasets for mobile streaming are indispensable in research but only sparsely dealt with in literature so far. With this public dataset, we provide 1,081 hours of time-synchronous video measurements at network, transport, and application layer with the native YouTube streaming client on mobile devices. The dataset includes 80 network scenarios with 171 different individual bandwidth settings measured in 5,181 runs with limited bandwidth, 1,939 runs with emulated 3 G/4 G traces, and 4,022 runs with pre-defined bandwidth changes. This corresponds to 332 GB video payload. We present the most relevant quality indicators for scientific use, i.e., initial playback delay, streaming video quality, adaptive video quality changes, video rebuffering events, and streaming phases.

  @article{info3-article-2022-17, abstract = {Around 4.9 billion Internet users worldwide watch billions of hours of online video every day. As a result, streaming is by far the predominant type of traffic in communication networks. According to Google statistics, three out of five video views come from mobile devices. Thus, in view of the continuous technological advances in end devices and increasing mobile use, datasets for mobile streaming are indispensable in research but only sparsely dealt with in literature so far. With this public dataset, we provide 1,081 hours of time-synchronous video measurements at network, transport, and application layer with the native YouTube streaming client on mobile devices. The dataset includes 80 network scenarios with 171 different individual bandwidth settings measured in 5,181 runs with limited bandwidth, 1,939 runs with emulated 3 G/4 G traces, and 4,022 runs with pre-defined bandwidth changes. This corresponds to 332 GB video payload. We present the most relevant quality indicators for scientific use, i.e., initial playback delay, streaming video quality, adaptive video quality changes, video rebuffering events, and streaming phases.}, author = {Loh, Frank and Wamser, Florian and Poignée, Fabian and Geißler, Stefan and Hoßfeld, Tobias}, journal = {Nature, Scientific Data}, keywords = {sys:hidden:article}, month = {06}, title = {YouTube Dataset on Mobile Streaming for Internet Traffic Modeling and Streaming Analysis}, year = 2022 }

  %0 Journal Article %1 info3-article-2022-17 %A Loh, Frank %A Wamser, Florian %A Poignée, Fabian %A Geißler, Stefan %A Hoßfeld, Tobias %D 2022 %J Nature, Scientific Data %T YouTube Dataset on Mobile Streaming for Internet Traffic Modeling and Streaming Analysis %X Around 4.9 billion Internet users worldwide watch billions of hours of online video every day. As a result, streaming is by far the predominant type of traffic in communication networks. According to Google statistics, three out of five video views come from mobile devices. Thus, in view of the continuous technological advances in end devices and increasing mobile use, datasets for mobile streaming are indispensable in research but only sparsely dealt with in literature so far. With this public dataset, we provide 1,081 hours of time-synchronous video measurements at network, transport, and application layer with the native YouTube streaming client on mobile devices. The dataset includes 80 network scenarios with 171 different individual bandwidth settings measured in 5,181 runs with limited bandwidth, 1,939 runs with emulated 3 G/4 G traces, and 4,022 runs with pre-defined bandwidth changes. This corresponds to 332 GB video payload. We present the most relevant quality indicators for scientific use, i.e., initial playback delay, streaming video quality, adaptive video quality changes, video rebuffering events, and streaming phases.

• LoRaPlan: A Software to Evaluate Gateway Placement in LoRaWAN. Loh, Frank; Mehling, Noah; Metzger, Florian; Hoßfeld, Tobias. In 17th International Conference on Network and Service Management. 2021.
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  Long Range Wide Area Network (LoRaWAN) is one of the fastest growing Internet of Things (IoT) access network solutions. One major challenge in current LoRaWAN planning is message collision due to the random channel access. To study the collision behavior in LoRaWAN, we present LoRaPlan in this demonstration. LoRaPlan is a software to evaluate gateway placement decisions by studying the collision probability. Therefore, sensor and gateway locations can be imported to create a LoRaWAN. Furthermore, existing networks can be extended by additional gateways. Based on this setup, network coverage, network quality with regard to the number of sensors a single gateway has to manage, and also transmission quality and collision probabilities can be studied. In this demonstration, first the process of network creation with gateway and sensor import and additional manual gateway placement in LoRaPlan is presented. Different adjustable parameters are shown and the influence on network coverage and collision probability is discussed. At the end of this demonstration, it is possible for the audience to place their own gateways and evaluate own placements by means of collision probability and the coverage.

  @article{info3-article-2021-11, abstract = {Long Range Wide Area Network (LoRaWAN) is one of the fastest growing Internet of Things (IoT) access network solutions. One major challenge in current LoRaWAN planning is message collision due to the random channel access. To study the collision behavior in LoRaWAN, we present LoRaPlan in this demonstration. LoRaPlan is a software to evaluate gateway placement decisions by studying the collision probability. Therefore, sensor and gateway locations can be imported to create a LoRaWAN. Furthermore, existing networks can be extended by additional gateways. Based on this setup, network coverage, network quality with regard to the number of sensors a single gateway has to manage, and also transmission quality and collision probabilities can be studied. In this demonstration, first the process of network creation with gateway and sensor import and additional manual gateway placement in LoRaPlan is presented. Different adjustable parameters are shown and the influence on network coverage and collision probability is discussed. At the end of this demonstration, it is possible for the audience to place their own gateways and evaluate own placements by means of collision probability and the coverage.}, author = {Loh, Frank and Mehling, Noah and Metzger, Florian and Hoßfeld, Tobias}, journal = {17th International Conference on Network and Service Management}, keywords = {sys:hidden:article}, month = 10, title = {LoRaPlan: A Software to Evaluate Gateway Placement in LoRaWAN}, year = 2021 }

  %0 Journal Article %1 info3-article-2021-11 %A Loh, Frank %A Mehling, Noah %A Metzger, Florian %A Hoßfeld, Tobias %D 2021 %J 17th International Conference on Network and Service Management %T LoRaPlan: A Software to Evaluate Gateway Placement in LoRaWAN %X Long Range Wide Area Network (LoRaWAN) is one of the fastest growing Internet of Things (IoT) access network solutions. One major challenge in current LoRaWAN planning is message collision due to the random channel access. To study the collision behavior in LoRaWAN, we present LoRaPlan in this demonstration. LoRaPlan is a software to evaluate gateway placement decisions by studying the collision probability. Therefore, sensor and gateway locations can be imported to create a LoRaWAN. Furthermore, existing networks can be extended by additional gateways. Based on this setup, network coverage, network quality with regard to the number of sensors a single gateway has to manage, and also transmission quality and collision probabilities can be studied. In this demonstration, first the process of network creation with gateway and sensor import and additional manual gateway placement in LoRaPlan is presented. Different adjustable parameters are shown and the influence on network coverage and collision probability is discussed. At the end of this demonstration, it is possible for the audience to place their own gateways and evaluate own placements by means of collision probability and the coverage.
• Valid Statements by the Crowd: Statistical Measures for Precision in Crowdsourced Mobile Measurements. Wamser, Florian; Seufert, Anika; Hall, Andrew; Wunderer, Stefan; Hoßfeld, Tobias. In Network, 1(2), pp. 215–232. 2021.
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  Crowdsourced network measurements (CNMs) are becoming increasingly popular as they assess the performance of a mobile network from the end user’s perspective on a large scale. Here, network measurements are performed directly on the end-users’ devices, thus taking advantage of the real-world conditions end-users encounter. However, this type of uncontrolled measurement raises questions about its validity and reliability. The problem lies in the nature of this type of data collection. In CNMs, mobile network subscribers are involved to a large extent in the measurement process, and collect data themselves for the operator. The collection of data on user devices in arbitrary locations and at uncontrolled times requires means to ensure validity and reliability. To address this issue, our paper defines concepts and guidelines for analyzing the precision of CNMs; specifically, the number of measurements required to make valid statements. In addition to the formal definition of the aspect, we illustrate the problem and use an extensive sample data set to show possible assessment approaches. This data set consists of more than 20.4 million crowdsourced mobile measurements from across France, measured by a commercial data provider.

  @article{info3-article-2021-5, abstract = {Crowdsourced network measurements (CNMs) are becoming increasingly popular as they assess the performance of a mobile network from the end user’s perspective on a large scale. Here, network measurements are performed directly on the end-users’ devices, thus taking advantage of the real-world conditions end-users encounter. However, this type of uncontrolled measurement raises questions about its validity and reliability. The problem lies in the nature of this type of data collection. In CNMs, mobile network subscribers are involved to a large extent in the measurement process, and collect data themselves for the operator. The collection of data on user devices in arbitrary locations and at uncontrolled times requires means to ensure validity and reliability. To address this issue, our paper defines concepts and guidelines for analyzing the precision of CNMs; specifically, the number of measurements required to make valid statements. In addition to the formal definition of the aspect, we illustrate the problem and use an extensive sample data set to show possible assessment approaches. This data set consists of more than 20.4 million crowdsourced mobile measurements from across France, measured by a commercial data provider.}, author = {Wamser, Florian and Seufert, Anika and Hall, Andrew and Wunderer, Stefan and Hoßfeld, Tobias}, journal = {Network}, keywords = {can}, month = {09}, number = 2, pages = {215–232}, title = {Valid Statements by the Crowd: Statistical Measures for Precision in Crowdsourced Mobile Measurements}, volume = 1, year = 2021 }

  %0 Journal Article %1 info3-article-2021-5 %A Wamser, Florian %A Seufert, Anika %A Hall, Andrew %A Wunderer, Stefan %A Hoßfeld, Tobias %D 2021 %J Network %N 2 %P 215--232 %T Valid Statements by the Crowd: Statistical Measures for Precision in Crowdsourced Mobile Measurements %V 1 %X Crowdsourced network measurements (CNMs) are becoming increasingly popular as they assess the performance of a mobile network from the end user’s perspective on a large scale. Here, network measurements are performed directly on the end-users’ devices, thus taking advantage of the real-world conditions end-users encounter. However, this type of uncontrolled measurement raises questions about its validity and reliability. The problem lies in the nature of this type of data collection. In CNMs, mobile network subscribers are involved to a large extent in the measurement process, and collect data themselves for the operator. The collection of data on user devices in arbitrary locations and at uncontrolled times requires means to ensure validity and reliability. To address this issue, our paper defines concepts and guidelines for analyzing the precision of CNMs; specifically, the number of measurements required to make valid statements. In addition to the formal definition of the aspect, we illustrate the problem and use an extensive sample data set to show possible assessment approaches. This data set consists of more than 20.4 million crowdsourced mobile measurements from across France, measured by a commercial data provider.
• Delivering User Experience over Networks: Towards a Quality of Experience Centered Design Cycle for Improved Design of Networked Applications. Seufert, Anika; Schröder, Svenja; Seufert, Michael. In SN Computer Science, 2. 2021.
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  To deliver the best user experience (UX), the human-centered design cycle (HCDC) serves as a well-established guideline to application developers. However, it does not yet cover network-specific requirements, which become increasingly crucial, as most applications deliver experience over the Internet. The missing network-centric view is provided by Quality of Experience (QoE), which could team up with UX towards an improved overall experience. By considering QoE aspects during the development process, it can be achieved that applications become network-aware by design. In this paper, the Quality of Experience Centered Design Cycle (QoE-CDC) is proposed, which provides guidelines on how to design applications with respect to network-specific requirements and QoE. Its practical value is showcased for popular application types and validated by outlining the design of a new smartphone application. We show that combining HCDC and QoE-CDC will result in an application design, which reaches a high UX and avoids QoE degradation.

  @article{info3-article-2021-6, abstract = {To deliver the best user experience (UX), the human-centered design cycle (HCDC) serves as a well-established guideline to application developers. However, it does not yet cover network-specific requirements, which become increasingly crucial, as most applications deliver experience over the Internet. The missing network-centric view is provided by Quality of Experience (QoE), which could team up with UX towards an improved overall experience. By considering QoE aspects during the development process, it can be achieved that applications become network-aware by design. In this paper, the Quality of Experience Centered Design Cycle (QoE-CDC) is proposed, which provides guidelines on how to design applications with respect to network-specific requirements and QoE. Its practical value is showcased for popular application types and validated by outlining the design of a new smartphone application. We show that combining HCDC and QoE-CDC will result in an application design, which reaches a high UX and avoids QoE degradation.}, author = {Seufert, Anika and Schröder, Svenja and Seufert, Michael}, journal = {SN Computer Science}, keywords = {sys:hidden:article}, month = {09}, title = {Delivering User Experience over Networks: Towards a Quality of Experience Centered Design Cycle for Improved Design of Networked Applications}, volume = 2, year = 2021 }

  %0 Journal Article %1 info3-article-2021-6 %A Seufert, Anika %A Schröder, Svenja %A Seufert, Michael %D 2021 %J SN Computer Science %T Delivering User Experience over Networks: Towards a Quality of Experience Centered Design Cycle for Improved Design of Networked Applications %V 2 %X To deliver the best user experience (UX), the human-centered design cycle (HCDC) serves as a well-established guideline to application developers. However, it does not yet cover network-specific requirements, which become increasingly crucial, as most applications deliver experience over the Internet. The missing network-centric view is provided by Quality of Experience (QoE), which could team up with UX towards an improved overall experience. By considering QoE aspects during the development process, it can be achieved that applications become network-aware by design. In this paper, the Quality of Experience Centered Design Cycle (QoE-CDC) is proposed, which provides guidelines on how to design applications with respect to network-specific requirements and QoE. Its practical value is showcased for popular application types and validated by outlining the design of a new smartphone application. We show that combining HCDC and QoE-CDC will result in an application design, which reaches a high UX and avoids QoE degradation.
• Discrete-Time Modeling of NFV Accelerators that Exploit Batched Processing. Geissler, Stefan; Lange, Stanislav; Linguaglossa, Leonardo; Rossi, Dario; Zinner, Thomas; Hoßfeld, Tobias. In ACM Transactions on Modeling and Performance Evaluation of Computing Systems, 6(3), pp. 1–27. 2021.
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  @article{info3-article-2021-12, author = {Geissler, Stefan and Lange, Stanislav and Linguaglossa, Leonardo and Rossi, Dario and Zinner, Thomas and Hoßfeld, Tobias}, journal = {ACM Transactions on Modeling and Performance Evaluation of Computing Systems}, keywords = {can}, month = {09}, number = 3, pages = {1-27}, title = {Discrete-Time Modeling of NFV Accelerators that Exploit Batched Processing}, volume = 6, year = 2021 }

  %0 Journal Article %1 info3-article-2021-12 %A Geissler, Stefan %A Lange, Stanislav %A Linguaglossa, Leonardo %A Rossi, Dario %A Zinner, Thomas %A Hoßfeld, Tobias %D 2021 %J ACM Transactions on Modeling and Performance Evaluation of Computing Systems %N 3 %P 1-27 %T Discrete-Time Modeling of NFV Accelerators that Exploit Batched Processing %V 6
• Performance Evaluation of Hybrid Crowdsensing and Fixed Sensor Systems for Event Detection in Urban Environments. Hirth, Matthias; Seufert, Michael; Lange, Stanislav; Meixner, Markus; Tran-Gia, Phuoc. In Sensors, 21(17), pp. 5880 (1–19). 2021.
  • [ Abstract ]
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  Crowdsensing offers a cost-effective way to collect large amounts of environmental sensor data. However, the spatial distribution of crowdsensing sensors can hardly be influenced, as the participants carry the sensors, and, additionally, the quality of the crowdsensed data can vary significantly. Hybrid systems that use mobile users in conjunction with fixed sensors might help to overcome these limitations, as such system allow assessing the quality of the submitted crowdsensed data and provide sensor values where no crowdsensing data is available. In this work, we use a simulation study to first analyze a simple crowdsensing system concerning the detection performance of spatial events to highlight the potential and limitations of a pure crowdsourcing system. The results indicate that even if only a small share of inhabitants participates in crowdsensing, events that have locations correlated with the population density can be easily and quickly detected using such a system. On the contrary, events with uniformly randomly distributed locations are much harder to detect using a simple crowdsensing-based approach. A second evaluation shows that hybrid systems improve the detection probability and time. Finally, we illustrate how to compute the minimum number of fixed sensors for given detection time thresholds in our exemplary scenario.

  @article{info3-article-2021-4, abstract = {Crowdsensing offers a cost-effective way to collect large amounts of environmental sensor data. However, the spatial distribution of crowdsensing sensors can hardly be influenced, as the participants carry the sensors, and, additionally, the quality of the crowdsensed data can vary significantly. Hybrid systems that use mobile users in conjunction with fixed sensors might help to overcome these limitations, as such system allow assessing the quality of the submitted crowdsensed data and provide sensor values where no crowdsensing data is available. In this work, we use a simulation study to first analyze a simple crowdsensing system concerning the detection performance of spatial events to highlight the potential and limitations of a pure crowdsourcing system. The results indicate that even if only a small share of inhabitants participates in crowdsensing, events that have locations correlated with the population density can be easily and quickly detected using such a system. On the contrary, events with uniformly randomly distributed locations are much harder to detect using a simple crowdsensing-based approach. A second evaluation shows that hybrid systems improve the detection probability and time. Finally, we illustrate how to compute the minimum number of fixed sensors for given detection time thresholds in our exemplary scenario.}, author = {Hirth, Matthias and Seufert, Michael and Lange, Stanislav and Meixner, Markus and Tran-Gia, Phuoc}, journal = {Sensors}, keywords = {ucn}, month = {08}, number = 17, pages = {5880 (1-19)}, title = {Performance Evaluation of Hybrid Crowdsensing and Fixed Sensor Systems for Event Detection in Urban Environments}, volume = 21, year = 2021 }

  %0 Journal Article %1 info3-article-2021-4 %A Hirth, Matthias %A Seufert, Michael %A Lange, Stanislav %A Meixner, Markus %A Tran-Gia, Phuoc %D 2021 %J Sensors %N 17 %P 5880 (1-19) %T Performance Evaluation of Hybrid Crowdsensing and Fixed Sensor Systems for Event Detection in Urban Environments %V 21 %X Crowdsensing offers a cost-effective way to collect large amounts of environmental sensor data. However, the spatial distribution of crowdsensing sensors can hardly be influenced, as the participants carry the sensors, and, additionally, the quality of the crowdsensed data can vary significantly. Hybrid systems that use mobile users in conjunction with fixed sensors might help to overcome these limitations, as such system allow assessing the quality of the submitted crowdsensed data and provide sensor values where no crowdsensing data is available. In this work, we use a simulation study to first analyze a simple crowdsensing system concerning the detection performance of spatial events to highlight the potential and limitations of a pure crowdsourcing system. The results indicate that even if only a small share of inhabitants participates in crowdsensing, events that have locations correlated with the population density can be easily and quickly detected using such a system. On the contrary, events with uniformly randomly distributed locations are much harder to detect using a simple crowdsensing-based approach. A second evaluation shows that hybrid systems improve the detection probability and time. Finally, we illustrate how to compute the minimum number of fixed sensors for given detection time thresholds in our exemplary scenario.
• Cumulative Quality Modeling for HTTP Adaptive Streaming. Tran, Huyen TT; Pham Ngoc, Nam; Hoßfeld, Tobias; Seufert, Michael; Thang, Truong Cong. In ACM Transactions on Multimedia Computing, Communications, and Applications, 17(1), pp. 22 (1–24). 2021.
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  @article{info3-article-2021-1, author = {Tran, Huyen TT and Pham Ngoc, Nam and Hoßfeld, Tobias and Seufert, Michael and Thang, Truong Cong}, journal = {ACM Transactions on Multimedia Computing, Communications, and Applications}, keywords = {ucn}, month = {04}, number = 1, pages = {22 (1-24)}, title = {Cumulative Quality Modeling for HTTP Adaptive Streaming}, volume = 17, year = 2021 }

  %0 Journal Article %1 info3-article-2021-1 %A Tran, Huyen TT %A Pham Ngoc, Nam %A Hoßfeld, Tobias %A Seufert, Michael %A Thang, Truong Cong %D 2021 %J ACM Transactions on Multimedia Computing, Communications, and Applications %N 1 %P 22 (1-24) %T Cumulative Quality Modeling for HTTP Adaptive Streaming %V 17
• Energy-Aware Service Function Chain Embedding in Edge-Cloud Environments for IoT Applications. Nguyen Huu, Thanh; TrungKien, Nguyen; Van Hoa, Ngo; Thu Huong, Truong; Wamser, Florian; Hoßfeld, Tobias. In IEEE Internet of Things Journal. 2021.
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  The implementation of IoT applications faces several challenges in practice, such as compliance with QoS requirements, resource constraints and energy consumption. In this context, the joint paradigm for IoT applications can resolve some of the issues arising in pure cloud computing scenarios, such as those related to latency, energy or privacy. Therefore, an environment could be promising for resource and energy-efficient IoT applications that implement VNF bound together into SFC. However, a resource and energy efficient SFC placement requires smart SFC embedding mechanisms in the environment, as several challenges arise, such as IoT service chain modeling and evaluation, the trade-off between resource allocation, energy efficiency and performance, and the resource dynamics. In this article, we address issues in modeling resource and energy utilization for IoT applications in environments. A smart traffic monitoring IP camera system is deployed as a use case for a realistic modeling of a service chain. The system is implemented in our testbed, which is designed and developed specifically to model and investigate the resource and energy utilization of SFC embedding strategies. A resource and energy-aware SFC strategy in the environment for IoT applications is then proposed. Our algorithm is able to cope with dynamic load and resource situations emerging from dynamic SFC requests. The strategy is evaluated systematically in terms of acceptance ratio of SFC requests, resource efficiency and utilization, power consumption, and VNF migrations depending on the offered system load. Results show that our strategy outperforms some existing approaches in terms of resource and energy efficiency, thus it overcomes the relevant challenges from practice and meets the demands of IoT applications.

  @article{info3-article-2021-2, abstract = {The implementation of IoT applications faces several challenges in practice, such as compliance with QoS requirements, resource constraints and energy consumption. In this context, the joint paradigm for IoT applications can resolve some of the issues arising in pure cloud computing scenarios, such as those related to latency, energy or privacy. Therefore, an environment could be promising for resource and energy-efficient IoT applications that implement VNF bound together into SFC. However, a resource and energy efficient SFC placement requires smart SFC embedding mechanisms in the environment, as several challenges arise, such as IoT service chain modeling and evaluation, the trade-off between resource allocation, energy efficiency and performance, and the resource dynamics. In this article, we address issues in modeling resource and energy utilization for IoT applications in environments. A smart traffic monitoring IP camera system is deployed as a use case for a realistic modeling of a service chain. The system is implemented in our testbed, which is designed and developed specifically to model and investigate the resource and energy utilization of SFC embedding strategies. A resource and energy-aware SFC strategy in the environment for IoT applications is then proposed. Our algorithm is able to cope with dynamic load and resource situations emerging from dynamic SFC requests. The strategy is evaluated systematically in terms of acceptance ratio of SFC requests, resource efficiency and utilization, power consumption, and VNF migrations depending on the offered system load. Results show that our strategy outperforms some existing approaches in terms of resource and energy efficiency, thus it overcomes the relevant challenges from practice and meets the demands of IoT applications.}, author = {Nguyen Huu, Thanh and TrungKien, Nguyen and Van Hoa, Ngo and Thu Huong, Truong and Wamser, Florian and Hoßfeld, Tobias}, journal = {IEEE Internet of Things Journal}, keywords = {sys:hidden:article}, month = {03}, title = {Energy-Aware Service Function Chain Embedding in Edge-Cloud Environments for IoT Applications}, year = 2021 }

  %0 Journal Article %1 info3-article-2021-2 %A Nguyen Huu, Thanh %A TrungKien, Nguyen %A Van Hoa, Ngo %A Thu Huong, Truong %A Wamser, Florian %A Hoßfeld, Tobias %D 2021 %J IEEE Internet of Things Journal %T Energy-Aware Service Function Chain Embedding in Edge-Cloud Environments for IoT Applications %X The implementation of IoT applications faces several challenges in practice, such as compliance with QoS requirements, resource constraints and energy consumption. In this context, the joint paradigm for IoT applications can resolve some of the issues arising in pure cloud computing scenarios, such as those related to latency, energy or privacy. Therefore, an environment could be promising for resource and energy-efficient IoT applications that implement VNF bound together into SFC. However, a resource and energy efficient SFC placement requires smart SFC embedding mechanisms in the environment, as several challenges arise, such as IoT service chain modeling and evaluation, the trade-off between resource allocation, energy efficiency and performance, and the resource dynamics. In this article, we address issues in modeling resource and energy utilization for IoT applications in environments. A smart traffic monitoring IP camera system is deployed as a use case for a realistic modeling of a service chain. The system is implemented in our testbed, which is designed and developed specifically to model and investigate the resource and energy utilization of SFC embedding strategies. A resource and energy-aware SFC strategy in the environment for IoT applications is then proposed. Our algorithm is able to cope with dynamic load and resource situations emerging from dynamic SFC requests. The strategy is evaluated systematically in terms of acceptance ratio of SFC requests, resource efficiency and utilization, power consumption, and VNF migrations depending on the offered system load. Results show that our strategy outperforms some existing approaches in terms of resource and energy efficiency, thus it overcomes the relevant challenges from practice and meets the demands of IoT applications.
• Improving Web QoE Monitoring for Encrypted Network Traffic through Time Series Modeling. Wehner, Nikolas; Seufert, Michael; Schüler, Joshua; Wassermann, Sarah; Casas, Pedro; Hoßfeld, Tobias. In ACM SIGMETRICS Performance Evaluation Review, 48(4), pp. 37–40. 2021.
  • [ Abstract ]
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  This paper addresses the problem of Quality of Experience (QoE) monitoring for web browsing. In particular, the inference of common Web QoE metrics such as Speed Index (SI) is investigated. Based on a large dataset collected with open web-measurement platforms on different device-types, a unique feature set is designed and used to estimate the RUMSI -- an efficient approximation to SI, with machine-learning based regression and classification approaches. Results indicate that it is possible to estimate the RUMSI accurately, and that in particular, recurrent neural networks are highly suitable for the task, as they capture the network dynamics more precisely.

  @article{info3-article-2020-4, abstract = {This paper addresses the problem of Quality of Experience (QoE) monitoring for web browsing. In particular, the inference of common Web QoE metrics such as Speed Index (SI) is investigated. Based on a large dataset collected with open web-measurement platforms on different device-types, a unique feature set is designed and used to estimate the RUMSI – an efficient approximation to SI, with machine-learning based regression and classification approaches. Results indicate that it is possible to estimate the RUMSI accurately, and that in particular, recurrent neural networks are highly suitable for the task, as they capture the network dynamics more precisely.}, author = {Wehner, Nikolas and Seufert, Michael and Schüler, Joshua and Wassermann, Sarah and Casas, Pedro and Hoßfeld, Tobias}, journal = {ACM SIGMETRICS Performance Evaluation Review}, keywords = {ucn}, month = {03}, number = 4, pages = {37-40}, title = {Improving Web QoE Monitoring for Encrypted Network Traffic through Time Series Modeling}, volume = 48, year = 2021 }

  %0 Journal Article %1 info3-article-2020-4 %A Wehner, Nikolas %A Seufert, Michael %A Schüler, Joshua %A Wassermann, Sarah %A Casas, Pedro %A Hoßfeld, Tobias %D 2021 %J ACM SIGMETRICS Performance Evaluation Review %N 4 %P 37-40 %T Improving Web QoE Monitoring for Encrypted Network Traffic through Time Series Modeling %V 48 %X This paper addresses the problem of Quality of Experience (QoE) monitoring for web browsing. In particular, the inference of common Web QoE metrics such as Speed Index (SI) is investigated. Based on a large dataset collected with open web-measurement platforms on different device-types, a unique feature set is designed and used to estimate the RUMSI -- an efficient approximation to SI, with machine-learning based regression and classification approaches. Results indicate that it is possible to estimate the RUMSI accurately, and that in particular, recurrent neural networks are highly suitable for the task, as they capture the network dynamics more precisely.
• Uplink vs. Downlink: Machine Learning-Based Quality Prediction for HTTP Adaptive Video Streaming. Loh, Frank; Poignée, Fabian; Wamser, Florian; Leidinger, Ferdinand; Hoßfeld, Tobias. In Sensors, 21(12), p. 4172. 2021.
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  Streaming video is responsible for the bulk of Internet traffic these days. For this reason, Internet providers and network operators try to make predictions and assessments about the streaming quality for an end user. Current monitoring solutions are based on a variety of different machine learning approaches. The challenge for providers and operators nowadays is that existing approaches require large amounts of data. In this work, the most relevant quality of experience metrics, i.e., the initial playback delay, the video streaming quality, video quality changes, and video rebuffering events, are examined using a voluminous data set of more than 13,000 YouTube video streaming runs that were collected with the native YouTube mobile app. Three Machine Learning models are developed and compared to estimate playback behavior based on uplink request information. The main focus has been on developing a lightweight approach using as few features and as little data as possible, while maintaining state-of-the-art performance.

  @article{info3-article-2021-3, abstract = {Streaming video is responsible for the bulk of Internet traffic these days. For this reason, Internet providers and network operators try to make predictions and assessments about the streaming quality for an end user. Current monitoring solutions are based on a variety of different machine learning approaches. The challenge for providers and operators nowadays is that existing approaches require large amounts of data. In this work, the most relevant quality of experience metrics, i.e., the initial playback delay, the video streaming quality, video quality changes, and video rebuffering events, are examined using a voluminous data set of more than 13,000 YouTube video streaming runs that were collected with the native YouTube mobile app. Three Machine Learning models are developed and compared to estimate playback behavior based on uplink request information. The main focus has been on developing a lightweight approach using as few features and as little data as possible, while maintaining state-of-the-art performance.}, author = {Loh, Frank and Poignée, Fabian and Wamser, Florian and Leidinger, Ferdinand and Hoßfeld, Tobias}, journal = {Sensors}, keywords = {can}, number = 12, pages = 4172, title = {Uplink vs. Downlink: Machine Learning-Based Quality Prediction for HTTP Adaptive Video Streaming}, volume = 21, year = 2021 }

  %0 Journal Article %1 info3-article-2021-3 %A Loh, Frank %A Poignée, Fabian %A Wamser, Florian %A Leidinger, Ferdinand %A Hoßfeld, Tobias %D 2021 %J Sensors %N 12 %P 4172 %T Uplink vs. Downlink: Machine Learning-Based Quality Prediction for HTTP Adaptive Video Streaming %V 21 %X Streaming video is responsible for the bulk of Internet traffic these days. For this reason, Internet providers and network operators try to make predictions and assessments about the streaming quality for an end user. Current monitoring solutions are based on a variety of different machine learning approaches. The challenge for providers and operators nowadays is that existing approaches require large amounts of data. In this work, the most relevant quality of experience metrics, i.e., the initial playback delay, the video streaming quality, video quality changes, and video rebuffering events, are examined using a voluminous data set of more than 13,000 YouTube video streaming runs that were collected with the native YouTube mobile app. Three Machine Learning models are developed and compared to estimate playback behavior based on uplink request information. The main focus has been on developing a lightweight approach using as few features and as little data as possible, while maintaining state-of-the-art performance.

• Subjective perception of craniofacial growth asymmetries in patients with deformational plagiocephaly. Kunz, Felix; Hirth, Matthias; Schweitzer, Tilmann; Linz, Christian; Goetz, Berhard; Stellzig-Eisenhauer, Angelika; Borchert, Kathrin; Böhm, Hartmut. In Springer Clinical Oral Investigations, 24, pp. https://doi.org/10.1007/s00784–020. 2020.
  • [ BibTeX ]
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  @article{info3-article-2020-3, author = {Kunz, Felix and Hirth, Matthias and Schweitzer, Tilmann and Linz, Christian and Goetz, Berhard and Stellzig-Eisenhauer, Angelika and Borchert, Kathrin and Böhm, Hartmut}, journal = {Springer Clinical Oral Investigations}, keywords = {sys:hidden:article}, month = {07}, pages = {https://doi.org/10.1007/s00784-020-03417-y}, title = {Subjective perception of craniofacial growth asymmetries in patients with deformational plagiocephaly}, volume = 24, year = 2020 }

  %0 Journal Article %1 info3-article-2020-3 %A Kunz, Felix %A Hirth, Matthias %A Schweitzer, Tilmann %A Linz, Christian %A Goetz, Berhard %A Stellzig-Eisenhauer, Angelika %A Borchert, Kathrin %A Böhm, Hartmut %D 2020 %J Springer Clinical Oral Investigations %P https://doi.org/10.1007/s00784-020-03417-y %T Subjective perception of craniofacial growth asymmetries in patients with deformational plagiocephaly %V 24
• IJNM Special Issue - Editorial - QoE-centric Analysis and Management of Communication Networks. Wamser, Florian; Alay, Özgü; Metzger, Florian; Valentin, Stefan. In International Journal of Network Management, Special Issue: QoE-centric Analysis and Management of Communication Networks. 2020.
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  The heterogeneity and variability of Internet applications has increased considerably in recent years. Applications such as video streaming are responsible for a large part of data traffic on the Internet. Internet telephony and video conferencing systems have become part of our daily lives. At the same time, the Internet of Things is striving to exceed previous expectations regarding the number of devices. Furthermore, the proliferation of video games, virtual reality applications, and 360° video applications is increasing. All this leads to specific but different requirements from applications to frameworks, service platforms, and networks. For each service, users desire special service criteria, such as smooth interactivity, fast downloads, high availability, or extensive content. Such requirements can usually be summarized under the term Quality of Experience, i.e., the overall satisfaction of a user with the system cur- rently in use. In the age of big data and dynamic networks, Quality of Experience is still looking for its place, and good solutions are in high demand. This Special Issue addresses the latest advances and challenges in analysis, design, modeling, measurement, and performance evaluation of Quality of Experience and Quality of Experience-oriented metrics and management.

  @article{info3-article-2020-1, abstract = {The heterogeneity and variability of Internet applications has increased considerably in recent years. Applications such as video streaming are responsible for a large part of data traffic on the Internet. Internet telephony and video conferencing systems have become part of our daily lives. At the same time, the Internet of Things is striving to exceed previous expectations regarding the number of devices. Furthermore, the proliferation of video games, virtual reality applications, and 360° video applications is increasing. All this leads to specific but different requirements from applications to frameworks, service platforms, and networks. For each service, users desire special service criteria, such as smooth interactivity, fast downloads, high availability, or extensive content. Such requirements can usually be summarized under the term Quality of Experience, i.e., the overall satisfaction of a user with the system cur- rently in use. In the age of big data and dynamic networks, Quality of Experience is still looking for its place, and good solutions are in high demand. This Special Issue addresses the latest advances and challenges in analysis, design, modeling, measurement, and performance evaluation of Quality of Experience and Quality of Experience-oriented metrics and management.}, author = {Wamser, Florian and Alay, Özgü and Metzger, Florian and Valentin, Stefan}, journal = {International Journal of Network Management}, keywords = {can}, month = {03}, title = {IJNM Special Issue - Editorial - QoE-centric Analysis and Management of Communication Networks}, volume = {Special Issue: QoE-centric Analysis and Management of Communication Networks}, year = 2020 }

  %0 Journal Article %1 info3-article-2020-1 %A Wamser, Florian %A Alay, Özgü %A Metzger, Florian %A Valentin, Stefan %D 2020 %J International Journal of Network Management %T IJNM Special Issue - Editorial - QoE-centric Analysis and Management of Communication Networks %V Special Issue: QoE-centric Analysis and Management of Communication Networks %X The heterogeneity and variability of Internet applications has increased considerably in recent years. Applications such as video streaming are responsible for a large part of data traffic on the Internet. Internet telephony and video conferencing systems have become part of our daily lives. At the same time, the Internet of Things is striving to exceed previous expectations regarding the number of devices. Furthermore, the proliferation of video games, virtual reality applications, and 360° video applications is increasing. All this leads to specific but different requirements from applications to frameworks, service platforms, and networks. For each service, users desire special service criteria, such as smooth interactivity, fast downloads, high availability, or extensive content. Such requirements can usually be summarized under the term Quality of Experience, i.e., the overall satisfaction of a user with the system cur- rently in use. In the age of big data and dynamic networks, Quality of Experience is still looking for its place, and good solutions are in high demand. This Special Issue addresses the latest advances and challenges in analysis, design, modeling, measurement, and performance evaluation of Quality of Experience and Quality of Experience-oriented metrics and management.
• ViCrypt to the Rescue: Real-time, Machine-Learning-driven Video-QoE Monitoring for Encrypted Streaming Traffic. Wassermann, Sarah; Seufert, Michael; Casas, Pedro; Li, Gang; Kuang, Li. In IEEE Transactions on Network and Service Management, 17(4), pp. 2007–2023. 2020.
  • [ Abstract ]
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  Video streaming is the killer application of the Internet today. In this paper, we address the problem of real-time, passive Quality-of-Experience (QoE) monitoring of HTTP Adaptive Video Streaming (HAS), from the Internet-Service-Provider (ISP) perspective - i.e., relying exclusively on in-network traffic measurements. Given the wide adoption of end-to-end encryption, we resort to machine-learning (ML) models to estimate multiple key video-QoE indicators (KQIs) from the analysis of the encrypted traffic. We present ViCrypt, an ML-driven monitoring solution able to infer the most important KQIs for HTTP Adaptive Streaming (HAS), namely stalling, initial delay, video resolution, and average video bitrate. ViCrypt performs estimations in real-time, during the playback of an ongoing video-streaming session, with a fine-grained temporal resolution of just one second. For this, it relies on lightweight, stream-like features continuously extracted from the encrypted stream of packets. Empirical evaluations on a large and heterogeneous corpus of YouTube measurements show that ViCrypt can infer the targeted KQIs with high accuracy, enabling large-scale passive video-QoE monitoring and proactive QoE-aware traffic management. Different from the state of the art, and besides real-time operation, ViCrypt is not bound to coarse-grained KQI-classes, providing better and sharper insights than other solutions. Finally, ViCrypt does not require chunk-detection approaches for feature extraction, significantly reducing the complexity of the monitoring approach, and potentially improving on generalization to different HAS protocols used by other video-streaming services such as Netflix and Amazon.

  @article{info3-article-2020-5, abstract = {Video streaming is the killer application of the Internet today. In this paper, we address the problem of real-time, passive Quality-of-Experience (QoE) monitoring of HTTP Adaptive Video Streaming (HAS), from the Internet-Service-Provider (ISP) perspective - i.e., relying exclusively on in-network traffic measurements. Given the wide adoption of end-to-end encryption, we resort to machine-learning (ML) models to estimate multiple key video-QoE indicators (KQIs) from the analysis of the encrypted traffic. We present ViCrypt, an ML-driven monitoring solution able to infer the most important KQIs for HTTP Adaptive Streaming (HAS), namely stalling, initial delay, video resolution, and average video bitrate. ViCrypt performs estimations in real-time, during the playback of an ongoing video-streaming session, with a fine-grained temporal resolution of just one second. For this, it relies on lightweight, stream-like features continuously extracted from the encrypted stream of packets. Empirical evaluations on a large and heterogeneous corpus of YouTube measurements show that ViCrypt can infer the targeted KQIs with high accuracy, enabling large-scale passive video-QoE monitoring and proactive QoE-aware traffic management. Different from the state of the art, and besides real-time operation, ViCrypt is not bound to coarse-grained KQI-classes, providing better and sharper insights than other solutions. Finally, ViCrypt does not require chunk-detection approaches for feature extraction, significantly reducing the complexity of the monitoring approach, and potentially improving on generalization to different HAS protocols used by other video-streaming services such as Netflix and Amazon.}, author = {Wassermann, Sarah and Seufert, Michael and Casas, Pedro and Li, Gang and Kuang, Li}, journal = {IEEE Transactions on Network and Service Management}, keywords = {ucn}, month = 12, number = 4, pages = {2007 - 2023}, title = {ViCrypt to the Rescue: Real-time, Machine-Learning-driven Video-QoE Monitoring for Encrypted Streaming Traffic}, volume = 17, year = 2020 }

  %0 Journal Article %1 info3-article-2020-5 %A Wassermann, Sarah %A Seufert, Michael %A Casas, Pedro %A Li, Gang %A Kuang, Li %D 2020 %J IEEE Transactions on Network and Service Management %N 4 %P 2007 - 2023 %T ViCrypt to the Rescue: Real-time, Machine-Learning-driven Video-QoE Monitoring for Encrypted Streaming Traffic %V 17 %X Video streaming is the killer application of the Internet today. In this paper, we address the problem of real-time, passive Quality-of-Experience (QoE) monitoring of HTTP Adaptive Video Streaming (HAS), from the Internet-Service-Provider (ISP) perspective - i.e., relying exclusively on in-network traffic measurements. Given the wide adoption of end-to-end encryption, we resort to machine-learning (ML) models to estimate multiple key video-QoE indicators (KQIs) from the analysis of the encrypted traffic. We present ViCrypt, an ML-driven monitoring solution able to infer the most important KQIs for HTTP Adaptive Streaming (HAS), namely stalling, initial delay, video resolution, and average video bitrate. ViCrypt performs estimations in real-time, during the playback of an ongoing video-streaming session, with a fine-grained temporal resolution of just one second. For this, it relies on lightweight, stream-like features continuously extracted from the encrypted stream of packets. Empirical evaluations on a large and heterogeneous corpus of YouTube measurements show that ViCrypt can infer the targeted KQIs with high accuracy, enabling large-scale passive video-QoE monitoring and proactive QoE-aware traffic management. Different from the state of the art, and besides real-time operation, ViCrypt is not bound to coarse-grained KQI-classes, providing better and sharper insights than other solutions. Finally, ViCrypt does not require chunk-detection approaches for feature extraction, significantly reducing the complexity of the monitoring approach, and potentially improving on generalization to different HAS protocols used by other video-streaming services such as Netflix and Amazon.
• Deriving QoE in systems: from fundamental relationships to a QoE‑based Service‑level Quality Index. Hoßfeld, Tobias; Heegaard, Poul E.; Skorin-Kapov, Lea; Varela, Martin. In Springer Quality and User Experience, 5(7), p. https://rdcu.be/b483m. 2020.
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  With Quality of Experience (QoE) research having made significant advances over the years, service and network providers aim at user-centric evaluation of the services provided in their system. The question arises how to derive QoE in systems. In the context of subjective user studies conducted to derive relationships between influence factors and QoE, user diversity leads to varying distributions of user rating scores for different test conditions. Such models are commonly exploited by providers to derive various QoE metrics in their system, such as expected QoE, or the percentage of users rating above a certain threshold. The question then becomes how to combine (a) user rating distributions obtained from subjective studies, and (b) system parameter distributions, so as to obtain the actual observed QoE distribution in the system? Moreover, how can various QoE metrics of interest in the system be derived? We prove fundamental relationships for the derivation of QoE in systems, thus providing an important link between the QoE community and the systems community. In our numerical examples, we focus mainly on QoE metrics. We furthermore provide a more generalized view on quantifying the quality of systems by defining a QoE-based Service-level Quality Index. This index exploits the fact that quality can be seen as a proxy measure for utility. Following the assumption that not all user sessions should be weighted equally, we aim to provide a generic framework that can be utilized to quantify the overall utility of a service delivered by a system.

  @article{info3-article-2020-2, abstract = {With Quality of Experience (QoE) research having made significant advances over the years, service and network providers aim at user-centric evaluation of the services provided in their system. The question arises how to derive QoE in systems. In the context of subjective user studies conducted to derive relationships between influence factors and QoE, user diversity leads to varying distributions of user rating scores for different test conditions. Such models are commonly exploited by providers to derive various QoE metrics in their system, such as expected QoE, or the percentage of users rating above a certain threshold. The question then becomes how to combine (a) user rating distributions obtained from subjective studies, and (b) system parameter distributions, so as to obtain the actual observed QoE distribution in the system? Moreover, how can various QoE metrics of interest in the system be derived? We prove fundamental relationships for the derivation of QoE in systems, thus providing an important link between the QoE community and the systems community. In our numerical examples, we focus mainly on QoE metrics. We furthermore provide a more generalized view on quantifying the quality of systems by defining a QoE-based Service-level Quality Index. This index exploits the fact that quality can be seen as a proxy measure for utility. Following the assumption that not all user sessions should be weighted equally, we aim to provide a generic framework that can be utilized to quantify the overall utility of a service delivered by a system.}, author = {Hoßfeld, Tobias and Heegaard, Poul E. and Skorin-Kapov, Lea and Varela, Martin}, journal = {Springer Quality and User Experience}, keywords = {sys:hidden:article}, month = {07}, number = 7, pages = {https://rdcu.be/b483m}, title = {Deriving QoE in systems: from fundamental relationships to a QoE‑based Service‑level Quality Index}, volume = 5, year = 2020 }

  %0 Journal Article %1 info3-article-2020-2 %A Hoßfeld, Tobias %A Heegaard, Poul E. %A Skorin-Kapov, Lea %A Varela, Martin %D 2020 %J Springer Quality and User Experience %N 7 %P https://rdcu.be/b483m %T Deriving QoE in systems: from fundamental relationships to a QoE‑based Service‑level Quality Index %V 5 %X With Quality of Experience (QoE) research having made significant advances over the years, service and network providers aim at user-centric evaluation of the services provided in their system. The question arises how to derive QoE in systems. In the context of subjective user studies conducted to derive relationships between influence factors and QoE, user diversity leads to varying distributions of user rating scores for different test conditions. Such models are commonly exploited by providers to derive various QoE metrics in their system, such as expected QoE, or the percentage of users rating above a certain threshold. The question then becomes how to combine (a) user rating distributions obtained from subjective studies, and (b) system parameter distributions, so as to obtain the actual observed QoE distribution in the system? Moreover, how can various QoE metrics of interest in the system be derived? We prove fundamental relationships for the derivation of QoE in systems, thus providing an important link between the QoE community and the systems community. In our numerical examples, we focus mainly on QoE metrics. We furthermore provide a more generalized view on quantifying the quality of systems by defining a QoE-based Service-level Quality Index. This index exploits the fact that quality can be seen as a proxy measure for utility. Following the assumption that not all user sessions should be weighted equally, we aim to provide a generic framework that can be utilized to quantify the overall utility of a service delivered by a system.
• Statistical Methods and Models based on Quality of Experience Distributions. Seufert, Michael. In Quality and User Experience, 6(1). 2020.
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  Due to biased assumptions on the underlying ordinal rating scale in subjective Quality of Experience (QoE) studies, Mean Opinion Score (MOS)-based evaluations provide results, which are hard to interpret and can be misleading. This paper proposes to consider the full QoE distribution for evaluating, reporting, and modeling QoE results instead of relying on MOS-based metrics derived from results based on ordinal rating scales. The QoE distribution can be represented in a concise way by using the parameters of a multinomial distribution without losing any information about the underlying QoE ratings, and even keeps backward compatibility with previous, biased MOS-based results. Considering QoE results as a realization of a multinomial distribution allows to rely on a well-established theoretical background, which enables meaningful evaluations also for ordinal rating scales. Moreover, QoE models based on QoE distributions keep detailed information from the results of a QoE study of a technical system, and thus, give an unprecedented richness of insights into the end users’ experience with the technical system. In this work, existing and novel statistical methods for QoE distributions are summarized and exemplary evaluations are outlined. Furthermore, using the novel concept of quality steps, simulative and analytical QoE models based on QoE distributions are presented and showcased. The goal is to demonstrate the fundamental advantages of considering QoE distributions over MOS-based evaluations if the underlying rating data is ordinal in nature.

  @article{info3-article-2020-7, abstract = {Due to biased assumptions on the underlying ordinal rating scale in subjective Quality of Experience (QoE) studies, Mean Opinion Score (MOS)-based evaluations provide results, which are hard to interpret and can be misleading. This paper proposes to consider the full QoE distribution for evaluating, reporting, and modeling QoE results instead of relying on MOS-based metrics derived from results based on ordinal rating scales. The QoE distribution can be represented in a concise way by using the parameters of a multinomial distribution without losing any information about the underlying QoE ratings, and even keeps backward compatibility with previous, biased MOS-based results. Considering QoE results as a realization of a multinomial distribution allows to rely on a well-established theoretical background, which enables meaningful evaluations also for ordinal rating scales. Moreover, QoE models based on QoE distributions keep detailed information from the results of a QoE study of a technical system, and thus, give an unprecedented richness of insights into the end users’ experience with the technical system. In this work, existing and novel statistical methods for QoE distributions are summarized and exemplary evaluations are outlined. Furthermore, using the novel concept of quality steps, simulative and analytical QoE models based on QoE distributions are presented and showcased. The goal is to demonstrate the fundamental advantages of considering QoE distributions over MOS-based evaluations if the underlying rating data is ordinal in nature.}, author = {Seufert, Michael}, journal = {Quality and User Experience}, keywords = {ucn}, month = 12, number = 1, title = {Statistical Methods and Models based on Quality of Experience Distributions}, volume = 6, year = 2020 }

  %0 Journal Article %1 info3-article-2020-7 %A Seufert, Michael %D 2020 %J Quality and User Experience %N 1 %T Statistical Methods and Models based on Quality of Experience Distributions %V 6 %X Due to biased assumptions on the underlying ordinal rating scale in subjective Quality of Experience (QoE) studies, Mean Opinion Score (MOS)-based evaluations provide results, which are hard to interpret and can be misleading. This paper proposes to consider the full QoE distribution for evaluating, reporting, and modeling QoE results instead of relying on MOS-based metrics derived from results based on ordinal rating scales. The QoE distribution can be represented in a concise way by using the parameters of a multinomial distribution without losing any information about the underlying QoE ratings, and even keeps backward compatibility with previous, biased MOS-based results. Considering QoE results as a realization of a multinomial distribution allows to rely on a well-established theoretical background, which enables meaningful evaluations also for ordinal rating scales. Moreover, QoE models based on QoE distributions keep detailed information from the results of a QoE study of a technical system, and thus, give an unprecedented richness of insights into the end users’ experience with the technical system. In this work, existing and novel statistical methods for QoE distributions are summarized and exemplary evaluations are outlined. Furthermore, using the novel concept of quality steps, simulative and analytical QoE models based on QoE distributions are presented and showcased. The goal is to demonstrate the fundamental advantages of considering QoE distributions over MOS-based evaluations if the underlying rating data is ordinal in nature.
• In vitro vs in vivo: does the study’s interface design influence crowdsourced video QoE?. Borchert, Kathrin; Seufert, Anika; Gamboa, Edwin; Hirth, Matthias; Hoßfeld, Tobias. In Quality and User Experience. 2020.
  • [ Abstract ]
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  Evaluating the Quality of Experience (QoE) of video streaming and its influence factors has become paramount for streaming providers, as they want to maintain high satisfaction for their customers. In this context, crowdsourced user studies became a valuable tool to evaluate different factors which can affect the perceived user experience on a large scale. In general, most of these crowdsourcing studies either use, what we refer to, as an in vivo or an in vitro interface design. In vivo design means that the study participant has to rate the QoE of a video that is embedded in an application similar to a real streaming service, e.g., YouTube or Netflix. In vitro design refers to a setting, in which the video stream is separated from a specific service and thus, the video plays on a plain background. Although these interface designs vary widely, the results are often compared and generalized. In this work, we use a crowdsourcing study to investigate the influence of three interface design alternatives, an in vitro and two in vivo designs with different levels of interactiveness, on the perceived video QoE. Contrary to our expectations, the results indicate that there is no significant influence of the study’s interface design in general on the video experience. Furthermore, we found that the in vivo design does not reduce the test takers’ attentiveness. However, we observed that participants who interacted with the test interface reported a higher video QoE than other groups.

  @article{info3-article-2020-6, abstract = {Evaluating the Quality of Experience (QoE) of video streaming and its influence factors has become paramount for streaming providers, as they want to maintain high satisfaction for their customers. In this context, crowdsourced user studies became a valuable tool to evaluate different factors which can affect the perceived user experience on a large scale. In general, most of these crowdsourcing studies either use, what we refer to, as an in vivo or an in vitro interface design. In vivo design means that the study participant has to rate the QoE of a video that is embedded in an application similar to a real streaming service, e.g., YouTube or Netflix. In vitro design refers to a setting, in which the video stream is separated from a specific service and thus, the video plays on a plain background. Although these interface designs vary widely, the results are often compared and generalized. In this work, we use a crowdsourcing study to investigate the influence of three interface design alternatives, an in vitro and two in vivo designs with different levels of interactiveness, on the perceived video QoE. Contrary to our expectations, the results indicate that there is no significant influence of the study’s interface design in general on the video experience. Furthermore, we found that the in vivo design does not reduce the test takers’ attentiveness. However, we observed that participants who interacted with the test interface reported a higher video QoE than other groups.}, author = {Borchert, Kathrin and Seufert, Anika and Gamboa, Edwin and Hirth, Matthias and Hoßfeld, Tobias}, journal = {Quality and User Experience}, keywords = {ua-net}, month = 11, title = {In vitro vs in vivo: does the study’s interface design influence crowdsourced video QoE?}, year = 2020 }

  %0 Journal Article %1 info3-article-2020-6 %A Borchert, Kathrin %A Seufert, Anika %A Gamboa, Edwin %A Hirth, Matthias %A Hoßfeld, Tobias %D 2020 %J Quality and User Experience %T In vitro vs in vivo: does the study’s interface design influence crowdsourced video QoE? %X Evaluating the Quality of Experience (QoE) of video streaming and its influence factors has become paramount for streaming providers, as they want to maintain high satisfaction for their customers. In this context, crowdsourced user studies became a valuable tool to evaluate different factors which can affect the perceived user experience on a large scale. In general, most of these crowdsourcing studies either use, what we refer to, as an in vivo or an in vitro interface design. In vivo design means that the study participant has to rate the QoE of a video that is embedded in an application similar to a real streaming service, e.g., YouTube or Netflix. In vitro design refers to a setting, in which the video stream is separated from a specific service and thus, the video plays on a plain background. Although these interface designs vary widely, the results are often compared and generalized. In this work, we use a crowdsourcing study to investigate the influence of three interface design alternatives, an in vitro and two in vivo designs with different levels of interactiveness, on the perceived video QoE. Contrary to our expectations, the results indicate that there is no significant influence of the study’s interface design in general on the video experience. Furthermore, we found that the in vivo design does not reduce the test takers’ attentiveness. However, we observed that participants who interacted with the test interface reported a higher video QoE than other groups.

• The Power of Composition: Abstracting a Multi-Device SDN Data Path Through a Single API. Geissler, Stefan; Herrnleben, Stefan; Bauer, Robert; Grigorjew, Alexej; Jarschel, Michael; Zinner, Thomas. In IEEE Transactions on Network and Service Management. 2019.
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  @article{info3-article-2019-11, author = {Geissler, Stefan and Herrnleben, Stefan and Bauer, Robert and Grigorjew, Alexej and Jarschel, Michael and Zinner, Thomas}, journal = {IEEE Transactions on Network and Service Management}, keywords = {sys:hidden:article}, month = 11, title = {The Power of Composition: Abstracting a Multi-Device SDN Data Path Through a Single API}, year = 2019 }

  %0 Journal Article %1 info3-article-2019-11 %A Geissler, Stefan %A Herrnleben, Stefan %A Bauer, Robert %A Grigorjew, Alexej %A Jarschel, Michael %A Zinner, Thomas %D 2019 %J IEEE Transactions on Network and Service Management %T The Power of Composition: Abstracting a Multi-Device SDN Data Path Through a Single API
• Considering User Behavior in the Quality of Experience Cycle: Towards Proactive QoE-aware Traffic Management. Seufert, Michael; Wassermann, Sarah; Casas, Pedro. In IEEE Communications Letters, 23(7), pp. 1145–1148. 2019.
  • [ Abstract ]
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  The concept of Quality of Experience (QoE) of Internet services is widely recognized by service providers and network operators. They strive to deliver the best experience to their customers in order to increase revenues and avoid churn. Therefore, QoE is increasingly considered as an integral part of the reactive traffic management cycle of network operators. Additionally, QoE also constitutes a cycle of its own, which includes the user behavior and the service requirements. This work describes this QoE cycle, which is not widely taken into account yet, discusses the interactions of the two cycles, and derives implications towards an improved and proactive QoE-aware traffic management. A showcase on how network operators can obtain hints on the change of network requirements from detecting user behavior in encrypted video traffic is also presented in this paper.

  @article{info3-article-2019-5, abstract = {The concept of Quality of Experience (QoE) of Internet services is widely recognized by service providers and network operators. They strive to deliver the best experience to their customers in order to increase revenues and avoid churn. Therefore, QoE is increasingly considered as an integral part of the reactive traffic management cycle of network operators. Additionally, QoE also constitutes a cycle of its own, which includes the user behavior and the service requirements. This work describes this QoE cycle, which is not widely taken into account yet, discusses the interactions of the two cycles, and derives implications towards an improved and proactive QoE-aware traffic management. A showcase on how network operators can obtain hints on the change of network requirements from detecting user behavior in encrypted video traffic is also presented in this paper.}, author = {Seufert, Michael and Wassermann, Sarah and Casas, Pedro}, journal = {IEEE Communications Letters}, keywords = {ua-net}, month = {07}, number = 7, pages = {1145-1148}, title = {Considering User Behavior in the Quality of Experience Cycle: Towards Proactive QoE-aware Traffic Management}, volume = 23, year = 2019 }

  %0 Journal Article %1 info3-article-2019-5 %A Seufert, Michael %A Wassermann, Sarah %A Casas, Pedro %D 2019 %J IEEE Communications Letters %N 7 %P 1145-1148 %T Considering User Behavior in the Quality of Experience Cycle: Towards Proactive QoE-aware Traffic Management %V 23 %X The concept of Quality of Experience (QoE) of Internet services is widely recognized by service providers and network operators. They strive to deliver the best experience to their customers in order to increase revenues and avoid churn. Therefore, QoE is increasingly considered as an integral part of the reactive traffic management cycle of network operators. Additionally, QoE also constitutes a cycle of its own, which includes the user behavior and the service requirements. This work describes this QoE cycle, which is not widely taken into account yet, discusses the interactions of the two cycles, and derives implications towards an improved and proactive QoE-aware traffic management. A showcase on how network operators can obtain hints on the change of network requirements from detecting user behavior in encrypted video traffic is also presented in this paper.
• Using Attention Testing to Select Crowdsourced Workers and Research Participants. Göritz, Anja; Borchert, Kathrin; Hirth, Matthias. In Social Science Computer Review. 2019.
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  @article{info3-article-2019-7, author = {Göritz, Anja and Borchert, Kathrin and Hirth, Matthias}, journal = {Social Science Computer Review}, keywords = {sys:hidden:article}, month = {06}, title = {Using Attention Testing to Select Crowdsourced Workers and Research Participants}, year = 2019 }

  %0 Journal Article %1 info3-article-2019-7 %A Göritz, Anja %A Borchert, Kathrin %A Hirth, Matthias %D 2019 %J Social Science Computer Review %T Using Attention Testing to Select Crowdsourced Workers and Research Participants
• A Fair Share for All: TCP-inspired Adaptation Logic for QoE Fairness among Heterogeneous HTTP Adaptive Video Streaming Clients. Seufert, Michael; Wehner, Nikolas; Casas, Pedro. In IEEE Transactions on Network and Service Management, 16(2), pp. 475–488. 2019.
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  @article{info3-article-2019-4, author = {Seufert, Michael and Wehner, Nikolas and Casas, Pedro}, journal = {IEEE Transactions on Network and Service Management}, keywords = {sys:hidden:article}, month = {06}, number = 2, pages = {475-488}, title = {A Fair Share for All: TCP-inspired Adaptation Logic for QoE Fairness among Heterogeneous HTTP Adaptive Video Streaming Clients}, volume = 16, year = 2019 }

  %0 Journal Article %1 info3-article-2019-4 %A Seufert, Michael %A Wehner, Nikolas %A Casas, Pedro %D 2019 %J IEEE Transactions on Network and Service Management %N 2 %P 475-488 %T A Fair Share for All: TCP-inspired Adaptation Logic for QoE Fairness among Heterogeneous HTTP Adaptive Video Streaming Clients %V 16
• Modeling of Aggregated IoT Traffic and Its Application to an IoT Cloud. Metzger, Florian; Hoßfeld, Tobias; Bauer, André; Kounev, Samuel; Heegaard, Poul E. In Proceedings of the IEEE, 107(4), pp. 679–694. 2019.
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  As the Internet of Things (IoT) continues to gain traction in telecommunication networks, a very large number of devices are expected to be connected and used in the near future. In order to appropriately plan and dimension the network, as well as the back-end cloud systems and the resulting signaling load, traffic models are employed. These models are designed to accurately capture and predict the properties of IoT traffic in a concise manner. To achieve this, Poisson process approximations, based on the Palm–Khintchine theorem, have often been used in the past. Due to the scale (and the difference in scales in various IoT networks) of the modeled systems, the fidelity of this approximation is crucial, as, in practice, it is very challenging to accurately measure or simulate large-scale IoT deployments. The main goal of this paper is to understand the level of accuracy of the Poisson approximation model. To this end, we first survey both common IoT network properties and network scales as well as traffic types. Second, we explain and discuss the Palm–Khintiche theorem, how it is applied to the problem, and which inaccuracies can occur when using it. Based on this, we derive guidelines as to when a Poisson process can be assumed for aggregated periodic IoT traffic. Finally, we evaluate our approach in the context of an IoT cloud scaler use case.

  @article{info3-article-2019-3, abstract = {As the Internet of Things (IoT) continues to gain traction in telecommunication networks, a very large number of devices are expected to be connected and used in the near future. In order to appropriately plan and dimension the network, as well as the back-end cloud systems and the resulting signaling load, traffic models are employed. These models are designed to accurately capture and predict the properties of IoT traffic in a concise manner. To achieve this, Poisson process approximations, based on the Palm–Khintchine theorem, have often been used in the past. Due to the scale (and the difference in scales in various IoT networks) of the modeled systems, the fidelity of this approximation is crucial, as, in practice, it is very challenging to accurately measure or simulate large-scale IoT deployments. The main goal of this paper is to understand the level of accuracy of the Poisson approximation model. To this end, we first survey both common IoT network properties and network scales as well as traffic types. Second, we explain and discuss the Palm–Khintiche theorem, how it is applied to the problem, and which inaccuracies can occur when using it. Based on this, we derive guidelines as to when a Poisson process can be assumed for aggregated periodic IoT traffic. Finally, we evaluate our approach in the context of an IoT cloud scaler use case.}, author = {Metzger, Florian and Hoßfeld, Tobias and Bauer, André and Kounev, Samuel and Heegaard, Poul E.}, journal = {Proceedings of the IEEE}, keywords = {doi:10.1109/JPROC.2019.2901578}, month = {04}, number = 4, pages = {679-694}, title = {Modeling of Aggregated IoT Traffic and Its Application to an IoT Cloud}, volume = 107, year = 2019 }

  %0 Journal Article %1 info3-article-2019-3 %A Metzger, Florian %A Hoßfeld, Tobias %A Bauer, André %A Kounev, Samuel %A Heegaard, Poul E. %D 2019 %J Proceedings of the IEEE %N 4 %P 679-694 %T Modeling of Aggregated IoT Traffic and Its Application to an IoT Cloud %V 107 %X As the Internet of Things (IoT) continues to gain traction in telecommunication networks, a very large number of devices are expected to be connected and used in the near future. In order to appropriately plan and dimension the network, as well as the back-end cloud systems and the resulting signaling load, traffic models are employed. These models are designed to accurately capture and predict the properties of IoT traffic in a concise manner. To achieve this, Poisson process approximations, based on the Palm–Khintchine theorem, have often been used in the past. Due to the scale (and the difference in scales in various IoT networks) of the modeled systems, the fidelity of this approximation is crucial, as, in practice, it is very challenging to accurately measure or simulate large-scale IoT deployments. The main goal of this paper is to understand the level of accuracy of the Poisson approximation model. To this end, we first survey both common IoT network properties and network scales as well as traffic types. Second, we explain and discuss the Palm–Khintiche theorem, how it is applied to the problem, and which inaccuracies can occur when using it. Based on this, we derive guidelines as to when a Poisson process can be assumed for aggregated periodic IoT traffic. Finally, we evaluate our approach in the context of an IoT cloud scaler use case.
• Machine Learning Models for YouTube QoE and User Engagement Prediction in Smartphones. Wassermann, Sarah; Wehner, Nikolas; Casas, Pedro. In ACM SIGMETRICS Performance Evaluation Review, 46(3), pp. 155–158. 2019.
  • [ Abstract ]
  • [ BibTeX ]
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  Measuring and monitoring YouTube Quality of Experience is a challenging task, especially when dealing with cellular networks and smartphone users. Using a large-scale database of crowdsourced YouTube-QoE measurements in smartphones, we conceive multiple machine-learning models to infer different YouTube-QoE-relevant metrics and userbehavior- related metrics from network-level measurements, without requiring root access to the smartphone, video-player embedding, or any other reverse-engineering-like approaches. The dataset includes measurements from more than 360 users worldwide, spanning over the last five years. Our preliminary results suggest that QoE-based monitoring of YouTube mobile can be realized through machine learning models with high accuracy, relying only on network-related features and without accessing any higher-layer metric to perform the estimations.

  @article{info3-article-2019-10, abstract = {Measuring and monitoring YouTube Quality of Experience is a challenging task, especially when dealing with cellular networks and smartphone users. Using a large-scale database of crowdsourced YouTube-QoE measurements in smartphones, we conceive multiple machine-learning models to infer different YouTube-QoE-relevant metrics and userbehavior- related metrics from network-level measurements, without requiring root access to the smartphone, video-player embedding, or any other reverse-engineering-like approaches. The dataset includes measurements from more than 360 users worldwide, spanning over the last five years. Our preliminary results suggest that QoE-based monitoring of YouTube mobile can be realized through machine learning models with high accuracy, relying only on network-related features and without accessing any higher-layer metric to perform the estimations.}, author = {Wassermann, Sarah and Wehner, Nikolas and Casas, Pedro}, journal = {ACM SIGMETRICS Performance Evaluation Review}, keywords = {sys:hidden:article}, month = {01}, number = 3, pages = {155-158}, title = {Machine Learning Models for YouTube QoE and User Engagement Prediction in Smartphones}, volume = 46, year = 2019 }

  %0 Journal Article %1 info3-article-2019-10 %A Wassermann, Sarah %A Wehner, Nikolas %A Casas, Pedro %D 2019 %J ACM SIGMETRICS Performance Evaluation Review %N 3 %P 155-158 %T Machine Learning Models for YouTube QoE and User Engagement Prediction in Smartphones %V 46 %X Measuring and monitoring YouTube Quality of Experience is a challenging task, especially when dealing with cellular networks and smartphone users. Using a large-scale database of crowdsourced YouTube-QoE measurements in smartphones, we conceive multiple machine-learning models to infer different YouTube-QoE-relevant metrics and userbehavior- related metrics from network-level measurements, without requiring root access to the smartphone, video-player embedding, or any other reverse-engineering-like approaches. The dataset includes measurements from more than 360 users worldwide, spanning over the last five years. Our preliminary results suggest that QoE-based monitoring of YouTube mobile can be realized through machine learning models with high accuracy, relying only on network-related features and without accessing any higher-layer metric to perform the estimations.
• Dissecting the performance of YouTube video streaming in mobile networks. Schwind, Anika; Midoglu, Cise; Alay, Özgü; Griwodz, Carsten; Wamser, Florian. In International Journal of Network Management. 2019.
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  Video streaming applications constitute a significant portion of the Internet traffic today, with mobile accounting for more than half of the online video views. The high share of video in the current Internet traffic mix has prompted many studies that examine video streaming through measurements. However, streaming performance depends on many different factors at different layers of the TCP/IP stack. For example, browser selection at the application layer or the choice of protocol in transport layer can have significant impact on the video performance. Furthermore, video performance heavily depends on the underlying network conditions (eg, network and link layers). For mobile networks, the conditions vary significantly, since each operator has a different deployment strategy and configuration. In this paper, we focus on YouTube and carry out a comprehensive study investigating the influence of different factors on streaming performance. Leveraging the Measuring Mobile Broadband Networks in Europe (MONROE) test bed that enables experimentation with 13 different network configurations in four countries, we collect more than 1800 measurement samples in operational mobile networks. With this campaign, our goal is to quantify the impact of parameters from different layers on YouTube's streaming quality of experience (QoE). More specifically, we analyze the role of the browser (eg, Firefox and Chrome), the impact of transport protocol (eg, TCP or QUIC), the influence of network bandwidth, and signal coverage on streaming QoE. Our analysis reveals that all these parameters need to be taken into account jointly for network management practices, in order to ensure a high end‐user experience.

  @article{info3-article-2019-2, abstract = {Video streaming applications constitute a significant portion of the Internet traffic today, with mobile accounting for more than half of the online video views. The high share of video in the current Internet traffic mix has prompted many studies that examine video streaming through measurements. However, streaming performance depends on many different factors at different layers of the TCP/IP stack. For example, browser selection at the application layer or the choice of protocol in transport layer can have significant impact on the video performance. Furthermore, video performance heavily depends on the underlying network conditions (eg, network and link layers). For mobile networks, the conditions vary significantly, since each operator has a different deployment strategy and configuration. In this paper, we focus on YouTube and carry out a comprehensive study investigating the influence of different factors on streaming performance. Leveraging the Measuring Mobile Broadband Networks in Europe (MONROE) test bed that enables experimentation with 13 different network configurations in four countries, we collect more than 1800 measurement samples in operational mobile networks. With this campaign, our goal is to quantify the impact of parameters from different layers on YouTube's streaming quality of experience (QoE). More specifically, we analyze the role of the browser (eg, Firefox and Chrome), the impact of transport protocol (eg, TCP or QUIC), the influence of network bandwidth, and signal coverage on streaming QoE. Our analysis reveals that all these parameters need to be taken into account jointly for network management practices, in order to ensure a high end‐user experience.}, author = {Schwind, Anika and Midoglu, Cise and Alay, Özgü and Griwodz, Carsten and Wamser, Florian}, journal = {International Journal of Network Management}, keywords = {can}, month = {01}, title = {Dissecting the performance of YouTube video streaming in mobile networks}, year = 2019 }

  %0 Journal Article %1 info3-article-2019-2 %A Schwind, Anika %A Midoglu, Cise %A Alay, Özgü %A Griwodz, Carsten %A Wamser, Florian %D 2019 %J International Journal of Network Management %T Dissecting the performance of YouTube video streaming in mobile networks %X Video streaming applications constitute a significant portion of the Internet traffic today, with mobile accounting for more than half of the online video views. The high share of video in the current Internet traffic mix has prompted many studies that examine video streaming through measurements. However, streaming performance depends on many different factors at different layers of the TCP/IP stack. For example, browser selection at the application layer or the choice of protocol in transport layer can have significant impact on the video performance. Furthermore, video performance heavily depends on the underlying network conditions (eg, network and link layers). For mobile networks, the conditions vary significantly, since each operator has a different deployment strategy and configuration. In this paper, we focus on YouTube and carry out a comprehensive study investigating the influence of different factors on streaming performance. Leveraging the Measuring Mobile Broadband Networks in Europe (MONROE) test bed that enables experimentation with 13 different network configurations in four countries, we collect more than 1800 measurement samples in operational mobile networks. With this campaign, our goal is to quantify the impact of parameters from different layers on YouTube's streaming quality of experience (QoE). More specifically, we analyze the role of the browser (eg, Firefox and Chrome), the impact of transport protocol (eg, TCP or QUIC), the influence of network bandwidth, and signal coverage on streaming QoE. Our analysis reveals that all these parameters need to be taken into account jointly for network management practices, in order to ensure a high end‐user experience.
• Survey of Performance Acceleration Techniques for Network Function Virtualization. Linguaglossa, Leonardo; Lange, Stanislav; Pontarelli, Salvatore; Retvari, Gabor; Rossi, Dario; Zinner, Thomas; Bificulo, Roberto; Jarschel, Michael; Bianchi, Giuseppe. In Proceedings of the IEEE. 2019.
  • [ Abstract ]
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  The ongoing network softwarization trend holds the promise to revolutionize network infrastructures by making them more flexible, reconfigurable, portable, and more adaptive than ever. Still, the migration from hard-coded/hardwired network functions towards their software-programmable counterparts comes along with the need for tailored optimizations and acceleration techniques, so as to avoid, or at least mitigate, the throughput/latency performance degradation with respect to fixed function network elements. The contribution of this article is twofold. First, we provide a comprehensive overview of the host-based Network Function Virtualization (NFV) ecosystem, covering a broad range of techniques, from low level hardware acceleration and bump-in-the-wire offloading approaches, to high-level software acceleration solutions, including the virtualization technique itself. Second, we derive guidelines regarding the design, development, and operation of NFV-based deployments that meet the flexibility and scalability requirements of modern communication networks.

  @article{info3-article-2019-1, abstract = {The ongoing network softwarization trend holds the promise to revolutionize network infrastructures by making them more flexible, reconfigurable, portable, and more adaptive than ever. Still, the migration from hard-coded/hardwired network functions towards their software-programmable counterparts comes along with the need for tailored optimizations and acceleration techniques, so as to avoid, or at least mitigate, the throughput/latency performance degradation with respect to fixed function network elements. The contribution of this article is twofold. First, we provide a comprehensive overview of the host-based Network Function Virtualization (NFV) ecosystem, covering a broad range of techniques, from low level hardware acceleration and bump-in-the-wire offloading approaches, to high-level software acceleration solutions, including the virtualization technique itself. Second, we derive guidelines regarding the design, development, and operation of NFV-based deployments that meet the flexibility and scalability requirements of modern communication networks.}, author = {Linguaglossa, Leonardo and Lange, Stanislav and Pontarelli, Salvatore and Retvari, Gabor and Rossi, Dario and Zinner, Thomas and Bificulo, Roberto and Jarschel, Michael and Bianchi, Giuseppe}, journal = {Proceedings of the IEEE}, keywords = {sys:hidden:article}, month = {01}, title = {Survey of Performance Acceleration Techniques for Network Function Virtualization}, year = 2019 }

  %0 Journal Article %1 info3-article-2019-1 %A Linguaglossa, Leonardo %A Lange, Stanislav %A Pontarelli, Salvatore %A Retvari, Gabor %A Rossi, Dario %A Zinner, Thomas %A Bificulo, Roberto %A Jarschel, Michael %A Bianchi, Giuseppe %D 2019 %J Proceedings of the IEEE %T Survey of Performance Acceleration Techniques for Network Function Virtualization %X The ongoing network softwarization trend holds the promise to revolutionize network infrastructures by making them more flexible, reconfigurable, portable, and more adaptive than ever. Still, the migration from hard-coded/hardwired network functions towards their software-programmable counterparts comes along with the need for tailored optimizations and acceleration techniques, so as to avoid, or at least mitigate, the throughput/latency performance degradation with respect to fixed function network elements. The contribution of this article is twofold. First, we provide a comprehensive overview of the host-based Network Function Virtualization (NFV) ecosystem, covering a broad range of techniques, from low level hardware acceleration and bump-in-the-wire offloading approaches, to high-level software acceleration solutions, including the virtualization technique itself. Second, we derive guidelines regarding the design, development, and operation of NFV-based deployments that meet the flexibility and scalability requirements of modern communication networks.

• Active Learning for Crowdsourced QoE Modeling. Chang, Haw-Shiuan; Hsu, Chih-Fan; Hoßfeld, Tobias; Chen, Kuan-Ta. In IEEE Transactions on Multimedia. 2018.
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  @article{info3-article-2018-11, author = {Chang, Haw-Shiuan and Hsu, Chih-Fan and Hoßfeld, Tobias and Chen, Kuan-Ta}, journal = {IEEE Transactions on Multimedia}, keywords = {sys:hidden:article}, title = {Active Learning for Crowdsourced QoE Modeling}, year = 2018 }

  %0 Journal Article %1 info3-article-2018-11 %A Chang, Haw-Shiuan %A Hsu, Chih-Fan %A Hoßfeld, Tobias %A Chen, Kuan-Ta %D 2018 %J IEEE Transactions on Multimedia %T Active Learning for Crowdsourced QoE Modeling
• Confidence Interval Estimators for MOS Values. Hoßfeld, Tobias; Heegaard, Poul E.; Varela, Martin; Skorin-Kapov, Lea. In arXiv preprint arXiv:1806.01126. 2018.
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  @article{info3-article-2018-10, author = {Hoßfeld, Tobias and Heegaard, Poul E. and Varela, Martin and Skorin-Kapov, Lea}, journal = {arXiv preprint arXiv:1806.01126}, keywords = {sys:hidden:article}, title = {Confidence Interval Estimators for MOS Values}, year = 2018 }

  %0 Journal Article %1 info3-article-2018-10 %A Hoßfeld, Tobias %A Heegaard, Poul E. %A Varela, Martin %A Skorin-Kapov, Lea %D 2018 %J arXiv preprint arXiv:1806.01126 %T Confidence Interval Estimators for MOS Values
• Quality of experience column: an introduction. Hoßfeld, Tobias; Timmerer, Christian. In ACM SIGMultimedia Records, (3), p. 10. 2018.
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  @article{info3-article-2018-9, author = {Hoßfeld, Tobias and Timmerer, Christian}, journal = {ACM SIGMultimedia Records}, keywords = {sys:hidden:article}, number = 3, pages = 10, title = {Quality of experience column: an introduction}, year = 2018 }

  %0 Journal Article %1 info3-article-2018-9 %A Hoßfeld, Tobias %A Timmerer, Christian %D 2018 %J ACM SIGMultimedia Records %N 3 %P 10 %T Quality of experience column: an introduction
• Towards Machine Learning-Based Optimal HAS. Sieber, Christian; Hagn, Korbinian; Moldovan, Christian; Hoßfeld, Tobias; Kellerer, Wolfgang. In arXiv preprint arXiv:1808.08065. 2018.
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  @article{info3-article-2018-8, author = {Sieber, Christian and Hagn, Korbinian and Moldovan, Christian and Hoßfeld, Tobias and Kellerer, Wolfgang}, journal = {arXiv preprint arXiv:1808.08065}, keywords = {sys:hidden:article}, title = {Towards Machine Learning-Based Optimal HAS}, year = 2018 }

  %0 Journal Article %1 info3-article-2018-8 %A Sieber, Christian %A Hagn, Korbinian %A Moldovan, Christian %A Hoßfeld, Tobias %A Kellerer, Wolfgang %D 2018 %J arXiv preprint arXiv:1808.08065 %T Towards Machine Learning-Based Optimal HAS
• Vertrauen ist gut, Blockchain ist besser - Einsatzmöglichkeiten von Blockchain für Vertrauensprobleme im Crowdsourcing. Schütz, Andreas; Fertig, Tobias; Weber, Kerstin; Vu, Henry; Hirth, Matthias; Tran-Gia, Thomas. In HMD Praxis der Wirtschaftsinformatik. 2018.
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  Beim Crowdsourcing schreiben Unternehmen auf speziellen Marktplätzen Arbeiten aus, wo sie von einer großen Anzahl von anonymen Arbeitern bearbeitet werden können. Im Gegensatz zu traditionellen Arbeitsverhältnissen geht beim Crowdsourcing der Arbeitnehmer in Vorleistung. Der Auftraggeber entscheidet anhand der übermittelten Bearbeitung, ob der Arbeitnehmer entlohnt wird oder nicht. Vertrauen zwischen beiden Parteien ist daher ein entscheidender Erfolgsfaktor für Crowdsourcing. Dieser Beitrag beschreibt die Vertrauensprobleme im Crowdsourcing und stellt ein Konzept für ein neuartiges Reputationssystem für Crowdsourcing-Plattformen vor. Das Konzept soll helfen, das Vertrauen im Crowdsourcing zu erhöhen. Umgesetzt wird dieses Konzept mittels Smart Contracts auf der Ethereum Blockchain im Projekt CrowdPrecision. Die Profile von Auftraggeber und Arbeitnehmer werden mit einem Reputationsscore verknüpft, der transparent und fälschungssicher in der Blockchain gespeichert wird. Die einzelnen Aufträge werden über Smart Contracts abgebildet, die eine automatisierte Entlohnung und Bewertung unter Einhaltung der vereinbarten Bedingungen garantieren.

  @article{info3-article-2018-5, abstract = {Beim Crowdsourcing schreiben Unternehmen auf speziellen Marktplätzen Arbeiten aus, wo sie von einer großen Anzahl von anonymen Arbeitern bearbeitet werden können. Im Gegensatz zu traditionellen Arbeitsverhältnissen geht beim Crowdsourcing der Arbeitnehmer in Vorleistung. Der Auftraggeber entscheidet anhand der übermittelten Bearbeitung, ob der Arbeitnehmer entlohnt wird oder nicht. Vertrauen zwischen beiden Parteien ist daher ein entscheidender Erfolgsfaktor für Crowdsourcing. Dieser Beitrag beschreibt die Vertrauensprobleme im Crowdsourcing und stellt ein Konzept für ein neuartiges Reputationssystem für Crowdsourcing-Plattformen vor. Das Konzept soll helfen, das Vertrauen im Crowdsourcing zu erhöhen. Umgesetzt wird dieses Konzept mittels Smart Contracts auf der Ethereum Blockchain im Projekt CrowdPrecision. Die Profile von Auftraggeber und Arbeitnehmer werden mit einem Reputationsscore verknüpft, der transparent und fälschungssicher in der Blockchain gespeichert wird. Die einzelnen Aufträge werden über Smart Contracts abgebildet, die eine automatisierte Entlohnung und Bewertung unter Einhaltung der vereinbarten Bedingungen garantieren.}, author = {Schütz, Andreas and Fertig, Tobias and Weber, Kerstin and Vu, Henry and Hirth, Matthias and Tran-Gia, Thomas}, journal = {HMD Praxis der Wirtschaftsinformatik}, keywords = {sys:hidden:article}, month = 10, title = {Vertrauen ist gut, Blockchain ist besser - Einsatzmöglichkeiten von Blockchain für Vertrauensprobleme im Crowdsourcing}, year = 2018 }

  %0 Journal Article %1 info3-article-2018-5 %A Schütz, Andreas %A Fertig, Tobias %A Weber, Kerstin %A Vu, Henry %A Hirth, Matthias %A Tran-Gia, Thomas %D 2018 %J HMD Praxis der Wirtschaftsinformatik %T Vertrauen ist gut, Blockchain ist besser - Einsatzmöglichkeiten von Blockchain für Vertrauensprobleme im Crowdsourcing %X Beim Crowdsourcing schreiben Unternehmen auf speziellen Marktplätzen Arbeiten aus, wo sie von einer großen Anzahl von anonymen Arbeitern bearbeitet werden können. Im Gegensatz zu traditionellen Arbeitsverhältnissen geht beim Crowdsourcing der Arbeitnehmer in Vorleistung. Der Auftraggeber entscheidet anhand der übermittelten Bearbeitung, ob der Arbeitnehmer entlohnt wird oder nicht. Vertrauen zwischen beiden Parteien ist daher ein entscheidender Erfolgsfaktor für Crowdsourcing. Dieser Beitrag beschreibt die Vertrauensprobleme im Crowdsourcing und stellt ein Konzept für ein neuartiges Reputationssystem für Crowdsourcing-Plattformen vor. Das Konzept soll helfen, das Vertrauen im Crowdsourcing zu erhöhen. Umgesetzt wird dieses Konzept mittels Smart Contracts auf der Ethereum Blockchain im Projekt CrowdPrecision. Die Profile von Auftraggeber und Arbeitnehmer werden mit einem Reputationsscore verknüpft, der transparent und fälschungssicher in der Blockchain gespeichert wird. Die einzelnen Aufträge werden über Smart Contracts abgebildet, die eine automatisierte Entlohnung und Bewertung unter Einhaltung der vereinbarten Bedingungen garantieren.
• Guest Editorial: Special Issue on “QoE Management for Multimedia Services.”. Hoßfeld, Tobias; Skorin-Kapov, Lea; Varela, Martin; Chen, Kuan-Ta. In ACM Transactions on Multimedia Computing, Communications, and Applications (TOMM). 2018.
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  @article{info3-article-2018-12, author = {Hoßfeld, Tobias and Skorin-Kapov, Lea and Varela, Martin and Chen, Kuan-Ta}, journal = {ACM Transactions on Multimedia Computing, Communications, and Applications (TOMM)}, keywords = {sys:hidden:article}, title = {Guest Editorial: Special Issue on “QoE Management for Multimedia Services”}, year = 2018 }

  %0 Journal Article %1 info3-article-2018-12 %A Hoßfeld, Tobias %A Skorin-Kapov, Lea %A Varela, Martin %A Chen, Kuan-Ta %D 2018 %J ACM Transactions on Multimedia Computing, Communications, and Applications (TOMM) %T Guest Editorial: Special Issue on “QoE Management for Multimedia Services”
• A new QoE fairness index for QoE management. Hoßfeld, Tobias; Skorin-Kapov, Lea; Heegaard, Poul E.; Varela, Martin. In Quality and User Experience. 2018.
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  @article{info3-article-2018-2, author = {Hoßfeld, Tobias and Skorin-Kapov, Lea and Heegaard, Poul E. and Varela, Martin}, journal = {Quality and User Experience}, keywords = {sys:hidden:article}, month = {02}, title = {A new QoE fairness index for QoE management}, year = 2018 }

  %0 Journal Article %1 info3-article-2018-2 %A Hoßfeld, Tobias %A Skorin-Kapov, Lea %A Heegaard, Poul E. %A Varela, Martin %D 2018 %J Quality and User Experience %T A new QoE fairness index for QoE management
• A Survey of Emerging Concepts and Challenges for QoE Management of Multimedia Services. Skorin-Kapov, Lea; Varela, Martin; Hoßfeld, Tobias; Chen, Kuan-Ta. In ACM Transactions on Multimedia Computing, Communications and Applications. 2018.
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  @article{info3-article-2018-3, author = {Skorin-Kapov, Lea and Varela, Martin and Hoßfeld, Tobias and Chen, Kuan-Ta}, journal = {ACM Transactions on Multimedia Computing, Communications and Applications}, keywords = {sys:hidden:article}, month = {03}, title = {A Survey of Emerging Concepts and Challenges for QoE Management of Multimedia Services}, year = 2018 }

  %0 Journal Article %1 info3-article-2018-3 %A Skorin-Kapov, Lea %A Varela, Martin %A Hoßfeld, Tobias %A Chen, Kuan-Ta %D 2018 %J ACM Transactions on Multimedia Computing, Communications and Applications %T A Survey of Emerging Concepts and Challenges for QoE Management of Multimedia Services
• A Generic Approach to Video Buffer Modeling using Discrete-Time Analysis. Burger, Valentin; Zinner, Thomas; Dinh-Xuan, Lam; Wamser, Florian; Tran-Gia, Phuoc. In ACM Transactions on Multimedia Computing, Communications, and Applications (TOMM), 14(33), p. 23. 2018.
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  @article{info3-article-2018-1, author = {Burger, Valentin and Zinner, Thomas and Dinh-Xuan, Lam and Wamser, Florian and Tran-Gia, Phuoc}, journal = {ACM Transactions on Multimedia Computing, Communications, and Applications (TOMM)}, keywords = {sys:hidden:article}, month = {04}, number = 33, pages = 23, title = {A Generic Approach to Video Buffer Modeling using Discrete-Time Analysis}, volume = 14, year = 2018 }

  %0 Journal Article %1 info3-article-2018-1 %A Burger, Valentin %A Zinner, Thomas %A Dinh-Xuan, Lam %A Wamser, Florian %A Tran-Gia, Phuoc %D 2018 %J ACM Transactions on Multimedia Computing, Communications, and Applications (TOMM) %N 33 %P 23 %T A Generic Approach to Video Buffer Modeling using Discrete-Time Analysis %V 14
• Impact of VNF Placements on QoE Monitoring in the Cloud. Dinh-Xuan, Lam; Popp, Christian; Burger, Valentin; Wamser, Florian; Hoßfeld, Tobias. In International Journal of Network Management, (NEM-18-0120.R1). 2018.
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  @article{info3-article-2018-6, author = {Dinh-Xuan, Lam and Popp, Christian and Burger, Valentin and Wamser, Florian and Hoßfeld, Tobias}, journal = {International Journal of Network Management}, keywords = {video-quality}, month = 10, number = {NEM-18-0120.R1}, title = {Impact of VNF Placements on QoE Monitoring in the Cloud}, year = 2018 }

  %0 Journal Article %1 info3-article-2018-6 %A Dinh-Xuan, Lam %A Popp, Christian %A Burger, Valentin %A Wamser, Florian %A Hoßfeld, Tobias %D 2018 %J International Journal of Network Management %N NEM-18-0120.R1 %T Impact of VNF Placements on QoE Monitoring in the Cloud

• Design and Performance Evaluation of Network-assisted Control Strategies for HTTP Adaptive Streaming. Cofano, Giuseppe; De Cicco, Luca; Zinner, Thomas; Nguyen-Ngoc, Anh; Tran-Gia, Phuoc; Mascolo, Saverio. In ACM Transactions on Multimedia Computing, Communications, and Applications. 2017.
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  @article{info3-article-2017-2, author = {Cofano, Giuseppe and De Cicco, Luca and Zinner, Thomas and Nguyen-Ngoc, Anh and Tran-Gia, Phuoc and Mascolo, Saverio}, journal = {ACM Transactions on Multimedia Computing, Communications, and Applications}, keywords = {sys:hidden:article}, title = {Design and Performance Evaluation of Network-assisted Control Strategies for HTTP Adaptive Streaming}, year = 2017 }

  %0 Journal Article %1 info3-article-2017-2 %A Cofano, Giuseppe %A De Cicco, Luca %A Zinner, Thomas %A Nguyen-Ngoc, Anh %A Tran-Gia, Phuoc %A Mascolo, Saverio %D 2017 %J ACM Transactions on Multimedia Computing, Communications, and Applications %T Design and Performance Evaluation of Network-assisted Control Strategies for HTTP Adaptive Streaming
• 2016 International Teletraffic Congress (ITC 28) Report. Hoßfeld, Tobias. In ACM SIGCOMM Computer Communication Review. 2017.
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  @article{info3-article-2017-9, author = {Hoßfeld, Tobias}, journal = {ACM SIGCOMM Computer Communication Review}, keywords = {sys:hidden:article}, title = {2016 International Teletraffic Congress (ITC 28) Report}, year = 2017 }

  %0 Journal Article %1 info3-article-2017-9 %A Hoßfeld, Tobias %D 2017 %J ACM SIGCOMM Computer Communication Review %T 2016 International Teletraffic Congress (ITC 28) Report
• A Discrete-Time Model for Optimizing the Processing Time of Virtualized Network Functions. Zinner, Thomas; Geissler, Stefan; Lange, Stanislav; Gebert, Steffen; Seufert, Michael; Tran-Gia, Phuoc. In Computer Networks, 125, pp. 4–14. 2017.
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  The softwarization of networks promises cost savings and better scalability of network functions by moving functionality from specialized devices into commercial off-the-shelf hardware. Generalized computing hardware offers many degrees of adjustment and tuning, which can affect performance and resource utilization. One of these adjustments are interrupt moderation techniques implemented by modern network interface cards and operating systems. Using these, an administrator can optimize either for low latencies or low CPU overhead for processing of network traffic. In this work, an analytical model that allows the computation of relevant performance metrics like packet processing time and packet loss for generic virtualized network functions running on commodity hardware is presented. Based on this model, impact factors like average packet interarrival time, interarrival time distribution, and duration of the interrupt aggregation interval are studied. Furthermore, we significantly improve the computational tractability of this discrete-time model by proving and leveraging a property regarding its limit behavior. We also demonstrate that using this property does not affect the accuracy of the model in the context of realistic parameter combinations. Finally, the improved runtime for numerical evaluations allows administrators to dynamically adapt their interrupt mitigation settings to changing network conditions by recalculating optimal parameters.

  @article{info3-article-2017-1, abstract = {The softwarization of networks promises cost savings and better scalability of network functions by moving functionality from specialized devices into commercial off-the-shelf hardware. Generalized computing hardware offers many degrees of adjustment and tuning, which can affect performance and resource utilization. One of these adjustments are interrupt moderation techniques implemented by modern network interface cards and operating systems. Using these, an administrator can optimize either for low latencies or low CPU overhead for processing of network traffic. In this work, an analytical model that allows the computation of relevant performance metrics like packet processing time and packet loss for generic virtualized network functions running on commodity hardware is presented. Based on this model, impact factors like average packet interarrival time, interarrival time distribution, and duration of the interrupt aggregation interval are studied. Furthermore, we significantly improve the computational tractability of this discrete-time model by proving and leveraging a property regarding its limit behavior. We also demonstrate that using this property does not affect the accuracy of the model in the context of realistic parameter combinations. Finally, the improved runtime for numerical evaluations allows administrators to dynamically adapt their interrupt mitigation settings to changing network conditions by recalculating optimal parameters.}, author = {Zinner, Thomas and Geissler, Stefan and Lange, Stanislav and Gebert, Steffen and Seufert, Michael and Tran-Gia, Phuoc}, journal = {Computer Networks}, keywords = {sys:hidden:article}, pages = {4-14}, title = {A Discrete-Time Model for Optimizing the Processing Time of Virtualized Network Functions}, volume = 125, year = 2017 }

  %0 Journal Article %1 info3-article-2017-1 %A Zinner, Thomas %A Geissler, Stefan %A Lange, Stanislav %A Gebert, Steffen %A Seufert, Michael %A Tran-Gia, Phuoc %D 2017 %J Computer Networks %P 4-14 %T A Discrete-Time Model for Optimizing the Processing Time of Virtualized Network Functions %V 125 %X The softwarization of networks promises cost savings and better scalability of network functions by moving functionality from specialized devices into commercial off-the-shelf hardware. Generalized computing hardware offers many degrees of adjustment and tuning, which can affect performance and resource utilization. One of these adjustments are interrupt moderation techniques implemented by modern network interface cards and operating systems. Using these, an administrator can optimize either for low latencies or low CPU overhead for processing of network traffic. In this work, an analytical model that allows the computation of relevant performance metrics like packet processing time and packet loss for generic virtualized network functions running on commodity hardware is presented. Based on this model, impact factors like average packet interarrival time, interarrival time distribution, and duration of the interrupt aggregation interval are studied. Furthermore, we significantly improve the computational tractability of this discrete-time model by proving and leveraging a property regarding its limit behavior. We also demonstrate that using this property does not affect the accuracy of the model in the context of realistic parameter combinations. Finally, the improved runtime for numerical evaluations allows administrators to dynamically adapt their interrupt mitigation settings to changing network conditions by recalculating optimal parameters.
• SDN and NFV as Enabler for the Distributed Network Cloud. Hoffmann, Marco; Jarschel, Michael; Pries, Rastin; Schneider, Peter; Jukan, Admela; Bziuk, Wolfgang; Gebert, Steffen; Zinner, Thomas; Tran-Gia, Phuoc. In Mobile Networks and Applications. 2017.
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  @article{info3-article-2017-8, author = {Hoffmann, Marco and Jarschel, Michael and Pries, Rastin and Schneider, Peter and Jukan, Admela and Bziuk, Wolfgang and Gebert, Steffen and Zinner, Thomas and Tran-Gia, Phuoc}, journal = {Mobile Networks and Applications}, keywords = {sys:hidden:article}, title = {SDN and NFV as Enabler for the Distributed Network Cloud}, year = 2017 }

  %0 Journal Article %1 info3-article-2017-8 %A Hoffmann, Marco %A Jarschel, Michael %A Pries, Rastin %A Schneider, Peter %A Jukan, Admela %A Bziuk, Wolfgang %A Gebert, Steffen %A Zinner, Thomas %A Tran-Gia, Phuoc %D 2017 %J Mobile Networks and Applications %T SDN and NFV as Enabler for the Distributed Network Cloud
• Softwarization and Caching in NGN. Hoßfeld, Tobias; Chan, S-H Gary; Mark, Brian L; Timm-Giel, Andreas. In Computer Networks, 125, pp. 1–3. 2017.
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  • [ EndNote ]
  @article{info3-misc-2017-1, author = {Hoßfeld, Tobias and Chan, S-H Gary and Mark, Brian L and Timm-Giel, Andreas}, journal = {Computer Networks}, keywords = {sys:hidden:article}, month = 10, pages = {1-3}, title = {Softwarization and Caching in NGN}, volume = 125, year = 2017 }

  %0 Journal Article %1 info3-misc-2017-1 %A Hoßfeld, Tobias %A Chan, S-H Gary %A Mark, Brian L %A Timm-Giel, Andreas %D 2017 %J Computer Networks %P 1-3 %T Softwarization and Caching in NGN %V 125
• An SDN/NFV-enabled Enterprise Network Architecture Offering Fine-Grained Security Policy Enforcement. Lorenz, Claas; Hock, David; Scherer, Johann; Durner, Raphael; Kellerer, Wolfgang; Gebert, Steffen; Gray, Nicholas; Zinner, Thomas; Tran-Gia, Phuoc. In IEEE Communications Magazine, 55(3), pp. 217–223. 2017.
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  In recent years, the number of attacks and threat vectors against enterprise networks have been constantly increasing in numbers and variety. In addition, new challenges arise not only to the level of provided security, but also to the scalability and manageability of the deployed countermeasures such as firewalls and intrusion detection systems. Despite these attacks, the main security systems, e.g., network firewalls, have remained rather unchanged. Due to the tight integration into the physical network’s infrastructure, a dynamic resource allocation to adapt the security measures to the current network conditions is a difficult undertaking. Therefore, in this work, we analyze and compare different architectural design patterns for the integration of SDN/NFV-based security solutions into enterprise networks.

  @article{info3-article-2016-9, abstract = {In recent years, the number of attacks and threat vectors against enterprise networks have been constantly increasing in numbers and variety. In addition, new challenges arise not only to the level of provided security, but also to the scalability and manageability of the deployed countermeasures such as firewalls and intrusion detection systems. Despite these attacks, the main security systems, e.g., network firewalls, have remained rather unchanged. Due to the tight integration into the physical network’s infrastructure, a dynamic resource allocation to adapt the security measures to the current network conditions is a difficult undertaking. Therefore, in this work, we analyze and compare different architectural design patterns for the integration of SDN/NFV-based security solutions into enterprise networks.}, author = {Lorenz, Claas and Hock, David and Scherer, Johann and Durner, Raphael and Kellerer, Wolfgang and Gebert, Steffen and Gray, Nicholas and Zinner, Thomas and Tran-Gia, Phuoc}, journal = {IEEE Communications Magazine}, keywords = {sys:hidden:article}, month = {03}, number = 3, pages = {217 - 223}, title = {An SDN/NFV-enabled Enterprise Network Architecture Offering Fine-Grained Security Policy Enforcement}, volume = 55, year = 2017 }

  %0 Journal Article %1 info3-article-2016-9 %A Lorenz, Claas %A Hock, David %A Scherer, Johann %A Durner, Raphael %A Kellerer, Wolfgang %A Gebert, Steffen %A Gray, Nicholas %A Zinner, Thomas %A Tran-Gia, Phuoc %D 2017 %J IEEE Communications Magazine %N 3 %P 217 - 223 %T An SDN/NFV-enabled Enterprise Network Architecture Offering Fine-Grained Security Policy Enforcement %V 55 %X In recent years, the number of attacks and threat vectors against enterprise networks have been constantly increasing in numbers and variety. In addition, new challenges arise not only to the level of provided security, but also to the scalability and manageability of the deployed countermeasures such as firewalls and intrusion detection systems. Despite these attacks, the main security systems, e.g., network firewalls, have remained rather unchanged. Due to the tight integration into the physical network’s infrastructure, a dynamic resource allocation to adapt the security measures to the current network conditions is a difficult undertaking. Therefore, in this work, we analyze and compare different architectural design patterns for the integration of SDN/NFV-based security solutions into enterprise networks.
• Analytical Model for SDN Signaling Traffic and Flow Table Occupancy and its Application for Various Types of Traffic. Metter, Christopher; Seufert, Michael; Wamser, Florian; Zinner, Thomas; Tran-Gia, Phuoc. In IEEE Transactions on Network and Service Management, 14(3), pp. 603–615. 2017.
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  Software Defined Networking (SDN) has emerged as a promising networking paradigm overcoming various drawbacks of current communication networks. The control and data plane of switching devices is decoupled and control functions are centralized at the network controller. In SDN, each new flow introduces additional signaling traffic between the switch and the controller. Based on this traffic, rules are created in the flow table of the switch, which specify the forwarding behavior. To avoid table overflows, unused entries are removed after a predefined time-out period. Given a specific traffic mix, the choice of this time-out period affects the trade-off between signaling rate and table occupancy. As a result, network operators have to adjust this parameter to enable a smooth and efficient network operation. Due to the complexity of this problem caused by the various traffic flows in a network, a suitable abstraction is necessary in order to derive valid parameter values in time. The contribution of this work is threefold. Firstly, we formulate a simple analytical model that allows optimizing the network performance with respect to the table occupancy and the signaling rate. Secondly, we validate the model by means of simulation. Thirdly, we illustrate the impact of the time-out period on the signaling traffic and the flow table occupancy for different data-plane traffic mixes and characteristics. This includes scenarios with single application instances, as well as multiple application instances of different application types in an SDN-enabled network.

  @article{info3-article-2017-5, abstract = {Software Defined Networking (SDN) has emerged as a promising networking paradigm overcoming various drawbacks of current communication networks. The control and data plane of switching devices is decoupled and control functions are centralized at the network controller. In SDN, each new flow introduces additional signaling traffic between the switch and the controller. Based on this traffic, rules are created in the flow table of the switch, which specify the forwarding behavior. To avoid table overflows, unused entries are removed after a predefined time-out period. Given a specific traffic mix, the choice of this time-out period affects the trade-off between signaling rate and table occupancy. As a result, network operators have to adjust this parameter to enable a smooth and efficient network operation. Due to the complexity of this problem caused by the various traffic flows in a network, a suitable abstraction is necessary in order to derive valid parameter values in time. The contribution of this work is threefold. Firstly, we formulate a simple analytical model that allows optimizing the network performance with respect to the table occupancy and the signaling rate. Secondly, we validate the model by means of simulation. Thirdly, we illustrate the impact of the time-out period on the signaling traffic and the flow table occupancy for different data-plane traffic mixes and characteristics. This includes scenarios with single application instances, as well as multiple application instances of different application types in an SDN-enabled network.}, author = {Metter, Christopher and Seufert, Michael and Wamser, Florian and Zinner, Thomas and Tran-Gia, Phuoc}, journal = {IEEE Transactions on Network and Service Management}, keywords = {can}, month = {09}, number = 3, pages = {603-615}, title = {Analytical Model for SDN Signaling Traffic and Flow Table Occupancy and its Application for Various Types of Traffic}, volume = 14, year = 2017 }

  %0 Journal Article %1 info3-article-2017-5 %A Metter, Christopher %A Seufert, Michael %A Wamser, Florian %A Zinner, Thomas %A Tran-Gia, Phuoc %D 2017 %J IEEE Transactions on Network and Service Management %N 3 %P 603-615 %T Analytical Model for SDN Signaling Traffic and Flow Table Occupancy and its Application for Various Types of Traffic %V 14 %X Software Defined Networking (SDN) has emerged as a promising networking paradigm overcoming various drawbacks of current communication networks. The control and data plane of switching devices is decoupled and control functions are centralized at the network controller. In SDN, each new flow introduces additional signaling traffic between the switch and the controller. Based on this traffic, rules are created in the flow table of the switch, which specify the forwarding behavior. To avoid table overflows, unused entries are removed after a predefined time-out period. Given a specific traffic mix, the choice of this time-out period affects the trade-off between signaling rate and table occupancy. As a result, network operators have to adjust this parameter to enable a smooth and efficient network operation. Due to the complexity of this problem caused by the various traffic flows in a network, a suitable abstraction is necessary in order to derive valid parameter values in time. The contribution of this work is threefold. Firstly, we formulate a simple analytical model that allows optimizing the network performance with respect to the table occupancy and the signaling rate. Secondly, we validate the model by means of simulation. Thirdly, we illustrate the impact of the time-out period on the signaling traffic and the flow table occupancy for different data-plane traffic mixes and characteristics. This includes scenarios with single application instances, as well as multiple application instances of different application types in an SDN-enabled network.
• Quantitative Comparison of Application-Network Interaction: A Case Study of Adaptive Video Streaming. Schwarzmann, Susanna; Zinner, Thomas; Dobrijevic, Ognjen. In Springer Quality and User Experience. 2017.
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  Managing quality of experience (QoE) is now widely accepted as a critical objective for multimedia applications and the supporting communication systems. In general, QoE management encompasses: (i) monitoring of the key influence factors and QoE indicators, and (ii) deciding on the appropriate control actions as specified by the management goal. Many multimedia applications, e.g. video streaming and audio conferencing, are able to adjust their operational parameters so as to react to variations in the network performance. However, such an adaptation feature is mostly based on a local client view of the network conditions, which may lead to an unfair allocation of network resources among heterogeneous clients and, thus, an unfair QoE distribution. In order to tackle this issue, there is the call for a cooperation between the applications and the underlying network, which includes application-network interaction (App-Net) in terms of: (1) exchanging information on the monitored QoE indicators, and (2) coordinating the QoE control actions. Various App-Net mechanisms focusing on specific use cases and applications have been proposed to date. This paper gives an overview of App-Net mechanisms and proposes a generic App-Net model that provides the means to realize a coordinated QoE-centric management. Based on the App-Net model, we develop an evaluation methodology to compare three App-Net mechanisms for managing QoE of HTTP adaptive streaming (HAS) against a baseline HAS service. The aim of this quantitative comparison is to explore the trade-offs between QoE gains and the complexity of App-Net implementation, with respect to the number of monitoring and control messages, achieved video quality, and QoE fairness among heterogeneous clients. Our ultimate goal is to set up reproducible experiments that facilitate a holistic evaluation of different App-Net mechanisms.

  @article{info3-article-2017-4, abstract = {Managing quality of experience (QoE) is now widely accepted as a critical objective for multimedia applications and the supporting communication systems. In general, QoE management encompasses: (i) monitoring of the key influence factors and QoE indicators, and (ii) deciding on the appropriate control actions as specified by the management goal. Many multimedia applications, e.g. video streaming and audio conferencing, are able to adjust their operational parameters so as to react to variations in the network performance. However, such an adaptation feature is mostly based on a local client view of the network conditions, which may lead to an unfair allocation of network resources among heterogeneous clients and, thus, an unfair QoE distribution. In order to tackle this issue, there is the call for a cooperation between the applications and the underlying network, which includes application-network interaction (App-Net) in terms of: (1) exchanging information on the monitored QoE indicators, and (2) coordinating the QoE control actions. Various App-Net mechanisms focusing on specific use cases and applications have been proposed to date. This paper gives an overview of App-Net mechanisms and proposes a generic App-Net model that provides the means to realize a coordinated QoE-centric management. Based on the App-Net model, we develop an evaluation methodology to compare three App-Net mechanisms for managing QoE of HTTP adaptive streaming (HAS) against a baseline HAS service. The aim of this quantitative comparison is to explore the trade-offs between QoE gains and the complexity of App-Net implementation, with respect to the number of monitoring and control messages, achieved video quality, and QoE fairness among heterogeneous clients. Our ultimate goal is to set up reproducible experiments that facilitate a holistic evaluation of different App-Net mechanisms.}, author = {Schwarzmann, Susanna and Zinner, Thomas and Dobrijevic, Ognjen}, journal = {Springer Quality and User Experience}, keywords = {sys:hidden:article}, title = {Quantitative Comparison of Application-Network Interaction: A Case Study of Adaptive Video Streaming}, year = 2017 }

  %0 Journal Article %1 info3-article-2017-4 %A Schwarzmann, Susanna %A Zinner, Thomas %A Dobrijevic, Ognjen %D 2017 %J Springer Quality and User Experience %T Quantitative Comparison of Application-Network Interaction: A Case Study of Adaptive Video Streaming %X Managing quality of experience (QoE) is now widely accepted as a critical objective for multimedia applications and the supporting communication systems. In general, QoE management encompasses: (i) monitoring of the key influence factors and QoE indicators, and (ii) deciding on the appropriate control actions as specified by the management goal. Many multimedia applications, e.g. video streaming and audio conferencing, are able to adjust their operational parameters so as to react to variations in the network performance. However, such an adaptation feature is mostly based on a local client view of the network conditions, which may lead to an unfair allocation of network resources among heterogeneous clients and, thus, an unfair QoE distribution. In order to tackle this issue, there is the call for a cooperation between the applications and the underlying network, which includes application-network interaction (App-Net) in terms of: (1) exchanging information on the monitored QoE indicators, and (2) coordinating the QoE control actions. Various App-Net mechanisms focusing on specific use cases and applications have been proposed to date. This paper gives an overview of App-Net mechanisms and proposes a generic App-Net model that provides the means to realize a coordinated QoE-centric management. Based on the App-Net model, we develop an evaluation methodology to compare three App-Net mechanisms for managing QoE of HTTP adaptive streaming (HAS) against a baseline HAS service. The aim of this quantitative comparison is to explore the trade-offs between QoE gains and the complexity of App-Net implementation, with respect to the number of monitoring and control messages, achieved video quality, and QoE fairness among heterogeneous clients. Our ultimate goal is to set up reproducible experiments that facilitate a holistic evaluation of different App-Net mechanisms.

• More than Topology: Joint Topology and Attribute Sampling and Generation of Social Network Graphs. Seufert, Michael; Lange, Stanislav; Hoßfeld, Tobias. In Computer Communications, 73(Part B), pp. 176–187. 2016.
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  Graph sampling refers to the process of deriving a small subset of nodes from a possibly huge graph in order to estimate properties of the whole graph from examining the sample. Whereas topological properties can already be obtained accurately by sampling, current approaches do not take possibly hidden dependencies between node topology and attributes into account. Especially in the context of online social networks, node attributes are of importance as they correspond to properties of the social network's users. Therefore, existing sampling algorithms can be extended to attribute sampling, but still lack the capturing of structural properties. Analyzing topology (e.g., node degree, clustering coefficient) and attribute properties (e.g., age, location) jointly can provide valuable insights into the social network and allows for a better understanding of social processes. As major contribution, this work proposes a novel sampling algorithm which provides unbiased and reliable estimates of joint topological and attribute based graph properties in a resource efficient fashion. Furthermore, the obtained samples allow for the generation of synthetic graphs, which show high similarity to the original graph with respect to topology and attributes. The proposed sampling and generation algorithms are evaluated on real world social network graphs, for which they demonstrate to be effective.

  @article{info3-article-2016-1, abstract = {Graph sampling refers to the process of deriving a small subset of nodes from a possibly huge graph in order to estimate properties of the whole graph from examining the sample. Whereas topological properties can already be obtained accurately by sampling, current approaches do not take possibly hidden dependencies between node topology and attributes into account. Especially in the context of online social networks, node attributes are of importance as they correspond to properties of the social network's users. Therefore, existing sampling algorithms can be extended to attribute sampling, but still lack the capturing of structural properties. Analyzing topology (e.g., node degree, clustering coefficient) and attribute properties (e.g., age, location) jointly can provide valuable insights into the social network and allows for a better understanding of social processes. As major contribution, this work proposes a novel sampling algorithm which provides unbiased and reliable estimates of joint topological and attribute based graph properties in a resource efficient fashion. Furthermore, the obtained samples allow for the generation of synthetic graphs, which show high similarity to the original graph with respect to topology and attributes. The proposed sampling and generation algorithms are evaluated on real world social network graphs, for which they demonstrate to be effective.}, author = {Seufert, Michael and Lange, Stanislav and Hoßfeld, Tobias}, journal = {Computer Communications}, keywords = {can}, month = {01}, number = {Part B}, pages = {176-187}, title = {More than Topology: Joint Topology and Attribute Sampling and Generation of Social Network Graphs}, volume = 73, year = 2016 }

  %0 Journal Article %1 info3-article-2016-1 %A Seufert, Michael %A Lange, Stanislav %A Hoßfeld, Tobias %D 2016 %J Computer Communications %N Part B %P 176-187 %T More than Topology: Joint Topology and Attribute Sampling and Generation of Social Network Graphs %V 73 %X Graph sampling refers to the process of deriving a small subset of nodes from a possibly huge graph in order to estimate properties of the whole graph from examining the sample. Whereas topological properties can already be obtained accurately by sampling, current approaches do not take possibly hidden dependencies between node topology and attributes into account. Especially in the context of online social networks, node attributes are of importance as they correspond to properties of the social network's users. Therefore, existing sampling algorithms can be extended to attribute sampling, but still lack the capturing of structural properties. Analyzing topology (e.g., node degree, clustering coefficient) and attribute properties (e.g., age, location) jointly can provide valuable insights into the social network and allows for a better understanding of social processes. As major contribution, this work proposes a novel sampling algorithm which provides unbiased and reliable estimates of joint topological and attribute based graph properties in a resource efficient fashion. Furthermore, the obtained samples allow for the generation of synthetic graphs, which show high similarity to the original graph with respect to topology and attributes. The proposed sampling and generation algorithms are evaluated on real world social network graphs, for which they demonstrate to be effective.
• Formal definition of QoE metrics. Hoßfeld, Tobias; Heegaard, Poul E.; Varela, Martin; Möller, Sebastian. In arXiv preprint arXiv:1607.00321. 2016.
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  @article{info3-article-2016-13, author = {Hoßfeld, Tobias and Heegaard, Poul E. and Varela, Martin and Möller, Sebastian}, journal = {arXiv preprint arXiv:1607.00321}, keywords = {sys:hidden:article}, title = {Formal definition of QoE metrics}, year = 2016 }

  %0 Journal Article %1 info3-article-2016-13 %A Hoßfeld, Tobias %A Heegaard, Poul E. %A Varela, Martin %A Möller, Sebastian %D 2016 %J arXiv preprint arXiv:1607.00321 %T Formal definition of QoE metrics
• Definition of QoE Fairness in Shared Systems. Hoßfeld, Tobias; Skorin-Kapov, Lea; Heegaard, Poul E.; Varela, Martin. In IEEE Communications Letters. 2016.
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  @article{info3-article-2016-11, author = {Hoßfeld, Tobias and Skorin-Kapov, Lea and Heegaard, Poul E. and Varela, Martin}, journal = {IEEE Communications Letters}, keywords = {sys:hidden:article}, title = {Definition of QoE Fairness in Shared Systems}, year = 2016 }

  %0 Journal Article %1 info3-article-2016-11 %A Hoßfeld, Tobias %A Skorin-Kapov, Lea %A Heegaard, Poul E. %A Varela, Martin %D 2016 %J IEEE Communications Letters %T Definition of QoE Fairness in Shared Systems
• TCP video streaming and mobile networks: Not a love story, but better with context. Metzger, Florian; Liotou, Eirini; Moldovan, Christian; Hoßfeld, Tobias. In Computer Networks, 109, pp. 246–256. 2016.
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  @article{info3-article-2016-12, author = {Metzger, Florian and Liotou, Eirini and Moldovan, Christian and Hoßfeld, Tobias}, journal = {Computer Networks}, keywords = {sys:hidden:article}, pages = {246–256}, title = {TCP video streaming and mobile networks: Not a love story, but better with context}, volume = 109, year = 2016 }

  %0 Journal Article %1 info3-article-2016-12 %A Metzger, Florian %A Liotou, Eirini %A Moldovan, Christian %A Hoßfeld, Tobias %D 2016 %J Computer Networks %P 246--256 %T TCP video streaming and mobile networks: Not a love story, but better with context %V 109
• Leistungsbewertung von Ressourcenmanagementstrategien für zelluläre und drahtlose Mesh-Netzwerke. Wamser, Florian. In Lecture Notes in Informatics (LNI), Ausgezeichnete Informatikdissertationen 2015. 2016.
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  Heutige Kommunikationsnetzwerke müssen eine große Anzahl an heterogenen Anwendungen und Diensten schultern. Dies gilt zusätzlich zu den Herausforderungen, dass sie kostengünstig sein sollen und schnelles, qualitativ-hochwertiges Internet anbieten müssen. Ein spezialisiertes Ressourcenmanagement kann in vielen dieser Fälle helfen und kann eine Win-Win-Situation für beide Parteien - den Benutzer und das Netzwerk - darstellen. In meiner Dissertation untersuche ich verschiedene neue Ressourcenmanagementansätze zur Leistungsoptimierung und Steigerung der Ressourceneffizienz in Zugangsnetzen. Die untersuchten Ansätze arbeiten auf verschiedenen Kommunikationsschichten und erfüllen unterschiedliche Ziele. Am Ende stellt diese Arbeit Empfehlungen für Netzbetreiber dar, wie ein Ressourcenmanagement für unterschiedliche Netzwerktypen und Ziele aussehen kann und welcher Nutzen in Vergleich mit dem erforderlichen Aufwand und der höheren Komplexität zu erwarten ist.

  @article{info3-article-2016-8, abstract = {Heutige Kommunikationsnetzwerke müssen eine große Anzahl an heterogenen Anwendungen und Diensten schultern. Dies gilt zusätzlich zu den Herausforderungen, dass sie kostengünstig sein sollen und schnelles, qualitativ-hochwertiges Internet anbieten müssen. Ein spezialisiertes Ressourcenmanagement kann in vielen dieser Fälle helfen und kann eine Win-Win-Situation für beide Parteien - den Benutzer und das Netzwerk - darstellen. In meiner Dissertation untersuche ich verschiedene neue Ressourcenmanagementansätze zur Leistungsoptimierung und Steigerung der Ressourceneffizienz in Zugangsnetzen. Die untersuchten Ansätze arbeiten auf verschiedenen Kommunikationsschichten und erfüllen unterschiedliche Ziele. Am Ende stellt diese Arbeit Empfehlungen für Netzbetreiber dar, wie ein Ressourcenmanagement für unterschiedliche Netzwerktypen und Ziele aussehen kann und welcher Nutzen in Vergleich mit dem erforderlichen Aufwand und der höheren Komplexität zu erwarten ist.}, author = {Wamser, Florian}, journal = {Lecture Notes in Informatics (LNI)}, keywords = {can}, title = {Leistungsbewertung von Ressourcenmanagementstrategien für zelluläre und drahtlose Mesh-Netzwerke}, volume = {Ausgezeichnete Informatikdissertationen 2015}, year = 2016 }

  %0 Journal Article %1 info3-article-2016-8 %A Wamser, Florian %D 2016 %J Lecture Notes in Informatics (LNI) %T Leistungsbewertung von Ressourcenmanagementstrategien für zelluläre und drahtlose Mesh-Netzwerke %V Ausgezeichnete Informatikdissertationen 2015 %X Heutige Kommunikationsnetzwerke müssen eine große Anzahl an heterogenen Anwendungen und Diensten schultern. Dies gilt zusätzlich zu den Herausforderungen, dass sie kostengünstig sein sollen und schnelles, qualitativ-hochwertiges Internet anbieten müssen. Ein spezialisiertes Ressourcenmanagement kann in vielen dieser Fälle helfen und kann eine Win-Win-Situation für beide Parteien - den Benutzer und das Netzwerk - darstellen. In meiner Dissertation untersuche ich verschiedene neue Ressourcenmanagementansätze zur Leistungsoptimierung und Steigerung der Ressourceneffizienz in Zugangsnetzen. Die untersuchten Ansätze arbeiten auf verschiedenen Kommunikationsschichten und erfüllen unterschiedliche Ziele. Am Ende stellt diese Arbeit Empfehlungen für Netzbetreiber dar, wie ein Ressourcenmanagement für unterschiedliche Netzwerktypen und Ziele aussehen kann und welcher Nutzen in Vergleich mit dem erforderlichen Aufwand und der höheren Komplexität zu erwarten ist.
• QoE beyond the MOS: an in-depth look at QoE via better metrics and their relation to MOS. Hoßfeld, Tobias; Heegaard, Poul E.; Varela, Martin; Möller, Sebastian. In Quality and User Experience, 1(2). 2016.
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  @article{info3-article-2016-10, author = {Hoßfeld, Tobias and Heegaard, Poul E. and Varela, Martin and Möller, Sebastian}, journal = {Quality and User Experience}, keywords = {sys:hidden:article}, number = 2, title = {QoE beyond the MOS: an in-depth look at QoE via better metrics and their relation to MOS}, volume = 1, year = 2016 }

  %0 Journal Article %1 info3-article-2016-10 %A Hoßfeld, Tobias %A Heegaard, Poul E. %A Varela, Martin %A Möller, Sebastian %D 2016 %J Quality and User Experience %N 2 %T QoE beyond the MOS: an in-depth look at QoE via better metrics and their relation to MOS %V 1
• A Simple WiFi Hotspot Model for Cities. Seufert, Michael; Griepentrog, Tobias; Burger, Valentin; Hoßfeld, Tobias. In IEEE Communications Letters, 20(2), pp. 384–387. 2016.
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  WiFi offloading has become increasingly popular. Many private and public institutions (e.g., libraries, cafes, restaurants) already provide an alternative free Internet link via WiFi, but also commercial services emerge to mitigate the load on mobile networks. Moreover, smart cities start to establish WiFi infrastructure for current and future civic services. In this work, the hotspot locations of ten diverse large cities are characterized, and a surprisingly simple model for the distribution of WiFi hotspots in an urban environment is derived.

  @article{info3-article-2016-2, abstract = {WiFi offloading has become increasingly popular. Many private and public institutions (e.g., libraries, cafes, restaurants) already provide an alternative free Internet link via WiFi, but also commercial services emerge to mitigate the load on mobile networks. Moreover, smart cities start to establish WiFi infrastructure for current and future civic services. In this work, the hotspot locations of ten diverse large cities are characterized, and a surprisingly simple model for the distribution of WiFi hotspots in an urban environment is derived.}, author = {Seufert, Michael and Griepentrog, Tobias and Burger, Valentin and Hoßfeld, Tobias}, journal = {IEEE Communications Letters}, keywords = {can}, month = {02}, number = 2, pages = {384 - 387}, title = {A Simple WiFi Hotspot Model for Cities}, volume = 20, year = 2016 }

  %0 Journal Article %1 info3-article-2016-2 %A Seufert, Michael %A Griepentrog, Tobias %A Burger, Valentin %A Hoßfeld, Tobias %D 2016 %J IEEE Communications Letters %N 2 %P 384 - 387 %T A Simple WiFi Hotspot Model for Cities %V 20 %X WiFi offloading has become increasingly popular. Many private and public institutions (e.g., libraries, cafes, restaurants) already provide an alternative free Internet link via WiFi, but also commercial services emerge to mitigate the load on mobile networks. Moreover, smart cities start to establish WiFi infrastructure for current and future civic services. In this work, the hotspot locations of ten diverse large cities are characterized, and a surprisingly simple model for the distribution of WiFi hotspots in an urban environment is derived.
• Next to You: Monitoring Quality of Experience in Cellular Networks from the End-devices. Casas, Pedro; Seufert, Michael; Wamser, Florian; Gardlo, Bruno; Sackl, Andreas; Schatz, Raimund. In IEEE Transactions on Network and Service Management, 13(2), pp. 181–196. 2016.
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  A quarter of the world population will be using smartphones to access the Internet in the near future. In this context, understanding the Quality of Experience (QoE) of popular apps in such devices becomes paramount to cellular network operators, who need to offer high quality levels to reduce the risks of customers churning for quality dissatisfaction. In this paper we address the problem of QoE provisioning in smartphones from a double perspective, combining the results obtained from subjective lab tests with end-device passive measurements and QoE crowd-sourced feedback obtained in operational cellular networks. The study addresses the impact of both access bandwidth and latency on the QoE of five different services and mobile apps: YouTube, Facebook, Web browsing through Chrome, Google Maps, and WhatsApp. We evaluate the influence of both constant and dynamically changing network access conditions, tackling in particular the case of fluctuating downlink bandwidth, which is typical in cellular networks. As a main contribution, we show that the results obtained in the lab are highly applicable in the live scenario, as mappings track the QoE provided by users in real networks. We additionally provide hints and bandwidth thresholds for good QoE levels on such apps, as well as discussion on end-device passive measurements and analysis. The results presented in this paper provide a sound basis to better understand the QoE requirements of popular mobile apps, as well as for monitoring the underlying provisioning network. To the best of our knowledge, this is the first paper providing such a comprehensive analysis of QoE in mobile devices, combining network measurements with users QoE feedback in lab tests and operational networks.

  @article{info3-article-2016-4, abstract = {A quarter of the world population will be using smartphones to access the Internet in the near future. In this context, understanding the Quality of Experience (QoE) of popular apps in such devices becomes paramount to cellular network operators, who need to offer high quality levels to reduce the risks of customers churning for quality dissatisfaction. In this paper we address the problem of QoE provisioning in smartphones from a double perspective, combining the results obtained from subjective lab tests with end-device passive measurements and QoE crowd-sourced feedback obtained in operational cellular networks. The study addresses the impact of both access bandwidth and latency on the QoE of five different services and mobile apps: YouTube, Facebook, Web browsing through Chrome, Google Maps, and WhatsApp. We evaluate the influence of both constant and dynamically changing network access conditions, tackling in particular the case of fluctuating downlink bandwidth, which is typical in cellular networks. As a main contribution, we show that the results obtained in the lab are highly applicable in the live scenario, as mappings track the QoE provided by users in real networks. We additionally provide hints and bandwidth thresholds for good QoE levels on such apps, as well as discussion on end-device passive measurements and analysis. The results presented in this paper provide a sound basis to better understand the QoE requirements of popular mobile apps, as well as for monitoring the underlying provisioning network. To the best of our knowledge, this is the first paper providing such a comprehensive analysis of QoE in mobile devices, combining network measurements with users QoE feedback in lab tests and operational networks.}, author = {Casas, Pedro and Seufert, Michael and Wamser, Florian and Gardlo, Bruno and Sackl, Andreas and Schatz, Raimund}, journal = {IEEE Transactions on Network and Service Management}, keywords = {can}, month = {03}, number = 2, pages = {181-196}, title = {Next to You: Monitoring Quality of Experience in Cellular Networks from the End-devices}, volume = 13, year = 2016 }

  %0 Journal Article %1 info3-article-2016-4 %A Casas, Pedro %A Seufert, Michael %A Wamser, Florian %A Gardlo, Bruno %A Sackl, Andreas %A Schatz, Raimund %D 2016 %J IEEE Transactions on Network and Service Management %N 2 %P 181-196 %T Next to You: Monitoring Quality of Experience in Cellular Networks from the End-devices %V 13 %X A quarter of the world population will be using smartphones to access the Internet in the near future. In this context, understanding the Quality of Experience (QoE) of popular apps in such devices becomes paramount to cellular network operators, who need to offer high quality levels to reduce the risks of customers churning for quality dissatisfaction. In this paper we address the problem of QoE provisioning in smartphones from a double perspective, combining the results obtained from subjective lab tests with end-device passive measurements and QoE crowd-sourced feedback obtained in operational cellular networks. The study addresses the impact of both access bandwidth and latency on the QoE of five different services and mobile apps: YouTube, Facebook, Web browsing through Chrome, Google Maps, and WhatsApp. We evaluate the influence of both constant and dynamically changing network access conditions, tackling in particular the case of fluctuating downlink bandwidth, which is typical in cellular networks. As a main contribution, we show that the results obtained in the lab are highly applicable in the live scenario, as mappings track the QoE provided by users in real networks. We additionally provide hints and bandwidth thresholds for good QoE levels on such apps, as well as discussion on end-device passive measurements and analysis. The results presented in this paper provide a sound basis to better understand the QoE requirements of popular mobile apps, as well as for monitoring the underlying provisioning network. To the best of our knowledge, this is the first paper providing such a comprehensive analysis of QoE in mobile devices, combining network measurements with users QoE feedback in lab tests and operational networks.
• Performance Evaluation of Backhaul Bandwidth Aggregation Using a Partial Sharing Scheme. Burger, Valentin; Seufert, Michael; Hoßfeld, Tobias; Tran-Gia, Phuoc. In Physical Communication, 19, pp. 135–144. 2016.
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  To cope with the increasing demand of mobile devices and the limited capacity of cellular networks mobile connections are offloaded to WiFi. The access capacity is further increased, by aggregating bandwidth of WiFi access links. To analyse the performance of aggregated access links we model the most simple case of two cooperating systems interchanging capacities using an offloading scheme. The resulting analytic model is computed by means of a two-dimensional birth and death process. It can be used to seamlessly evaluate the performance of systems between partitioning and complete sharing. This allows to optimize the setting of thresholds dependent on the load of the cooperating system. Furthermore the benefit of aggregating bandwidth in different scenarios with homogeneous and heterogeneous workloads is quantified and the performance of more than two cooperating systems is evaluated by simulation.

  @article{info3-article-2016-3, abstract = {To cope with the increasing demand of mobile devices and the limited capacity of cellular networks mobile connections are offloaded to WiFi. The access capacity is further increased, by aggregating bandwidth of WiFi access links. To analyse the performance of aggregated access links we model the most simple case of two cooperating systems interchanging capacities using an offloading scheme. The resulting analytic model is computed by means of a two-dimensional birth and death process. It can be used to seamlessly evaluate the performance of systems between partitioning and complete sharing. This allows to optimize the setting of thresholds dependent on the load of the cooperating system. Furthermore the benefit of aggregating bandwidth in different scenarios with homogeneous and heterogeneous workloads is quantified and the performance of more than two cooperating systems is evaluated by simulation.}, author = {Burger, Valentin and Seufert, Michael and Hoßfeld, Tobias and Tran-Gia, Phuoc}, journal = {Physical Communication}, keywords = {can}, month = {06}, pages = {135-144}, title = {Performance Evaluation of Backhaul Bandwidth Aggregation Using a Partial Sharing Scheme}, volume = 19, year = 2016 }

  %0 Journal Article %1 info3-article-2016-3 %A Burger, Valentin %A Seufert, Michael %A Hoßfeld, Tobias %A Tran-Gia, Phuoc %D 2016 %J Physical Communication %P 135-144 %T Performance Evaluation of Backhaul Bandwidth Aggregation Using a Partial Sharing Scheme %V 19 %X To cope with the increasing demand of mobile devices and the limited capacity of cellular networks mobile connections are offloaded to WiFi. The access capacity is further increased, by aggregating bandwidth of WiFi access links. To analyse the performance of aggregated access links we model the most simple case of two cooperating systems interchanging capacities using an offloading scheme. The resulting analytic model is computed by means of a two-dimensional birth and death process. It can be used to seamlessly evaluate the performance of systems between partitioning and complete sharing. This allows to optimize the setting of thresholds dependent on the load of the cooperating system. Furthermore the benefit of aggregating bandwidth in different scenarios with homogeneous and heterogeneous workloads is quantified and the performance of more than two cooperating systems is evaluated by simulation.
• Perceptual Quality of HTTP Adaptive Streaming Strategies: Cross-Experimental Analysis of Multi-Laboratory and Crowdsourced Subjective Studies. Tavakoli, Samira; Egger, Sebastian; Seufert, Michael; Schatz, Raimund; Brunnström, Kjell; García, Narciso. In IEEE Journal on Selected Areas in Communications, 34(8), pp. 2141–2153. 2016.
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  Today’s packet-switched networks are subject to bandwidth fluctuations that cause for degradation of user experience of multimedia services. In order to cope with this problem, HTTP Adaptive Streaming (HAS) has been proposed in recent years as a video delivery solution for the future Internet and being adopted by an increasing number of streaming services such as Netflix and Youtube. HAS enables service providers to improve users’ Quality of Experience (QoE) and network resource utilization by adapting the quality of the video stream to the current network conditions. However, the resulting timevarying video quality caused by adaptation introduces a new type of impairment and thus novel QoE research challenges. Despite of various recent attempts to investigate these challenges, many fundamental questions regarding HAS perceptual performance are still open. In this paper, the QoE impact of different technical adaptation parameters including chunk length, switching amplitude, switching frequency and temporal recency are investigated. In addition, the influence of content on perceptual quality of these parameters is analyzed. To this end, a large number of adaptation scenarios have been subjectively evaluated in four laboratory experiments and one crowdsourcing study. Statistical analysis of the combined dataset reveals results that partly contradict widely held assumptions and provide novel insights in perceptual quality of adapted video sequences, e.g. interaction effects between quality switching direction (up/down) and switching strategy (smooth/abrupt). The large variety of experimental configurations across different studies ensures the consistency and external validity of the presented results that can be utilized for enhancing the perceptual performance of adaptive streaming services.

  @article{info3-article-2016-5, abstract = {Today’s packet-switched networks are subject to bandwidth fluctuations that cause for degradation of user experience of multimedia services. In order to cope with this problem, HTTP Adaptive Streaming (HAS) has been proposed in recent years as a video delivery solution for the future Internet and being adopted by an increasing number of streaming services such as Netflix and Youtube. HAS enables service providers to improve users’ Quality of Experience (QoE) and network resource utilization by adapting the quality of the video stream to the current network conditions. However, the resulting timevarying video quality caused by adaptation introduces a new type of impairment and thus novel QoE research challenges. Despite of various recent attempts to investigate these challenges, many fundamental questions regarding HAS perceptual performance are still open. In this paper, the QoE impact of different technical adaptation parameters including chunk length, switching amplitude, switching frequency and temporal recency are investigated. In addition, the influence of content on perceptual quality of these parameters is analyzed. To this end, a large number of adaptation scenarios have been subjectively evaluated in four laboratory experiments and one crowdsourcing study. Statistical analysis of the combined dataset reveals results that partly contradict widely held assumptions and provide novel insights in perceptual quality of adapted video sequences, e.g. interaction effects between quality switching direction (up/down) and switching strategy (smooth/abrupt). The large variety of experimental configurations across different studies ensures the consistency and external validity of the presented results that can be utilized for enhancing the perceptual performance of adaptive streaming services.}, author = {Tavakoli, Samira and Egger, Sebastian and Seufert, Michael and Schatz, Raimund and Brunnström, Kjell and García, Narciso}, journal = {IEEE Journal on Selected Areas in Communications}, keywords = {can}, month = {06}, number = 8, pages = {2141-2153}, title = {Perceptual Quality of HTTP Adaptive Streaming Strategies: Cross-Experimental Analysis of Multi-Laboratory and Crowdsourced Subjective Studies}, volume = 34, year = 2016 }

  %0 Journal Article %1 info3-article-2016-5 %A Tavakoli, Samira %A Egger, Sebastian %A Seufert, Michael %A Schatz, Raimund %A Brunnström, Kjell %A García, Narciso %D 2016 %J IEEE Journal on Selected Areas in Communications %N 8 %P 2141-2153 %T Perceptual Quality of HTTP Adaptive Streaming Strategies: Cross-Experimental Analysis of Multi-Laboratory and Crowdsourced Subjective Studies %V 34 %X Today’s packet-switched networks are subject to bandwidth fluctuations that cause for degradation of user experience of multimedia services. In order to cope with this problem, HTTP Adaptive Streaming (HAS) has been proposed in recent years as a video delivery solution for the future Internet and being adopted by an increasing number of streaming services such as Netflix and Youtube. HAS enables service providers to improve users’ Quality of Experience (QoE) and network resource utilization by adapting the quality of the video stream to the current network conditions. However, the resulting timevarying video quality caused by adaptation introduces a new type of impairment and thus novel QoE research challenges. Despite of various recent attempts to investigate these challenges, many fundamental questions regarding HAS perceptual performance are still open. In this paper, the QoE impact of different technical adaptation parameters including chunk length, switching amplitude, switching frequency and temporal recency are investigated. In addition, the influence of content on perceptual quality of these parameters is analyzed. To this end, a large number of adaptation scenarios have been subjectively evaluated in four laboratory experiments and one crowdsourcing study. Statistical analysis of the combined dataset reveals results that partly contradict widely held assumptions and provide novel insights in perceptual quality of adapted video sequences, e.g. interaction effects between quality switching direction (up/down) and switching strategy (smooth/abrupt). The large variety of experimental configurations across different studies ensures the consistency and external validity of the presented results that can be utilized for enhancing the perceptual performance of adaptive streaming services.
• Assessment of Subjective Influence and Trust with an Online Social Network Game. Seufert, Michael; Burger, Valentin; Lorey, Karl; Seith, Alexander; Loh, Frank; Tran-Gia, Phuoc. In Computers in Human Behavior, 64, pp. 233–246. 2016.
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  The deduction of influence and trust between two individuals only from objective data in online social networks (OSNs) is a rather vague approach. Subjective assessments via surveys produce better results, but are harder to conduct considering the vast amount of friendships of OSN users. This work presents a framework for personalized surveys on relationships in OSNs, which follows a gamification approach. A Facebook game was developed, which was used to subjectively assess social influence and interpersonal trust based on models from psychology. The results show that it is possible to obtain subjective opinions and (limited) objective data about relationships with an OSN game. Also an implicit assessment of influence and trust with subcategory questions is feasible in this case.

  @article{info3-article-2016-7, abstract = {The deduction of influence and trust between two individuals only from objective data in online social networks (OSNs) is a rather vague approach. Subjective assessments via surveys produce better results, but are harder to conduct considering the vast amount of friendships of OSN users. This work presents a framework for personalized surveys on relationships in OSNs, which follows a gamification approach. A Facebook game was developed, which was used to subjectively assess social influence and interpersonal trust based on models from psychology. The results show that it is possible to obtain subjective opinions and (limited) objective data about relationships with an OSN game. Also an implicit assessment of influence and trust with subcategory questions is feasible in this case.}, author = {Seufert, Michael and Burger, Valentin and Lorey, Karl and Seith, Alexander and Loh, Frank and Tran-Gia, Phuoc}, journal = {Computers in Human Behavior}, keywords = {can}, month = 11, pages = {233-246}, title = {Assessment of Subjective Influence and Trust with an Online Social Network Game}, volume = 64, year = 2016 }

  %0 Journal Article %1 info3-article-2016-7 %A Seufert, Michael %A Burger, Valentin %A Lorey, Karl %A Seith, Alexander %A Loh, Frank %A Tran-Gia, Phuoc %D 2016 %J Computers in Human Behavior %P 233-246 %T Assessment of Subjective Influence and Trust with an Online Social Network Game %V 64 %X The deduction of influence and trust between two individuals only from objective data in online social networks (OSNs) is a rather vague approach. Subjective assessments via surveys produce better results, but are harder to conduct considering the vast amount of friendships of OSN users. This work presents a framework for personalized surveys on relationships in OSNs, which follows a gamification approach. A Facebook game was developed, which was used to subjectively assess social influence and interpersonal trust based on models from psychology. The results show that it is possible to obtain subjective opinions and (limited) objective data about relationships with an OSN game. Also an implicit assessment of influence and trust with subcategory questions is feasible in this case.
• Modeling the YouTube Stack: from Packets to Quality of Experience. Wamser, Florian; Casas, Pedro; Seufert, Michael; Moldovan, Christian; Tran-Gia, Phuoc; Hoßfeld, Tobias. In Computer Networks, 109(2), pp. 211–224. 2016.
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  YouTube is one of the most popular and volume-dominant services in today’s Internet, and has changed the Web for ever. Consequently, network operators are forced to consider it in the design, deployment, and optimization of their networks. Taming YouTube requires a good understanding of the complete YouTube stack, from the network streaming service to the application itself. Understanding the interplays between individual YouTube functionalities and their implications for traffic and user Quality of Experience (QoE) becomes paramount nowadays. In this paper we characterize and model the YouTube stack at different layers, going from the generated network traffic to the QoE perceived by the users watching YouTube videos. Firstly, we present a network traffic model for the YouTube flow control mechanism, which permits to understand how YouTube provisions video traffic flows to users. Secondly, we investigate how traffic is consumed at the client side, deriving a simple model for the YouTube application. Thirdly, we analyze the implications for the end user, and present a model for the quality as perceived by them. This model is finally integrated into a system for real time QoE-based YouTube monitoring, highly useful to operators to assess the performance of their networks for provisioning YouTube videos. The central parameter for all the presented models is the buffer level at the YouTube application layer. This paper provides an extensive compendium of objective tools and models for network operators to better understand the YouTube traffic in their networks, to predict the playback behavior of the video player, and to assess how well they do it in the practice with the satisfaction of their customers watching YouTube.

  @article{info3-article-2016-6, abstract = {YouTube is one of the most popular and volume-dominant services in today’s Internet, and has changed the Web for ever. Consequently, network operators are forced to consider it in the design, deployment, and optimization of their networks. Taming YouTube requires a good understanding of the complete YouTube stack, from the network streaming service to the application itself. Understanding the interplays between individual YouTube functionalities and their implications for traffic and user Quality of Experience (QoE) becomes paramount nowadays. In this paper we characterize and model the YouTube stack at different layers, going from the generated network traffic to the QoE perceived by the users watching YouTube videos. Firstly, we present a network traffic model for the YouTube flow control mechanism, which permits to understand how YouTube provisions video traffic flows to users. Secondly, we investigate how traffic is consumed at the client side, deriving a simple model for the YouTube application. Thirdly, we analyze the implications for the end user, and present a model for the quality as perceived by them. This model is finally integrated into a system for real time QoE-based YouTube monitoring, highly useful to operators to assess the performance of their networks for provisioning YouTube videos. The central parameter for all the presented models is the buffer level at the YouTube application layer. This paper provides an extensive compendium of objective tools and models for network operators to better understand the YouTube traffic in their networks, to predict the playback behavior of the video player, and to assess how well they do it in the practice with the satisfaction of their customers watching YouTube.}, author = {Wamser, Florian and Casas, Pedro and Seufert, Michael and Moldovan, Christian and Tran-Gia, Phuoc and Hoßfeld, Tobias}, journal = {Computer Networks}, keywords = {can}, month = 11, number = 2, pages = {211-224}, title = {Modeling the YouTube Stack: from Packets to Quality of Experience}, volume = 109, year = 2016 }

  %0 Journal Article %1 info3-article-2016-6 %A Wamser, Florian %A Casas, Pedro %A Seufert, Michael %A Moldovan, Christian %A Tran-Gia, Phuoc %A Hoßfeld, Tobias %D 2016 %J Computer Networks %N 2 %P 211-224 %T Modeling the YouTube Stack: from Packets to Quality of Experience %V 109 %X YouTube is one of the most popular and volume-dominant services in today’s Internet, and has changed the Web for ever. Consequently, network operators are forced to consider it in the design, deployment, and optimization of their networks. Taming YouTube requires a good understanding of the complete YouTube stack, from the network streaming service to the application itself. Understanding the interplays between individual YouTube functionalities and their implications for traffic and user Quality of Experience (QoE) becomes paramount nowadays. In this paper we characterize and model the YouTube stack at different layers, going from the generated network traffic to the QoE perceived by the users watching YouTube videos. Firstly, we present a network traffic model for the YouTube flow control mechanism, which permits to understand how YouTube provisions video traffic flows to users. Secondly, we investigate how traffic is consumed at the client side, deriving a simple model for the YouTube application. Thirdly, we analyze the implications for the end user, and present a model for the quality as perceived by them. This model is finally integrated into a system for real time QoE-based YouTube monitoring, highly useful to operators to assess the performance of their networks for provisioning YouTube videos. The central parameter for all the presented models is the buffer level at the YouTube application layer. This paper provides an extensive compendium of objective tools and models for network operators to better understand the YouTube traffic in their networks, to predict the playback behavior of the video player, and to assess how well they do it in the practice with the satisfaction of their customers watching YouTube.

• Crowdsourced Network Measurements: Benefits and Best Practices. Hirth, Matthias; Hoßfeld, Tobias; Mellia, Marco; Schwartz, Christian; Lehrieder, Frank. In Computer Networks Special Issue on Crowdsourcing. 2015.
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  Network measurements are of high importance both for the operation of networks and for the design and evaluation of new management mechanisms. Therefore, several approaches exist for running network measurements, ranging from analyzing live traffic traces from campus or Internet Service Provider (ISP) networks to performing active measurements on distributed testbeds, e.g., PlanetLab, or involving volunteers. However, each method falls short, offering only a partial view of the network. For instance, the scope of passive traffic traces is limited to an ISP’s network and customers’ habits, whereas active measurements might be biased by the population or node location involved. To complement these techniques, we pro- pose to use (commercial) crowdsourcing platforms for network measurements. They permit a controllable, diverse and realistic view of the Internet and pro- vide better control than do measurements with voluntary participants. In this study, we compare crowdsourcing with traditional measurement techniques, describe possible pitfalls and limitations, and present best practices to overcome these issues. The contribution of this paper is a guideline for researchers to understand when and how to exploit crowdsourcing for network measurements.

  @article{info3-article-2015-135, abstract = {Network measurements are of high importance both for the operation of networks and for the design and evaluation of new management mechanisms. Therefore, several approaches exist for running network measurements, ranging from analyzing live traffic traces from campus or Internet Service Provider (ISP) networks to performing active measurements on distributed testbeds, e.g., PlanetLab, or involving volunteers. However, each method falls short, offering only a partial view of the network. For instance, the scope of passive traffic traces is limited to an ISP’s network and customers’ habits, whereas active measurements might be biased by the population or node location involved. To complement these techniques, we pro- pose to use (commercial) crowdsourcing platforms for network measurements. They permit a controllable, diverse and realistic view of the Internet and pro- vide better control than do measurements with voluntary participants. In this study, we compare crowdsourcing with traditional measurement techniques, describe possible pitfalls and limitations, and present best practices to overcome these issues. The contribution of this paper is a guideline for researchers to understand when and how to exploit crowdsourcing for network measurements.}, author = {Hirth, Matthias and Hoßfeld, Tobias and Mellia, Marco and Schwartz, Christian and Lehrieder, Frank}, journal = {Computer Networks Special Issue on Crowdsourcing}, keywords = {sys:hidden:article}, title = {Crowdsourced Network Measurements: Benefits and Best Practices}, year = 2015 }

  %0 Journal Article %1 info3-article-2015-135 %A Hirth, Matthias %A Hoßfeld, Tobias %A Mellia, Marco %A Schwartz, Christian %A Lehrieder, Frank %D 2015 %J Computer Networks Special Issue on Crowdsourcing %T Crowdsourced Network Measurements: Benefits and Best Practices %X Network measurements are of high importance both for the operation of networks and for the design and evaluation of new management mechanisms. Therefore, several approaches exist for running network measurements, ranging from analyzing live traffic traces from campus or Internet Service Provider (ISP) networks to performing active measurements on distributed testbeds, e.g., PlanetLab, or involving volunteers. However, each method falls short, offering only a partial view of the network. For instance, the scope of passive traffic traces is limited to an ISP’s network and customers’ habits, whereas active measurements might be biased by the population or node location involved. To complement these techniques, we pro- pose to use (commercial) crowdsourcing platforms for network measurements. They permit a controllable, diverse and realistic view of the Internet and pro- vide better control than do measurements with voluntary participants. In this study, we compare crowdsourcing with traditional measurement techniques, describe possible pitfalls and limitations, and present best practices to overcome these issues. The contribution of this paper is a guideline for researchers to understand when and how to exploit crowdsourcing for network measurements.
• Heuristic Approaches to the Controller Placement Problem in Large Scale SDN Networks. Lange, Stanislav; Gebert, Steffen; Zinner, Thomas; Tran-Gia, Phuoc; Hock, David; Jarschel, Michael; Hoffmann, Marco. In IEEE Transactions on Network and Service Management - Special Issue on Efficient Management of SDN and NFV-based Systems, 12(1), pp. 4–17. 2015.
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  Software Defined Networking (SDN) marks a paradigm shift towards an externalized and logically centralized network control plane. A particularly important task in SDN architectures is that of controller placement, i.e., the positioning of a limited number of resources within a network in order to meet various requirements. These requirements range from latency constraints to failure tolerance and load balancing. In most scenarios, at least some of these objectives are competing, thus no single best placement is available and decision makers need to find a balanced trade-off. This work presents POCO, a framework for Pareto-based Optimal COntroller placement that provides operators with Pareto optimal placements with respect to different performance metrics. In its default configuration, POCO performs an exhaustive evaluation of all possible placements. While this is practically feasible for small and medium sized networks, realistic time and resource constraints call for an alternative in the context of large scale networks or dynamic networks whose properties change over time. For these scenarios, the POCO toolset is extended by a heuristic approach that is less accurate, but yields faster computation times. An evaluation of this heuristic is performed on a collection of real world network topologies from the Internet Topology Zoo. Utilizing a measure for quantifying the error introduced by the heuristic approach allows an analysis of the resulting trade-off between time and accuracy. Additionally, the proposed methods can be extended to solve similar virtual functions placement problems which appear in the context of Network Functions Virtualization (NFV).

  @article{info3-article-2015-131, abstract = {Software Defined Networking (SDN) marks a paradigm shift towards an externalized and logically centralized network control plane. A particularly important task in SDN architectures is that of controller placement, i.e., the positioning of a limited number of resources within a network in order to meet various requirements. These requirements range from latency constraints to failure tolerance and load balancing. In most scenarios, at least some of these objectives are competing, thus no single best placement is available and decision makers need to find a balanced trade-off. This work presents POCO, a framework for Pareto-based Optimal COntroller placement that provides operators with Pareto optimal placements with respect to different performance metrics. In its default configuration, POCO performs an exhaustive evaluation of all possible placements. While this is practically feasible for small and medium sized networks, realistic time and resource constraints call for an alternative in the context of large scale networks or dynamic networks whose properties change over time. For these scenarios, the POCO toolset is extended by a heuristic approach that is less accurate, but yields faster computation times. An evaluation of this heuristic is performed on a collection of real world network topologies from the Internet Topology Zoo. Utilizing a measure for quantifying the error introduced by the heuristic approach allows an analysis of the resulting trade-off between time and accuracy. Additionally, the proposed methods can be extended to solve similar virtual functions placement problems which appear in the context of Network Functions Virtualization (NFV).}, author = {Lange, Stanislav and Gebert, Steffen and Zinner, Thomas and Tran-Gia, Phuoc and Hock, David and Jarschel, Michael and Hoffmann, Marco}, journal = {IEEE Transactions on Network and Service Management - Special Issue on Efficient Management of SDN and NFV-based Systems}, keywords = {poco}, number = 1, pages = {4 - 17}, title = {Heuristic Approaches to the Controller Placement Problem in Large Scale SDN Networks}, volume = 12, year = 2015 }

  %0 Journal Article %1 info3-article-2015-131 %A Lange, Stanislav %A Gebert, Steffen %A Zinner, Thomas %A Tran-Gia, Phuoc %A Hock, David %A Jarschel, Michael %A Hoffmann, Marco %D 2015 %J IEEE Transactions on Network and Service Management - Special Issue on Efficient Management of SDN and NFV-based Systems %N 1 %P 4 - 17 %T Heuristic Approaches to the Controller Placement Problem in Large Scale SDN Networks %V 12 %X Software Defined Networking (SDN) marks a paradigm shift towards an externalized and logically centralized network control plane. A particularly important task in SDN architectures is that of controller placement, i.e., the positioning of a limited number of resources within a network in order to meet various requirements. These requirements range from latency constraints to failure tolerance and load balancing. In most scenarios, at least some of these objectives are competing, thus no single best placement is available and decision makers need to find a balanced trade-off. This work presents POCO, a framework for Pareto-based Optimal COntroller placement that provides operators with Pareto optimal placements with respect to different performance metrics. In its default configuration, POCO performs an exhaustive evaluation of all possible placements. While this is practically feasible for small and medium sized networks, realistic time and resource constraints call for an alternative in the context of large scale networks or dynamic networks whose properties change over time. For these scenarios, the POCO toolset is extended by a heuristic approach that is less accurate, but yields faster computation times. An evaluation of this heuristic is performed on a collection of real world network topologies from the Internet Topology Zoo. Utilizing a measure for quantifying the error introduced by the heuristic approach allows an analysis of the resulting trade-off between time and accuracy. Additionally, the proposed methods can be extended to solve similar virtual functions placement problems which appear in the context of Network Functions Virtualization (NFV).
• Special issue on crowdsourcing. Hoßfeld, Tobias; Tran-Gia, Phuoc; Vukovic, Maja. In Computer Networks: The International Journal of Computer and Telecommunications Networking. 2015.
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  @article{info3-article-2015-10, author = {Hoßfeld, Tobias and Tran-Gia, Phuoc and Vukovic, Maja}, journal = {Computer Networks: The International Journal of Computer and Telecommunications Networking}, keywords = {sys:hidden:article}, title = {Special issue on crowdsourcing}, year = 2015 }

  %0 Journal Article %1 info3-article-2015-10 %A Hoßfeld, Tobias %A Tran-Gia, Phuoc %A Vukovic, Maja %D 2015 %J Computer Networks: The International Journal of Computer and Telecommunications Networking %T Special issue on crowdsourcing
• A Survey on Quality of Experience of HTTP Adaptive Streaming. Seufert, Michael; Egger, Sebastian; Slanina, Martin; Zinner, Thomas; Hoßfeld, Tobias; Tran-Gia, Phuoc. In IEEE Communications Surveys & Tutorials, 17, pp. 469–492. 2015.
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  Changing network conditions pose severe problems to video streaming in the Internet. HTTP adaptive streaming (HAS) is a technology employed by numerous video services which relieves these issues by adapting the video to the current network conditions. It enables service providers to improve resource utilization and Quality of Experience (QoE) by incorporating information from different layers in order to deliver and adapt a video in its best possible quality. Thereby, it allows to take into account end user device capabilities, available video quality levels, current network conditions, and current server load. For end users, the major benefits of HAS compared to classical HTTP video streaming are reduced interruptions of the video playback and higher bandwidth utilization, which both generally result in a higher QoE. Adaptation is possible by changing the frame rate, resolution, or quantization of the video, which can be done with various adaptation strategies and related client- and server-side actions. The technical development of HAS, existing open standardized solutions, but also proprietary solutions are reviewed in this article as fundament to derive the QoE influence factors which emerge as a result of adaptation. The main contribution is a comprehensive survey of QoE related works from human computer interaction and networking domains which are structured according to the QoE impact of video adaptation. To be more precise, subjective studies which cover QoE aspects of adaptation dimensions and strategies are revisited. As a result, QoE influence factors of HAS and corresponding QoE models are identified, but also open issues and conflicting results are discussed. Furthermore, technical influence factors, which are often ignored in the context of HAS, affect perceptual QoE influence factors and are consequently analyzed. This survey gives the reader an overview of the current state of the art and recent developments. At the same time it targets networking researchers who develop new solutions for HTTP video streaming or assess video streaming from a user centric point of view. Therefore, the article is a major step towards truly improving HAS.

  @article{info3-article-2015-126, abstract = {Changing network conditions pose severe problems to video streaming in the Internet. HTTP adaptive streaming (HAS) is a technology employed by numerous video services which relieves these issues by adapting the video to the current network conditions. It enables service providers to improve resource utilization and Quality of Experience (QoE) by incorporating information from different layers in order to deliver and adapt a video in its best possible quality. Thereby, it allows to take into account end user device capabilities, available video quality levels, current network conditions, and current server load. For end users, the major benefits of HAS compared to classical HTTP video streaming are reduced interruptions of the video playback and higher bandwidth utilization, which both generally result in a higher QoE. Adaptation is possible by changing the frame rate, resolution, or quantization of the video, which can be done with various adaptation strategies and related client- and server-side actions. The technical development of HAS, existing open standardized solutions, but also proprietary solutions are reviewed in this article as fundament to derive the QoE influence factors which emerge as a result of adaptation. The main contribution is a comprehensive survey of QoE related works from human computer interaction and networking domains which are structured according to the QoE impact of video adaptation. To be more precise, subjective studies which cover QoE aspects of adaptation dimensions and strategies are revisited. As a result, QoE influence factors of HAS and corresponding QoE models are identified, but also open issues and conflicting results are discussed. Furthermore, technical influence factors, which are often ignored in the context of HAS, affect perceptual QoE influence factors and are consequently analyzed. This survey gives the reader an overview of the current state of the art and recent developments. At the same time it targets networking researchers who develop new solutions for HTTP video streaming or assess video streaming from a user centric point of view. Therefore, the article is a major step towards truly improving HAS.}, author = {Seufert, Michael and Egger, Sebastian and Slanina, Martin and Zinner, Thomas and Hoßfeld, Tobias and Tran-Gia, Phuoc}, journal = {IEEE Communications Surveys & Tutorials}, keywords = {sys:hidden:article}, month = {03}, pages = {469-492}, title = {A Survey on Quality of Experience of HTTP Adaptive Streaming}, volume = 17, year = 2015 }

  %0 Journal Article %1 info3-article-2015-126 %A Seufert, Michael %A Egger, Sebastian %A Slanina, Martin %A Zinner, Thomas %A Hoßfeld, Tobias %A Tran-Gia, Phuoc %D 2015 %J IEEE Communications Surveys & Tutorials %P 469-492 %T A Survey on Quality of Experience of HTTP Adaptive Streaming %V 17 %X Changing network conditions pose severe problems to video streaming in the Internet. HTTP adaptive streaming (HAS) is a technology employed by numerous video services which relieves these issues by adapting the video to the current network conditions. It enables service providers to improve resource utilization and Quality of Experience (QoE) by incorporating information from different layers in order to deliver and adapt a video in its best possible quality. Thereby, it allows to take into account end user device capabilities, available video quality levels, current network conditions, and current server load. For end users, the major benefits of HAS compared to classical HTTP video streaming are reduced interruptions of the video playback and higher bandwidth utilization, which both generally result in a higher QoE. Adaptation is possible by changing the frame rate, resolution, or quantization of the video, which can be done with various adaptation strategies and related client- and server-side actions. The technical development of HAS, existing open standardized solutions, but also proprietary solutions are reviewed in this article as fundament to derive the QoE influence factors which emerge as a result of adaptation. The main contribution is a comprehensive survey of QoE related works from human computer interaction and networking domains which are structured according to the QoE impact of video adaptation. To be more precise, subjective studies which cover QoE aspects of adaptation dimensions and strategies are revisited. As a result, QoE influence factors of HAS and corresponding QoE models are identified, but also open issues and conflicting results are discussed. Furthermore, technical influence factors, which are often ignored in the context of HAS, affect perceptual QoE influence factors and are consequently analyzed. This survey gives the reader an overview of the current state of the art and recent developments. At the same time it targets networking researchers who develop new solutions for HTTP video streaming or assess video streaming from a user centric point of view. Therefore, the article is a major step towards truly improving HAS.
• Network Functions Virtualization (NFV) und Software Defined Networking (SDN): Forschungsfragen und Anwendungsfälle. Blenk, Andreas; Basta, Arsany; Kellerer, Wolfgang; Zinner, Thomas; Wamser, Florian; Tran-Gia, Phuoc. In ITG Mitgliederbeiträge / VDE dialog (invited article), pp. 10–13. 2015.
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  @article{info3-article-2015-8, author = {Blenk, Andreas and Basta, Arsany and Kellerer, Wolfgang and Zinner, Thomas and Wamser, Florian and Tran-Gia, Phuoc}, journal = {ITG Mitgliederbeiträge / VDE dialog (invited article)}, keywords = {sys:hidden:article}, month = {01}, pages = {10-13}, title = {Network Functions Virtualization (NFV) und Software Defined Networking (SDN): Forschungsfragen und Anwendungsfälle}, year = 2015 }

  %0 Journal Article %1 info3-article-2015-8 %A Blenk, Andreas %A Basta, Arsany %A Kellerer, Wolfgang %A Zinner, Thomas %A Wamser, Florian %A Tran-Gia, Phuoc %D 2015 %J ITG Mitgliederbeiträge / VDE dialog (invited article) %P 10-13 %T Network Functions Virtualization (NFV) und Software Defined Networking (SDN): Forschungsfragen und Anwendungsfälle
• Identifying QoE Optimal Adaptation of HTTP Adaptive Streaming Based on Subjective Studies. Hoßfeld, Tobias; Seufert, Michael; Sieber, Christian; Zinner, Thomas; Tran-Gia, Phuoc. In Computer Networks, 81, pp. 320–332. 2015.
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  HTTP Adaptive Streaming (HAS) technologies, e.g., Apple HLS or MPEG-DASH, automatically adapt the delivered video quality to the available network. This reduces stalling of the video but additionally introduces quality switches, which also influence the user-perceived Quality of Experience (QoE). In this work, we conduct a subjective study to identify the impact of adaptation parameters on QoE. The results indicate that the video quality has to be maximized first, and that the number of quality switches is less important. Based on these results, a method to compute the optimal QoE-optimal adaptation strategy for HAS on a per user basis with mixed-integer linear programming is presented. This QoE-optimal adaptation enables the benchmarking of existing adaptation algorithms for any given network condition. Moreover, the investigated concept is extended to a multi-user IPTV scenario. The question is answered whether video quality, and thereby, the QoE can be shared in a fair manner among the involved users.

  @article{info3-article-2015-132, abstract = {HTTP Adaptive Streaming (HAS) technologies, e.g., Apple HLS or MPEG-DASH, automatically adapt the delivered video quality to the available network. This reduces stalling of the video but additionally introduces quality switches, which also influence the user-perceived Quality of Experience (QoE). In this work, we conduct a subjective study to identify the impact of adaptation parameters on QoE. The results indicate that the video quality has to be maximized first, and that the number of quality switches is less important. Based on these results, a method to compute the optimal QoE-optimal adaptation strategy for HAS on a per user basis with mixed-integer linear programming is presented. This QoE-optimal adaptation enables the benchmarking of existing adaptation algorithms for any given network condition. Moreover, the investigated concept is extended to a multi-user IPTV scenario. The question is answered whether video quality, and thereby, the QoE can be shared in a fair manner among the involved users.}, author = {Hoßfeld, Tobias and Seufert, Michael and Sieber, Christian and Zinner, Thomas and Tran-Gia, Phuoc}, journal = {Computer Networks}, keywords = {sys:hidden:article}, month = {04}, pages = {320-332}, title = {Identifying QoE Optimal Adaptation of HTTP Adaptive Streaming Based on Subjective Studies}, volume = 81, year = 2015 }

  %0 Journal Article %1 info3-article-2015-132 %A Hoßfeld, Tobias %A Seufert, Michael %A Sieber, Christian %A Zinner, Thomas %A Tran-Gia, Phuoc %D 2015 %J Computer Networks %P 320-332 %T Identifying QoE Optimal Adaptation of HTTP Adaptive Streaming Based on Subjective Studies %V 81 %X HTTP Adaptive Streaming (HAS) technologies, e.g., Apple HLS or MPEG-DASH, automatically adapt the delivered video quality to the available network. This reduces stalling of the video but additionally introduces quality switches, which also influence the user-perceived Quality of Experience (QoE). In this work, we conduct a subjective study to identify the impact of adaptation parameters on QoE. The results indicate that the video quality has to be maximized first, and that the number of quality switches is less important. Based on these results, a method to compute the optimal QoE-optimal adaptation strategy for HAS on a per user basis with mixed-integer linear programming is presented. This QoE-optimal adaptation enables the benchmarking of existing adaptation algorithms for any given network condition. Moreover, the investigated concept is extended to a multi-user IPTV scenario. The question is answered whether video quality, and thereby, the QoE can be shared in a fair manner among the involved users.
• Modeling and Performance Analysis of Application-Aware Resource Management. Wamser, Florian; Blenk, Andreas; Seufert, Michael; Zinner, Thomas; Kellerer, Wolfgang; Tran-Gia, Phuoc. In International Journal of Network Management, 25, pp. 223–241. 2015.
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  Application-aware resource management is the approach to tailor access networks to have characteristics beneficial for the running applications and services. This is achieved through the monitoring and integration of key performance indicators from the application layer within the network resource management. The aim is to increase user-perceived quality and network resource efficiency by traffic engineering with the help of these indicators. Using analytic and simulative approaches, this paper provides analysis methods for network operators to quantify the performance gains of alternative resource allocation algorithms that implement the application-aware concept. Network operators can use the proposed methods to evaluate possible performance gain trade-offs between investing in a pure capacity increase (over-provisioning) and the realization of an application-aware resource allocation. For this purpose, we model and analyze the application quality trade-offs of four algorithms for application-aware resource management at a single link in varying traffic situations. The algorithms are chosen with respect to different complexity and implementation level in order to cover the design space in a systematic way. The study of the algorithms focuses on the application-layer performance for the most used applications today, namely web browsing and video streaming with constant bit-rate as well as HTTP progressive streaming with variable bit-rate. Application quality trade-offs are analyzed in particular for a high resource utilization at a bottleneck link. The results confirm that application-aware resource management outperforms best-effort resource management in terms of QoE. Moreover, our study provides guidelines for the selection and configuration of the evaluated algorithms.

  @article{info3-article-2015-134, abstract = {Application-aware resource management is the approach to tailor access networks to have characteristics beneficial for the running applications and services. This is achieved through the monitoring and integration of key performance indicators from the application layer within the network resource management. The aim is to increase user-perceived quality and network resource efficiency by traffic engineering with the help of these indicators. Using analytic and simulative approaches, this paper provides analysis methods for network operators to quantify the performance gains of alternative resource allocation algorithms that implement the application-aware concept. Network operators can use the proposed methods to evaluate possible performance gain trade-offs between investing in a pure capacity increase (over-provisioning) and the realization of an application-aware resource allocation. For this purpose, we model and analyze the application quality trade-offs of four algorithms for application-aware resource management at a single link in varying traffic situations. The algorithms are chosen with respect to different complexity and implementation level in order to cover the design space in a systematic way. The study of the algorithms focuses on the application-layer performance for the most used applications today, namely web browsing and video streaming with constant bit-rate as well as HTTP progressive streaming with variable bit-rate. Application quality trade-offs are analyzed in particular for a high resource utilization at a bottleneck link. The results confirm that application-aware resource management outperforms best-effort resource management in terms of QoE. Moreover, our study provides guidelines for the selection and configuration of the evaluated algorithms.}, author = {Wamser, Florian and Blenk, Andreas and Seufert, Michael and Zinner, Thomas and Kellerer, Wolfgang and Tran-Gia, Phuoc}, journal = {International Journal of Network Management}, keywords = {sys:hidden:article}, month = {07}, pages = {223-241}, title = {Modeling and Performance Analysis of Application-Aware Resource Management}, volume = 25, year = 2015 }

  %0 Journal Article %1 info3-article-2015-134 %A Wamser, Florian %A Blenk, Andreas %A Seufert, Michael %A Zinner, Thomas %A Kellerer, Wolfgang %A Tran-Gia, Phuoc %D 2015 %J International Journal of Network Management %P 223-241 %T Modeling and Performance Analysis of Application-Aware Resource Management %V 25 %X Application-aware resource management is the approach to tailor access networks to have characteristics beneficial for the running applications and services. This is achieved through the monitoring and integration of key performance indicators from the application layer within the network resource management. The aim is to increase user-perceived quality and network resource efficiency by traffic engineering with the help of these indicators. Using analytic and simulative approaches, this paper provides analysis methods for network operators to quantify the performance gains of alternative resource allocation algorithms that implement the application-aware concept. Network operators can use the proposed methods to evaluate possible performance gain trade-offs between investing in a pure capacity increase (over-provisioning) and the realization of an application-aware resource allocation. For this purpose, we model and analyze the application quality trade-offs of four algorithms for application-aware resource management at a single link in varying traffic situations. The algorithms are chosen with respect to different complexity and implementation level in order to cover the design space in a systematic way. The study of the algorithms focuses on the application-layer performance for the most used applications today, namely web browsing and video streaming with constant bit-rate as well as HTTP progressive streaming with variable bit-rate. Application quality trade-offs are analyzed in particular for a high resource utilization at a bottleneck link. The results confirm that application-aware resource management outperforms best-effort resource management in terms of QoE. Moreover, our study provides guidelines for the selection and configuration of the evaluated algorithms.
• QoE for Cloud Gaming. Hoßfeld, Tobias; Metzger, Florian; Jarschel, Michael. In IEEE Communications Society E-Letter. 2015.
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  Cloud Gaming combines the successful concepts of Cloud Computing and Online Gaming. It provides the entire game experience to the users by processing the game in the cloud and streaming the contents to the player. The player is no longer dependent on a specific type or quality of gaming hardware, but is able to use common devices. However, at the same time the end device needs a broadband internet connection and the ability to display a video stream properly. While this may reduce hardware costs for users and increase the revenue for developers by leaving out the retail chain, it also raises new challenges for Quality of Service (QoS) in terms of bandwidth and latency for the underlying network. In particular, there is a strong interest in the player’s Quality of Experience (QoE) by the involved stakeholders, ie, the game providers and the network operators. Given similar pricing schemes, players are likely to be influenced by expected and experienced quality. Thus, a provider is interested to understand QoE and to react on QoE problems by managing or adapting the service. There is also a strong academic interest, since QoE for cloud gaming as well as managing QoE for cloud gaming addresses a multitude of fascinating challenges in QoE. One might think that the topic of online video games is equally popular in research, but efforts are often solely focused on cloud gaming and its subjective QoE through user studies. Compared to plain video streaming, the inner properties of video games are not that straight-forward to observe from the outside. But to conduct proper measurements, it is essential to understand them.

  @article{info3-article-2015-9, abstract = {Cloud Gaming combines the successful concepts of Cloud Computing and Online Gaming. It provides the entire game experience to the users by processing the game in the cloud and streaming the contents to the player. The player is no longer dependent on a specific type or quality of gaming hardware, but is able to use common devices. However, at the same time the end device needs a broadband internet connection and the ability to display a video stream properly. While this may reduce hardware costs for users and increase the revenue for developers by leaving out the retail chain, it also raises new challenges for Quality of Service (QoS) in terms of bandwidth and latency for the underlying network. In particular, there is a strong interest in the player’s Quality of Experience (QoE) by the involved stakeholders, ie, the game providers and the network operators. Given similar pricing schemes, players are likely to be influenced by expected and experienced quality. Thus, a provider is interested to understand QoE and to react on QoE problems by managing or adapting the service. There is also a strong academic interest, since QoE for cloud gaming as well as managing QoE for cloud gaming addresses a multitude of fascinating challenges in QoE. One might think that the topic of online video games is equally popular in research, but efforts are often solely focused on cloud gaming and its subjective QoE through user studies. Compared to plain video streaming, the inner properties of video games are not that straight-forward to observe from the outside. But to conduct proper measurements, it is essential to understand them.}, author = {Hoßfeld, Tobias and Metzger, Florian and Jarschel, Michael}, journal = {IEEE Communications Society E-Letter}, keywords = {sys:hidden:article}, month = 11, title = {QoE for Cloud Gaming}, year = 2015 }

  %0 Journal Article %1 info3-article-2015-9 %A Hoßfeld, Tobias %A Metzger, Florian %A Jarschel, Michael %D 2015 %J IEEE Communications Society E-Letter %T QoE for Cloud Gaming %X Cloud Gaming combines the successful concepts of Cloud Computing and Online Gaming. It provides the entire game experience to the users by processing the game in the cloud and streaming the contents to the player. The player is no longer dependent on a specific type or quality of gaming hardware, but is able to use common devices. However, at the same time the end device needs a broadband internet connection and the ability to display a video stream properly. While this may reduce hardware costs for users and increase the revenue for developers by leaving out the retail chain, it also raises new challenges for Quality of Service (QoS) in terms of bandwidth and latency for the underlying network. In particular, there is a strong interest in the player’s Quality of Experience (QoE) by the involved stakeholders, ie, the game providers and the network operators. Given similar pricing schemes, players are likely to be influenced by expected and experienced quality. Thus, a provider is interested to understand QoE and to react on QoE problems by managing or adapting the service. There is also a strong academic interest, since QoE for cloud gaming as well as managing QoE for cloud gaming addresses a multitude of fascinating challenges in QoE. One might think that the topic of online video games is equally popular in research, but efforts are often solely focused on cloud gaming and its subjective QoE through user studies. Compared to plain video streaming, the inner properties of video games are not that straight-forward to observe from the outside. But to conduct proper measurements, it is essential to understand them.

• Future Internet Research and Experimentation: The G-Lab Approach. Schwerdel, Dennis; Reuther, Bernd; Zinner, Thomas; Müller, Paul; Tran-Gia, Phuoc. In Computer Networks. 2014.
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  The German Lab (G-Lab) project aims to investigate architectural concepts and technologies for a new inter-networking architecture as an integrated approach between theoretic and experimental studies. Thus G-Lab consists of two major fields of activities: research studies of future network components and the design and setup of experimental facilities. Both are controlled by the same community to ensure that the experimental facility meets the demands of the researchers. Researchers gain access to virtualized resources or may gain exclusive access to resources if necessary. We present the current setup of the experimental facility, describing the available hardware, management of the platform, the utilization of the PlanetLab software and the user management. Moreover, a new approach to setup and deploy virtual network topologies will be described.

  @article{info3-article-2014-119, abstract = {The German Lab (G-Lab) project aims to investigate architectural concepts and technologies for a new inter-networking architecture as an integrated approach between theoretic and experimental studies. Thus G-Lab consists of two major fields of activities: research studies of future network components and the design and setup of experimental facilities. Both are controlled by the same community to ensure that the experimental facility meets the demands of the researchers. Researchers gain access to virtualized resources or may gain exclusive access to resources if necessary. We present the current setup of the experimental facility, describing the available hardware, management of the platform, the utilization of the PlanetLab software and the user management. Moreover, a new approach to setup and deploy virtual network topologies will be described.}, author = {Schwerdel, Dennis and Reuther, Bernd and Zinner, Thomas and Müller, Paul and Tran-Gia, Phuoc}, journal = {Computer Networks}, keywords = {sys:hidden:article}, title = {Future Internet Research and Experimentation: The G-Lab Approach}, year = 2014 }

  %0 Journal Article %1 info3-article-2014-119 %A Schwerdel, Dennis %A Reuther, Bernd %A Zinner, Thomas %A Müller, Paul %A Tran-Gia, Phuoc %D 2014 %J Computer Networks %T Future Internet Research and Experimentation: The G-Lab Approach %X The German Lab (G-Lab) project aims to investigate architectural concepts and technologies for a new inter-networking architecture as an integrated approach between theoretic and experimental studies. Thus G-Lab consists of two major fields of activities: research studies of future network components and the design and setup of experimental facilities. Both are controlled by the same community to ensure that the experimental facility meets the demands of the researchers. Researchers gain access to virtualized resources or may gain exclusive access to resources if necessary. We present the current setup of the experimental facility, describing the available hardware, management of the platform, the utilization of the PlanetLab software and the user management. Moreover, a new approach to setup and deploy virtual network topologies will be described.
• A new power profiling method and power scaling mechanism for energy-aware NetFPGA gigabit router. Pham Ngoc, Nam; Nguyen Huu, Thanh; Vu Quang, Trong; Tran Hoang, Vu; Truong Thu, Huong; Tran-Gia, Phuoc; Schwartz, Christian. In Computer Networks. 2014.
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  Today the ICT industry accounts for 2–4% of the worldwide carbon emissions that are estimated to double in a business-as-usual scenario by 2020. A remarkable part of the large energy volume consumed in the Internet today is due to the over-provisioning of network resources such as routers, switches and links to meet the stringent requirements on reliability. Therefore, performance and energy issues are important factors in designing gigabit routers for future networks. However, the design and prototyping of energy-efficient routers is challenging because of multiple reasons, such as the lack of power measurements from live networks and a good understanding of how the energy consumption varies under different traffic loads and switch/router configuration settings. Moreover, the exact energy saving level gained by adopting different energy-efficient techniques in different hardware prototypes is often poorly known. In this article, we first propose a measurement framework that is able to quantify and profile the detailed energy consumption of sub-components in the NetFPGA OpenFlow switch. We then propose a new power-scaling algorithm that can adapt the operational clock frequencies as well as the corresponding energy consumption of the FPGA core and the Ethernet ports to the actual traffic load. We propose a new energy profiling method, which allows studying the detailed power performance of network devices. Results show that our energy efficient solution obtains higher level of energy efficiency compared to some existing approaches as the upper and lower bounds of power consumption of the NetFPGA Openflow switch are proved to be 30% lower than ones of the commercial HP Enterprise switch. Moreover, the new switch architecture can save up to 97% of dynamic power consumption of the FPGA chip at lowest frequency mode.

  @article{info3-article-2014-133, abstract = {Today the ICT industry accounts for 2–4% of the worldwide carbon emissions that are estimated to double in a business-as-usual scenario by 2020. A remarkable part of the large energy volume consumed in the Internet today is due to the over-provisioning of network resources such as routers, switches and links to meet the stringent requirements on reliability. Therefore, performance and energy issues are important factors in designing gigabit routers for future networks. However, the design and prototyping of energy-efficient routers is challenging because of multiple reasons, such as the lack of power measurements from live networks and a good understanding of how the energy consumption varies under different traffic loads and switch/router configuration settings. Moreover, the exact energy saving level gained by adopting different energy-efficient techniques in different hardware prototypes is often poorly known. In this article, we first propose a measurement framework that is able to quantify and profile the detailed energy consumption of sub-components in the NetFPGA OpenFlow switch. We then propose a new power-scaling algorithm that can adapt the operational clock frequencies as well as the corresponding energy consumption of the FPGA core and the Ethernet ports to the actual traffic load. We propose a new energy profiling method, which allows studying the detailed power performance of network devices. Results show that our energy efficient solution obtains higher level of energy efficiency compared to some existing approaches as the upper and lower bounds of power consumption of the NetFPGA Openflow switch are proved to be 30% lower than ones of the commercial HP Enterprise switch. Moreover, the new switch architecture can save up to 97% of dynamic power consumption of the FPGA chip at lowest frequency mode.}, author = {Pham Ngoc, Nam and Nguyen Huu, Thanh and Vu Quang, Trong and Tran Hoang, Vu and Truong Thu, Huong and Tran-Gia, Phuoc and Schwartz, Christian}, journal = {Computer Networks}, keywords = {sys:hidden:article}, title = {A new power profiling method and power scaling mechanism for energy-aware NetFPGA gigabit router}, year = 2014 }

  %0 Journal Article %1 info3-article-2014-133 %A Pham Ngoc, Nam %A Nguyen Huu, Thanh %A Vu Quang, Trong %A Tran Hoang, Vu %A Truong Thu, Huong %A Tran-Gia, Phuoc %A Schwartz, Christian %D 2014 %J Computer Networks %T A new power profiling method and power scaling mechanism for energy-aware NetFPGA gigabit router %X Today the ICT industry accounts for 2–4% of the worldwide carbon emissions that are estimated to double in a business-as-usual scenario by 2020. A remarkable part of the large energy volume consumed in the Internet today is due to the over-provisioning of network resources such as routers, switches and links to meet the stringent requirements on reliability. Therefore, performance and energy issues are important factors in designing gigabit routers for future networks. However, the design and prototyping of energy-efficient routers is challenging because of multiple reasons, such as the lack of power measurements from live networks and a good understanding of how the energy consumption varies under different traffic loads and switch/router configuration settings. Moreover, the exact energy saving level gained by adopting different energy-efficient techniques in different hardware prototypes is often poorly known. In this article, we first propose a measurement framework that is able to quantify and profile the detailed energy consumption of sub-components in the NetFPGA OpenFlow switch. We then propose a new power-scaling algorithm that can adapt the operational clock frequencies as well as the corresponding energy consumption of the FPGA core and the Ethernet ports to the actual traffic load. We propose a new energy profiling method, which allows studying the detailed power performance of network devices. Results show that our energy efficient solution obtains higher level of energy efficiency compared to some existing approaches as the upper and lower bounds of power consumption of the NetFPGA Openflow switch are proved to be 30% lower than ones of the commercial HP Enterprise switch. Moreover, the new switch architecture can save up to 97% of dynamic power consumption of the FPGA chip at lowest frequency mode.
• Exploratory Analysis of a GGSN’s PDP Context Signaling Load. Metzger, Florian; Rafetseder, Albert; Romirer-Maierhofer, Peter; Tutschku, Kurt. In Journal of Computer Networks and Communications. 2014.
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  @article{info3-article-2014-12, author = {Metzger, Florian and Rafetseder, Albert and Romirer-Maierhofer, Peter and Tutschku, Kurt}, journal = {Journal of Computer Networks and Communications}, keywords = {sys:hidden:article}, month = {02}, title = {Exploratory Analysis of a GGSN’s PDP Context Signaling Load}, year = 2014 }

  %0 Journal Article %1 info3-article-2014-12 %A Metzger, Florian %A Rafetseder, Albert %A Romirer-Maierhofer, Peter %A Tutschku, Kurt %D 2014 %J Journal of Computer Networks and Communications %T Exploratory Analysis of a GGSN’s PDP Context Signaling Load
• On Training the Crowd for Subjective Quality Studies. Hoßfeld, Tobias. In VQEG eLetter, 1. 2014.
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  “On Training the Crowd for Subjective Quality Studies” by Tobias Hossfeld from University of Würzburg presents new possibilities for quality evaluation by conducting subjective studies with the crowd of Internet users. The challenges of conducting training sessions for different methods of crowd sourcing are also elaborated in the article. The eLetter is online at the <a href='http://www.its.bldrdoc.gov/vqeg/eletter.aspx'>Video Quality Experts Group (VQEG) homepage</a>.

  @article{info3-article-2014-120, abstract = {“On Training the Crowd for Subjective Quality Studies” by Tobias Hossfeld from University of Würzburg presents new possibilities for quality evaluation by conducting subjective studies with the crowd of Internet users. The challenges of conducting training sessions for different methods of crowd sourcing are also elaborated in the article. The eLetter is online at the <a href='http://www.its.bldrdoc.gov/vqeg/eletter.aspx'>Video Quality Experts Group (VQEG) homepage</a>.}, author = {Hoßfeld, Tobias}, journal = {VQEG eLetter}, keywords = {sys:hidden:article}, month = {03}, title = {On Training the Crowd for Subjective Quality Studies}, volume = 1, year = 2014 }

  %0 Journal Article %1 info3-article-2014-120 %A Hoßfeld, Tobias %D 2014 %J VQEG eLetter %T On Training the Crowd for Subjective Quality Studies %V 1 %X “On Training the Crowd for Subjective Quality Studies” by Tobias Hossfeld from University of Würzburg presents new possibilities for quality evaluation by conducting subjective studies with the crowd of Internet users. The challenges of conducting training sessions for different methods of crowd sourcing are also elaborated in the article. The eLetter is online at the <a href='http://www.its.bldrdoc.gov/vqeg/eletter.aspx'>Video Quality Experts Group (VQEG) homepage</a>.
• Best Practices for QoE Crowdtesting: QoE Assessment with Crowdsourcing. Hoßfeld, Tobias; Keimel, Christian; Hirth, Matthias; Gardlo, Bruno; Habigt, Julian; Diepold, Klaus; Tran-Gia, Phuoc. In Transactions on Multimedia, 16. 2014.
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  Quality of Experience (QoE) in multimedia applications is closely linked to the end users’ perception and therefore its assessment requires subjective user studies in order to evaluate the degree of delight or annoyance as experienced by the users. QoE crowdtesting refers to QoE assessment using crowdsourcing, where anonymous test subjects conduct subjective tests remotely in their preferred environment. The advantages of QoE crowdtesting lie not only in the reduced time and costs for the tests, but also in a large and diverse panel of international, geographically distributed users in realistic user settings. However, conceptual and technical challenges emerge due to the remote test settings. Key issues arising from QoE crowdtesting include the reliability of user ratings, the influence of incentives, payment schemes and the unknown environmental context of the tests on the results. In order to counter these issues, strategies and methods need to be developed, included in the test design, and also implemented in the actual test campaign, while statistical methods are required to identify reliable user ratings and to ensure high data quality. This contribution therefore provides a collection of best practices addressing these issues based on our experience gained in a large set of conducted QoE crowdtesting studies. The focus of this article is in particular on the issue of reliability and we use video quality assessment as an example for the proposed best practices, showing that our recommended two-stage QoE crowdtesting design leads to more reliable results.

  @article{info3-article-2014-117, abstract = {Quality of Experience (QoE) in multimedia applications is closely linked to the end users’ perception and therefore its assessment requires subjective user studies in order to evaluate the degree of delight or annoyance as experienced by the users. QoE crowdtesting refers to QoE assessment using crowdsourcing, where anonymous test subjects conduct subjective tests remotely in their preferred environment. The advantages of QoE crowdtesting lie not only in the reduced time and costs for the tests, but also in a large and diverse panel of international, geographically distributed users in realistic user settings. However, conceptual and technical challenges emerge due to the remote test settings. Key issues arising from QoE crowdtesting include the reliability of user ratings, the influence of incentives, payment schemes and the unknown environmental context of the tests on the results. In order to counter these issues, strategies and methods need to be developed, included in the test design, and also implemented in the actual test campaign, while statistical methods are required to identify reliable user ratings and to ensure high data quality. This contribution therefore provides a collection of best practices addressing these issues based on our experience gained in a large set of conducted QoE crowdtesting studies. The focus of this article is in particular on the issue of reliability and we use video quality assessment as an example for the proposed best practices, showing that our recommended two-stage QoE crowdtesting design leads to more reliable results.}, author = {Hoßfeld, Tobias and Keimel, Christian and Hirth, Matthias and Gardlo, Bruno and Habigt, Julian and Diepold, Klaus and Tran-Gia, Phuoc}, journal = {Transactions on Multimedia}, keywords = {sys:hidden:article}, month = {02}, title = {Best Practices for QoE Crowdtesting: QoE Assessment with Crowdsourcing}, volume = 16, year = 2014 }

  %0 Journal Article %1 info3-article-2014-117 %A Hoßfeld, Tobias %A Keimel, Christian %A Hirth, Matthias %A Gardlo, Bruno %A Habigt, Julian %A Diepold, Klaus %A Tran-Gia, Phuoc %D 2014 %J Transactions on Multimedia %T Best Practices for QoE Crowdtesting: QoE Assessment with Crowdsourcing %V 16 %X Quality of Experience (QoE) in multimedia applications is closely linked to the end users’ perception and therefore its assessment requires subjective user studies in order to evaluate the degree of delight or annoyance as experienced by the users. QoE crowdtesting refers to QoE assessment using crowdsourcing, where anonymous test subjects conduct subjective tests remotely in their preferred environment. The advantages of QoE crowdtesting lie not only in the reduced time and costs for the tests, but also in a large and diverse panel of international, geographically distributed users in realistic user settings. However, conceptual and technical challenges emerge due to the remote test settings. Key issues arising from QoE crowdtesting include the reliability of user ratings, the influence of incentives, payment schemes and the unknown environmental context of the tests on the results. In order to counter these issues, strategies and methods need to be developed, included in the test design, and also implemented in the actual test campaign, while statistical methods are required to identify reliable user ratings and to ensure high data quality. This contribution therefore provides a collection of best practices addressing these issues based on our experience gained in a large set of conducted QoE crowdtesting studies. The focus of this article is in particular on the issue of reliability and we use video quality assessment as an example for the proposed best practices, showing that our recommended two-stage QoE crowdtesting design leads to more reliable results.
• Interfaces, Attributes, and Use Cases: A Compass for SDN. Jarschel, Michael; Zinner, Thomas; Hoßfeld, Tobias; Tran-Gia, Phuoc; Kellerer, Wolfgang. In IEEE Communications Magazine, 52, pp. 210–217. 2014.
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  The term Software Defined Networking (SDN) is prevalent in today’s discussion about future communication networks. As with any new term or paradigm, however, no consistent definition regarding this technology has formed. The fragmented view on SDN results in legacy products being passed off by equipment vendors as SDN, academics mixing up the attributes of SDN with those of network virtualization, and users not fully understanding the benefits. Therefore, establishing SDN as a widely adopted technology beyond laboratories and insular deployments requires a compass to navigate the multitude of ideas and concepts that make up SDN today. The contribution of this article represents an important step toward such an instrument. It gives a thorough definition of SDN and its interfaces as well as a list of its key attributes. Furthermore, a mapping of interfaces and attributes to SDN use cases is provided, highlighting the relevance of the interfaces and attributes for each scenario. This compass gives guidance to a potential adopter of SDN on whether SDN is in fact the right technology for a specific use case.

  @article{info3-article-2014-124, abstract = {The term Software Defined Networking (SDN) is prevalent in today’s discussion about future communication networks. As with any new term or paradigm, however, no consistent definition regarding this technology has formed. The fragmented view on SDN results in legacy products being passed off by equipment vendors as SDN, academics mixing up the attributes of SDN with those of network virtualization, and users not fully understanding the benefits. Therefore, establishing SDN as a widely adopted technology beyond laboratories and insular deployments requires a compass to navigate the multitude of ideas and concepts that make up SDN today. The contribution of this article represents an important step toward such an instrument. It gives a thorough definition of SDN and its interfaces as well as a list of its key attributes. Furthermore, a mapping of interfaces and attributes to SDN use cases is provided, highlighting the relevance of the interfaces and attributes for each scenario. This compass gives guidance to a potential adopter of SDN on whether SDN is in fact the right technology for a specific use case.}, author = {Jarschel, Michael and Zinner, Thomas and Hoßfeld, Tobias and Tran-Gia, Phuoc and Kellerer, Wolfgang}, journal = {IEEE Communications Magazine}, keywords = {sys:hidden:article}, month = {06}, pages = {210-217}, title = {Interfaces, Attributes, and Use Cases: A Compass for SDN}, volume = 52, year = 2014 }

  %0 Journal Article %1 info3-article-2014-124 %A Jarschel, Michael %A Zinner, Thomas %A Hoßfeld, Tobias %A Tran-Gia, Phuoc %A Kellerer, Wolfgang %D 2014 %J IEEE Communications Magazine %P 210-217 %T Interfaces, Attributes, and Use Cases: A Compass for SDN %V 52 %X The term Software Defined Networking (SDN) is prevalent in today’s discussion about future communication networks. As with any new term or paradigm, however, no consistent definition regarding this technology has formed. The fragmented view on SDN results in legacy products being passed off by equipment vendors as SDN, academics mixing up the attributes of SDN with those of network virtualization, and users not fully understanding the benefits. Therefore, establishing SDN as a widely adopted technology beyond laboratories and insular deployments requires a compass to navigate the multitude of ideas and concepts that make up SDN today. The contribution of this article represents an important step toward such an instrument. It gives a thorough definition of SDN and its interfaces as well as a list of its key attributes. Furthermore, a mapping of interfaces and attributes to SDN use cases is provided, highlighting the relevance of the interfaces and attributes for each scenario. This compass gives guidance to a potential adopter of SDN on whether SDN is in fact the right technology for a specific use case.
• On the computation of entropy production in stationary social networks. Hoßfeld, Tobias; Burger, Valentin; Hinrichsen, Haye; Hirth, Matthias; Tran-Gia, Phuoc. In Social Network Analysis and Mining, 4. 2014.
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  Completing their initial phase of rapid growth, social networks are expected to reach a plateau from where on they are in a statistically stationary state. Such stationary conditions may have different dynamical properties. For example, if each message in a network is followed by a reply in opposite direction, the dynamics is locally balanced. Otherwise, if messages are ignored or forwarded to a different user, one may reach a stationary state with a directed flow of information. To distinguish between the two situations, we propose a quantity called entropy production that was introduced in statistical physics as a measure for non-vanishing probability currents in nonequilibrium stationary states. The proposed quantity closes a gap for characterizing online social networks. As major contribution, we show the relation and difference between entropy production and existing metrics. The comparison shows that computational intensive metrics like centrality can be approximated by entropy production for typical online social networks. To compute the entropy production from real-world measurements, the need for Bayesian inference and the limits of naïve estimates for those probability currents are shown. As further contribution, a general scheme is presented to measure the entropy production in small-world networks using Bayesian inference. The scheme is then applied for a specific example of the R mailing list.

  @article{info3-article-2014-123, abstract = {Completing their initial phase of rapid growth, social networks are expected to reach a plateau from where on they are in a statistically stationary state. Such stationary conditions may have different dynamical properties. For example, if each message in a network is followed by a reply in opposite direction, the dynamics is locally balanced. Otherwise, if messages are ignored or forwarded to a different user, one may reach a stationary state with a directed flow of information. To distinguish between the two situations, we propose a quantity called entropy production that was introduced in statistical physics as a measure for non-vanishing probability currents in nonequilibrium stationary states. The proposed quantity closes a gap for characterizing online social networks. As major contribution, we show the relation and difference between entropy production and existing metrics. The comparison shows that computational intensive metrics like centrality can be approximated by entropy production for typical online social networks. To compute the entropy production from real-world measurements, the need for Bayesian inference and the limits of naïve estimates for those probability currents are shown. As further contribution, a general scheme is presented to measure the entropy production in small-world networks using Bayesian inference. The scheme is then applied for a specific example of the R mailing list.}, author = {Hoßfeld, Tobias and Burger, Valentin and Hinrichsen, Haye and Hirth, Matthias and Tran-Gia, Phuoc}, journal = {Social Network Analysis and Mining}, keywords = {sys:hidden:article}, month = {04}, title = {On the computation of entropy production in stationary social networks}, volume = 4, year = 2014 }

  %0 Journal Article %1 info3-article-2014-123 %A Hoßfeld, Tobias %A Burger, Valentin %A Hinrichsen, Haye %A Hirth, Matthias %A Tran-Gia, Phuoc %D 2014 %J Social Network Analysis and Mining %T On the computation of entropy production in stationary social networks %V 4 %X Completing their initial phase of rapid growth, social networks are expected to reach a plateau from where on they are in a statistically stationary state. Such stationary conditions may have different dynamical properties. For example, if each message in a network is followed by a reply in opposite direction, the dynamics is locally balanced. Otherwise, if messages are ignored or forwarded to a different user, one may reach a stationary state with a directed flow of information. To distinguish between the two situations, we propose a quantity called entropy production that was introduced in statistical physics as a measure for non-vanishing probability currents in nonequilibrium stationary states. The proposed quantity closes a gap for characterizing online social networks. As major contribution, we show the relation and difference between entropy production and existing metrics. The comparison shows that computational intensive metrics like centrality can be approximated by entropy production for typical online social networks. To compute the entropy production from real-world measurements, the need for Bayesian inference and the limits of naïve estimates for those probability currents are shown. As further contribution, a general scheme is presented to measure the entropy production in small-world networks using Bayesian inference. The scheme is then applied for a specific example of the R mailing list.
• Close to Optimum? User-centric Evaluation of Adaptation Logics for HTTP Adaptive Streaming. Hoßfeld, Tobias; Seufert, Michael; Sieber, Christian; Zinner, Thomas; Tran-Gia, Phuoc. In PIK - Praxis der Informationsverarbeitung und Kommunikation, 37, pp. 275–285. 2014.
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  HTTP Adaptive Streaming (HAS) is the de-facto standard for over-the-top (OTT) video streaming services. It allows to react to fluctuating network conditions on short time scales by adapting the video bit rate in order to avoid stalling of the video playback. With HAS the video content is split into small segments of a few seconds playtime each, which are available in different bit rates, i.e., quality level representations. Depending on the current conditions, the adaptation algorithm on the client side chooses the appropriate quality level and downloads the respective segment. This allows to avoid stalling, which is seen as the worst possible disturbance of HTTP video streaming, to the most possible extend. Nevertheless, the user perceived Quality of Experience (QoE) may be affected, namely by playing back lower qualities and by switching between different qualities. Therefore, adaptation algorithms are desired which maximize the user’sQoEfor the currently available network resources. Many downloading strategies have been proposed in literature, but a solid user-centric comparison of these mechanisms among each other and with the global optimum is missing. The major contributions of this work are as follows. A proper analysis of the influence of quality switches and played out representations on QoE is conducted by means of subjective user studies. The results suggest that, in order to optimize QoE, first, the quality level of the video stream has to be maximized and second, the number of quality switches should be minimized. Based on our findings, a QoEoptimization problem is formulated and the performance of our proposed algorithm is compared to other algorithms and to the QoE-optimal adaptation.

  @article{info3-article-2014-127, abstract = {HTTP Adaptive Streaming (HAS) is the de-facto standard for over-the-top (OTT) video streaming services. It allows to react to fluctuating network conditions on short time scales by adapting the video bit rate in order to avoid stalling of the video playback. With HAS the video content is split into small segments of a few seconds playtime each, which are available in different bit rates, i.e., quality level representations. Depending on the current conditions, the adaptation algorithm on the client side chooses the appropriate quality level and downloads the respective segment. This allows to avoid stalling, which is seen as the worst possible disturbance of HTTP video streaming, to the most possible extend. Nevertheless, the user perceived Quality of Experience (QoE) may be affected, namely by playing back lower qualities and by switching between different qualities. Therefore, adaptation algorithms are desired which maximize the user’sQoEfor the currently available network resources. Many downloading strategies have been proposed in literature, but a solid user-centric comparison of these mechanisms among each other and with the global optimum is missing. The major contributions of this work are as follows. A proper analysis of the influence of quality switches and played out representations on QoE is conducted by means of subjective user studies. The results suggest that, in order to optimize QoE, first, the quality level of the video stream has to be maximized and second, the number of quality switches should be minimized. Based on our findings, a QoEoptimization problem is formulated and the performance of our proposed algorithm is compared to other algorithms and to the QoE-optimal adaptation.}, author = {Hoßfeld, Tobias and Seufert, Michael and Sieber, Christian and Zinner, Thomas and Tran-Gia, Phuoc}, journal = {PIK - Praxis der Informationsverarbeitung und Kommunikation}, keywords = {sys:hidden:article}, month = 10, pages = {275-285}, title = {Close to Optimum? User-centric Evaluation of Adaptation Logics for HTTP Adaptive Streaming}, volume = 37, year = 2014 }

  %0 Journal Article %1 info3-article-2014-127 %A Hoßfeld, Tobias %A Seufert, Michael %A Sieber, Christian %A Zinner, Thomas %A Tran-Gia, Phuoc %D 2014 %J PIK - Praxis der Informationsverarbeitung und Kommunikation %P 275-285 %T Close to Optimum? User-centric Evaluation of Adaptation Logics for HTTP Adaptive Streaming %V 37 %X HTTP Adaptive Streaming (HAS) is the de-facto standard for over-the-top (OTT) video streaming services. It allows to react to fluctuating network conditions on short time scales by adapting the video bit rate in order to avoid stalling of the video playback. With HAS the video content is split into small segments of a few seconds playtime each, which are available in different bit rates, i.e., quality level representations. Depending on the current conditions, the adaptation algorithm on the client side chooses the appropriate quality level and downloads the respective segment. This allows to avoid stalling, which is seen as the worst possible disturbance of HTTP video streaming, to the most possible extend. Nevertheless, the user perceived Quality of Experience (QoE) may be affected, namely by playing back lower qualities and by switching between different qualities. Therefore, adaptation algorithms are desired which maximize the user’sQoEfor the currently available network resources. Many downloading strategies have been proposed in literature, but a solid user-centric comparison of these mechanisms among each other and with the global optimum is missing. The major contributions of this work are as follows. A proper analysis of the influence of quality switches and played out representations on QoE is conducted by means of subjective user studies. The results suggest that, in order to optimize QoE, first, the quality level of the video stream has to be maximized and second, the number of quality switches should be minimized. Based on our findings, a QoEoptimization problem is formulated and the performance of our proposed algorithm is compared to other algorithms and to the QoE-optimal adaptation.
• Quality of Experience Assessment using Crowdsourcing. Hoßfeld, Tobias; Timmerer, Christian. In IEEE COMSOC MMTC R-Letter, 5. 2014.
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  A short review for the article 'Best Practices for QoE Crowdtesting: QoE Assessment with Crowdsourcing' Edited by Tobias Hoßfeld and Christian Timmerer Online at: http://committees.comsoc.org/mmc/r-letters/MMTC-RLetter-Jun2014.pdf Tobias Hoßfeld, Christian Keimel, Matthias Hirth, Bruno Gardlo, Julian Habigt, Klaus Diepold, Phuoc Tran-Gia, 'Best Practices for QoE Crowdtesting: QoE Assessment with Crowdsourcing', IEEE Trans. on Multimedia, vol. 16, no. 2, pp. 541–558, Feb. 2014.

  @article{info3-article-2014-125, abstract = {A short review for the article 'Best Practices for QoE Crowdtesting: QoE Assessment with Crowdsourcing' Edited by Tobias Hoßfeld and Christian Timmerer Online at: http://committees.comsoc.org/mmc/r-letters/MMTC-RLetter-Jun2014.pdf Tobias Hoßfeld, Christian Keimel, Matthias Hirth, Bruno Gardlo, Julian Habigt, Klaus Diepold, Phuoc Tran-Gia, 'Best Practices for QoE Crowdtesting: QoE Assessment with Crowdsourcing', IEEE Trans. on Multimedia, vol. 16, no. 2, pp. 541–558, Feb. 2014.}, author = {Hoßfeld, Tobias and Timmerer, Christian}, journal = {IEEE COMSOC MMTC R-Letter}, keywords = {sys:hidden:article}, month = {06}, title = {Quality of Experience Assessment using Crowdsourcing}, volume = 5, year = 2014 }

  %0 Journal Article %1 info3-article-2014-125 %A Hoßfeld, Tobias %A Timmerer, Christian %D 2014 %J IEEE COMSOC MMTC R-Letter %T Quality of Experience Assessment using Crowdsourcing %V 5 %X A short review for the article 'Best Practices for QoE Crowdtesting: QoE Assessment with Crowdsourcing' Edited by Tobias Hoßfeld and Christian Timmerer Online at: http://committees.comsoc.org/mmc/r-letters/MMTC-RLetter-Jun2014.pdf Tobias Hoßfeld, Christian Keimel, Matthias Hirth, Bruno Gardlo, Julian Habigt, Klaus Diepold, Phuoc Tran-Gia, 'Best Practices for QoE Crowdtesting: QoE Assessment with Crowdsourcing', IEEE Trans. on Multimedia, vol. 16, no. 2, pp. 541–558, Feb. 2014.
• Crowdsourcing Quality-of-Experience Assessments. Hoßfeld, Tobias; Keimel, Christian; Timmerer, Christian. In IEEE Computer, 47, pp. 98–102. 2014.
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  Crowdsourced quality-of-experience (QoE) assessments are more costeffective and flexible than traditional in-lab evaluations but require careful test design, innovative incentive mechanisms, and technical expertise to address various implementation challenges.

  @article{info3-article-2014-129, abstract = {Crowdsourced quality-of-experience (QoE) assessments are more costeffective and flexible than traditional in-lab evaluations but require careful test design, innovative incentive mechanisms, and technical expertise to address various implementation challenges.}, author = {Hoßfeld, Tobias and Keimel, Christian and Timmerer, Christian}, journal = {IEEE Computer}, keywords = {sys:hidden:article}, month = {09}, pages = {98-102}, title = {Crowdsourcing Quality-of-Experience Assessments}, volume = 47, year = 2014 }

  %0 Journal Article %1 info3-article-2014-129 %A Hoßfeld, Tobias %A Keimel, Christian %A Timmerer, Christian %D 2014 %J IEEE Computer %P 98-102 %T Crowdsourcing Quality-of-Experience Assessments %V 47 %X Crowdsourced quality-of-experience (QoE) assessments are more costeffective and flexible than traditional in-lab evaluations but require careful test design, innovative incentive mechanisms, and technical expertise to address various implementation challenges.
• Requirement Driven Prospects for Realizing User-Centric Network Orchestration. Zinner, Thomas; Hoßfeld, Tobias; Fiedler, Markus; Liers, Florian; Volkert, Thomas; Khondoker, Rahamatullah; Schatz, Raimund. In Multimedia Tools and Applications. 2014.
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  The Internet’s infrastructure shows severe limitations when an optimal end user experience for multimedia applications should be achieved in a resource-efficiently way. In order to realize truly user-centric networking, an information exchange between applications and networks is required. To this end, network-application interfaces need to be deployed that enable a better mediation of application data through the Internet. For smart multimedia applications and services, the application and the network should directly communicate with each other and exchange information in order to ensure an optimal Quality of Experience (QoE). In this article, we follow a use-case driven approach towards user-centric network orchestration. We derive user, application, and network requirements for three complementary use cases: HD live TV streaming, video-on-demand streaming and user authentication with high security and privacy demands, as typically required for payed multimedia services. We provide practical guidelines for achieving an optimal QoE efficiently in the context of these use cases. Based on these results, we demonstrate how to overcome one of the main limitations of today’s Internet by introducing the major steps required for user-centric network orchestration. Finally, we show conceptual prospects for realizing these steps by discussing a possible implementation with an inter-network architecture based on functional blocks.

  @article{info3-article-2014-122, abstract = {The Internet’s infrastructure shows severe limitations when an optimal end user experience for multimedia applications should be achieved in a resource-efficiently way. In order to realize truly user-centric networking, an information exchange between applications and networks is required. To this end, network-application interfaces need to be deployed that enable a better mediation of application data through the Internet. For smart multimedia applications and services, the application and the network should directly communicate with each other and exchange information in order to ensure an optimal Quality of Experience (QoE). In this article, we follow a use-case driven approach towards user-centric network orchestration. We derive user, application, and network requirements for three complementary use cases: HD live TV streaming, video-on-demand streaming and user authentication with high security and privacy demands, as typically required for payed multimedia services. We provide practical guidelines for achieving an optimal QoE efficiently in the context of these use cases. Based on these results, we demonstrate how to overcome one of the main limitations of today’s Internet by introducing the major steps required for user-centric network orchestration. Finally, we show conceptual prospects for realizing these steps by discussing a possible implementation with an inter-network architecture based on functional blocks.}, author = {Zinner, Thomas and Hoßfeld, Tobias and Fiedler, Markus and Liers, Florian and Volkert, Thomas and Khondoker, Rahamatullah and Schatz, Raimund}, journal = {Multimedia Tools and Applications}, keywords = {sys:hidden:article}, month = {06}, title = {Requirement Driven Prospects for Realizing User-Centric Network Orchestration}, year = 2014 }

  %0 Journal Article %1 info3-article-2014-122 %A Zinner, Thomas %A Hoßfeld, Tobias %A Fiedler, Markus %A Liers, Florian %A Volkert, Thomas %A Khondoker, Rahamatullah %A Schatz, Raimund %D 2014 %J Multimedia Tools and Applications %T Requirement Driven Prospects for Realizing User-Centric Network Orchestration %X The Internet’s infrastructure shows severe limitations when an optimal end user experience for multimedia applications should be achieved in a resource-efficiently way. In order to realize truly user-centric networking, an information exchange between applications and networks is required. To this end, network-application interfaces need to be deployed that enable a better mediation of application data through the Internet. For smart multimedia applications and services, the application and the network should directly communicate with each other and exchange information in order to ensure an optimal Quality of Experience (QoE). In this article, we follow a use-case driven approach towards user-centric network orchestration. We derive user, application, and network requirements for three complementary use cases: HD live TV streaming, video-on-demand streaming and user authentication with high security and privacy demands, as typically required for payed multimedia services. We provide practical guidelines for achieving an optimal QoE efficiently in the context of these use cases. Based on these results, we demonstrate how to overcome one of the main limitations of today’s Internet by introducing the major steps required for user-centric network orchestration. Finally, we show conceptual prospects for realizing these steps by discussing a possible implementation with an inter-network architecture based on functional blocks.

• Modeling and Experimenting Combined Smart Sleep and Power Scaling Algorithms in Energy-aware Data Center Networks. Nguyen, Huu-Thanh; Pham Ngoc, Nam; Truong, Thu-Huong; Tran Ngoc, Thuan; Nguyen Minh, Duong; Giang Nguyen, Van; Nguyen, Tai-Hung; Ngo Quynh, Thu; Hock, David; Schwartz, Christian. In Simulation Modelling Practice and Theory, 39. 2013.
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  @article{info3-article-2013-118, author = {Nguyen, Huu-Thanh and Pham Ngoc, Nam and Truong, Thu-Huong and Tran Ngoc, Thuan and Nguyen Minh, Duong and Giang Nguyen, Van and Nguyen, Tai-Hung and Ngo Quynh, Thu and Hock, David and Schwartz, Christian}, journal = {Simulation Modelling Practice and Theory}, keywords = {sys:hidden:article}, month = 12, title = {Modeling and Experimenting Combined Smart Sleep and Power Scaling Algorithms in Energy-aware Data Center Networks.}, volume = 39, year = 2013 }

  %0 Journal Article %1 info3-article-2013-118 %A Nguyen, Huu-Thanh %A Pham Ngoc, Nam %A Truong, Thu-Huong %A Tran Ngoc, Thuan %A Nguyen Minh, Duong %A Giang Nguyen, Van %A Nguyen, Tai-Hung %A Ngo Quynh, Thu %A Hock, David %A Schwartz, Christian %D 2013 %J Simulation Modelling Practice and Theory %T Modeling and Experimenting Combined Smart Sleep and Power Scaling Algorithms in Energy-aware Data Center Networks. %V 39
• A Survey of Mapping Systems for Locator/Identifier Split Internet Routing. Hoefling, Michael; Menth, Michael; Hartmann, Matthias. In IEEE Communications Surveys & Tutorials, 14, pp. 1842–1858. 2013.
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  The locator/identifier split is a core principle of many recently proposed routing architectures for a scalable future Internet. It splits the function of today’s IP addresses into two separate pieces. End-hosts are addressed using identifiers which are not globally routable while network attachment points have globally routable locators assigned. In most architectures, either the sending host or an intermediate node has to query a mapping system to obtain locators for identifiers. Such a mapping system must be fast, reliable, secure, and may be able to relay data packets. In this paper, we propose requirements and a general taxonomy for mapping systems and use it to provide a survey on recent proposals. We address general aspects of mapping systems and point out remaining research opportunities.

  @article{info3-article-2013-106, abstract = {The locator/identifier split is a core principle of many recently proposed routing architectures for a scalable future Internet. It splits the function of today’s IP addresses into two separate pieces. End-hosts are addressed using identifiers which are not globally routable while network attachment points have globally routable locators assigned. In most architectures, either the sending host or an intermediate node has to query a mapping system to obtain locators for identifiers. Such a mapping system must be fast, reliable, secure, and may be able to relay data packets. In this paper, we propose requirements and a general taxonomy for mapping systems and use it to provide a survey on recent proposals. We address general aspects of mapping systems and point out remaining research opportunities.}, author = {Hoefling, Michael and Menth, Michael and Hartmann, Matthias}, journal = {IEEE Communications Surveys & Tutorials}, keywords = {sys:hidden:article}, month = 11, pages = {1842 - 1858}, title = {A Survey of Mapping Systems for Locator/Identifier Split Internet Routing}, volume = 14, year = 2013 }

  %0 Journal Article %1 info3-article-2013-106 %A Hoefling, Michael %A Menth, Michael %A Hartmann, Matthias %D 2013 %J IEEE Communications Surveys & Tutorials %P 1842 - 1858 %T A Survey of Mapping Systems for Locator/Identifier Split Internet Routing %V 14 %X The locator/identifier split is a core principle of many recently proposed routing architectures for a scalable future Internet. It splits the function of today’s IP addresses into two separate pieces. End-hosts are addressed using identifiers which are not globally routable while network attachment points have globally routable locators assigned. In most architectures, either the sending host or an intermediate node has to query a mapping system to obtain locators for identifiers. Such a mapping system must be fast, reliable, secure, and may be able to relay data packets. In this paper, we propose requirements and a general taxonomy for mapping systems and use it to provide a survey on recent proposals. We address general aspects of mapping systems and point out remaining research opportunities.
• Software defined Networks - Das Internet flexibler gestalten und dynamischer steuern. Zinner, Thomas; Hoßfeld, Tobias; Tran-Gia, Phuoc; Kellerer, Wolfgang. In ITG Mitgliederbeilage / VDE dialog (invited article), pp. 6–9. 2013.
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  Vor allem aufgrund seiner starren Architektur und mangelnden Ressourcennutzung ist die Flexibilität der aktuellen Internettechnologie eingeschränkt. Dies könnte sich durch Anwendung von Software Defined Networks (SDN) ändern. Hierbei wird die Steuerung der Netze und Datenflüsse von den bisherigen Netzkomponenten auf eine zentrale logische Einheit übertragen.

  @article{info3-article-2013-115, abstract = {Vor allem aufgrund seiner starren Architektur und mangelnden Ressourcennutzung ist die Flexibilität der aktuellen Internettechnologie eingeschränkt. Dies könnte sich durch Anwendung von Software Defined Networks (SDN) ändern. Hierbei wird die Steuerung der Netze und Datenflüsse von den bisherigen Netzkomponenten auf eine zentrale logische Einheit übertragen.}, author = {Zinner, Thomas and Hoßfeld, Tobias and Tran-Gia, Phuoc and Kellerer, Wolfgang}, journal = {ITG Mitgliederbeilage / VDE dialog (invited article)}, keywords = {sys:hidden:article}, month = 10, pages = {6-9}, title = {Software defined Networks - Das Internet flexibler gestalten und dynamischer steuern}, year = 2013 }

  %0 Journal Article %1 info3-article-2013-115 %A Zinner, Thomas %A Hoßfeld, Tobias %A Tran-Gia, Phuoc %A Kellerer, Wolfgang %D 2013 %J ITG Mitgliederbeilage / VDE dialog (invited article) %P 6-9 %T Software defined Networks - Das Internet flexibler gestalten und dynamischer steuern %X Vor allem aufgrund seiner starren Architektur und mangelnden Ressourcennutzung ist die Flexibilität der aktuellen Internettechnologie eingeschränkt. Dies könnte sich durch Anwendung von Software Defined Networks (SDN) ändern. Hierbei wird die Steuerung der Netze und Datenflüsse von den bisherigen Netzkomponenten auf eine zentrale logische Einheit übertragen.
• Crowdsourcing - Modell einer neuen Arbeitswelt im Internet. Hoßfeld, Tobias; Hirth, Matthias; Tran-Gia, Phuoc. In Informatik Spektrum, Wirtschaftsinformatik & Management, 5. 2013.
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  Das Internet hat bereits viele höchst erfolgreiche Geschäftsmodelle hervorgebracht. Jedoch basierten bisher die meisten neuen Anwendungen oder Dienstleistungen auf technischen Neuerungen, beispielsweise schnelleren Rechner, kürzeren Verbindungsdauern oder auf neuartigen algorithmischen Ansätzen, etwa der Page-Rank-Algorithmus von Google. Erst mit den Sozialen Medien wie Youtube oder Facebook wurden die Nutzer ein integraler Bestandteil der Wertschöpfungskette, ohne die das „Produkt“ nicht funktioniert. Einen ähnlich starken Einfluss auf den Erfolg eines Unternehmens haben Nutzer in Geschäftsmodellen, die auf dem Crowdsourcing-Paradigma beruhen, welches im Folgenden genauer beleuchtet werden soll.

  @article{info3-article-2013-116, abstract = {Das Internet hat bereits viele höchst erfolgreiche Geschäftsmodelle hervorgebracht. Jedoch basierten bisher die meisten neuen Anwendungen oder Dienstleistungen auf technischen Neuerungen, beispielsweise schnelleren Rechner, kürzeren Verbindungsdauern oder auf neuartigen algorithmischen Ansätzen, etwa der Page-Rank-Algorithmus von Google. Erst mit den Sozialen Medien wie Youtube oder Facebook wurden die Nutzer ein integraler Bestandteil der Wertschöpfungskette, ohne die das „Produkt“ nicht funktioniert. Einen ähnlich starken Einfluss auf den Erfolg eines Unternehmens haben Nutzer in Geschäftsmodellen, die auf dem Crowdsourcing-Paradigma beruhen, welches im Folgenden genauer beleuchtet werden soll.}, author = {Hoßfeld, Tobias and Hirth, Matthias and Tran-Gia, Phuoc}, journal = {Informatik Spektrum, Wirtschaftsinformatik & Management}, keywords = {sys:hidden:article}, month = 10, title = {Crowdsourcing - Modell einer neuen Arbeitswelt im Internet}, volume = 5, year = 2013 }

  %0 Journal Article %1 info3-article-2013-116 %A Hoßfeld, Tobias %A Hirth, Matthias %A Tran-Gia, Phuoc %D 2013 %J Informatik Spektrum, Wirtschaftsinformatik & Management %T Crowdsourcing - Modell einer neuen Arbeitswelt im Internet %V 5 %X Das Internet hat bereits viele höchst erfolgreiche Geschäftsmodelle hervorgebracht. Jedoch basierten bisher die meisten neuen Anwendungen oder Dienstleistungen auf technischen Neuerungen, beispielsweise schnelleren Rechner, kürzeren Verbindungsdauern oder auf neuartigen algorithmischen Ansätzen, etwa der Page-Rank-Algorithmus von Google. Erst mit den Sozialen Medien wie Youtube oder Facebook wurden die Nutzer ein integraler Bestandteil der Wertschöpfungskette, ohne die das „Produkt“ nicht funktioniert. Einen ähnlich starken Einfluss auf den Erfolg eines Unternehmens haben Nutzer in Geschäftsmodellen, die auf dem Crowdsourcing-Paradigma beruhen, welches im Folgenden genauer beleuchtet werden soll.
• Angry Apps: The Impact of Network Timer Selection on Power Consumption, Signalling Load, and Web QoE. Schwartz, Christian; Hoßfeld, Tobias; Lehrieder, Frank; Tran-Gia, Phuoc. In Journal of Computer Networks and Communications, pp. 1–22. 2013.
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  The popularity of smartphones and mobile applications has experienced a considerable growth during recent years and this growth is expected to continue in the future. Since smartphones have only very limited energy resources, battery efficiency is one of the deter- mining factors for a good user experience. Therefore, some smartphones tear down connec- tions to the mobile network soon after a completed data transmission to reduce the power consumption of their transmission unit. However, frequent connection re-establishments caused by apps which send or receive small amounts of data often lead to a heavy signalling load within the mobile network. One of the major contributions of this article is the investigation of the resulting trade-off between energy consumption at the smartphone and the generated signalling traffic in the mobile network. We explain that this trade-off can be controlled by the connection release timeout and study the impact of this parameter for a number of popular apps that cover a wide range of traffic characteristics in terms of bandwidth requirements and resulting signalling traffic. Finally, we study the impact of the timer settings on QoE for web traffic. This is an important aspect since connection establishments do not only lead to signalling traffic, but they also increase the load time of web pages.

  @article{info3-article-2013-108, abstract = {The popularity of smartphones and mobile applications has experienced a considerable growth during recent years and this growth is expected to continue in the future. Since smartphones have only very limited energy resources, battery efficiency is one of the deter- mining factors for a good user experience. Therefore, some smartphones tear down connec- tions to the mobile network soon after a completed data transmission to reduce the power consumption of their transmission unit. However, frequent connection re-establishments caused by apps which send or receive small amounts of data often lead to a heavy signalling load within the mobile network. One of the major contributions of this article is the investigation of the resulting trade-off between energy consumption at the smartphone and the generated signalling traffic in the mobile network. We explain that this trade-off can be controlled by the connection release timeout and study the impact of this parameter for a number of popular apps that cover a wide range of traffic characteristics in terms of bandwidth requirements and resulting signalling traffic. Finally, we study the impact of the timer settings on QoE for web traffic. This is an important aspect since connection establishments do not only lead to signalling traffic, but they also increase the load time of web pages.}, author = {Schwartz, Christian and Hoßfeld, Tobias and Lehrieder, Frank and Tran-Gia, Phuoc}, journal = {Journal of Computer Networks and Communications}, keywords = {sys:hidden:article}, month = {09}, pages = {1 - 22}, title = {Angry Apps: The Impact of Network Timer Selection on Power Consumption, Signalling Load, and Web QoE}, year = 2013 }

  %0 Journal Article %1 info3-article-2013-108 %A Schwartz, Christian %A Hoßfeld, Tobias %A Lehrieder, Frank %A Tran-Gia, Phuoc %D 2013 %J Journal of Computer Networks and Communications %P 1 - 22 %T Angry Apps: The Impact of Network Timer Selection on Power Consumption, Signalling Load, and Web QoE %X The popularity of smartphones and mobile applications has experienced a considerable growth during recent years and this growth is expected to continue in the future. Since smartphones have only very limited energy resources, battery efficiency is one of the deter- mining factors for a good user experience. Therefore, some smartphones tear down connec- tions to the mobile network soon after a completed data transmission to reduce the power consumption of their transmission unit. However, frequent connection re-establishments caused by apps which send or receive small amounts of data often lead to a heavy signalling load within the mobile network. One of the major contributions of this article is the investigation of the resulting trade-off between energy consumption at the smartphone and the generated signalling traffic in the mobile network. We explain that this trade-off can be controlled by the connection release timeout and study the impact of this parameter for a number of popular apps that cover a wide range of traffic characteristics in terms of bandwidth requirements and resulting signalling traffic. Finally, we study the impact of the timer settings on QoE for web traffic. This is an important aspect since connection establishments do not only lead to signalling traffic, but they also increase the load time of web pages.
• Crowdsourcing and its Impact on Future Internet Usage. Tran-Gia, Phuoc; Hoßfeld, Tobias; Hartmann, Matthias; Hirth, Matthias. In it - Information Technology, 55, pp. 139–145. 2013.
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  Crowdsourcing is an emerging service platform and business model in the Internet. In contrast to outsourcing where a job is performed by a designated contractor, with Crowdsourcing, jobs are outsourced to a large, anonymous crowd of workers, the so-called human cloud. The rise of Crowdsourcing and its seamless integration in current workflows may have a huge impact on the Internet and on society, and will be a guiding paradigm that can form the evolution of work in the years to come. In this article, we discuss applications and use cases of Crowdsourcing to demonstrate the impact on Internet usage. Novel measurement approaches are presented and the impact of Crowdsourcing on Internet traffic is evaluated by measuring the activity of a particular Crowdsourcing platform. New technical solutions are necessary for the operation of efficient, distributed Crowdsourcing platforms. Special attention is drawn to the integration of machine clouds and human crowds, and appropriate inter-cloud solutions. Finally, we discuss current research challenges from a scientific and from the platform provider’s point of view.

  @article{info3-article-2013-113, abstract = {Crowdsourcing is an emerging service platform and business model in the Internet. In contrast to outsourcing where a job is performed by a designated contractor, with Crowdsourcing, jobs are outsourced to a large, anonymous crowd of workers, the so-called human cloud. The rise of Crowdsourcing and its seamless integration in current workflows may have a huge impact on the Internet and on society, and will be a guiding paradigm that can form the evolution of work in the years to come. In this article, we discuss applications and use cases of Crowdsourcing to demonstrate the impact on Internet usage. Novel measurement approaches are presented and the impact of Crowdsourcing on Internet traffic is evaluated by measuring the activity of a particular Crowdsourcing platform. New technical solutions are necessary for the operation of efficient, distributed Crowdsourcing platforms. Special attention is drawn to the integration of machine clouds and human crowds, and appropriate inter-cloud solutions. Finally, we discuss current research challenges from a scientific and from the platform provider’s point of view.}, author = {Tran-Gia, Phuoc and Hoßfeld, Tobias and Hartmann, Matthias and Hirth, Matthias}, journal = {it - Information Technology}, keywords = {sys:hidden:article}, month = {07}, pages = {139-145}, title = {Crowdsourcing and its Impact on Future Internet Usage}, volume = 55, year = 2013 }

  %0 Journal Article %1 info3-article-2013-113 %A Tran-Gia, Phuoc %A Hoßfeld, Tobias %A Hartmann, Matthias %A Hirth, Matthias %D 2013 %J it - Information Technology %P 139-145 %T Crowdsourcing and its Impact on Future Internet Usage %V 55 %X Crowdsourcing is an emerging service platform and business model in the Internet. In contrast to outsourcing where a job is performed by a designated contractor, with Crowdsourcing, jobs are outsourced to a large, anonymous crowd of workers, the so-called human cloud. The rise of Crowdsourcing and its seamless integration in current workflows may have a huge impact on the Internet and on society, and will be a guiding paradigm that can form the evolution of work in the years to come. In this article, we discuss applications and use cases of Crowdsourcing to demonstrate the impact on Internet usage. Novel measurement approaches are presented and the impact of Crowdsourcing on Internet traffic is evaluated by measuring the activity of a particular Crowdsourcing platform. New technical solutions are necessary for the operation of efficient, distributed Crowdsourcing platforms. Special attention is drawn to the integration of machine clouds and human crowds, and appropriate inter-cloud solutions. Finally, we discuss current research challenges from a scientific and from the platform provider’s point of view.
• Aktuelles Schlagwort: Big Data. Klein, Dominik; Tran-Gia, Phuoc; Hartmann, Matthias. In Informatik-Spektrum, 36, pp. 319–323. 2013.
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  Big Data ist neben Cloud Computing und Crowdsourcing eine der wichtigsten neuen Technologie-Treiber und wird daher im Aktuellen Schlagwort näher beleuchtet. Zu Beginn gehen wir auf die Definition von Big Data ein und erläutern die Unterschiede zu traditionellen Verfahren. Im Anschluss daran stellen wir zugrundeliegende Technologien vor und geben einen kurzen Überblick über wissenschaftliche Herausforderungen in diesem Bereich.

  @article{info3-article-2013-111, abstract = {Big Data ist neben Cloud Computing und Crowdsourcing eine der wichtigsten neuen Technologie-Treiber und wird daher im Aktuellen Schlagwort näher beleuchtet. Zu Beginn gehen wir auf die Definition von Big Data ein und erläutern die Unterschiede zu traditionellen Verfahren. Im Anschluss daran stellen wir zugrundeliegende Technologien vor und geben einen kurzen Überblick über wissenschaftliche Herausforderungen in diesem Bereich.}, author = {Klein, Dominik and Tran-Gia, Phuoc and Hartmann, Matthias}, journal = {Informatik-Spektrum}, keywords = {sys:hidden:article}, month = {06}, pages = {319-323}, title = {Aktuelles Schlagwort: Big Data}, volume = 36, year = 2013 }

  %0 Journal Article %1 info3-article-2013-111 %A Klein, Dominik %A Tran-Gia, Phuoc %A Hartmann, Matthias %D 2013 %J Informatik-Spektrum %P 319-323 %T Aktuelles Schlagwort: Big Data %V 36 %X Big Data ist neben Cloud Computing und Crowdsourcing eine der wichtigsten neuen Technologie-Treiber und wird daher im Aktuellen Schlagwort näher beleuchtet. Zu Beginn gehen wir auf die Definition von Big Data ein und erläutern die Unterschiede zu traditionellen Verfahren. Im Anschluss daran stellen wir zugrundeliegende Technologien vor und geben einen kurzen Überblick über wissenschaftliche Herausforderungen in diesem Bereich.
• Using Buffered Playtime for QoE-Oriented Resource Management of YouTube Video Streaming. Wamser, Florian; Hock, David; Seufert, Michael; Staehle, Barbara; Pries, Rastin; Tran-Gia, Phuoc. In Transactions on Emerging Telecommunications Technologies, 24, pp. 288–302. 2013.
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  YouTube is the most important online platform for streaming video clips. The popularity and the continuously increasing number of users pose new challenges for Internet Service Providers (ISPs). In particular, in access networks where the transmission resources are limited and the providers are interested in reducing their operational expenditure, it is worth to efficiently optimize the network for popular services such as YouTube. In this paper, we propose different resource management mechanisms to improve the Quality of Experience (QoE) of YouTube users. In particular, we investigate the benefit of cross-layer resource management actions at the client and in the access network for YouTube video streaming. The proposed algorithms are evaluated in a wireless mesh testbed. The results show how to improve the YouTube QoE for the users with the help of client-based or network-based control actions.

  @article{info3-article-2013-109, abstract = {YouTube is the most important online platform for streaming video clips. The popularity and the continuously increasing number of users pose new challenges for Internet Service Providers (ISPs). In particular, in access networks where the transmission resources are limited and the providers are interested in reducing their operational expenditure, it is worth to efficiently optimize the network for popular services such as YouTube. In this paper, we propose different resource management mechanisms to improve the Quality of Experience (QoE) of YouTube users. In particular, we investigate the benefit of cross-layer resource management actions at the client and in the access network for YouTube video streaming. The proposed algorithms are evaluated in a wireless mesh testbed. The results show how to improve the YouTube QoE for the users with the help of client-based or network-based control actions.}, author = {Wamser, Florian and Hock, David and Seufert, Michael and Staehle, Barbara and Pries, Rastin and Tran-Gia, Phuoc}, journal = {Transactions on Emerging Telecommunications Technologies}, keywords = {sys:hidden:article}, month = {04}, pages = {288–302}, title = {Using Buffered Playtime for QoE-Oriented Resource Management of YouTube Video Streaming}, volume = 24, year = 2013 }

  %0 Journal Article %1 info3-article-2013-109 %A Wamser, Florian %A Hock, David %A Seufert, Michael %A Staehle, Barbara %A Pries, Rastin %A Tran-Gia, Phuoc %D 2013 %J Transactions on Emerging Telecommunications Technologies %P 288–302 %T Using Buffered Playtime for QoE-Oriented Resource Management of YouTube Video Streaming %V 24 %X YouTube is the most important online platform for streaming video clips. The popularity and the continuously increasing number of users pose new challenges for Internet Service Providers (ISPs). In particular, in access networks where the transmission resources are limited and the providers are interested in reducing their operational expenditure, it is worth to efficiently optimize the network for popular services such as YouTube. In this paper, we propose different resource management mechanisms to improve the Quality of Experience (QoE) of YouTube users. In particular, we investigate the benefit of cross-layer resource management actions at the client and in the access network for YouTube video streaming. The proposed algorithms are evaluated in a wireless mesh testbed. The results show how to improve the YouTube QoE for the users with the help of client-based or network-based control actions.
• Global Locator, Local Locator, and Identifier Split (GLI-Split). Menth, Michael; Hartmann, Matthias; Klein, Dominik. In Future Internet, 5, pp. 67–94. 2013.
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  The locator/identifier split is an approach for a new addressing and routing architecture to make routing in the core of the Internet more scalable. Based on this principle, we developed the GLI-Split framework, which separates the functionality of current IP addresses into a stable identifier and two independent locators, one for routing in the Internet core and one for edge networks. This makes routing in the Internet more stable and provides more flexibility for edge networks. GLI-Split can be incrementally deployed and it is backward-compatible with the IPv6 Internet. We describe its architecture, compare it to other approaches, present its benefits, and finally present a proof-of-concept implementation of GLI-Split.

  @article{info3-article-2013-110, abstract = {The locator/identifier split is an approach for a new addressing and routing architecture to make routing in the core of the Internet more scalable. Based on this principle, we developed the GLI-Split framework, which separates the functionality of current IP addresses into a stable identifier and two independent locators, one for routing in the Internet core and one for edge networks. This makes routing in the Internet more stable and provides more flexibility for edge networks. GLI-Split can be incrementally deployed and it is backward-compatible with the IPv6 Internet. We describe its architecture, compare it to other approaches, present its benefits, and finally present a proof-of-concept implementation of GLI-Split.}, author = {Menth, Michael and Hartmann, Matthias and Klein, Dominik}, journal = {Future Internet}, keywords = {sys:hidden:article}, month = {03}, pages = {67-94}, title = {Global Locator, Local Locator, and Identifier Split (GLI-Split)}, volume = 5, year = 2013 }

  %0 Journal Article %1 info3-article-2013-110 %A Menth, Michael %A Hartmann, Matthias %A Klein, Dominik %D 2013 %J Future Internet %P 67-94 %T Global Locator, Local Locator, and Identifier Split (GLI-Split) %V 5 %X The locator/identifier split is an approach for a new addressing and routing architecture to make routing in the core of the Internet more scalable. Based on this principle, we developed the GLI-Split framework, which separates the functionality of current IP addresses into a stable identifier and two independent locators, one for routing in the Internet core and one for edge networks. This makes routing in the Internet more stable and provides more flexibility for edge networks. GLI-Split can be incrementally deployed and it is backward-compatible with the IPv6 Internet. We describe its architecture, compare it to other approaches, present its benefits, and finally present a proof-of-concept implementation of GLI-Split.
• OC²E²AN: Optimized Control Center for Experience Enhancements in Access Networks. Hock, David; Wamser, Florian; Seufert, Michael; Pries, Rastin; Tran-Gia, Phuoc. In PIK - Praxis der Informationsverarbeitung und Kommunikation, 36, p. 40. 2013.
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  @article{info3-article-2013-112, author = {Hock, David and Wamser, Florian and Seufert, Michael and Pries, Rastin and Tran-Gia, Phuoc}, journal = {PIK - Praxis der Informationsverarbeitung und Kommunikation}, keywords = {sys:hidden:article}, month = {02}, pages = 40, title = {OC²E²AN: Optimized Control Center for Experience Enhancements in Access Networks}, volume = 36, year = 2013 }

  %0 Journal Article %1 info3-article-2013-112 %A Hock, David %A Wamser, Florian %A Seufert, Michael %A Pries, Rastin %A Tran-Gia, Phuoc %D 2013 %J PIK - Praxis der Informationsverarbeitung und Kommunikation %P 40 %T OC²E²AN: Optimized Control Center for Experience Enhancements in Access Networks %V 36
• Sensorium – A Generic Sensor Framework. Rafetseder, Albert; Metzger, Florian; Pühringer, Lukas; Tutschku, Kurt; Zhuang, Yanyan; Cappos, Justin. In PIK - Praxis der Informationsverarbeitung und Kommunikation, 36(1). 2013.
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  @article{info3-article-2013-14, author = {Rafetseder, Albert and Metzger, Florian and Pühringer, Lukas and Tutschku, Kurt and Zhuang, Yanyan and Cappos, Justin}, journal = {PIK - Praxis der Informationsverarbeitung und Kommunikation}, keywords = {sys:hidden:article}, month = {02}, number = 1, title = {Sensorium – A Generic Sensor Framework}, volume = 36, year = 2013 }

  %0 Journal Article %1 info3-article-2013-14 %A Rafetseder, Albert %A Metzger, Florian %A Pühringer, Lukas %A Tutschku, Kurt %A Zhuang, Yanyan %A Cappos, Justin %D 2013 %J PIK - Praxis der Informationsverarbeitung und Kommunikation %N 1 %T Sensorium – A Generic Sensor Framework %V 36
• Comparison of IP-Based and Explicit Paths for One-to-One Fast Reroute in MPLS Networks. Hock, David; Hartmann, Matthias; Menth, Michael; Pióro, Michał; Tomaszewski, Artur; Żukowski, Cezary. In Telecommunication Systems (TS) Journal, 52, pp. 947–958. 2013.
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  Primary and backup paths in MPLS fast reroute (FRR) may be established as shortest paths according to the administrative link costs of the IP control plane, or as explicitly calculated arbitrary paths. In both cases, the path layout can be optimized so that the maximum link utilization for a specific traffic matrix and for a set of considered failure scenarios is minimized. In this paper, we propose a linear program for the optimization of the path layout for explicitly calculated paths, which can either produce single paths and route entire traffic along those paths, or generate multiple paths and spread the traffic among those paths providing load balancing. We compare the resulting lowest maximum link utilization in both cases with the lowest maximum link utilization that can be obtained by optimizing unique IP-based paths. Our results quantify the gain in resource efficiency usage provided by optimized explicit multiple paths or explicit single paths as compared to optimized IP-based paths. Furthermore, we investigate if explicit path layouts cause an increased configuration effort compared to IP-based layouts and if yes, to what extend.

  @article{info3-article-2013-86, abstract = {Primary and backup paths in MPLS fast reroute (FRR) may be established as shortest paths according to the administrative link costs of the IP control plane, or as explicitly calculated arbitrary paths. In both cases, the path layout can be optimized so that the maximum link utilization for a specific traffic matrix and for a set of considered failure scenarios is minimized. In this paper, we propose a linear program for the optimization of the path layout for explicitly calculated paths, which can either produce single paths and route entire traffic along those paths, or generate multiple paths and spread the traffic among those paths providing load balancing. We compare the resulting lowest maximum link utilization in both cases with the lowest maximum link utilization that can be obtained by optimizing unique IP-based paths. Our results quantify the gain in resource efficiency usage provided by optimized explicit multiple paths or explicit single paths as compared to optimized IP-based paths. Furthermore, we investigate if explicit path layouts cause an increased configuration effort compared to IP-based layouts and if yes, to what extend.}, author = {Hock, David and Hartmann, Matthias and Menth, Michael and Pióro, Michał and Tomaszewski, Artur and Żukowski, Cezary}, journal = {Telecommunication Systems (TS) Journal}, keywords = {sys:hidden:article}, month = {02}, pages = {947-958}, title = {Comparison of IP-Based and Explicit Paths for One-to-One Fast Reroute in MPLS Networks}, volume = 52, year = 2013 }

  %0 Journal Article %1 info3-article-2013-86 %A Hock, David %A Hartmann, Matthias %A Menth, Michael %A Pióro, Michał %A Tomaszewski, Artur %A Żukowski, Cezary %D 2013 %J Telecommunication Systems (TS) Journal %P 947-958 %T Comparison of IP-Based and Explicit Paths for One-to-One Fast Reroute in MPLS Networks %V 52 %X Primary and backup paths in MPLS fast reroute (FRR) may be established as shortest paths according to the administrative link costs of the IP control plane, or as explicitly calculated arbitrary paths. In both cases, the path layout can be optimized so that the maximum link utilization for a specific traffic matrix and for a set of considered failure scenarios is minimized. In this paper, we propose a linear program for the optimization of the path layout for explicitly calculated paths, which can either produce single paths and route entire traffic along those paths, or generate multiple paths and spread the traffic among those paths providing load balancing. We compare the resulting lowest maximum link utilization in both cases with the lowest maximum link utilization that can be obtained by optimizing unique IP-based paths. Our results quantify the gain in resource efficiency usage provided by optimized explicit multiple paths or explicit single paths as compared to optimized IP-based paths. Furthermore, we investigate if explicit path layouts cause an increased configuration effort compared to IP-based layouts and if yes, to what extend.
• RCFT: A Termination Method for Simple PCN-Based Flow Control. Lehrieder, Frank; Menth, Michael. In Journal of Network and Systems Management. 2013.
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  Pre-congestion notification (PCN) conveys information about load conditions in Differentiated Services IP networks to boundary nodes. This information is currently used for admission control and flow termination. Flow termination complements admission control, e.g., in case of failures when admitted traffic is rerouted and causes overload on backup paths. Existing approaches for PCN-based admission control and flow termination operate on ingress-egress aggregates and rely on a signalling protocol that regularly reports measured PCN feedback from all egress nodes to all ingress nodes. However, this signalling protocol is neither defined nor available, and the methods have also other intrinsic shortcomings that result from their operations on ingress-egress aggregates. While there is already a PCN-based admission control method that works without additional signalling of measured PCN feedback, a solid flow termination method with that property is still missing. In this paper we present the novel regular-check-based flow termination method (RCFT). It does not rely on measured PCN feedback, fills the identified gap, and allows for a PCN architecture without signalling of measured feedback. We explain RCFT in detail and investigate its termination behavior under various conditions. Moreover, we study the use of PCN-based flow control for on/off traffic. These results are of general nature and apply to any system using PCN-based flow termination.

  @article{info3-article-2013-107, abstract = {Pre-congestion notification (PCN) conveys information about load conditions in Differentiated Services IP networks to boundary nodes. This information is currently used for admission control and flow termination. Flow termination complements admission control, e.g., in case of failures when admitted traffic is rerouted and causes overload on backup paths. Existing approaches for PCN-based admission control and flow termination operate on ingress-egress aggregates and rely on a signalling protocol that regularly reports measured PCN feedback from all egress nodes to all ingress nodes. However, this signalling protocol is neither defined nor available, and the methods have also other intrinsic shortcomings that result from their operations on ingress-egress aggregates. While there is already a PCN-based admission control method that works without additional signalling of measured PCN feedback, a solid flow termination method with that property is still missing. In this paper we present the novel regular-check-based flow termination method (RCFT). It does not rely on measured PCN feedback, fills the identified gap, and allows for a PCN architecture without signalling of measured feedback. We explain RCFT in detail and investigate its termination behavior under various conditions. Moreover, we study the use of PCN-based flow control for on/off traffic. These results are of general nature and apply to any system using PCN-based flow termination.}, author = {Lehrieder, Frank and Menth, Michael}, journal = {Journal of Network and Systems Management}, keywords = {sys:hidden:article}, title = {RCFT: A Termination Method for Simple PCN-Based Flow Control}, year = 2013 }

  %0 Journal Article %1 info3-article-2013-107 %A Lehrieder, Frank %A Menth, Michael %D 2013 %J Journal of Network and Systems Management %T RCFT: A Termination Method for Simple PCN-Based Flow Control %X Pre-congestion notification (PCN) conveys information about load conditions in Differentiated Services IP networks to boundary nodes. This information is currently used for admission control and flow termination. Flow termination complements admission control, e.g., in case of failures when admitted traffic is rerouted and causes overload on backup paths. Existing approaches for PCN-based admission control and flow termination operate on ingress-egress aggregates and rely on a signalling protocol that regularly reports measured PCN feedback from all egress nodes to all ingress nodes. However, this signalling protocol is neither defined nor available, and the methods have also other intrinsic shortcomings that result from their operations on ingress-egress aggregates. While there is already a PCN-based admission control method that works without additional signalling of measured PCN feedback, a solid flow termination method with that property is still missing. In this paper we present the novel regular-check-based flow termination method (RCFT). It does not rely on measured PCN feedback, fills the identified gap, and allows for a PCN architecture without signalling of measured feedback. We explain RCFT in detail and investigate its termination behavior under various conditions. Moreover, we study the use of PCN-based flow control for on/off traffic. These results are of general nature and apply to any system using PCN-based flow termination.
• YOUQMON: A System for On-line Monitoring of YouTube QoE in Operational 3G Networks. Casas, Pedro; Seufert, Michael; Schatz, Raimund. In ACM SIGMETRICS Performance Evaluation Review, 41, pp. 44–46. 2013.
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  YouTube is changing the way operators manage network performance monitoring. In this paper we introduce YOUQMON, a novel on-line monitoring system for assessing the Quality of Experience (QoE) undergone by HSPA/3G customers watching YouTube videos, using network-layer measurements only. YOUQMON combines passive traffic analysis techniques to detect stalling events in YouTube video streams, with a QoE model to map stallings into a Mean Opinion Score reflecting the end-user experience. We evaluate the stalling detection performance of YOUQMON with hundreds of YouTube video streams, and present results showing the feasibility of performing real-time YouTube QoE monitoring in an operational mobile broadband network.

  @article{info3-article-2013-114, abstract = {YouTube is changing the way operators manage network performance monitoring. In this paper we introduce YOUQMON, a novel on-line monitoring system for assessing the Quality of Experience (QoE) undergone by HSPA/3G customers watching YouTube videos, using network-layer measurements only. YOUQMON combines passive traffic analysis techniques to detect stalling events in YouTube video streams, with a QoE model to map stallings into a Mean Opinion Score reflecting the end-user experience. We evaluate the stalling detection performance of YOUQMON with hundreds of YouTube video streams, and present results showing the feasibility of performing real-time YouTube QoE monitoring in an operational mobile broadband network.}, author = {Casas, Pedro and Seufert, Michael and Schatz, Raimund}, journal = {ACM SIGMETRICS Performance Evaluation Review}, keywords = {sys:hidden:article}, month = {09}, pages = {44-46}, title = {YOUQMON: A System for On-line Monitoring of YouTube QoE in Operational 3G Networks}, volume = 41, year = 2013 }

  %0 Journal Article %1 info3-article-2013-114 %A Casas, Pedro %A Seufert, Michael %A Schatz, Raimund %D 2013 %J ACM SIGMETRICS Performance Evaluation Review %P 44-46 %T YOUQMON: A System for On-line Monitoring of YouTube QoE in Operational 3G Networks %V 41 %X YouTube is changing the way operators manage network performance monitoring. In this paper we introduce YOUQMON, a novel on-line monitoring system for assessing the Quality of Experience (QoE) undergone by HSPA/3G customers watching YouTube videos, using network-layer measurements only. YOUQMON combines passive traffic analysis techniques to detect stalling events in YouTube video streams, with a QoE model to map stallings into a Mean Opinion Score reflecting the end-user experience. We evaluate the stalling detection performance of YOUQMON with hundreds of YouTube video streams, and present results showing the feasibility of performing real-time YouTube QoE monitoring in an operational mobile broadband network.

• The Network of Excellence Euro-NF and its Specific Joint Research Projects. Fiedler, Markus; Hoßfeld, Tobias; Norros, Ilkka; Rodrigues, Joel; Rogério Pereira, Paulo. In ICST Global Community Magazine. 2012.
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  This article presents the European FP7 Network of Excellence “Euro-NF” (Networks of the Future) and reviews its set of activities. Specific attention is paid to the concept of Specific Joint Research Projects (SJRP), a series of small but focused projects, integrating at least three Euro-NF partners and targeting joint seminal work, publications as well as full-size follow-up projects. Further to the description of the SJRP concept, a set of three selected SJRP from different areas are presented in detail with respect to motivation, goal, contents, results, and impact.

  @article{info3-article-2012-98, abstract = {This article presents the European FP7 Network of Excellence “Euro-NF” (Networks of the Future) and reviews its set of activities. Specific attention is paid to the concept of Specific Joint Research Projects (SJRP), a series of small but focused projects, integrating at least three Euro-NF partners and targeting joint seminal work, publications as well as full-size follow-up projects. Further to the description of the SJRP concept, a set of three selected SJRP from different areas are presented in detail with respect to motivation, goal, contents, results, and impact.}, author = {Fiedler, Markus and Hoßfeld, Tobias and Norros, Ilkka and Rodrigues, Joel and Rogério Pereira, Paulo}, journal = {ICST Global Community Magazine}, keywords = {sys:hidden:article}, title = {The Network of Excellence Euro-NF and its Specific Joint Research Projects}, year = 2012 }

  %0 Journal Article %1 info3-article-2012-98 %A Fiedler, Markus %A Hoßfeld, Tobias %A Norros, Ilkka %A Rodrigues, Joel %A Rogério Pereira, Paulo %D 2012 %J ICST Global Community Magazine %T The Network of Excellence Euro-NF and its Specific Joint Research Projects %X This article presents the European FP7 Network of Excellence “Euro-NF” (Networks of the Future) and reviews its set of activities. Specific attention is paid to the concept of Specific Joint Research Projects (SJRP), a series of small but focused projects, integrating at least three Euro-NF partners and targeting joint seminal work, publications as well as full-size follow-up projects. Further to the description of the SJRP concept, a set of three selected SJRP from different areas are presented in detail with respect to motivation, goal, contents, results, and impact.
• On the influence of network impairments on YouTube video streaming. Biernacki, Arkadiusz; Metzger, Florian; Tutschku, Kurt. In Journal of Telecommunications and Information Technology. 2012.
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  Video sharing services like YouTube have become very popular which consequently results in a drastic shift of the Internet traffic statistic. When transmitting video content over packet based networks, stringent quality of service (QoS) constraints must be met in order to provide the comparable level of quality to a traditional broadcast television. However, the packet transmission is influenced by delays and losses of data packets which can have devastating influence on the perceived quality of the video. Therefore, we conducted an experimental evaluation of HTTP based video transmission focusing on how they react to packet delay and loss. Through this analysis we investigated how long video playback is stalled and how often re-buffering events take place. Our analysis revealed threshold levels for the packet delay, packet losses and network throughput which should not be exceeded in order to preserve smooth video transmission.

  @article{info3-article-2012-11, abstract = {Video sharing services like YouTube have become very popular which consequently results in a drastic shift of the Internet traffic statistic. When transmitting video content over packet based networks, stringent quality of service (QoS) constraints must be met in order to provide the comparable level of quality to a traditional broadcast television. However, the packet transmission is influenced by delays and losses of data packets which can have devastating influence on the perceived quality of the video. Therefore, we conducted an experimental evaluation of HTTP based video transmission focusing on how they react to packet delay and loss. Through this analysis we investigated how long video playback is stalled and how often re-buffering events take place. Our analysis revealed threshold levels for the packet delay, packet losses and network throughput which should not be exceeded in order to preserve smooth video transmission.}, author = {Biernacki, Arkadiusz and Metzger, Florian and Tutschku, Kurt}, journal = {Journal of Telecommunications and Information Technology}, keywords = {sys:hidden:article}, title = {On the influence of network impairments on YouTube video streaming}, year = 2012 }

  %0 Journal Article %1 info3-article-2012-11 %A Biernacki, Arkadiusz %A Metzger, Florian %A Tutschku, Kurt %D 2012 %J Journal of Telecommunications and Information Technology %T On the influence of network impairments on YouTube video streaming %X Video sharing services like YouTube have become very popular which consequently results in a drastic shift of the Internet traffic statistic. When transmitting video content over packet based networks, stringent quality of service (QoS) constraints must be met in order to provide the comparable level of quality to a traditional broadcast television. However, the packet transmission is influenced by delays and losses of data packets which can have devastating influence on the perceived quality of the video. Therefore, we conducted an experimental evaluation of HTTP based video transmission focusing on how they react to packet delay and loss. Through this analysis we investigated how long video playback is stalled and how often re-buffering events take place. Our analysis revealed threshold levels for the packet delay, packet losses and network throughput which should not be exceeded in order to preserve smooth video transmission.
• Analyzing Costs and Accuracy of Validation Mechanisms for Crowdsourcing Platforms. Hirth, Matthias; Hoßfeld, Tobias; Tran-Gia, Phuoc. In Mathematical and Computer Modelling. 2012.
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  Crowdsourcing is becoming more and more important for commercial purposes. With the growth of crowdsourcing platforms like Amazon Mechanical Turk or Microworkers, a huge work force and a large knowledge base can be easily accessed and utilized. But due to the anonymity of the workers, they are encouraged to cheat the employers in order to maximize their income. Thus, this paper we analyze two widely used crowd-based approaches to validate the submitted work. Both approaches are evaluated with regard to their detection quality, their costs and their applicability to different types of typical crowdsourcing tasks

  @article{info3-article-2012-96, abstract = {Crowdsourcing is becoming more and more important for commercial purposes. With the growth of crowdsourcing platforms like Amazon Mechanical Turk or Microworkers, a huge work force and a large knowledge base can be easily accessed and utilized. But due to the anonymity of the workers, they are encouraged to cheat the employers in order to maximize their income. Thus, this paper we analyze two widely used crowd-based approaches to validate the submitted work. Both approaches are evaluated with regard to their detection quality, their costs and their applicability to different types of typical crowdsourcing tasks}, author = {Hirth, Matthias and Hoßfeld, Tobias and Tran-Gia, Phuoc}, journal = {Mathematical and Computer Modelling}, keywords = {sys:hidden:article}, title = {Analyzing Costs and Accuracy of Validation Mechanisms for Crowdsourcing Platforms}, year = 2012 }

  %0 Journal Article %1 info3-article-2012-96 %A Hirth, Matthias %A Hoßfeld, Tobias %A Tran-Gia, Phuoc %D 2012 %J Mathematical and Computer Modelling %T Analyzing Costs and Accuracy of Validation Mechanisms for Crowdsourcing Platforms %X Crowdsourcing is becoming more and more important for commercial purposes. With the growth of crowdsourcing platforms like Amazon Mechanical Turk or Microworkers, a huge work force and a large knowledge base can be easily accessed and utilized. But due to the anonymity of the workers, they are encouraged to cheat the employers in order to maximize their income. Thus, this paper we analyze two widely used crowd-based approaches to validate the submitted work. Both approaches are evaluated with regard to their detection quality, their costs and their applicability to different types of typical crowdsourcing tasks
• Caching for BitTorrent-like P2P Systems: A Simple Fluid Model and its Implications. Lehrieder, Frank; Dán, György; Hoßfeld, Tobias; Oechsner, Simon; Singeorzan, Vlad. In IEEE/ACM Transactions on Networking, 20(4). 2012.
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  Peer-to-peer file-sharing systems are responsible for a significant share of the traffic between Internet service providers (ISPs) in the Internet. In order to decrease their peer-to-peer-related transit traffic costs, many ISPs have deployed caches for peer-to-peer traffic in recent years. We consider how the different types of peer-to-peer caches—caches already available on the market and caches expected to become available in the future—can possibly affect the amount of inter-ISP traffic. We develop a fluid model that captures the effects of the caches on the system dynamics of peer-to-peer networks and show that caches can have adverse effects on the system dynamics depending on the system parameters. We combine the fluid model with a simple model of inter-ISP traffic and show that the impact of caches cannot be accurately assessed without considering the effects of the caches on the system dynamics. We identify scenarios when caching actually leads to increased transit traffic. Motivated by our findings, we propose a proximity-aware peer-selection mechanism that avoids the increase of the transit traffic and improves the cache efficiency.We support the analytical results by extensive simulations and experiments with real BitTorrent clients.

  @article{info3-article-2012-94, abstract = {Peer-to-peer file-sharing systems are responsible for a significant share of the traffic between Internet service providers (ISPs) in the Internet. In order to decrease their peer-to-peer-related transit traffic costs, many ISPs have deployed caches for peer-to-peer traffic in recent years. We consider how the different types of peer-to-peer caches—caches already available on the market and caches expected to become available in the future—can possibly affect the amount of inter-ISP traffic. We develop a fluid model that captures the effects of the caches on the system dynamics of peer-to-peer networks and show that caches can have adverse effects on the system dynamics depending on the system parameters. We combine the fluid model with a simple model of inter-ISP traffic and show that the impact of caches cannot be accurately assessed without considering the effects of the caches on the system dynamics. We identify scenarios when caching actually leads to increased transit traffic. Motivated by our findings, we propose a proximity-aware peer-selection mechanism that avoids the increase of the transit traffic and improves the cache efficiency.We support the analytical results by extensive simulations and experiments with real BitTorrent clients.}, author = {Lehrieder, Frank and Dán, György and Hoßfeld, Tobias and Oechsner, Simon and Singeorzan, Vlad}, journal = {IEEE/ACM Transactions on Networking}, keywords = {sys:hidden:article}, title = {Caching for BitTorrent-like P2P Systems: A Simple Fluid Model and its Implications}, volume = {20(4)}, year = 2012 }

  %0 Journal Article %1 info3-article-2012-94 %A Lehrieder, Frank %A Dán, György %A Hoßfeld, Tobias %A Oechsner, Simon %A Singeorzan, Vlad %D 2012 %J IEEE/ACM Transactions on Networking %T Caching for BitTorrent-like P2P Systems: A Simple Fluid Model and its Implications %V 20(4) %X Peer-to-peer file-sharing systems are responsible for a significant share of the traffic between Internet service providers (ISPs) in the Internet. In order to decrease their peer-to-peer-related transit traffic costs, many ISPs have deployed caches for peer-to-peer traffic in recent years. We consider how the different types of peer-to-peer caches—caches already available on the market and caches expected to become available in the future—can possibly affect the amount of inter-ISP traffic. We develop a fluid model that captures the effects of the caches on the system dynamics of peer-to-peer networks and show that caches can have adverse effects on the system dynamics depending on the system parameters. We combine the fluid model with a simple model of inter-ISP traffic and show that the impact of caches cannot be accurately assessed without considering the effects of the caches on the system dynamics. We identify scenarios when caching actually leads to increased transit traffic. Motivated by our findings, we propose a proximity-aware peer-selection mechanism that avoids the increase of the transit traffic and improves the cache efficiency.We support the analytical results by extensive simulations and experiments with real BitTorrent clients.
• Cooperative Traffic Management for Video Streaming Overlays. Pussep, Konstantin; Lehrieder, Frank; Gross, Christian; Oechsner, Simon; Guenther, Markus; Meyer, Sebastian. In Computer Networks, 56(3), pp. 1118–1130. 2012.
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  Peer-to-Peer (P2P) based overlays often ignore the boundaries of network domains and make traffic management challenging for network operators. Locality-aware techniques are a promising approach to alleviate this impact, but often benefit only network operators and fail to provide similar benefits to end-users and overlay providers. This is especially severe with video streaming overlays that are responsible for large amount of Internet traffic. In this paper we present and evaluate a collaborative approach where a network operator measures the behavior of overlay users and promotes a subset of them in terms of up- and download bandwidth. This creates an incentive to users and overlay providers to cooperate by using locality awareness according to the operator's policies. We evaluate our approach both with a real application and via extensive simulations to analyze the user selection metrics and the impact on different network operators. Our study shows that this cooperative traffic management approach leads to a situation that is beneficial for users, content providers, and network operators.

  @article{info3-article-2012-92, abstract = {Peer-to-Peer (P2P) based overlays often ignore the boundaries of network domains and make traffic management challenging for network operators. Locality-aware techniques are a promising approach to alleviate this impact, but often benefit only network operators and fail to provide similar benefits to end-users and overlay providers. This is especially severe with video streaming overlays that are responsible for large amount of Internet traffic. In this paper we present and evaluate a collaborative approach where a network operator measures the behavior of overlay users and promotes a subset of them in terms of up- and download bandwidth. This creates an incentive to users and overlay providers to cooperate by using locality awareness according to the operator's policies. We evaluate our approach both with a real application and via extensive simulations to analyze the user selection metrics and the impact on different network operators. Our study shows that this cooperative traffic management approach leads to a situation that is beneficial for users, content providers, and network operators.}, author = {Pussep, Konstantin and Lehrieder, Frank and Gross, Christian and Oechsner, Simon and Guenther, Markus and Meyer, Sebastian}, journal = {Computer Networks}, keywords = {sys:hidden:article}, pages = {1118–1130}, title = {Cooperative Traffic Management for Video Streaming Overlays}, volume = {56(3)}, year = 2012 }

  %0 Journal Article %1 info3-article-2012-92 %A Pussep, Konstantin %A Lehrieder, Frank %A Gross, Christian %A Oechsner, Simon %A Guenther, Markus %A Meyer, Sebastian %D 2012 %J Computer Networks %P 1118–1130 %T Cooperative Traffic Management for Video Streaming Overlays %V 56(3) %X Peer-to-Peer (P2P) based overlays often ignore the boundaries of network domains and make traffic management challenging for network operators. Locality-aware techniques are a promising approach to alleviate this impact, but often benefit only network operators and fail to provide similar benefits to end-users and overlay providers. This is especially severe with video streaming overlays that are responsible for large amount of Internet traffic. In this paper we present and evaluate a collaborative approach where a network operator measures the behavior of overlay users and promotes a subset of them in terms of up- and download bandwidth. This creates an incentive to users and overlay providers to cooperate by using locality awareness according to the operator's policies. We evaluate our approach both with a real application and via extensive simulations to analyze the user selection metrics and the impact on different network operators. Our study shows that this cooperative traffic management approach leads to a situation that is beneficial for users, content providers, and network operators.
• Quality of Experience Management for YouTube: Clouds, FoG and the AquareYoum. Hoßfeld, Tobias; Liers, Florian; Schatz, Raimund; Staehle, Barbara; Staehle, Dirk; Volkert, Thomas; Wamser, Florian. In PIK - Praxis der Informationverarbeitung und -kommunikation (PIK). 2012.
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  Over the last decade, Quality of Experience (QoE) has become a new, central paradigm for understanding the quality of networks and services. In particular, the concept has attracted the interest of communication network and service providers, since being able to guarantee good QoE to customers provides an opportunity for differentiation. In this paper we investigate the potential as well as the implementation challenges of QoE management in the Internet. Using YouTube video streaming service as example, we discuss the different elements that are required for the realization of the paradigm-shift towards truly user-centric network orchestration. To this end, we elaborate QoE management requirements for two complementary network scenarios (wireless mesh Internet access networks vs. global Internet delivery) and provide a QoE model for YouTube taking into account impairments like stalling and initial delay. We present two YouTube QoE monitoring approaches operating on the network and the end user level. Finally, we demonstrate how QoE can be dynamically optimized in both network scenarios with two exemplary concepts, AquareYoum and FoG, respectively. Our results show how QoE management can truly improve the user experience while at the same time increase the efficiency of network resource allocation.

  @article{info3-article-2012-103, abstract = {Over the last decade, Quality of Experience (QoE) has become a new, central paradigm for understanding the quality of networks and services. In particular, the concept has attracted the interest of communication network and service providers, since being able to guarantee good QoE to customers provides an opportunity for differentiation. In this paper we investigate the potential as well as the implementation challenges of QoE management in the Internet. Using YouTube video streaming service as example, we discuss the different elements that are required for the realization of the paradigm-shift towards truly user-centric network orchestration. To this end, we elaborate QoE management requirements for two complementary network scenarios (wireless mesh Internet access networks vs. global Internet delivery) and provide a QoE model for YouTube taking into account impairments like stalling and initial delay. We present two YouTube QoE monitoring approaches operating on the network and the end user level. Finally, we demonstrate how QoE can be dynamically optimized in both network scenarios with two exemplary concepts, AquareYoum and FoG, respectively. Our results show how QoE management can truly improve the user experience while at the same time increase the efficiency of network resource allocation.}, author = {Hoßfeld, Tobias and Liers, Florian and Schatz, Raimund and Staehle, Barbara and Staehle, Dirk and Volkert, Thomas and Wamser, Florian}, journal = {PIK - Praxis der Informationverarbeitung und -kommunikation (PIK)}, keywords = {sys:hidden:article}, month = {08}, title = {Quality of Experience Management for YouTube: Clouds, FoG and the AquareYoum}, year = 2012 }

  %0 Journal Article %1 info3-article-2012-103 %A Hoßfeld, Tobias %A Liers, Florian %A Schatz, Raimund %A Staehle, Barbara %A Staehle, Dirk %A Volkert, Thomas %A Wamser, Florian %D 2012 %J PIK - Praxis der Informationverarbeitung und -kommunikation (PIK) %T Quality of Experience Management for YouTube: Clouds, FoG and the AquareYoum %X Over the last decade, Quality of Experience (QoE) has become a new, central paradigm for understanding the quality of networks and services. In particular, the concept has attracted the interest of communication network and service providers, since being able to guarantee good QoE to customers provides an opportunity for differentiation. In this paper we investigate the potential as well as the implementation challenges of QoE management in the Internet. Using YouTube video streaming service as example, we discuss the different elements that are required for the realization of the paradigm-shift towards truly user-centric network orchestration. To this end, we elaborate QoE management requirements for two complementary network scenarios (wireless mesh Internet access networks vs. global Internet delivery) and provide a QoE model for YouTube taking into account impairments like stalling and initial delay. We present two YouTube QoE monitoring approaches operating on the network and the end user level. Finally, we demonstrate how QoE can be dynamically optimized in both network scenarios with two exemplary concepts, AquareYoum and FoG, respectively. Our results show how QoE management can truly improve the user experience while at the same time increase the efficiency of network resource allocation.
• Gaming in the clouds: QoE and the users’ perspective. Jarschel, Michael; Schlosser, Daniel; Scheuring, Sven; Hoßfeld, Tobias. In Mathematical and Computer Modelling. 2012.
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  Cloud Gaming is a new kind of service, which combines the successful concepts of Cloud Computing and Online Gaming. It provides the entire game experience to the users remotely from a data center. The player is no longer dependent on a specific type or quality of gaming hardware, but is able to use common devices. The end device only needs a broadband internet connection and the ability to display High Definition (HD) video. While this may reduce hardware costs for users and increase the revenue for developers by leaving out the retail chain, it also raises new challenges for service quality in terms of bandwidth and latency for the underlying network. In this paper we present the results of a subjective user study we conducted into the user-perceived quality of experience (QoE) in Cloud Gaming. We design a measurement environment, that emulates this new type of service, define tests for users to assess the QoE, derive Key Influence Factors (KFI) and influences of content and perception from our results.

  @article{info3-article-2012-95, abstract = {Cloud Gaming is a new kind of service, which combines the successful concepts of Cloud Computing and Online Gaming. It provides the entire game experience to the users remotely from a data center. The player is no longer dependent on a specific type or quality of gaming hardware, but is able to use common devices. The end device only needs a broadband internet connection and the ability to display High Definition (HD) video. While this may reduce hardware costs for users and increase the revenue for developers by leaving out the retail chain, it also raises new challenges for service quality in terms of bandwidth and latency for the underlying network. In this paper we present the results of a subjective user study we conducted into the user-perceived quality of experience (QoE) in Cloud Gaming. We design a measurement environment, that emulates this new type of service, define tests for users to assess the QoE, derive Key Influence Factors (KFI) and influences of content and perception from our results.}, author = {Jarschel, Michael and Schlosser, Daniel and Scheuring, Sven and Hoßfeld, Tobias}, journal = {Mathematical and Computer Modelling}, keywords = {sys:hidden:article}, title = {Gaming in the clouds: QoE and the users’ perspective}, year = 2012 }

  %0 Journal Article %1 info3-article-2012-95 %A Jarschel, Michael %A Schlosser, Daniel %A Scheuring, Sven %A Hoßfeld, Tobias %D 2012 %J Mathematical and Computer Modelling %T Gaming in the clouds: QoE and the users’ perspective %X Cloud Gaming is a new kind of service, which combines the successful concepts of Cloud Computing and Online Gaming. It provides the entire game experience to the users remotely from a data center. The player is no longer dependent on a specific type or quality of gaming hardware, but is able to use common devices. The end device only needs a broadband internet connection and the ability to display High Definition (HD) video. While this may reduce hardware costs for users and increase the revenue for developers by leaving out the retail chain, it also raises new challenges for service quality in terms of bandwidth and latency for the underlying network. In this paper we present the results of a subjective user study we conducted into the user-perceived quality of experience (QoE) in Cloud Gaming. We design a measurement environment, that emulates this new type of service, define tests for users to assess the QoE, derive Key Influence Factors (KFI) and influences of content and perception from our results.
• Challenges of QoE Management for Cloud Applications. Hoßfeld, Tobias; Schatz, Raimund; Varela, Martin; Timmerer, Christian. In IEEE Communications Magazine, April issue. 2012.
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  Cloud computing is currently gaining enormous momentum due to a number of promised benefits: ease of use in terms of deployment, administration and maintenance, high scalability and flexibility to create new services. However, as more personal and business applications migrate to the Cloud, the service quality will become an important differentiator between providers. In particular, Quality of Experience (QoE) as perceived by users has the potential become the guiding paradigm for managing quality in the Cloud. In this article, we discuss technical challenges emerging from shifting services to the Cloud, as well as how this shift impacts QoE and QoE management. Thereby, a particular focus is on multimedia Cloud applications. Together with a novel QoE-based classification scheme of cloud applications, these challenges drive the research agenda on QoE management for Cloud applications.

  @article{info3-article-2012-97, abstract = {Cloud computing is currently gaining enormous momentum due to a number of promised benefits: ease of use in terms of deployment, administration and maintenance, high scalability and flexibility to create new services. However, as more personal and business applications migrate to the Cloud, the service quality will become an important differentiator between providers. In particular, Quality of Experience (QoE) as perceived by users has the potential become the guiding paradigm for managing quality in the Cloud. In this article, we discuss technical challenges emerging from shifting services to the Cloud, as well as how this shift impacts QoE and QoE management. Thereby, a particular focus is on multimedia Cloud applications. Together with a novel QoE-based classification scheme of cloud applications, these challenges drive the research agenda on QoE management for Cloud applications.}, author = {Hoßfeld, Tobias and Schatz, Raimund and Varela, Martin and Timmerer, Christian}, journal = {IEEE Communications Magazine}, keywords = {sys:hidden:article}, month = {04}, title = {Challenges of QoE Management for Cloud Applications}, volume = {April issue}, year = 2012 }

  %0 Journal Article %1 info3-article-2012-97 %A Hoßfeld, Tobias %A Schatz, Raimund %A Varela, Martin %A Timmerer, Christian %D 2012 %J IEEE Communications Magazine %T Challenges of QoE Management for Cloud Applications %V April issue %X Cloud computing is currently gaining enormous momentum due to a number of promised benefits: ease of use in terms of deployment, administration and maintenance, high scalability and flexibility to create new services. However, as more personal and business applications migrate to the Cloud, the service quality will become an important differentiator between providers. In particular, Quality of Experience (QoE) as perceived by users has the potential become the guiding paradigm for managing quality in the Cloud. In this article, we discuss technical challenges emerging from shifting services to the Cloud, as well as how this shift impacts QoE and QoE management. Thereby, a particular focus is on multimedia Cloud applications. Together with a novel QoE-based classification scheme of cloud applications, these challenges drive the research agenda on QoE management for Cloud applications.
• Aktuelles Schlagwort: Crowdsourcing. Hoßfeld, Tobias; Hirth, Matthias; Tran-Gia, Phuoc. In Informatik Spektrum, 35. 2012.
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  Seit der Öffnung des Internets für die Allgemeinheit Anfang der 90er Jahre hat eine rasante Entwicklung stattgefunden. Neue Paradigmen wie Peer-to-Peer (P2P), Web 2.0 oder Cloud Computing führen zu neuartigen Diensten und Anwendungen, welche bei den Anwendern längst etabliert sind und einen Großteil des Datenverkehrs im Internet ausmachen. Beispiele hierfür sind unter anderem P2P-Anwendungen wie BitTorrent zum Austausch riesiger Datenmengen, Skype für Sprach- und Videokonferenzen, Soziale Medien wie Facebook oder Twitter, Cloud Anwendungen wie DropBox als synchronisiertes Netzwerk-Dateisystem für verteilte Rechner oder Cloud Gaming. Aktuell taucht ein neues Schlagwort im Internet auf: „Crowdsourcing“. Einige Aufgaben und Probleme, die für Menschen relativ einfach zu lösen sind, können derzeit selbst von modernen Machine Clouds noch nicht algorithmisch bewältigt werden. Hierzu zählen etwa Text- und Bilderkennung, das Verifizieren, Analysieren und Kategorisieren von Videoinhalten, das Schaffen von Wissen, das Verbessern und Kreieren von Produkten oder wissenschaftliche Forschung. Diese stellen Anwendungsgebiete von Crowdsourcing dar. Statt (oder zusätzlich zu) Machine Clouds wird die Masse der Internetnutzer in die Wertschöpfungskette eingebunden. Man spricht hier auch von Human Clouds. Neben Sozialen Medien ist Crowdsourcing eine der wichtigsten aktuell aufstrebenden Technologien und Geschäftsmodelle im Internet, die die Zukunft des Arbeitens und der Arbeitsorganisation von Grund auf verändern wird. Die wirtschaftliche und gesellschaftliche Bedeutung von Crowdsourcing-Plattformen wächst ständig und fördert die Entstehung neuer Formen der Arbeitsorganisation. Jobs in Crowdsourcing-Plattformen besitzen eine viel kleinere Granularität im Vergleich zu denen im traditionellen Outsourcing bzw. Outtasking Bereich. Das Aktuelle Schlagwort beleuchtet den Begriff „Crowdsourcing“ näher und wird zunächst wichtige Begriffe einführen, bevor die Anwendungsgebiete von Crowdsourcing sowie dessen Bedeutung in der Praxis und zukünftige Weiterentwicklung betrachtet werden.

  @article{info3-article-2012-102, abstract = {Seit der Öffnung des Internets für die Allgemeinheit Anfang der 90er Jahre hat eine rasante Entwicklung stattgefunden. Neue Paradigmen wie Peer-to-Peer (P2P), Web 2.0 oder Cloud Computing führen zu neuartigen Diensten und Anwendungen, welche bei den Anwendern längst etabliert sind und einen Großteil des Datenverkehrs im Internet ausmachen. Beispiele hierfür sind unter anderem P2P-Anwendungen wie BitTorrent zum Austausch riesiger Datenmengen, Skype für Sprach- und Videokonferenzen, Soziale Medien wie Facebook oder Twitter, Cloud Anwendungen wie DropBox als synchronisiertes Netzwerk-Dateisystem für verteilte Rechner oder Cloud Gaming. Aktuell taucht ein neues Schlagwort im Internet auf: „Crowdsourcing“. Einige Aufgaben und Probleme, die für Menschen relativ einfach zu lösen sind, können derzeit selbst von modernen Machine Clouds noch nicht algorithmisch bewältigt werden. Hierzu zählen etwa Text- und Bilderkennung, das Verifizieren, Analysieren und Kategorisieren von Videoinhalten, das Schaffen von Wissen, das Verbessern und Kreieren von Produkten oder wissenschaftliche Forschung. Diese stellen Anwendungsgebiete von Crowdsourcing dar. Statt (oder zusätzlich zu) Machine Clouds wird die Masse der Internetnutzer in die Wertschöpfungskette eingebunden. Man spricht hier auch von Human Clouds. Neben Sozialen Medien ist Crowdsourcing eine der wichtigsten aktuell aufstrebenden Technologien und Geschäftsmodelle im Internet, die die Zukunft des Arbeitens und der Arbeitsorganisation von Grund auf verändern wird. Die wirtschaftliche und gesellschaftliche Bedeutung von Crowdsourcing-Plattformen wächst ständig und fördert die Entstehung neuer Formen der Arbeitsorganisation. Jobs in Crowdsourcing-Plattformen besitzen eine viel kleinere Granularität im Vergleich zu denen im traditionellen Outsourcing bzw. Outtasking Bereich. Das Aktuelle Schlagwort beleuchtet den Begriff „Crowdsourcing“ näher und wird zunächst wichtige Begriffe einführen, bevor die Anwendungsgebiete von Crowdsourcing sowie dessen Bedeutung in der Praxis und zukünftige Weiterentwicklung betrachtet werden.}, author = {Hoßfeld, Tobias and Hirth, Matthias and Tran-Gia, Phuoc}, journal = {Informatik Spektrum}, keywords = {sys:hidden:article}, month = {04}, title = {Aktuelles Schlagwort: Crowdsourcing}, volume = 35, year = 2012 }

  %0 Journal Article %1 info3-article-2012-102 %A Hoßfeld, Tobias %A Hirth, Matthias %A Tran-Gia, Phuoc %D 2012 %J Informatik Spektrum %T Aktuelles Schlagwort: Crowdsourcing %V 35 %X Seit der Öffnung des Internets für die Allgemeinheit Anfang der 90er Jahre hat eine rasante Entwicklung stattgefunden. Neue Paradigmen wie Peer-to-Peer (P2P), Web 2.0 oder Cloud Computing führen zu neuartigen Diensten und Anwendungen, welche bei den Anwendern längst etabliert sind und einen Großteil des Datenverkehrs im Internet ausmachen. Beispiele hierfür sind unter anderem P2P-Anwendungen wie BitTorrent zum Austausch riesiger Datenmengen, Skype für Sprach- und Videokonferenzen, Soziale Medien wie Facebook oder Twitter, Cloud Anwendungen wie DropBox als synchronisiertes Netzwerk-Dateisystem für verteilte Rechner oder Cloud Gaming. Aktuell taucht ein neues Schlagwort im Internet auf: „Crowdsourcing“. Einige Aufgaben und Probleme, die für Menschen relativ einfach zu lösen sind, können derzeit selbst von modernen Machine Clouds noch nicht algorithmisch bewältigt werden. Hierzu zählen etwa Text- und Bilderkennung, das Verifizieren, Analysieren und Kategorisieren von Videoinhalten, das Schaffen von Wissen, das Verbessern und Kreieren von Produkten oder wissenschaftliche Forschung. Diese stellen Anwendungsgebiete von Crowdsourcing dar. Statt (oder zusätzlich zu) Machine Clouds wird die Masse der Internetnutzer in die Wertschöpfungskette eingebunden. Man spricht hier auch von Human Clouds. Neben Sozialen Medien ist Crowdsourcing eine der wichtigsten aktuell aufstrebenden Technologien und Geschäftsmodelle im Internet, die die Zukunft des Arbeitens und der Arbeitsorganisation von Grund auf verändern wird. Die wirtschaftliche und gesellschaftliche Bedeutung von Crowdsourcing-Plattformen wächst ständig und fördert die Entstehung neuer Formen der Arbeitsorganisation. Jobs in Crowdsourcing-Plattformen besitzen eine viel kleinere Granularität im Vergleich zu denen im traditionellen Outsourcing bzw. Outtasking Bereich. Das Aktuelle Schlagwort beleuchtet den Begriff „Crowdsourcing“ näher und wird zunächst wichtige Begriffe einführen, bevor die Anwendungsgebiete von Crowdsourcing sowie dessen Bedeutung in der Praxis und zukünftige Weiterentwicklung betrachtet werden.
• Performance of PCN-Based Admission Control under Challenging Conditions. Menth, Michael; Lehrieder, Frank. In IEEE/ACM Transactions on Networking, 20(2), pp. 422–435. 2012.
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  Pre-congestion notification (PCN) is a packet marking technique for IP networks to notify egress nodes of a socalled PCN domain whether the traffic rate on some links exceeds certain configurable bounds. This feedback is used by decision points for admission control (AC) to block new flows when the traffic load is already high. PCN-based AC is simpler than other AC methods because interior routers do not need to keep perflow states. Therefore, it is currently being standardized by the IETF. We discuss various realization options and analyze their performance in the presence of flash crowds or with multipath routing by means of simulation and mathematical modeling. Such situations can be aggravated by insufficient flow aggregation, long round-trip times, on/off traffic, delayed media, inappropriate marker configuration, and smoothed feedback.

  @article{info3-article-2012-91, abstract = {Pre-congestion notification (PCN) is a packet marking technique for IP networks to notify egress nodes of a socalled PCN domain whether the traffic rate on some links exceeds certain configurable bounds. This feedback is used by decision points for admission control (AC) to block new flows when the traffic load is already high. PCN-based AC is simpler than other AC methods because interior routers do not need to keep perflow states. Therefore, it is currently being standardized by the IETF. We discuss various realization options and analyze their performance in the presence of flash crowds or with multipath routing by means of simulation and mathematical modeling. Such situations can be aggravated by insufficient flow aggregation, long round-trip times, on/off traffic, delayed media, inappropriate marker configuration, and smoothed feedback.}, author = {Menth, Michael and Lehrieder, Frank}, journal = {IEEE/ACM Transactions on Networking}, keywords = {sys:hidden:article}, month = {04}, pages = {422-435}, title = {Performance of PCN-Based Admission Control under Challenging Conditions}, volume = {20(2)}, year = 2012 }

  %0 Journal Article %1 info3-article-2012-91 %A Menth, Michael %A Lehrieder, Frank %D 2012 %J IEEE/ACM Transactions on Networking %P 422-435 %T Performance of PCN-Based Admission Control under Challenging Conditions %V 20(2) %X Pre-congestion notification (PCN) is a packet marking technique for IP networks to notify egress nodes of a socalled PCN domain whether the traffic rate on some links exceeds certain configurable bounds. This feedback is used by decision points for admission control (AC) to block new flows when the traffic load is already high. PCN-based AC is simpler than other AC methods because interior routers do not need to keep perflow states. Therefore, it is currently being standardized by the IETF. We discuss various realization options and analyze their performance in the presence of flash crowds or with multipath routing by means of simulation and mathematical modeling. Such situations can be aggravated by insufficient flow aggregation, long round-trip times, on/off traffic, delayed media, inappropriate marker configuration, and smoothed feedback.
• Energy Efficient Virtual Network Embedding. Felipe Botero, Juan; Hesselbach, Xavier; Duelli, Michael; Schlosser, Daniel; Fischer, Andreas; de Meer, Hermann. In IEEE Communication Letters, PP. 2012.
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  Waste of energy due to over-provisioning and over-dimensioning of network infrastructures has recently stimulated the interest on energy consumption reduction by Internet Service Providers (ISPs). By means of resource consolidation, network virtualization based architectures will enable energy saving. In this letter, we extend the well-known virtual network embedding problem (VNE) to energy awareness and propose a mixed integer program (MIP) which provides optimal energy efficient embeddings. Simulation results show the energy gains of the proposed MIP over the existing cost-based VNE approach.

  @article{info3-article-2012-100, abstract = {Waste of energy due to over-provisioning and over-dimensioning of network infrastructures has recently stimulated the interest on energy consumption reduction by Internet Service Providers (ISPs). By means of resource consolidation, network virtualization based architectures will enable energy saving. In this letter, we extend the well-known virtual network embedding problem (VNE) to energy awareness and propose a mixed integer program (MIP) which provides optimal energy efficient embeddings. Simulation results show the energy gains of the proposed MIP over the existing cost-based VNE approach.}, author = {Felipe Botero, Juan and Hesselbach, Xavier and Duelli, Michael and Schlosser, Daniel and Fischer, Andreas and de Meer, Hermann}, journal = {IEEE Communication Letters}, keywords = {sys:hidden:article}, month = {03}, title = {Energy Efficient Virtual Network Embedding}, volume = {PP}, year = 2012 }

  %0 Journal Article %1 info3-article-2012-100 %A Felipe Botero, Juan %A Hesselbach, Xavier %A Duelli, Michael %A Schlosser, Daniel %A Fischer, Andreas %A de Meer, Hermann %D 2012 %J IEEE Communication Letters %T Energy Efficient Virtual Network Embedding %V PP %X Waste of energy due to over-provisioning and over-dimensioning of network infrastructures has recently stimulated the interest on energy consumption reduction by Internet Service Providers (ISPs). By means of resource consolidation, network virtualization based architectures will enable energy saving. In this letter, we extend the well-known virtual network embedding problem (VNE) to energy awareness and propose a mixed integer program (MIP) which provides optimal energy efficient embeddings. Simulation results show the energy gains of the proposed MIP over the existing cost-based VNE approach.

• ALEVIN - A Framework to Develop, Compare, and Analyze Virtual Network Embedding Algorithms. Fischer, Andreas; Felipe Botero, Juan; Duelli, Michael; Schlosser, Daniel; Hesselbach, Xavier; de Meer, Hermann. In Electronic Communications of the EASST, Kommunikation in Verteilten Systemen 2011, 37. 2011.
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  Network virtualization is recognized as an enabling technology for the Future Internet. Applying virtualization of network resources leads to the problem of mapping virtual resources to physical resources, known as “Virtual Network Embedding” (VNE). Several algorithms attempting to solve this problem have been discussed in the literature, so far. However, comparison of VNE algorithms is hard, as each algorithm focuses on different criteria. To that end, we introduce a framework to compare different algorithms according to a set of metrics, which allow to evaluate the algorithms and compute their results on a given scenario for arbitrary parameters.

  @article{info3-article-2011-88, abstract = {Network virtualization is recognized as an enabling technology for the Future Internet. Applying virtualization of network resources leads to the problem of mapping virtual resources to physical resources, known as “Virtual Network Embedding” (VNE). Several algorithms attempting to solve this problem have been discussed in the literature, so far. However, comparison of VNE algorithms is hard, as each algorithm focuses on different criteria. To that end, we introduce a framework to compare different algorithms according to a set of metrics, which allow to evaluate the algorithms and compute their results on a given scenario for arbitrary parameters.}, author = {Fischer, Andreas and Felipe Botero, Juan and Duelli, Michael and Schlosser, Daniel and Hesselbach, Xavier and de Meer, Hermann}, journal = {Electronic Communications of the EASST, Kommunikation in Verteilten Systemen 2011}, keywords = {sys:hidden:article}, month = {03}, title = {ALEVIN - A Framework to Develop, Compare, and Analyze Virtual Network Embedding Algorithms}, volume = 37, year = 2011 }

  %0 Journal Article %1 info3-article-2011-88 %A Fischer, Andreas %A Felipe Botero, Juan %A Duelli, Michael %A Schlosser, Daniel %A Hesselbach, Xavier %A de Meer, Hermann %D 2011 %J Electronic Communications of the EASST, Kommunikation in Verteilten Systemen 2011 %T ALEVIN - A Framework to Develop, Compare, and Analyze Virtual Network Embedding Algorithms %V 37 %X Network virtualization is recognized as an enabling technology for the Future Internet. Applying virtualization of network resources leads to the problem of mapping virtual resources to physical resources, known as “Virtual Network Embedding” (VNE). Several algorithms attempting to solve this problem have been discussed in the literature, so far. However, comparison of VNE algorithms is hard, as each algorithm focuses on different criteria. To that end, we introduce a framework to compare different algorithms according to a set of metrics, which allow to evaluate the algorithms and compute their results on a given scenario for arbitrary parameters.
• On Max-Min Fair Flow Optimization in Wireless Mesh Networks. Pióro, Michał; Zotkiewicz, Mateusz; Staehle, Barbara; Staehle, Dirk; Yuan, Di. In Ad Hoc Networks, Special Issue on Models and Algorithms for Wireless Mesh Networks. 2011.
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  The paper is devoted to WMN modeling using mixed-integer programming (MIP) formulations that allow to precisely characterize the link data rate capacity and transmission scheduling within time slots. Such MIP models are formulated for several cases of the modulation and coding schemes (MCS) assignment. We present a general way of solving the MMF traffic objective for WMN and use it for the formulated capacity models. Thus the paper combines WMN radio link modeling with a non-standard way of dealing with uncertain traffic, a combination that has not been to our knowledge considered so far in terms of exact optimization models. This combination, involving integer programming, forms the main contribution of the paper. We discuss several ways of solving the considered MMF problems and present an extensive numerical study that illustrates the running time efficiency of the different solution approaches, and the in uence of the MCS selection options and the number of time slots on the traffic performance of a WMN.

  @article{info3-article-2011-84, abstract = {The paper is devoted to WMN modeling using mixed-integer programming (MIP) formulations that allow to precisely characterize the link data rate capacity and transmission scheduling within time slots. Such MIP models are formulated for several cases of the modulation and coding schemes (MCS) assignment. We present a general way of solving the MMF traffic objective for WMN and use it for the formulated capacity models. Thus the paper combines WMN radio link modeling with a non-standard way of dealing with uncertain traffic, a combination that has not been to our knowledge considered so far in terms of exact optimization models. This combination, involving integer programming, forms the main contribution of the paper. We discuss several ways of solving the considered MMF problems and present an extensive numerical study that illustrates the running time efficiency of the different solution approaches, and the in uence of the MCS selection options and the number of time slots on the traffic performance of a WMN.}, author = {Pióro, Michał and Zotkiewicz, Mateusz and Staehle, Barbara and Staehle, Dirk and Yuan, Di}, journal = {Ad Hoc Networks, Special Issue on Models and Algorithms for Wireless Mesh Networks}, keywords = {sys:hidden:article}, title = {On Max-Min Fair Flow Optimization in Wireless Mesh Networks}, year = 2011 }

  %0 Journal Article %1 info3-article-2011-84 %A Pióro, Michał %A Zotkiewicz, Mateusz %A Staehle, Barbara %A Staehle, Dirk %A Yuan, Di %D 2011 %J Ad Hoc Networks, Special Issue on Models and Algorithms for Wireless Mesh Networks %T On Max-Min Fair Flow Optimization in Wireless Mesh Networks %X The paper is devoted to WMN modeling using mixed-integer programming (MIP) formulations that allow to precisely characterize the link data rate capacity and transmission scheduling within time slots. Such MIP models are formulated for several cases of the modulation and coding schemes (MCS) assignment. We present a general way of solving the MMF traffic objective for WMN and use it for the formulated capacity models. Thus the paper combines WMN radio link modeling with a non-standard way of dealing with uncertain traffic, a combination that has not been to our knowledge considered so far in terms of exact optimization models. This combination, involving integer programming, forms the main contribution of the paper. We discuss several ways of solving the considered MMF problems and present an extensive numerical study that illustrates the running time efficiency of the different solution approaches, and the in uence of the MCS selection options and the number of time slots on the traffic performance of a WMN.
• AquareYoum: Application and Quality of Experience-Aware Resource Management for YouTube in Wireless Mesh Networks. Staehle, Barbara; Wamser, Florian; Hirth, Matthias; Stezenbach, David; Staehle, Dirk. In PIK - Praxis der Informationsverarbeitung und Kommunikation. 2011.
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  The browser has become the users’ interface to a plethora of Internet applications which are accessible from nearly everywhere and every device. The price for the simple and cheap access over the Internet is often a reduced end-user quality of experience (QoE). The reason for this is that the network ignores the content of the packets it transports and thereby neither knows which services it supports, nor if and which quality requirements have to be given. In addition, the needs of the applications can be time varying, and the network might not be able to give strict quality guarantees. We therefore advocate the idea of an application-network interaction in order to dynamically adapt the network resources if a QoE degradation is imminent. The software suite AquareYoum implements this approach and enables a smooth YouTube video playback in a congested wireless mesh Internet access network by dynamically selecting the least congested Internet gateway.

  @article{info3-article-2011-85, abstract = {The browser has become the users’ interface to a plethora of Internet applications which are accessible from nearly everywhere and every device. The price for the simple and cheap access over the Internet is often a reduced end-user quality of experience (QoE). The reason for this is that the network ignores the content of the packets it transports and thereby neither knows which services it supports, nor if and which quality requirements have to be given. In addition, the needs of the applications can be time varying, and the network might not be able to give strict quality guarantees. We therefore advocate the idea of an application-network interaction in order to dynamically adapt the network resources if a QoE degradation is imminent. The software suite AquareYoum implements this approach and enables a smooth YouTube video playback in a congested wireless mesh Internet access network by dynamically selecting the least congested Internet gateway.}, author = {Staehle, Barbara and Wamser, Florian and Hirth, Matthias and Stezenbach, David and Staehle, Dirk}, journal = {PIK - Praxis der Informationsverarbeitung und Kommunikation}, keywords = {sys:hidden:article}, title = {AquareYoum: Application and Quality of Experience-Aware Resource Management for YouTube in Wireless Mesh Networks}, year = 2011 }

  %0 Journal Article %1 info3-article-2011-85 %A Staehle, Barbara %A Wamser, Florian %A Hirth, Matthias %A Stezenbach, David %A Staehle, Dirk %D 2011 %J PIK - Praxis der Informationsverarbeitung und Kommunikation %T AquareYoum: Application and Quality of Experience-Aware Resource Management for YouTube in Wireless Mesh Networks %X The browser has become the users’ interface to a plethora of Internet applications which are accessible from nearly everywhere and every device. The price for the simple and cheap access over the Internet is often a reduced end-user quality of experience (QoE). The reason for this is that the network ignores the content of the packets it transports and thereby neither knows which services it supports, nor if and which quality requirements have to be given. In addition, the needs of the applications can be time varying, and the network might not be able to give strict quality guarantees. We therefore advocate the idea of an application-network interaction in order to dynamically adapt the network resources if a QoE degradation is imminent. The software suite AquareYoum implements this approach and enables a smooth YouTube video playback in a congested wireless mesh Internet access network by dynamically selecting the least congested Internet gateway.
• Mitigating Unfairness in Locality-Aware Peer-to-Peer Networks. Lehrieder, Frank; Oechsner, Simon; Hoßfeld, Tobias; Staehle, Dirk; Despotovic, Zoran; Kellerer, Wolfgang; Michel, Maximilian. In International Journal of Network Management (IJNM), Special Issue on Economic Traffic Management, 21(1). 2011.
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  Locality-awareness is considered as a promising approach to increase the efficiency of content distribution by peer-to-peer (P2P) networks, e.g., BitTorrent. It is intended to reduce the inter-domain traffic which is costly for Internet service providers (ISPs) and to simultaneously increase the performance from the viewpoint of the P2P users, i.e., to shorten download times. This win-win situation should be achieved by a preferred exchange of information between peers which are located closely to each other in the underlying network topology. A set of studies shows that these approaches can lead to a win-win situation under certain conditions, and to a win-no lose situation in most cases. However, the scenarios used mostly assume homogeneous peer distributions. This is not the case in practice according to recent measurement studies. Therefore, we extend previous work in this paper by studying scenarios with real-life, skewed peer distributions. We show that even a win-no lose situation is difficult to achieve under those conditions and that the actual impact for a specific peer heavily depends on the used locality-aware peer selection and the specific scenario. This contradicts the principle of economic traffic management (ETM) which aims for a solution where all involved players benefit and consequently have an incentive to adopt locality-awareness. Therefore, we propose and evaluate refinements of current proposals, achieving that all users of P2P networks can be sure that their application performance is not reduced. This mitigates the unfairness introduced by current proposals which is a key requirement for a broad acceptance of the concept of locality-awareness in the user community of P2P networks.

  @article{info3-article-2011-82, abstract = {Locality-awareness is considered as a promising approach to increase the efficiency of content distribution by peer-to-peer (P2P) networks, e.g., BitTorrent. It is intended to reduce the inter-domain traffic which is costly for Internet service providers (ISPs) and to simultaneously increase the performance from the viewpoint of the P2P users, i.e., to shorten download times. This win-win situation should be achieved by a preferred exchange of information between peers which are located closely to each other in the underlying network topology. A set of studies shows that these approaches can lead to a win-win situation under certain conditions, and to a win-no lose situation in most cases. However, the scenarios used mostly assume homogeneous peer distributions. This is not the case in practice according to recent measurement studies. Therefore, we extend previous work in this paper by studying scenarios with real-life, skewed peer distributions. We show that even a win-no lose situation is difficult to achieve under those conditions and that the actual impact for a specific peer heavily depends on the used locality-aware peer selection and the specific scenario. This contradicts the principle of economic traffic management (ETM) which aims for a solution where all involved players benefit and consequently have an incentive to adopt locality-awareness. Therefore, we propose and evaluate refinements of current proposals, achieving that all users of P2P networks can be sure that their application performance is not reduced. This mitigates the unfairness introduced by current proposals which is a key requirement for a broad acceptance of the concept of locality-awareness in the user community of P2P networks.}, author = {Lehrieder, Frank and Oechsner, Simon and Hoßfeld, Tobias and Staehle, Dirk and Despotovic, Zoran and Kellerer, Wolfgang and Michel, Maximilian}, journal = {International Journal of Network Management (IJNM), Special Issue on Economic Traffic Management}, keywords = {sys:hidden:article}, month = {01}, title = {Mitigating Unfairness in Locality-Aware Peer-to-Peer Networks}, volume = {21(1)}, year = 2011 }

  %0 Journal Article %1 info3-article-2011-82 %A Lehrieder, Frank %A Oechsner, Simon %A Hoßfeld, Tobias %A Staehle, Dirk %A Despotovic, Zoran %A Kellerer, Wolfgang %A Michel, Maximilian %D 2011 %J International Journal of Network Management (IJNM), Special Issue on Economic Traffic Management %T Mitigating Unfairness in Locality-Aware Peer-to-Peer Networks %V 21(1) %X Locality-awareness is considered as a promising approach to increase the efficiency of content distribution by peer-to-peer (P2P) networks, e.g., BitTorrent. It is intended to reduce the inter-domain traffic which is costly for Internet service providers (ISPs) and to simultaneously increase the performance from the viewpoint of the P2P users, i.e., to shorten download times. This win-win situation should be achieved by a preferred exchange of information between peers which are located closely to each other in the underlying network topology. A set of studies shows that these approaches can lead to a win-win situation under certain conditions, and to a win-no lose situation in most cases. However, the scenarios used mostly assume homogeneous peer distributions. This is not the case in practice according to recent measurement studies. Therefore, we extend previous work in this paper by studying scenarios with real-life, skewed peer distributions. We show that even a win-no lose situation is difficult to achieve under those conditions and that the actual impact for a specific peer heavily depends on the used locality-aware peer selection and the specific scenario. This contradicts the principle of economic traffic management (ETM) which aims for a solution where all involved players benefit and consequently have an incentive to adopt locality-awareness. Therefore, we propose and evaluate refinements of current proposals, achieving that all users of P2P networks can be sure that their application performance is not reduced. This mitigates the unfairness introduced by current proposals which is a key requirement for a broad acceptance of the concept of locality-awareness in the user community of P2P networks.
• Provisioning and Operation of Virtual Networks. Meier, Sebastian; Barisch, Marc; Kirstädter, Andreas; Schlosser, Daniel; Duelli, Michael; Jarschel, Michael; Hoßfeld, Tobias; Hoffmann, Klaus; Hoffmann, Marco; Kellerer, Wolfgang; Khan, Ashiq; Jurca, Dan; Kozu, Kazuyuki. In Electronic Communications of the EASST, Kommunikation in Verteilten Systemen 2011, 37. 2011.
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  In today’s Internet, requirements of services regarding the underlying transport network are very diverse. In the future, this diversity will increase and make it harder to accommodate all services in a single network. A possible approach to keep up with this diversity in future networks is the deployment of isolated, custom tailored networks on top of a single shared physical substrate. The COMCON (COntrol and Monitoring of COexisting Networks) project aims to define a reference architecture for setup, control, and monitoring of virtual networks on a provider- and operator-grade level. In this paper, we present the building blocks and interfaces of our architecture.

  @article{info3-article-2011-87, abstract = {In today’s Internet, requirements of services regarding the underlying transport network are very diverse. In the future, this diversity will increase and make it harder to accommodate all services in a single network. A possible approach to keep up with this diversity in future networks is the deployment of isolated, custom tailored networks on top of a single shared physical substrate. The COMCON (COntrol and Monitoring of COexisting Networks) project aims to define a reference architecture for setup, control, and monitoring of virtual networks on a provider- and operator-grade level. In this paper, we present the building blocks and interfaces of our architecture.}, author = {Meier, Sebastian and Barisch, Marc and Kirstädter, Andreas and Schlosser, Daniel and Duelli, Michael and Jarschel, Michael and Hoßfeld, Tobias and Hoffmann, Klaus and Hoffmann, Marco and Kellerer, Wolfgang and Khan, Ashiq and Jurca, Dan and Kozu, Kazuyuki}, journal = {Electronic Communications of the EASST, Kommunikation in Verteilten Systemen 2011}, keywords = {sys:hidden:article}, month = {03}, title = {Provisioning and Operation of Virtual Networks}, volume = 37, year = 2011 }

  %0 Journal Article %1 info3-article-2011-87 %A Meier, Sebastian %A Barisch, Marc %A Kirstädter, Andreas %A Schlosser, Daniel %A Duelli, Michael %A Jarschel, Michael %A Hoßfeld, Tobias %A Hoffmann, Klaus %A Hoffmann, Marco %A Kellerer, Wolfgang %A Khan, Ashiq %A Jurca, Dan %A Kozu, Kazuyuki %D 2011 %J Electronic Communications of the EASST, Kommunikation in Verteilten Systemen 2011 %T Provisioning and Operation of Virtual Networks %V 37 %X In today’s Internet, requirements of services regarding the underlying transport network are very diverse. In the future, this diversity will increase and make it harder to accommodate all services in a single network. A possible approach to keep up with this diversity in future networks is the deployment of isolated, custom tailored networks on top of a single shared physical substrate. The COMCON (COntrol and Monitoring of COexisting Networks) project aims to define a reference architecture for setup, control, and monitoring of virtual networks on a provider- and operator-grade level. In this paper, we present the building blocks and interfaces of our architecture.
• Characterization of BitTorrent Swarms and their Distribution in the Internet. Hoßfeld, Tobias; Lehrieder, Frank; Hock, David; Oechsner, Simon; Despotovic, Zoran; Kellerer, Wolfgang; Michel, Maximilian. In Computer Networks, 55(5), pp. 1197–1215. 2011.
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  The optimization of overlay traffic resulting from applications such as BitTorrent is a challenge addressed by several recent research initiatives. However, the assessment of such optimization techniques and their performance in the real Internet remains difficult. Despite a considerable set of works measuring real-life BitTorrent swarms, several characteristics of those swarms relevant for the optimization of overlay traffic have not yet been investigated. In this work, we address this lack of realistic swarm statistics by presenting our measurement results. In particular, we provide a statistical characterization of the swarm sizes, the distribution of peers over autonomous systems (ASs), the fraction of peers in the largest AS, and the size of the shared files. To this end, we consider different types of shared content and identify particular characteristics of regional swarms. The selection of the presented data is inspired by ongoing discussions in the IETF working group on application layer traffic optimization (ALTO). Our study is intended to provide input for the design and the assessment of ALTO solutions for BitTorrent, but the applicability of the results is not limited to that purpose.

  @article{info3-article-2011-83, abstract = {The optimization of overlay traffic resulting from applications such as BitTorrent is a challenge addressed by several recent research initiatives. However, the assessment of such optimization techniques and their performance in the real Internet remains difficult. Despite a considerable set of works measuring real-life BitTorrent swarms, several characteristics of those swarms relevant for the optimization of overlay traffic have not yet been investigated. In this work, we address this lack of realistic swarm statistics by presenting our measurement results. In particular, we provide a statistical characterization of the swarm sizes, the distribution of peers over autonomous systems (ASs), the fraction of peers in the largest AS, and the size of the shared files. To this end, we consider different types of shared content and identify particular characteristics of regional swarms. The selection of the presented data is inspired by ongoing discussions in the IETF working group on application layer traffic optimization (ALTO). Our study is intended to provide input for the design and the assessment of ALTO solutions for BitTorrent, but the applicability of the results is not limited to that purpose.}, author = {Hoßfeld, Tobias and Lehrieder, Frank and Hock, David and Oechsner, Simon and Despotovic, Zoran and Kellerer, Wolfgang and Michel, Maximilian}, journal = {Computer Networks}, keywords = {sys:hidden:article}, month = {04}, pages = {1197-1215}, title = {Characterization of BitTorrent Swarms and their Distribution in the Internet}, volume = {55(5)}, year = 2011 }

  %0 Journal Article %1 info3-article-2011-83 %A Hoßfeld, Tobias %A Lehrieder, Frank %A Hock, David %A Oechsner, Simon %A Despotovic, Zoran %A Kellerer, Wolfgang %A Michel, Maximilian %D 2011 %J Computer Networks %P 1197-1215 %T Characterization of BitTorrent Swarms and their Distribution in the Internet %V 55(5) %X The optimization of overlay traffic resulting from applications such as BitTorrent is a challenge addressed by several recent research initiatives. However, the assessment of such optimization techniques and their performance in the real Internet remains difficult. Despite a considerable set of works measuring real-life BitTorrent swarms, several characteristics of those swarms relevant for the optimization of overlay traffic have not yet been investigated. In this work, we address this lack of realistic swarm statistics by presenting our measurement results. In particular, we provide a statistical characterization of the swarm sizes, the distribution of peers over autonomous systems (ASs), the fraction of peers in the largest AS, and the size of the shared files. To this end, we consider different types of shared content and identify particular characteristics of regional swarms. The selection of the presented data is inspired by ongoing discussions in the IETF working group on application layer traffic optimization (ALTO). Our study is intended to provide input for the design and the assessment of ALTO solutions for BitTorrent, but the applicability of the results is not limited to that purpose.
• Performance Evaluation of Packet Re-ordering on Concurrent Multipath Transmissions for Transport Virtualization. Zinner, Thomas; Tutschku, Kurt; Nakao, Akihiro; Tran-Gia, Phuoc. In JCNDS Special Issue on: Network Virtualization - Concepts and Performance Aspects, Vol. 6, pp. 322–340. 2011.
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  From the viewpoint of communication networks Network Virtualization (NV) extends beyond pure operational issues and addresses many impasses of the current Internet. The idea of Transport Virtualization (TV) progresses the capabilities of NV and enables the independence from a specific network transport resource. The independence is achieved by pooling multiple transport resources and selecting the best resources for exclusive or concurrent use. However, the application and selection of concurrent paths is rather complex and introduces inevitable packet re-ordering due to different stochastic delay characteristics on the used paths. Packets arriving at the destination out-of-order have to be stored in a re-sequencing buffer before reassembled packets are forwarded to the application. We provide a simulation framework based on discrete event simulation which allows an evaluation of the re-sequencing buffer occupancy. Further, we perform an analysis of the fundamental behaviors and factors for packet re-ordering in concurrent multipath transmissions.

  @article{info3-article-2011-74, abstract = {From the viewpoint of communication networks Network Virtualization (NV) extends beyond pure operational issues and addresses many impasses of the current Internet. The idea of Transport Virtualization (TV) progresses the capabilities of NV and enables the independence from a specific network transport resource. The independence is achieved by pooling multiple transport resources and selecting the best resources for exclusive or concurrent use. However, the application and selection of concurrent paths is rather complex and introduces inevitable packet re-ordering due to different stochastic delay characteristics on the used paths. Packets arriving at the destination out-of-order have to be stored in a re-sequencing buffer before reassembled packets are forwarded to the application. We provide a simulation framework based on discrete event simulation which allows an evaluation of the re-sequencing buffer occupancy. Further, we perform an analysis of the fundamental behaviors and factors for packet re-ordering in concurrent multipath transmissions.}, author = {Zinner, Thomas and Tutschku, Kurt and Nakao, Akihiro and Tran-Gia, Phuoc}, journal = {JCNDS Special Issue on: Network Virtualization - Concepts and Performance Aspects}, keywords = {sys:hidden:article}, month = {05}, pages = {322-340}, title = {Performance Evaluation of Packet Re-ordering on Concurrent Multipath Transmissions for Transport Virtualization}, volume = {Vol. 6}, year = 2011 }

  %0 Journal Article %1 info3-article-2011-74 %A Zinner, Thomas %A Tutschku, Kurt %A Nakao, Akihiro %A Tran-Gia, Phuoc %D 2011 %J JCNDS Special Issue on: Network Virtualization - Concepts and Performance Aspects %P 322-340 %T Performance Evaluation of Packet Re-ordering on Concurrent Multipath Transmissions for Transport Virtualization %V Vol. 6 %X From the viewpoint of communication networks Network Virtualization (NV) extends beyond pure operational issues and addresses many impasses of the current Internet. The idea of Transport Virtualization (TV) progresses the capabilities of NV and enables the independence from a specific network transport resource. The independence is achieved by pooling multiple transport resources and selecting the best resources for exclusive or concurrent use. However, the application and selection of concurrent paths is rather complex and introduces inevitable packet re-ordering due to different stochastic delay characteristics on the used paths. Packets arriving at the destination out-of-order have to be stored in a re-sequencing buffer before reassembled packets are forwarded to the application. We provide a simulation framework based on discrete event simulation which allows an evaluation of the re-sequencing buffer occupancy. Further, we perform an analysis of the fundamental behaviors and factors for packet re-ordering in concurrent multipath transmissions.
• EuroView 2010: Visions of Future Generation Networks. Hoßfeld, Tobias; Tran-Gia, Phuoc. In Computer Communications Review CCR, Volume 41, Number 2. 2011.
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  On August 2nd – 3rd, 2010, the EuroView 2010 workshop on 'Visions of Future Generation Networks' was held at the University of Würzburg. The event was sponsored by the European Network of Excellence Euro-NF, the German Information Technology Society ITG, and the International Teletraffic Congress ITC. EuroView 2010 brought together Internet and network technology researchers, network providers, as well as equipment and device manufacturers. In 2010, the focus was on 'Future Internet Design and Experimental Facilities' and on current efforts towards a Future Internet. Special sessions were organized reflecting the latest results of selected testbed expert groups as well as current and future national and international collaborative projects: (1) the German G-Lab project offering a national platform for Future Internet studies, (2) the Future Internet Activities in the European Framework FP7 organized by Max Lemke, and (3) the GENI project in US organized by Aaron Falk. A keynote talk was given by Lawrence Landweber on the challenges and paradigms emerging in the Future (Inter)Network.

  @article{info3-article-2011-89, abstract = {On August 2nd – 3rd, 2010, the EuroView 2010 workshop on 'Visions of Future Generation Networks' was held at the University of Würzburg. The event was sponsored by the European Network of Excellence Euro-NF, the German Information Technology Society ITG, and the International Teletraffic Congress ITC. EuroView 2010 brought together Internet and network technology researchers, network providers, as well as equipment and device manufacturers. In 2010, the focus was on 'Future Internet Design and Experimental Facilities' and on current efforts towards a Future Internet. Special sessions were organized reflecting the latest results of selected testbed expert groups as well as current and future national and international collaborative projects: (1) the German G-Lab project offering a national platform for Future Internet studies, (2) the Future Internet Activities in the European Framework FP7 organized by Max Lemke, and (3) the GENI project in US organized by Aaron Falk. A keynote talk was given by Lawrence Landweber on the challenges and paradigms emerging in the Future (Inter)Network.}, author = {Hoßfeld, Tobias and Tran-Gia, Phuoc}, journal = {Computer Communications Review CCR}, keywords = {sys:hidden:article}, month = {07}, title = {EuroView 2010: Visions of Future Generation Networks}, volume = {Volume 41, Number 2}, year = 2011 }

  %0 Journal Article %1 info3-article-2011-89 %A Hoßfeld, Tobias %A Tran-Gia, Phuoc %D 2011 %J Computer Communications Review CCR %T EuroView 2010: Visions of Future Generation Networks %V Volume 41, Number 2 %X On August 2nd – 3rd, 2010, the EuroView 2010 workshop on 'Visions of Future Generation Networks' was held at the University of Würzburg. The event was sponsored by the European Network of Excellence Euro-NF, the German Information Technology Society ITG, and the International Teletraffic Congress ITC. EuroView 2010 brought together Internet and network technology researchers, network providers, as well as equipment and device manufacturers. In 2010, the focus was on 'Future Internet Design and Experimental Facilities' and on current efforts towards a Future Internet. Special sessions were organized reflecting the latest results of selected testbed expert groups as well as current and future national and international collaborative projects: (1) the German G-Lab project offering a national platform for Future Internet studies, (2) the Future Internet Activities in the European Framework FP7 organized by Max Lemke, and (3) the GENI project in US organized by Aaron Falk. A keynote talk was given by Lawrence Landweber on the challenges and paradigms emerging in the Future (Inter)Network.
• ResiLyzer: Ein Werkzeug zur Analyse der Ausfallsicherheit in paketvermittelten Kommunikationsnetzen. Hock, David; Hartmann, Matthias; Schwartz, Christian; Menth, Michael. In PIK - Praxis der Informationsverarbeitung und Kommunikation, 34, pp. 158–159. 2011.
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  @article{info3-article-2011-105, author = {Hock, David and Hartmann, Matthias and Schwartz, Christian and Menth, Michael}, journal = {PIK - Praxis der Informationsverarbeitung und Kommunikation}, keywords = {sys:hidden:article}, month = {08}, pages = {158-159}, title = {ResiLyzer: Ein Werkzeug zur Analyse der Ausfallsicherheit in paketvermittelten Kommunikationsnetzen}, volume = 34, year = 2011 }

  %0 Journal Article %1 info3-article-2011-105 %A Hock, David %A Hartmann, Matthias %A Schwartz, Christian %A Menth, Michael %D 2011 %J PIK - Praxis der Informationsverarbeitung und Kommunikation %P 158-159 %T ResiLyzer: Ein Werkzeug zur Analyse der Ausfallsicherheit in paketvermittelten Kommunikationsnetzen %V 34
• MuLaNEO: Planung und Optimierung von Mehrdienstnetzen. Duelli, Michael; Ott, Julian; Qin, Xiaohua; Weber, Eduard. In PIK - Praxis der Informationsverarbeitung und Kommunikation, 34, pp. 138–139. 2011.
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  Telekommunikationsanbieter benötigen Netze, die mehrere Dienste/Technologien unterstützen und im Rahmen gegebener Anforderungsprofile ausfallsicher und zugleich kostengünstig sind. Die Planung solcher Netze kann auf ein kombinatorisches Optimierungsproblem mit exponentieller Komplexität zurückgeführt werden. In diesem Beitrag stellen wir eine offene und modulare Software für die vereinfachte Entwicklung und den Vergleich solcher Planungsverfahren vor.

  @article{info3-article-2011-99, abstract = {Telekommunikationsanbieter benötigen Netze, die mehrere Dienste/Technologien unterstützen und im Rahmen gegebener Anforderungsprofile ausfallsicher und zugleich kostengünstig sind. Die Planung solcher Netze kann auf ein kombinatorisches Optimierungsproblem mit exponentieller Komplexität zurückgeführt werden. In diesem Beitrag stellen wir eine offene und modulare Software für die vereinfachte Entwicklung und den Vergleich solcher Planungsverfahren vor.}, author = {Duelli, Michael and Ott, Julian and Qin, Xiaohua and Weber, Eduard}, journal = {PIK - Praxis der Informationsverarbeitung und Kommunikation}, keywords = {sys:hidden:article}, month = {08}, pages = {138–139}, title = {MuLaNEO: Planung und Optimierung von Mehrdienstnetzen}, volume = 34, year = 2011 }

  %0 Journal Article %1 info3-article-2011-99 %A Duelli, Michael %A Ott, Julian %A Qin, Xiaohua %A Weber, Eduard %D 2011 %J PIK - Praxis der Informationsverarbeitung und Kommunikation %P 138--139 %T MuLaNEO: Planung und Optimierung von Mehrdienstnetzen %V 34 %X Telekommunikationsanbieter benötigen Netze, die mehrere Dienste/Technologien unterstützen und im Rahmen gegebener Anforderungsprofile ausfallsicher und zugleich kostengünstig sind. Die Planung solcher Netze kann auf ein kombinatorisches Optimierungsproblem mit exponentieller Komplexität zurückgeführt werden. In diesem Beitrag stellen wir eine offene und modulare Software für die vereinfachte Entwicklung und den Vergleich solcher Planungsverfahren vor.
• Compact node-link formulations for the optimal single path MPLS Fast Reroute layout. Żukowski, Cezary; Tomaszewski, Artur; Pióro, Michał; Hock, David; Hartmann, Matthias; Menth, Michael. In Advances in Electronics and Telecommunications, 2. 2011.
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  This paper discusses compact node-link formulations for MPLS fast reroute optimal single path layout. We propose mathematical formulations for MPLS fast reroute local protection mechanisms. In fact, we compare one-to-one (also called detour) local protection and many-to-one (also called facility backup) local protection mechanisms with respect to minimized maximum link utilization. The optimal results provided by the node-links are compared with the suboptimal results provided by algorithms based on non-compact linear programming (path generation) approach and IP-based approach.

  @article{info3-article-2011-104, abstract = {This paper discusses compact node-link formulations for MPLS fast reroute optimal single path layout. We propose mathematical formulations for MPLS fast reroute local protection mechanisms. In fact, we compare one-to-one (also called detour) local protection and many-to-one (also called facility backup) local protection mechanisms with respect to minimized maximum link utilization. The optimal results provided by the node-links are compared with the suboptimal results provided by algorithms based on non-compact linear programming (path generation) approach and IP-based approach.}, author = {Żukowski, Cezary and Tomaszewski, Artur and Pióro, Michał and Hock, David and Hartmann, Matthias and Menth, Michael}, journal = {Advances in Electronics and Telecommunications}, keywords = {sys:hidden:article}, month = {09}, title = {Compact node-link formulations for the optimal single path MPLS Fast Reroute layout}, volume = 2, year = 2011 }

  %0 Journal Article %1 info3-article-2011-104 %A Żukowski, Cezary %A Tomaszewski, Artur %A Pióro, Michał %A Hock, David %A Hartmann, Matthias %A Menth, Michael %D 2011 %J Advances in Electronics and Telecommunications %T Compact node-link formulations for the optimal single path MPLS Fast Reroute layout %V 2 %X This paper discusses compact node-link formulations for MPLS fast reroute optimal single path layout. We propose mathematical formulations for MPLS fast reroute local protection mechanisms. In fact, we compare one-to-one (also called detour) local protection and many-to-one (also called facility backup) local protection mechanisms with respect to minimized maximum link utilization. The optimal results provided by the node-links are compared with the suboptimal results provided by algorithms based on non-compact linear programming (path generation) approach and IP-based approach.
• PCN-Based Marked Flow Termination. Menth, Michael; Lehrieder, Frank. In Computer Communications, 34, pp. 2082–2093. 2011.
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  Pre-congestion notification (PCN) uses packet metering and marking to notify boundary nodes of a Differentiated Services IP network if configured rate thresholds have been exceeded on some links. This feedback is used for PCN-based admission control and flow termination. While admission control is rather well understood, flow termination is a new flow control function and useful especially in case of failures or during flash crowds. We present marked flow termination as a new class of termination algorithms which terminate overload traffic gradually and that work well with multipath routing. We study their termination behavior, give recommendation for their configuration, and discuss their benefits and shortcomings.

  @article{info3-article-2011-90, abstract = {Pre-congestion notification (PCN) uses packet metering and marking to notify boundary nodes of a Differentiated Services IP network if configured rate thresholds have been exceeded on some links. This feedback is used for PCN-based admission control and flow termination. While admission control is rather well understood, flow termination is a new flow control function and useful especially in case of failures or during flash crowds. We present marked flow termination as a new class of termination algorithms which terminate overload traffic gradually and that work well with multipath routing. We study their termination behavior, give recommendation for their configuration, and discuss their benefits and shortcomings.}, author = {Menth, Michael and Lehrieder, Frank}, journal = {Computer Communications}, keywords = {sys:hidden:article}, month = 11, pages = {2082-2093}, title = {PCN-Based Marked Flow Termination}, volume = 34, year = 2011 }

  %0 Journal Article %1 info3-article-2011-90 %A Menth, Michael %A Lehrieder, Frank %D 2011 %J Computer Communications %P 2082-2093 %T PCN-Based Marked Flow Termination %V 34 %X Pre-congestion notification (PCN) uses packet metering and marking to notify boundary nodes of a Differentiated Services IP network if configured rate thresholds have been exceeded on some links. This feedback is used for PCN-based admission control and flow termination. While admission control is rather well understood, flow termination is a new flow control function and useful especially in case of failures or during flash crowds. We present marked flow termination as a new class of termination algorithms which terminate overload traffic gradually and that work well with multipath routing. We study their termination behavior, give recommendation for their configuration, and discuss their benefits and shortcomings.

• Loop-Free Alternates and Not-Via Addresses: A Proper Combination for IP Fast Reroute?. Menth, Michael; Hartmann, Matthias; Martin, Rüdiger; Cicic, Tarik; Kvalbein, Amund. In Computer Networks, 54, pp. 1300–1315. 2010.
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  The IETF currently discusses fast reroute mechanisms for IP networks (IP FRR). IP FRR accelerates the recovery in case of network element failures and avoids micro-loops during re-convergence. Several mechanisms are proposed. Loop-free alternates (LFAs) are simple but cannot cover all single link and node failures. Not-via addresses can protect against these failures but are more complex, in particular, they use tunneling techniques to deviate backup traffic. In the IETF it has been proposed to combine both mechanisms to merge their advantages: simplicity and full failure coverage. This work analyzes LFAs and classifies them according to their abilities. We qualitatively compare LFAs and not-via addresses and develop a concept for their combined application to achieve 100% single failure coverage, while using simple LFAs wherever possible. The applicability of existing LFAs depends on the resilience requirements of the network. We study the backup path length and the link utilization for both IP FRR methods and quantify the decapsulation load and the increase of the routing table size caused by not-via addresses. We conclude that the combined usage of both methods has no advantage compared to the application of not-via addresses only.

  @article{info3-article-2010-70, abstract = {The IETF currently discusses fast reroute mechanisms for IP networks (IP FRR). IP FRR accelerates the recovery in case of network element failures and avoids micro-loops during re-convergence. Several mechanisms are proposed. Loop-free alternates (LFAs) are simple but cannot cover all single link and node failures. Not-via addresses can protect against these failures but are more complex, in particular, they use tunneling techniques to deviate backup traffic. In the IETF it has been proposed to combine both mechanisms to merge their advantages: simplicity and full failure coverage. This work analyzes LFAs and classifies them according to their abilities. We qualitatively compare LFAs and not-via addresses and develop a concept for their combined application to achieve 100% single failure coverage, while using simple LFAs wherever possible. The applicability of existing LFAs depends on the resilience requirements of the network. We study the backup path length and the link utilization for both IP FRR methods and quantify the decapsulation load and the increase of the routing table size caused by not-via addresses. We conclude that the combined usage of both methods has no advantage compared to the application of not-via addresses only.}, author = {Menth, Michael and Hartmann, Matthias and Martin, Rüdiger and Cicic, Tarik and Kvalbein, Amund}, journal = {Computer Networks}, keywords = {sys:hidden:article}, month = {06}, pages = {1300-1315}, title = {Loop-Free Alternates and Not-Via Addresses: A Proper Combination for IP Fast Reroute?}, volume = 54, year = 2010 }

  %0 Journal Article %1 info3-article-2010-70 %A Menth, Michael %A Hartmann, Matthias %A Martin, Rüdiger %A Cicic, Tarik %A Kvalbein, Amund %D 2010 %J Computer Networks %P 1300-1315 %T Loop-Free Alternates and Not-Via Addresses: A Proper Combination for IP Fast Reroute? %V 54 %X The IETF currently discusses fast reroute mechanisms for IP networks (IP FRR). IP FRR accelerates the recovery in case of network element failures and avoids micro-loops during re-convergence. Several mechanisms are proposed. Loop-free alternates (LFAs) are simple but cannot cover all single link and node failures. Not-via addresses can protect against these failures but are more complex, in particular, they use tunneling techniques to deviate backup traffic. In the IETF it has been proposed to combine both mechanisms to merge their advantages: simplicity and full failure coverage. This work analyzes LFAs and classifies them according to their abilities. We qualitatively compare LFAs and not-via addresses and develop a concept for their combined application to achieve 100% single failure coverage, while using simple LFAs wherever possible. The applicability of existing LFAs depends on the resilience requirements of the network. We study the backup path length and the link utilization for both IP FRR methods and quantify the decapsulation load and the increase of the routing table size caused by not-via addresses. We conclude that the combined usage of both methods has no advantage compared to the application of not-via addresses only.
• Towards Quality of Experience-based Reputation Models for Future Web Service Provisioning. Ciszkowski, Tomasz; Mazurczyk, Wojciech; Kotulski, Zbigniew; Hoßfeld, Tobias; Fiedler, Markus; Collange, Denis. In Special Issue of the Springer Telecommunication Systems Journal: Future Internet Services and Architectures - Trends and Visions, print available in 2013, 51, pp. 283–295. 2010.
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  This paper concerns the applicability of reputations systems for assessing Quality of Experience (QoE) for web services in the Future Internet. Reputation systems provide mechanisms to manage subjective opinions in societies and yield a general scoring of a particular behavior. Thus, they are likely to become an important ingredient of the Future Internet. Parameters under evaluation by a reputation system may vary greatly and, particularly, may be chosen to assess the users' satisfaction with (composite) web services. Currently, this satisfaction is usually expressed by QoE, which represents subjective users' opinions. The goal of this paper is to present a novel framework of web services where a reputation system is incorporated for tracking and predicting of users' satisfaction. This approach is a beneficial tool which enables providers to facilitate service adaptation according to users' expectations and maintain QoE at a satisfactory level. Presented reputation systems operate in an environment of composite services that integrate client and server-side. This approach is highly suitable for effective QoE differentiating and maximizing user experience for specific customer profiles as even the service and network resources are shared.

  @article{info3-article-2010-77, abstract = {This paper concerns the applicability of reputations systems for assessing Quality of Experience (QoE) for web services in the Future Internet. Reputation systems provide mechanisms to manage subjective opinions in societies and yield a general scoring of a particular behavior. Thus, they are likely to become an important ingredient of the Future Internet. Parameters under evaluation by a reputation system may vary greatly and, particularly, may be chosen to assess the users' satisfaction with (composite) web services. Currently, this satisfaction is usually expressed by QoE, which represents subjective users' opinions. The goal of this paper is to present a novel framework of web services where a reputation system is incorporated for tracking and predicting of users' satisfaction. This approach is a beneficial tool which enables providers to facilitate service adaptation according to users' expectations and maintain QoE at a satisfactory level. Presented reputation systems operate in an environment of composite services that integrate client and server-side. This approach is highly suitable for effective QoE differentiating and maximizing user experience for specific customer profiles as even the service and network resources are shared.}, author = {Ciszkowski, Tomasz and Mazurczyk, Wojciech and Kotulski, Zbigniew and Hoßfeld, Tobias and Fiedler, Markus and Collange, Denis}, journal = {Special Issue of the Springer Telecommunication Systems Journal: Future Internet Services and Architectures - Trends and Visions, print available in 2013}, keywords = {sys:hidden:article}, pages = {283-295}, title = {Towards Quality of Experience-based Reputation Models for Future Web Service Provisioning}, volume = 51, year = 2010 }

  %0 Journal Article %1 info3-article-2010-77 %A Ciszkowski, Tomasz %A Mazurczyk, Wojciech %A Kotulski, Zbigniew %A Hoßfeld, Tobias %A Fiedler, Markus %A Collange, Denis %D 2010 %J Special Issue of the Springer Telecommunication Systems Journal: Future Internet Services and Architectures - Trends and Visions, print available in 2013 %P 283-295 %T Towards Quality of Experience-based Reputation Models for Future Web Service Provisioning %V 51 %X This paper concerns the applicability of reputations systems for assessing Quality of Experience (QoE) for web services in the Future Internet. Reputation systems provide mechanisms to manage subjective opinions in societies and yield a general scoring of a particular behavior. Thus, they are likely to become an important ingredient of the Future Internet. Parameters under evaluation by a reputation system may vary greatly and, particularly, may be chosen to assess the users' satisfaction with (composite) web services. Currently, this satisfaction is usually expressed by QoE, which represents subjective users' opinions. The goal of this paper is to present a novel framework of web services where a reputation system is incorporated for tracking and predicting of users' satisfaction. This approach is a beneficial tool which enables providers to facilitate service adaptation according to users' expectations and maintain QoE at a satisfactory level. Presented reputation systems operate in an environment of composite services that integrate client and server-side. This approach is highly suitable for effective QoE differentiating and maximizing user experience for specific customer profiles as even the service and network resources are shared.
• QoE based Bandwidth Management Supporting Real Time Flows in IEEE 802.11 Mesh Networks. Pries, Rastin; Hock, David; Staehle, Dirk. In PIK - Praxis der Informationsverarbeitung und Kommunikation, 32. 2010.
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  @article{info3-article-2010-64, author = {Pries, Rastin and Hock, David and Staehle, Dirk}, journal = {PIK - Praxis der Informationsverarbeitung und Kommunikation}, keywords = {sys:hidden:article}, month = {01}, title = {QoE based Bandwidth Management Supporting Real Time Flows in IEEE 802.11 Mesh Networks}, volume = 32, year = 2010 }

  %0 Journal Article %1 info3-article-2010-64 %A Pries, Rastin %A Hock, David %A Staehle, Dirk %D 2010 %J PIK - Praxis der Informationsverarbeitung und Kommunikation %T QoE based Bandwidth Management Supporting Real Time Flows in IEEE 802.11 Mesh Networks %V 32
• Efficiency of Routing and Resilience Mechanisms in Packet-Switched Communication Networks. Menth, Michael; Martin, Rüdiger; Hartmann, Matthias; Spörlein, Ulrich. In European Transactions on Telecommunications, 21, pp. 108–120. 2010.
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  In this work we compare the efficiency of various routing and resilience mechanisms. Their path layout determines the utilization of links in the network under normal operation and in failure scenarios. For the comparison, the performance measure is the maximum utilization rS of all links for a set of protected failures S. A routing mechanism is considered more efficient than another if it leads to a lower maximum link utilization rS. We consider standard and optimized versions of IP routing and rerouting, optimized routing using explicit paths and end-to-end protection switching, as well as standard and optimized versions of MPLS fast reroute. The results show that routing optimization reduces the maximum link utilization significantly both with and without failure protection. The optimization potential for resilient routing is limited by the applied mechanism and depends heavily on the network structure and the set of protected failure scenarios S.

  @article{info3-article-2010-66, abstract = {In this work we compare the efficiency of various routing and resilience mechanisms. Their path layout determines the utilization of links in the network under normal operation and in failure scenarios. For the comparison, the performance measure is the maximum utilization rS of all links for a set of protected failures S. A routing mechanism is considered more efficient than another if it leads to a lower maximum link utilization rS. We consider standard and optimized versions of IP routing and rerouting, optimized routing using explicit paths and end-to-end protection switching, as well as standard and optimized versions of MPLS fast reroute. The results show that routing optimization reduces the maximum link utilization significantly both with and without failure protection. The optimization potential for resilient routing is limited by the applied mechanism and depends heavily on the network structure and the set of protected failure scenarios S.}, author = {Menth, Michael and Martin, Rüdiger and Hartmann, Matthias and Spörlein, Ulrich}, journal = {European Transactions on Telecommunications}, keywords = {sys:hidden:article}, month = {03}, pages = {108-120}, title = {Efficiency of Routing and Resilience Mechanisms in Packet-Switched Communication Networks}, volume = 21, year = 2010 }

  %0 Journal Article %1 info3-article-2010-66 %A Menth, Michael %A Martin, Rüdiger %A Hartmann, Matthias %A Spörlein, Ulrich %D 2010 %J European Transactions on Telecommunications %P 108-120 %T Efficiency of Routing and Resilience Mechanisms in Packet-Switched Communication Networks %V 21 %X In this work we compare the efficiency of various routing and resilience mechanisms. Their path layout determines the utilization of links in the network under normal operation and in failure scenarios. For the comparison, the performance measure is the maximum utilization rS of all links for a set of protected failures S. A routing mechanism is considered more efficient than another if it leads to a lower maximum link utilization rS. We consider standard and optimized versions of IP routing and rerouting, optimized routing using explicit paths and end-to-end protection switching, as well as standard and optimized versions of MPLS fast reroute. The results show that routing optimization reduces the maximum link utilization significantly both with and without failure protection. The optimization potential for resilient routing is limited by the applied mechanism and depends heavily on the network structure and the set of protected failure scenarios S.
• Traffic characterization of a residential wireless Internet access. Wamser, Florian; Pries, Rastin; Staehle, Dirk; Heck, Klaus; Tran-Gia, Phuoc. In Special Issue of the Telecommunication Systems (TS) Journal, 48: 1-2. 2010.
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  Traffic characterization is an important means for Internet Service Providers (ISPs) to adapt and to optimize their networks to the requirements of the customers. Most network measurements are performed in the backbone of these ISPs, showing both, residential and business Internet traffic. However, the traffic characteristics of business and home users differ significantly. Therefore, we have performed measurements of home users at a broadband wireless access service provider in order to reflect only home user traffic characteristics. In this paper, we present the results of these measurements, showing daily traffic fluctuations, flow statistics as well as application distributions. The results show a difference to backbone traffic characteristics. Furthermore, we observed a shift from web and Peer-to-Peer (P2P) file sharing traffic to streaming applications.

  @article{info3-article-2010-73, abstract = {Traffic characterization is an important means for Internet Service Providers (ISPs) to adapt and to optimize their networks to the requirements of the customers. Most network measurements are performed in the backbone of these ISPs, showing both, residential and business Internet traffic. However, the traffic characteristics of business and home users differ significantly. Therefore, we have performed measurements of home users at a broadband wireless access service provider in order to reflect only home user traffic characteristics. In this paper, we present the results of these measurements, showing daily traffic fluctuations, flow statistics as well as application distributions. The results show a difference to backbone traffic characteristics. Furthermore, we observed a shift from web and Peer-to-Peer (P2P) file sharing traffic to streaming applications.}, author = {Wamser, Florian and Pries, Rastin and Staehle, Dirk and Heck, Klaus and Tran-Gia, Phuoc}, journal = {Special Issue of the Telecommunication Systems (TS) Journal}, keywords = {sys:hidden:article}, month = {05}, title = {Traffic characterization of a residential wireless Internet access}, volume = {48: 1-2}, year = 2010 }

  %0 Journal Article %1 info3-article-2010-73 %A Wamser, Florian %A Pries, Rastin %A Staehle, Dirk %A Heck, Klaus %A Tran-Gia, Phuoc %D 2010 %J Special Issue of the Telecommunication Systems (TS) Journal %T Traffic characterization of a residential wireless Internet access %V 48: 1-2 %X Traffic characterization is an important means for Internet Service Providers (ISPs) to adapt and to optimize their networks to the requirements of the customers. Most network measurements are performed in the backbone of these ISPs, showing both, residential and business Internet traffic. However, the traffic characteristics of business and home users differ significantly. Therefore, we have performed measurements of home users at a broadband wireless access service provider in order to reflect only home user traffic characteristics. In this paper, we present the results of these measurements, showing daily traffic fluctuations, flow statistics as well as application distributions. The results show a difference to backbone traffic characteristics. Furthermore, we observed a shift from web and Peer-to-Peer (P2P) file sharing traffic to streaming applications.
• Interaction Patterns between P2P Content Distribution Systems and ISPs. Dán, György; Stamoulis, George D.; Hoßfeld, Tobias; Oechsner, Simon; Cholda, Piotr; Stankiewicz, Rafal; Papafili, Ioanna. In to be published in IEEE Communications Magazine. 2010.
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  Peer-to-peer (P2P) content distribution systems are a major source of traffic in the Internet, but the application layer protocols they use are mostly unaware of the underlying network in accordance with the layered structure of the Internet’s protocol stack. Nevertheless, the need for improved network efficiency and the business interests of Internet service providers (ISPs) are both strong drivers towards a cross-layer approach in peer-to-peer protocol design, calling for P2P systems that would in some way interact with the ISPs. Recent research shows that the interaction, which can rely on information provided by both parties, can be mutually beneficial. In this paper first we give an overview of the kinds of information that could potentially be exchanged between the P2P systems and the ISPs, and discuss their usefulness and the ease of obtaining and exchanging them. We also present a classification of the possible approaches for interaction based on the level of involvement of the ISPs and the P2P systems, and we discuss the potential strengths and the weaknesses of these approaches.

  @article{info3-article-2010-78, abstract = {Peer-to-peer (P2P) content distribution systems are a major source of traffic in the Internet, but the application layer protocols they use are mostly unaware of the underlying network in accordance with the layered structure of the Internet’s protocol stack. Nevertheless, the need for improved network efficiency and the business interests of Internet service providers (ISPs) are both strong drivers towards a cross-layer approach in peer-to-peer protocol design, calling for P2P systems that would in some way interact with the ISPs. Recent research shows that the interaction, which can rely on information provided by both parties, can be mutually beneficial. In this paper first we give an overview of the kinds of information that could potentially be exchanged between the P2P systems and the ISPs, and discuss their usefulness and the ease of obtaining and exchanging them. We also present a classification of the possible approaches for interaction based on the level of involvement of the ISPs and the P2P systems, and we discuss the potential strengths and the weaknesses of these approaches.}, author = {Dán, György and Stamoulis, George D. and Hoßfeld, Tobias and Oechsner, Simon and Cholda, Piotr and Stankiewicz, Rafal and Papafili, Ioanna}, journal = {to be published in IEEE Communications Magazine}, keywords = {ispeer}, title = {Interaction Patterns between P2P Content Distribution Systems and ISPs}, year = 2010 }

  %0 Journal Article %1 info3-article-2010-78 %A Dán, György %A Stamoulis, George D. %A Hoßfeld, Tobias %A Oechsner, Simon %A Cholda, Piotr %A Stankiewicz, Rafal %A Papafili, Ioanna %D 2010 %J to be published in IEEE Communications Magazine %T Interaction Patterns between P2P Content Distribution Systems and ISPs %X Peer-to-peer (P2P) content distribution systems are a major source of traffic in the Internet, but the application layer protocols they use are mostly unaware of the underlying network in accordance with the layered structure of the Internet’s protocol stack. Nevertheless, the need for improved network efficiency and the business interests of Internet service providers (ISPs) are both strong drivers towards a cross-layer approach in peer-to-peer protocol design, calling for P2P systems that would in some way interact with the ISPs. Recent research shows that the interaction, which can rely on information provided by both parties, can be mutually beneficial. In this paper first we give an overview of the kinds of information that could potentially be exchanged between the P2P systems and the ISPs, and discuss their usefulness and the ease of obtaining and exchanging them. We also present a classification of the possible approaches for interaction based on the level of involvement of the ISPs and the P2P systems, and we discuss the potential strengths and the weaknesses of these approaches.
• A Generic Quantitative Relationship between Quality of Experience and Quality of Service. Fiedler, Markus; Hoßfeld, Tobias; Tran-Gia, Phuoc. In IEEE Network Special Issue on Improving QoE for Network Services. 2010.
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  Quality of Experience (QoE) ties together user perception, experience and expectations to application and network performance, typically expressed by Quality of Service (QoS) parameters. Quantitative relationships between QoE and QoS are required in order to be able to build effective QoE control mechanisms onto measurable QoS parameters. On this background, this paper proposes a generic formula in which QoE and QoS parameters are connected through an exponential relationship, called IQX hypothesis. The formula relates changes of QoE with respect to QoS to the current level of QoE, is simple to match, and its limit behaviours are straighforward to interpret. It validates the IQX hypothesis for streaming services, where QoE in terms of Mean Opinion Scores (MOS) is expressed as functions of loss and reordering ratio, the latter of which is caused by jitter. For web surfing as the second application area, matchings provided by the IQX hypothesis are shown to outperform previously published logarithmic functions. We conclude that the IQX hypothesis is a strong candidate to be taken into account when deriving relationships between QoE and QoS parameters.

  @article{info3-article-2010-71, abstract = {Quality of Experience (QoE) ties together user perception, experience and expectations to application and network performance, typically expressed by Quality of Service (QoS) parameters. Quantitative relationships between QoE and QoS are required in order to be able to build effective QoE control mechanisms onto measurable QoS parameters. On this background, this paper proposes a generic formula in which QoE and QoS parameters are connected through an exponential relationship, called IQX hypothesis. The formula relates changes of QoE with respect to QoS to the current level of QoE, is simple to match, and its limit behaviours are straighforward to interpret. It validates the IQX hypothesis for streaming services, where QoE in terms of Mean Opinion Scores (MOS) is expressed as functions of loss and reordering ratio, the latter of which is caused by jitter. For web surfing as the second application area, matchings provided by the IQX hypothesis are shown to outperform previously published logarithmic functions. We conclude that the IQX hypothesis is a strong candidate to be taken into account when deriving relationships between QoE and QoS parameters.}, author = {Fiedler, Markus and Hoßfeld, Tobias and Tran-Gia, Phuoc}, journal = {IEEE Network Special Issue on Improving QoE for Network Services}, keywords = {sys:hidden:article}, month = {06}, title = {A Generic Quantitative Relationship between Quality of Experience and Quality of Service}, year = 2010 }

  %0 Journal Article %1 info3-article-2010-71 %A Fiedler, Markus %A Hoßfeld, Tobias %A Tran-Gia, Phuoc %D 2010 %J IEEE Network Special Issue on Improving QoE for Network Services %T A Generic Quantitative Relationship between Quality of Experience and Quality of Service %X Quality of Experience (QoE) ties together user perception, experience and expectations to application and network performance, typically expressed by Quality of Service (QoS) parameters. Quantitative relationships between QoE and QoS are required in order to be able to build effective QoE control mechanisms onto measurable QoS parameters. On this background, this paper proposes a generic formula in which QoE and QoS parameters are connected through an exponential relationship, called IQX hypothesis. The formula relates changes of QoE with respect to QoS to the current level of QoE, is simple to match, and its limit behaviours are straighforward to interpret. It validates the IQX hypothesis for streaming services, where QoE in terms of Mean Opinion Scores (MOS) is expressed as functions of loss and reordering ratio, the latter of which is caused by jitter. For web surfing as the second application area, matchings provided by the IQX hypothesis are shown to outperform previously published logarithmic functions. We conclude that the IQX hypothesis is a strong candidate to be taken into account when deriving relationships between QoE and QoS parameters.
• On Optimization of Wireless Mesh Networks using Genetic Algorithms. Pries, Rastin; Staehle, Dirk; Staehle, Barbara; Tran-Gia, Phuoc. In International Journal On Advances in Internet Technology, 1&2. 2010.
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  @article{info3-article-2010-79, author = {Pries, Rastin and Staehle, Dirk and Staehle, Barbara and Tran-Gia, Phuoc}, journal = {International Journal On Advances in Internet Technology}, keywords = {sys:hidden:article}, month = {07}, title = {On Optimization of Wireless Mesh Networks using Genetic Algorithms}, volume = {1&2}, year = 2010 }

  %0 Journal Article %1 info3-article-2010-79 %A Pries, Rastin %A Staehle, Dirk %A Staehle, Barbara %A Tran-Gia, Phuoc %D 2010 %J International Journal On Advances in Internet Technology %T On Optimization of Wireless Mesh Networks using Genetic Algorithms %V 1&2
• Impact of Electrical and Mechanical Antenna Downtilt on a WiMAX System with Fractional Frequency Reuse. Wamser, Florian; Mittelstädt, David; Staehle, Dirk; Tran-Gia, Phuoc. In FREQUENZ - Journal of RF-Engineering and Telecommunications, September/October. 2010.
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  In an interference-limited mobile WiMAX network, efficient cell planning and tuning is an essential task to ensure a functioning network. This includes the selection of the optimal settings for the antenna to, on the one hand provide a good coverage and on the other hand achieve cell isolation. Two different antenna tilting methods are examined in this article, namely the mechanical and the electrical vertical downtilt. The evaluation is done with an advanced WiMAX IEEE 802.16e simulator. In particular, the impact of the antenna configuration on WiMAX fractional frequency reuse (FFR) is studied. The results show a high dependency of FFR to the downtilt configuration, since the inter-cell interference level changes significantly with different settings.

  @article{info3-article-2010-80, abstract = {In an interference-limited mobile WiMAX network, efficient cell planning and tuning is an essential task to ensure a functioning network. This includes the selection of the optimal settings for the antenna to, on the one hand provide a good coverage and on the other hand achieve cell isolation. Two different antenna tilting methods are examined in this article, namely the mechanical and the electrical vertical downtilt. The evaluation is done with an advanced WiMAX IEEE 802.16e simulator. In particular, the impact of the antenna configuration on WiMAX fractional frequency reuse (FFR) is studied. The results show a high dependency of FFR to the downtilt configuration, since the inter-cell interference level changes significantly with different settings.}, author = {Wamser, Florian and Mittelstädt, David and Staehle, Dirk and Tran-Gia, Phuoc}, journal = {FREQUENZ - Journal of RF-Engineering and Telecommunications}, keywords = {sys:hidden:article}, month = {09}, title = {Impact of Electrical and Mechanical Antenna Downtilt on a WiMAX System with Fractional Frequency Reuse}, volume = {September/October}, year = 2010 }

  %0 Journal Article %1 info3-article-2010-80 %A Wamser, Florian %A Mittelstädt, David %A Staehle, Dirk %A Tran-Gia, Phuoc %D 2010 %J FREQUENZ - Journal of RF-Engineering and Telecommunications %T Impact of Electrical and Mechanical Antenna Downtilt on a WiMAX System with Fractional Frequency Reuse %V September/October %X In an interference-limited mobile WiMAX network, efficient cell planning and tuning is an essential task to ensure a functioning network. This includes the selection of the optimal settings for the antenna to, on the one hand provide a good coverage and on the other hand achieve cell isolation. Two different antenna tilting methods are examined in this article, namely the mechanical and the electrical vertical downtilt. The evaluation is done with an advanced WiMAX IEEE 802.16e simulator. In particular, the impact of the antenna configuration on WiMAX fractional frequency reuse (FFR) is studied. The results show a high dependency of FFR to the downtilt configuration, since the inter-cell interference level changes significantly with different settings.
• PCN-Based Measured Rate Termination. Menth, Michael; Lehrieder, Frank. In Computer Networks, 54(13). 2010.
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  Overload in a packet-based network can be prevented by admitting or blocking new flows depending on its load conditions. However, overload can occur in spite of admission control due to unforseen events, e.g., when admitted traffic is rerouted in the network after a failure. To restore quality of service for the majority of admitted flows in such cases, flow termination has been proposed as a novel control function. We present several flow termination algorithms that measure so-called pre-congestion notification (PCN) feedback. We analyze their advantages and shortcomings in particular under challenging conditions. The results improve the understanding of PCN technology which is currently being standardized by the Internet Engineering Task Force (IETF).

  @article{info3-article-2010-75, abstract = {Overload in a packet-based network can be prevented by admitting or blocking new flows depending on its load conditions. However, overload can occur in spite of admission control due to unforseen events, e.g., when admitted traffic is rerouted in the network after a failure. To restore quality of service for the majority of admitted flows in such cases, flow termination has been proposed as a novel control function. We present several flow termination algorithms that measure so-called pre-congestion notification (PCN) feedback. We analyze their advantages and shortcomings in particular under challenging conditions. The results improve the understanding of PCN technology which is currently being standardized by the Internet Engineering Task Force (IETF).}, author = {Menth, Michael and Lehrieder, Frank}, journal = {Computer Networks}, keywords = {sys:hidden:article}, month = {09}, title = {PCN-Based Measured Rate Termination}, volume = {54(13)}, year = 2010 }

  %0 Journal Article %1 info3-article-2010-75 %A Menth, Michael %A Lehrieder, Frank %D 2010 %J Computer Networks %T PCN-Based Measured Rate Termination %V 54(13) %X Overload in a packet-based network can be prevented by admitting or blocking new flows depending on its load conditions. However, overload can occur in spite of admission control due to unforseen events, e.g., when admitted traffic is rerouted in the network after a failure. To restore quality of service for the majority of admitted flows in such cases, flow termination has been proposed as a novel control function. We present several flow termination algorithms that measure so-called pre-congestion notification (PCN) feedback. We analyze their advantages and shortcomings in particular under challenging conditions. The results improve the understanding of PCN technology which is currently being standardized by the Internet Engineering Task Force (IETF).
• FIRMS: A Mapping System for Future Internet Routing. Menth, Michael; Hartmann, Matthias; Hoefling, Michael. In IEEE Journal on Selected Areas in Communications (JSAC), Special Issue on Internet Routing Scalability, 28, pp. 1326–1331. 2010.
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  The locator/identifier split is a design principle for new routing architectures that make Internet routing more scalable. To find the location of a host, it requires a mapping system that returns appropriate locators in response to map-requests for specific identifiers. In this paper, we propose FIRMS, a 'Future Internet Routing Mapping System'. It is fast, scalable, reliable, secure, and it is able to relay initial packets. We introduce its design, show how it deals with partial failures, explain its security concept, and evaluate its scalability.

  @article{info3-article-2010-81, abstract = {The locator/identifier split is a design principle for new routing architectures that make Internet routing more scalable. To find the location of a host, it requires a mapping system that returns appropriate locators in response to map-requests for specific identifiers. In this paper, we propose FIRMS, a 'Future Internet Routing Mapping System'. It is fast, scalable, reliable, secure, and it is able to relay initial packets. We introduce its design, show how it deals with partial failures, explain its security concept, and evaluate its scalability.}, author = {Menth, Michael and Hartmann, Matthias and Hoefling, Michael}, journal = {IEEE Journal on Selected Areas in Communications (JSAC), Special Issue on Internet Routing Scalability}, keywords = {sys:hidden:article}, month = 10, pages = {1326-1331}, title = {FIRMS: A Mapping System for Future Internet Routing}, volume = 28, year = 2010 }

  %0 Journal Article %1 info3-article-2010-81 %A Menth, Michael %A Hartmann, Matthias %A Hoefling, Michael %D 2010 %J IEEE Journal on Selected Areas in Communications (JSAC), Special Issue on Internet Routing Scalability %P 1326-1331 %T FIRMS: A Mapping System for Future Internet Routing %V 28 %X The locator/identifier split is a design principle for new routing architectures that make Internet routing more scalable. To find the location of a host, it requires a mapping system that returns appropriate locators in response to map-requests for specific identifiers. In this paper, we propose FIRMS, a 'Future Internet Routing Mapping System'. It is fast, scalable, reliable, secure, and it is able to relay initial packets. We introduce its design, show how it deals with partial failures, explain its security concept, and evaluate its scalability.
• A Survey of PCN-Based Admission Control and Flow Termination. Menth, Michael; Lehrieder, Frank; Briscoe, Bob; Eardley, Philip; Moncaster, Toby; Babiarz, Jozef; Charny, Anna; (Joy) Zhang, Xinyang; Taylor, Tom; Chan, Kwok-Ho; Satoh, Daisuke; Geib, Ruediger; Karagiannis, Georgios. In IEEE Communications Surveys & Tutorials, 12(3). 2010.
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  Pre-congestion notification (PCN) provides feedback about load conditions in a network to its boundary nodes. The PCN working group of the IETF discusses the use of PCN to implement admission control (AC) and flow termination (FT) for prioritized realtime traffic in a DiffServ domain. Admission control (AC) is a well-known flow control function that blocks admission requests of new flows when they need to be carried over a link whose admitted PCN rate already exceeds an admissible rate. Flow termination (FT) is a new flow control function that terminates some already admitted flows when they are carried over a link whose admitted PCN rate exceeds a supportable rate. The latter condition can occur in spite of AC, e.g., when traffic is rerouted due to network failures. This survey gives an introduction to PCN and is a primer for this new technology. It presents and discusses the multitude of architectural design options in an early stage of the standardization process in a comprehensive and streamlined way before only a subset of them is standardized by the IETF. It brings PCN from the IETF to the research community and serves as historical record.

  @article{info3-article-2010-76, abstract = {Pre-congestion notification (PCN) provides feedback about load conditions in a network to its boundary nodes. The PCN working group of the IETF discusses the use of PCN to implement admission control (AC) and flow termination (FT) for prioritized realtime traffic in a DiffServ domain. Admission control (AC) is a well-known flow control function that blocks admission requests of new flows when they need to be carried over a link whose admitted PCN rate already exceeds an admissible rate. Flow termination (FT) is a new flow control function that terminates some already admitted flows when they are carried over a link whose admitted PCN rate exceeds a supportable rate. The latter condition can occur in spite of AC, e.g., when traffic is rerouted due to network failures. This survey gives an introduction to PCN and is a primer for this new technology. It presents and discusses the multitude of architectural design options in an early stage of the standardization process in a comprehensive and streamlined way before only a subset of them is standardized by the IETF. It brings PCN from the IETF to the research community and serves as historical record.}, author = {Menth, Michael and Lehrieder, Frank and Briscoe, Bob and Eardley, Philip and Moncaster, Toby and Babiarz, Jozef and Charny, Anna and (Joy) Zhang, Xinyang and Taylor, Tom and Chan, Kwok-Ho and Satoh, Daisuke and Geib, Ruediger and Karagiannis, Georgios}, journal = {IEEE Communications Surveys & Tutorials}, keywords = {sys:hidden:article}, month = {07}, title = {A Survey of PCN-Based Admission Control and Flow Termination}, volume = {12(3)}, year = 2010 }

  %0 Journal Article %1 info3-article-2010-76 %A Menth, Michael %A Lehrieder, Frank %A Briscoe, Bob %A Eardley, Philip %A Moncaster, Toby %A Babiarz, Jozef %A Charny, Anna %A (Joy) Zhang, Xinyang %A Taylor, Tom %A Chan, Kwok-Ho %A Satoh, Daisuke %A Geib, Ruediger %A Karagiannis, Georgios %D 2010 %J IEEE Communications Surveys & Tutorials %T A Survey of PCN-Based Admission Control and Flow Termination %V 12(3) %X Pre-congestion notification (PCN) provides feedback about load conditions in a network to its boundary nodes. The PCN working group of the IETF discusses the use of PCN to implement admission control (AC) and flow termination (FT) for prioritized realtime traffic in a DiffServ domain. Admission control (AC) is a well-known flow control function that blocks admission requests of new flows when they need to be carried over a link whose admitted PCN rate already exceeds an admissible rate. Flow termination (FT) is a new flow control function that terminates some already admitted flows when they are carried over a link whose admitted PCN rate exceeds a supportable rate. The latter condition can occur in spite of AC, e.g., when traffic is rerouted due to network failures. This survey gives an introduction to PCN and is a primer for this new technology. It presents and discusses the multitude of architectural design options in an early stage of the standardization process in a comprehensive and streamlined way before only a subset of them is standardized by the IETF. It brings PCN from the IETF to the research community and serves as historical record.

• Threshold Configuration and Routing Optimization for PCN-Based Resilient Admission Control. Menth, Michael; Hartmann, Matthias. In Computer Networks, Volume 53, Issue 11. 2009.
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  Pre-congestion notification (PCN) in IP networks uses packet metering and marking within a PCN domain to notify its egress nodes whether link-specific admissible or supportable rate thresholds have been exceeded by high priority traffic. Based on this information simple admission control and flow termination is implemented. The latter is a new flow control function and useful in case of overload through high priority traffic which can occur in spite of admission control, e.g., when traffic is rerouted in failure cases. Resilient admission control admits only so much traffic that admitted traffic can be rerouted without causing congestion on backup paths in case of a likely failures, e.g., single link failures. We propose algorithms to configure the link-specific PCN rate thresholds such that resources are utilized efficiently and fairly by competing traffic aggregates while meeting resilience constraints. This is done for the single and dual marking PCN architecture whereby the single marking case is more demanding since it requires that the supportable rate is a fixed multiple of the admissible rate on all links within a single PCN domain. Furthermore, we derive objective functions to optimize the underlying routing system for both cases. Our performance results for various network types show that the dual marking PCN architecture leads to significantly better resource efficiency than the single marking PCN architecture.

  @article{info3-article-2009-68, abstract = {Pre-congestion notification (PCN) in IP networks uses packet metering and marking within a PCN domain to notify its egress nodes whether link-specific admissible or supportable rate thresholds have been exceeded by high priority traffic. Based on this information simple admission control and flow termination is implemented. The latter is a new flow control function and useful in case of overload through high priority traffic which can occur in spite of admission control, e.g., when traffic is rerouted in failure cases. Resilient admission control admits only so much traffic that admitted traffic can be rerouted without causing congestion on backup paths in case of a likely failures, e.g., single link failures. We propose algorithms to configure the link-specific PCN rate thresholds such that resources are utilized efficiently and fairly by competing traffic aggregates while meeting resilience constraints. This is done for the single and dual marking PCN architecture whereby the single marking case is more demanding since it requires that the supportable rate is a fixed multiple of the admissible rate on all links within a single PCN domain. Furthermore, we derive objective functions to optimize the underlying routing system for both cases. Our performance results for various network types show that the dual marking PCN architecture leads to significantly better resource efficiency than the single marking PCN architecture.}, author = {Menth, Michael and Hartmann, Matthias}, journal = {Computer Networks}, keywords = {sys:hidden:article}, month = {07}, title = {Threshold Configuration and Routing Optimization for PCN-Based Resilient Admission Control}, volume = {Volume 53, Issue 11}, year = 2009 }

  %0 Journal Article %1 info3-article-2009-68 %A Menth, Michael %A Hartmann, Matthias %D 2009 %J Computer Networks %T Threshold Configuration and Routing Optimization for PCN-Based Resilient Admission Control %V Volume 53, Issue 11 %X Pre-congestion notification (PCN) in IP networks uses packet metering and marking within a PCN domain to notify its egress nodes whether link-specific admissible or supportable rate thresholds have been exceeded by high priority traffic. Based on this information simple admission control and flow termination is implemented. The latter is a new flow control function and useful in case of overload through high priority traffic which can occur in spite of admission control, e.g., when traffic is rerouted in failure cases. Resilient admission control admits only so much traffic that admitted traffic can be rerouted without causing congestion on backup paths in case of a likely failures, e.g., single link failures. We propose algorithms to configure the link-specific PCN rate thresholds such that resources are utilized efficiently and fairly by competing traffic aggregates while meeting resilience constraints. This is done for the single and dual marking PCN architecture whereby the single marking case is more demanding since it requires that the supportable rate is a fixed multiple of the admissible rate on all links within a single PCN domain. Furthermore, we derive objective functions to optimize the underlying routing system for both cases. Our performance results for various network types show that the dual marking PCN architecture leads to significantly better resource efficiency than the single marking PCN architecture.
• Spatial and Temporal Fairness in Heterogeneous HSDPA-enabled UMTS Networks. Mäder, Andreas; Staehle, Dirk. In Eurasip Journal on Wireless Communications and Networking (JWCN), to appear 2009. 2009.
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  @article{info3-article-2009-60, author = {Mäder, Andreas and Staehle, Dirk}, journal = {Eurasip Journal on Wireless Communications and Networking (JWCN)}, keywords = {sys:hidden:article}, title = {Spatial and Temporal Fairness in Heterogeneous HSDPA-enabled UMTS Networks}, volume = {to appear 2009}, year = 2009 }

  %0 Journal Article %1 info3-article-2009-60 %A Mäder, Andreas %A Staehle, Dirk %D 2009 %J Eurasip Journal on Wireless Communications and Networking (JWCN) %T Spatial and Temporal Fairness in Heterogeneous HSDPA-enabled UMTS Networks %V to appear 2009
• Mastering Selfishness and Heterogeneity in Mobile P2P Content Distribution Networks with Multiple Source Download in Cellular Networks. Schlosser, Daniel; Hoßfeld, Tobias. In Peer-to-Peer Networking and Applications, Special Issue on Mobile P2P Networking and Computing. 2009.
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  The performance of Peer-to-Peer (P2P) content distribution networks depends highly on the coordination of the peers. This is especially true for cellular networks with mobile and often selfish users, as the resource constraints on accessible bandwidth and battery power are even more limitating in this context. Thus, it is a major challenge to indentify mobile network specific problems and to develop sophisticated cooperation strategies to overcome these difficulties. Cooperation strategies, which are able to cope these problems, are the foundation for efficient mobile file exchange. The detailed performance of the strategies are determined by the peer capabilities and the peer behavior, such as the number of parallel upload connections, the selfishness, or the altruistic re-distribution of data. The purpose of this work is to evaluate and investigate different cooperation strategies which are based on multiple source download and select the best one for mobile scenarios with even leeching peers, i.e. peers which depart as soon as they have finished their download. The question arises whether the cooperation strategy can smoothen the overall performance degradation caused by a selfish peer behavior. As performance indicators the efficiency, fairness, and robustness of the cooperation strategies are applied. The considered scenarios comprise best-case (altruistic peers) and worst-case scenarios (selfish peers). We further propose a new cooperation strategy to improve the file transfer even when mainly selfish peers are present, the CycPriM (cyclic priority masking) strategy. The strategy allows an efficient P2P based content distribution using ordered chunk delivery with only local information available at a peer.

  @article{info3-article-2009-58, abstract = {The performance of Peer-to-Peer (P2P) content distribution networks depends highly on the coordination of the peers. This is especially true for cellular networks with mobile and often selfish users, as the resource constraints on accessible bandwidth and battery power are even more limitating in this context. Thus, it is a major challenge to indentify mobile network specific problems and to develop sophisticated cooperation strategies to overcome these difficulties. Cooperation strategies, which are able to cope these problems, are the foundation for efficient mobile file exchange. The detailed performance of the strategies are determined by the peer capabilities and the peer behavior, such as the number of parallel upload connections, the selfishness, or the altruistic re-distribution of data. The purpose of this work is to evaluate and investigate different cooperation strategies which are based on multiple source download and select the best one for mobile scenarios with even leeching peers, i.e. peers which depart as soon as they have finished their download. The question arises whether the cooperation strategy can smoothen the overall performance degradation caused by a selfish peer behavior. As performance indicators the efficiency, fairness, and robustness of the cooperation strategies are applied. The considered scenarios comprise best-case (altruistic peers) and worst-case scenarios (selfish peers). We further propose a new cooperation strategy to improve the file transfer even when mainly selfish peers are present, the CycPriM (cyclic priority masking) strategy. The strategy allows an efficient P2P based content distribution using ordered chunk delivery with only local information available at a peer.}, author = {Schlosser, Daniel and Hoßfeld, Tobias}, journal = {Peer-to-Peer Networking and Applications, Special Issue on Mobile P2P Networking and Computing}, keywords = {sys:hidden:article}, title = {Mastering Selfishness and Heterogeneity in Mobile P2P Content Distribution Networks with Multiple Source Download in Cellular Networks}, year = 2009 }

  %0 Journal Article %1 info3-article-2009-58 %A Schlosser, Daniel %A Hoßfeld, Tobias %D 2009 %J Peer-to-Peer Networking and Applications, Special Issue on Mobile P2P Networking and Computing %T Mastering Selfishness and Heterogeneity in Mobile P2P Content Distribution Networks with Multiple Source Download in Cellular Networks %X The performance of Peer-to-Peer (P2P) content distribution networks depends highly on the coordination of the peers. This is especially true for cellular networks with mobile and often selfish users, as the resource constraints on accessible bandwidth and battery power are even more limitating in this context. Thus, it is a major challenge to indentify mobile network specific problems and to develop sophisticated cooperation strategies to overcome these difficulties. Cooperation strategies, which are able to cope these problems, are the foundation for efficient mobile file exchange. The detailed performance of the strategies are determined by the peer capabilities and the peer behavior, such as the number of parallel upload connections, the selfishness, or the altruistic re-distribution of data. The purpose of this work is to evaluate and investigate different cooperation strategies which are based on multiple source download and select the best one for mobile scenarios with even leeching peers, i.e. peers which depart as soon as they have finished their download. The question arises whether the cooperation strategy can smoothen the overall performance degradation caused by a selfish peer behavior. As performance indicators the efficiency, fairness, and robustness of the cooperation strategies are applied. The considered scenarios comprise best-case (altruistic peers) and worst-case scenarios (selfish peers). We further propose a new cooperation strategy to improve the file transfer even when mainly selfish peers are present, the CycPriM (cyclic priority masking) strategy. The strategy allows an efficient P2P based content distribution using ordered chunk delivery with only local information available at a peer.
• Capacity Analysis of Reservation-Based Random Access for Braodband Wireless Access Networks. Vinel, Alexey; Ni, Qiang; Staehle, Dirk; Turlikov, Andrey. In IEEE Journal on Selected Areas in Communication (JSAC), 27. 2009.
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  @article{info3-article-2009-61, author = {Vinel, Alexey and Ni, Qiang and Staehle, Dirk and Turlikov, Andrey}, journal = {IEEE Journal on Selected Areas in Communication (JSAC)}, keywords = {sys:hidden:article}, month = {02}, title = {Capacity Analysis of Reservation-Based Random Access for Braodband Wireless Access Networks}, volume = 27, year = 2009 }

  %0 Journal Article %1 info3-article-2009-61 %A Vinel, Alexey %A Ni, Qiang %A Staehle, Dirk %A Turlikov, Andrey %D 2009 %J IEEE Journal on Selected Areas in Communication (JSAC) %T Capacity Analysis of Reservation-Based Random Access for Braodband Wireless Access Networks %V 27
• Relaxed Multiple Routing Configurations: IP Fast Reroute for Single and Correlated Failures. Cicic, Tarik; Fosselie Hansen, Audun; Kvalbein, Amund; Hartmann, Matthias; Martin, Rüdiger; Menth, Michael; Gjessing, Stein; Lysne, Olav. In IEEE Transactions on Network and Service Managment, 6, pp. 1–14. 2009.
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  Multi-topology routing is an increasingly popular IP network management concept that allows transport of different traffic types over disjoint network paths. The concept is of particular interest for implementation of IP fast reroute (IP FRR). The authors have previously proposed an IP FRR scheme based on multi-topology routing called Multiple Routing Configurations (MRC). MRC supports guaranteed, instantaneous recovery from any single link or node failure in biconnected networks as well as from many combined failures, provided sufficient bandwidth on the surviving links. Furthermore, in MRC different failures result in routing over different network topologies, which gives a good control of the traffic distribution in the networks after a failure. In this paper we present two contributions. First we define an enhanced IP FRR scheme which we call 'relaxed MRC' (rMRC). Through experiments we demonstrate that rMRC is an improvement over MRC in all important aspects. Resource utilization in the presence of failures is significantly better, both in terms of paths lengths and in terms of load distribution between the links. The requirement to internal state in the routers is reduced as rMRC requires fewer backup topologies to provide the same degree of protection. In addition to this, the preprocessing needed to generate the backup topologies is simplified. The second contribution is an extension of rMRC that can provide fast reroute in the presence of multiple correlated failures. Our evaluations demonstrate only a small penalty in path lengths and in the number of backup topologies required.

  @article{info3-article-2009-67, abstract = {Multi-topology routing is an increasingly popular IP network management concept that allows transport of different traffic types over disjoint network paths. The concept is of particular interest for implementation of IP fast reroute (IP FRR). The authors have previously proposed an IP FRR scheme based on multi-topology routing called Multiple Routing Configurations (MRC). MRC supports guaranteed, instantaneous recovery from any single link or node failure in biconnected networks as well as from many combined failures, provided sufficient bandwidth on the surviving links. Furthermore, in MRC different failures result in routing over different network topologies, which gives a good control of the traffic distribution in the networks after a failure. In this paper we present two contributions. First we define an enhanced IP FRR scheme which we call 'relaxed MRC' (rMRC). Through experiments we demonstrate that rMRC is an improvement over MRC in all important aspects. Resource utilization in the presence of failures is significantly better, both in terms of paths lengths and in terms of load distribution between the links. The requirement to internal state in the routers is reduced as rMRC requires fewer backup topologies to provide the same degree of protection. In addition to this, the preprocessing needed to generate the backup topologies is simplified. The second contribution is an extension of rMRC that can provide fast reroute in the presence of multiple correlated failures. Our evaluations demonstrate only a small penalty in path lengths and in the number of backup topologies required.}, author = {Cicic, Tarik and Fosselie Hansen, Audun and Kvalbein, Amund and Hartmann, Matthias and Martin, Rüdiger and Menth, Michael and Gjessing, Stein and Lysne, Olav}, journal = {IEEE Transactions on Network and Service Managment}, keywords = {sys:hidden:article}, month = {03}, pages = {1-14}, title = {Relaxed Multiple Routing Configurations: IP Fast Reroute for Single and Correlated Failures}, volume = 6, year = 2009 }

  %0 Journal Article %1 info3-article-2009-67 %A Cicic, Tarik %A Fosselie Hansen, Audun %A Kvalbein, Amund %A Hartmann, Matthias %A Martin, Rüdiger %A Menth, Michael %A Gjessing, Stein %A Lysne, Olav %D 2009 %J IEEE Transactions on Network and Service Managment %P 1-14 %T Relaxed Multiple Routing Configurations: IP Fast Reroute for Single and Correlated Failures %V 6 %X Multi-topology routing is an increasingly popular IP network management concept that allows transport of different traffic types over disjoint network paths. The concept is of particular interest for implementation of IP fast reroute (IP FRR). The authors have previously proposed an IP FRR scheme based on multi-topology routing called Multiple Routing Configurations (MRC). MRC supports guaranteed, instantaneous recovery from any single link or node failure in biconnected networks as well as from many combined failures, provided sufficient bandwidth on the surviving links. Furthermore, in MRC different failures result in routing over different network topologies, which gives a good control of the traffic distribution in the networks after a failure. In this paper we present two contributions. First we define an enhanced IP FRR scheme which we call 'relaxed MRC' (rMRC). Through experiments we demonstrate that rMRC is an improvement over MRC in all important aspects. Resource utilization in the presence of failures is significantly better, both in terms of paths lengths and in terms of load distribution between the links. The requirement to internal state in the routers is reduced as rMRC requires fewer backup topologies to provide the same degree of protection. In addition to this, the preprocessing needed to generate the backup topologies is simplified. The second contribution is an extension of rMRC that can provide fast reroute in the presence of multiple correlated failures. Our evaluations demonstrate only a small penalty in path lengths and in the number of backup topologies required.
• Radio Resource Management for the UMTS Enhanced Uplink in Presence of QoS Radio Bearers. Mäder, Andreas; Staehle, Dirk. In Special Issue of Annals of Operation Research on Stochastic Performance Models for Resource Allocati, 170. 2009.
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  @article{info3-article-2009-43, author = {Mäder, Andreas and Staehle, Dirk}, journal = {Special Issue of Annals of Operation Research on Stochastic Performance Models for Resource Allocati}, keywords = {sys:hidden:article}, month = {09}, title = {Radio Resource Management for the UMTS Enhanced Uplink in Presence of QoS Radio Bearers}, volume = 170, year = 2009 }

  %0 Journal Article %1 info3-article-2009-43 %A Mäder, Andreas %A Staehle, Dirk %D 2009 %J Special Issue of Annals of Operation Research on Stochastic Performance Models for Resource Allocati %T Radio Resource Management for the UMTS Enhanced Uplink in Presence of QoS Radio Bearers %V 170
• Challenges in the Development of Mobile P2P Applications and Services. Chan Hung, Nguyen; Hoßfeld, Tobias; Ngo Hoang, Giang; Thanh Vinh, Vu; Manh Thang, Nguyen. In Vietname Journal on Information and Communication Technologies, E-1, Number 2 (6). 2009.
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  The recent trends of decentralizing enterprise applications toward the new peer-to-peer (P2P) architecture and the fast growth of wireless communication lead to a new tendency of combining these technologies to inherit their great advantages of mobility, reliability, flexibility and scalability. However, this technological integration raises a large number of new challenges and issues to be addressed. This paper focuses on the challenges of the development of enterprise mobile applications and services based on P2P architecture. Using selected results from related projects, we present and analyze these important issues and also propose an exemplary solution to address some of these issues.

  @article{info3-article-2009-65, abstract = {The recent trends of decentralizing enterprise applications toward the new peer-to-peer (P2P) architecture and the fast growth of wireless communication lead to a new tendency of combining these technologies to inherit their great advantages of mobility, reliability, flexibility and scalability. However, this technological integration raises a large number of new challenges and issues to be addressed. This paper focuses on the challenges of the development of enterprise mobile applications and services based on P2P architecture. Using selected results from related projects, we present and analyze these important issues and also propose an exemplary solution to address some of these issues.}, author = {Chan Hung, Nguyen and Hoßfeld, Tobias and Ngo Hoang, Giang and Thanh Vinh, Vu and Manh Thang, Nguyen}, journal = {Vietname Journal on Information and Communication Technologies}, keywords = {sys:hidden:article}, month = {08}, title = {Challenges in the Development of Mobile P2P Applications and Services}, volume = {E-1, Number 2 (6)}, year = 2009 }

  %0 Journal Article %1 info3-article-2009-65 %A Chan Hung, Nguyen %A Hoßfeld, Tobias %A Ngo Hoang, Giang %A Thanh Vinh, Vu %A Manh Thang, Nguyen %D 2009 %J Vietname Journal on Information and Communication Technologies %T Challenges in the Development of Mobile P2P Applications and Services %V E-1, Number 2 (6) %X The recent trends of decentralizing enterprise applications toward the new peer-to-peer (P2P) architecture and the fast growth of wireless communication lead to a new tendency of combining these technologies to inherit their great advantages of mobility, reliability, flexibility and scalability. However, this technological integration raises a large number of new challenges and issues to be addressed. This paper focuses on the challenges of the development of enterprise mobile applications and services based on P2P architecture. Using selected results from related projects, we present and analyze these important issues and also propose an exemplary solution to address some of these issues.
• Emerging Issues in Current Future Internet Design. Tran-Gia, Phuoc; Hoßfeld, Tobias; Menth, Michael; Pries, Rastin. In e&i Elektrotechnik und Informationstechnik, Special Issue ’Future Internet’, ISSN: 0932-383X (print), ISSN: 1613-7620 (online), 07/08. 2009.
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  From its inception, the Internet was not intended as the worldwide universal communication platform. It developed over almost four decades to its current state. As a result of this unplanned evolution, we currently witness scalability problems, increased complexity, missing modularity as well as missing flexibility for emerging services. In this report we focus on two selected issues: i) the changing routing paradigm and ii) edge‐based intelligence. We will then present a variety of projects on future Internet and finally assess recently established experimental facilities and their role in the Future Internet design.

  @article{info3-article-2009-62, abstract = {From its inception, the Internet was not intended as the worldwide universal communication platform. It developed over almost four decades to its current state. As a result of this unplanned evolution, we currently witness scalability problems, increased complexity, missing modularity as well as missing flexibility for emerging services. In this report we focus on two selected issues: i) the changing routing paradigm and ii) edge‐based intelligence. We will then present a variety of projects on future Internet and finally assess recently established experimental facilities and their role in the Future Internet design.}, author = {Tran-Gia, Phuoc and Hoßfeld, Tobias and Menth, Michael and Pries, Rastin}, journal = {e&i Elektrotechnik und Informationstechnik, Special Issue 'Future Internet', ISSN: 0932-383X (print), ISSN: 1613-7620 (online)}, keywords = {sys:hidden:article}, month = {08}, title = {Emerging Issues in Current Future Internet Design}, volume = {07/08}, year = 2009 }

  %0 Journal Article %1 info3-article-2009-62 %A Tran-Gia, Phuoc %A Hoßfeld, Tobias %A Menth, Michael %A Pries, Rastin %D 2009 %J e&i Elektrotechnik und Informationstechnik, Special Issue 'Future Internet', ISSN: 0932-383X (print), ISSN: 1613-7620 (online) %T Emerging Issues in Current Future Internet Design %V 07/08 %X From its inception, the Internet was not intended as the worldwide universal communication platform. It developed over almost four decades to its current state. As a result of this unplanned evolution, we currently witness scalability problems, increased complexity, missing modularity as well as missing flexibility for emerging services. In this report we focus on two selected issues: i) the changing routing paradigm and ii) edge‐based intelligence. We will then present a variety of projects on future Internet and finally assess recently established experimental facilities and their role in the Future Internet design.
• BP-MAC: A High Reliable Backoff Preamble MAC Protocol for Wireless Sensor Networks. Klein, Alexander; Klaue, Jirka; Schalk, Josef. In EJSE - Electronic Journal of Structural Engineering: Special Issue on Sensor Network for Building Monitoring: From Theory to Real Application. 2009.
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  @article{info3-article-2009-69, author = {Klein, Alexander and Klaue, Jirka and Schalk, Josef}, journal = {EJSE - Electronic Journal of Structural Engineering: Special Issue on Sensor Network for Building Monitoring: From Theory to Real Application}, keywords = {sys:hidden:article}, month = 10, title = {BP-MAC: A High Reliable Backoff Preamble MAC Protocol for Wireless Sensor Networks}, year = 2009 }

  %0 Journal Article %1 info3-article-2009-69 %A Klein, Alexander %A Klaue, Jirka %A Schalk, Josef %D 2009 %J EJSE - Electronic Journal of Structural Engineering: Special Issue on Sensor Network for Building Monitoring: From Theory to Real Application %T BP-MAC: A High Reliable Backoff Preamble MAC Protocol for Wireless Sensor Networks
• Source Models for Speech Traffic Revisited. Menth, Michael; Binzenhöfer, Andreas; Mühleck, Stefan. In IEEE/ACM Transactions on Networking, 17(5). 2009.
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  @article{info3-article-2009-57, author = {Menth, Michael and Binzenhöfer, Andreas and Mühleck, Stefan}, journal = {IEEE/ACM Transactions on Networking}, keywords = {sys:hidden:article}, month = 10, title = {Source Models for Speech Traffic Revisited}, volume = {17(5)}, year = 2009 }

  %0 Journal Article %1 info3-article-2009-57 %A Menth, Michael %A Binzenhöfer, Andreas %A Mühleck, Stefan %D 2009 %J IEEE/ACM Transactions on Networking %T Source Models for Speech Traffic Revisited %V 17(5)
• Resilience Analysis for Packet-Switched Communication Networks. Menth, Michael; Duelli, Michael; Martin, Rüdiger; Milbrandt, Jens. In IEEE/ACM Transactions on Networking, 17. 2009.
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  In the presence of local network outages, restoration and protection switching mechanisms redirect the traffic over alternative paths to mitigate the effect of failures. However, some failure combinations still lead to loss of ingress-egress connectivity within a network or to severe congestion due to rerouted traffic. Congestion may also be caused by unexpected traffic shifts due to changed user behavior or due to changes of interdomain routing. This paper presents a framework for the analysis of ingress-egress unavailability and congestion due to (1) failures, (2) changes of user behavior, and (3) changed interdomain routing. It proposes algorithms to find the most probable combinations of (1), (2), and (3), and to evaluate the connectivity and the relative link load of the network under these conditions. We have implemented this concept in a software tool and its visualization of the results leads to a comprehensive view of the network’s resilience. It helps to anticipate potential ingress-egress disconnection and congestion before failures and overload occur or before planned modifications (new infrastructure, new routing, new customers) take effect. Thus, it detects weak points in a network, predicts the effectiveness of potential upgrades, and thereby supports careful bandwidth overprovisioning.

  @article{info3-article-2009-59, abstract = {In the presence of local network outages, restoration and protection switching mechanisms redirect the traffic over alternative paths to mitigate the effect of failures. However, some failure combinations still lead to loss of ingress-egress connectivity within a network or to severe congestion due to rerouted traffic. Congestion may also be caused by unexpected traffic shifts due to changed user behavior or due to changes of interdomain routing. This paper presents a framework for the analysis of ingress-egress unavailability and congestion due to (1) failures, (2) changes of user behavior, and (3) changed interdomain routing. It proposes algorithms to find the most probable combinations of (1), (2), and (3), and to evaluate the connectivity and the relative link load of the network under these conditions. We have implemented this concept in a software tool and its visualization of the results leads to a comprehensive view of the network’s resilience. It helps to anticipate potential ingress-egress disconnection and congestion before failures and overload occur or before planned modifications (new infrastructure, new routing, new customers) take effect. Thus, it detects weak points in a network, predicts the effectiveness of potential upgrades, and thereby supports careful bandwidth overprovisioning.}, author = {Menth, Michael and Duelli, Michael and Martin, Rüdiger and Milbrandt, Jens}, journal = {IEEE/ACM Transactions on Networking}, keywords = {sys:hidden:article}, month = 12, title = {Resilience Analysis for Packet-Switched Communication Networks}, volume = 17, year = 2009 }

  %0 Journal Article %1 info3-article-2009-59 %A Menth, Michael %A Duelli, Michael %A Martin, Rüdiger %A Milbrandt, Jens %D 2009 %J IEEE/ACM Transactions on Networking %T Resilience Analysis for Packet-Switched Communication Networks %V 17 %X In the presence of local network outages, restoration and protection switching mechanisms redirect the traffic over alternative paths to mitigate the effect of failures. However, some failure combinations still lead to loss of ingress-egress connectivity within a network or to severe congestion due to rerouted traffic. Congestion may also be caused by unexpected traffic shifts due to changed user behavior or due to changes of interdomain routing. This paper presents a framework for the analysis of ingress-egress unavailability and congestion due to (1) failures, (2) changes of user behavior, and (3) changed interdomain routing. It proposes algorithms to find the most probable combinations of (1), (2), and (3), and to evaluate the connectivity and the relative link load of the network under these conditions. We have implemented this concept in a software tool and its visualization of the results leads to a comprehensive view of the network’s resilience. It helps to anticipate potential ingress-egress disconnection and congestion before failures and overload occur or before planned modifications (new infrastructure, new routing, new customers) take effect. Thus, it detects weak points in a network, predicts the effectiveness of potential upgrades, and thereby supports careful bandwidth overprovisioning.

• Trends in Network and Service Operation for the Emerging Future Internet. Tran-Gia, Phuoc; Andersen, Frank-Uwe; Tutschku, Kurt. In International Journal of Electronics and Communication. 2008.
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  @article{info3-article-2008-44, author = {Tran-Gia, Phuoc and Andersen, Frank-Uwe and Tutschku, Kurt}, journal = {International Journal of Electronics and Communication}, keywords = {sys:hidden:article}, title = {Trends in Network and Service Operation for the Emerging Future Internet}, year = 2008 }

  %0 Journal Article %1 info3-article-2008-44 %A Tran-Gia, Phuoc %A Andersen, Frank-Uwe %A Tutschku, Kurt %D 2008 %J International Journal of Electronics and Communication %T Trends in Network and Service Operation for the Emerging Future Internet
• Admission Control for Speech Traffic in the Presence of Overbooking. Menth, Michael; Mühleck, Stefan. In Praxis der Informationsverarbeitung und Kommunikation (PIK), 30(4). 2008.
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  @article{info3-article-2008-54, author = {Menth, Michael and Mühleck, Stefan}, journal = {Praxis der Informationsverarbeitung und Kommunikation (PIK)}, keywords = {sys:hidden:article}, title = {Admission Control for Speech Traffic in the Presence of Overbooking}, volume = {30(4)}, year = 2008 }

  %0 Journal Article %1 info3-article-2008-54 %A Menth, Michael %A Mühleck, Stefan %D 2008 %J Praxis der Informationsverarbeitung und Kommunikation (PIK) %T Admission Control for Speech Traffic in the Presence of Overbooking %V 30(4)
• Future Internet Routing: Motivation and Design Issues. Menth, Michael; Hartmann, Matthias; Tran-Gia, Phuoc; Klein, Dominik. In it - Information Technology, 50(6). 2008.
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  Pre-congestion notification (PCN) in IP networks uses packet metering and marking within a PCN domain to notify its egress nodes whether link-specific admissible or supportable rate thresholds have been exceeded by high priority traffic. Based on this information simple admission control and flow termination is implemented. The latter is a new flow control function and useful in case of overload through high priority traffic which can occur in spite of admission control, e.g., when traffic is rerouted in failure cases. Resilient admission control admits only so much traffic that admitted traffic can be rerouted without causing congestion on backup paths in case of a likely failures, e.g., single link failures. We propose algorithms to configure the link-specific PCN rate thresholds such that resources are utilized efficiently and fairly by competing traffic aggregates while meeting resilience constraints. This is done for the single and dual marking PCN architecture whereby the single marking case is more demanding since it requires that the supportable rate is a fixed multiple of the admissible rate on all links within a single PCN domain. Furthermore, we derive objective functions to optimize the underlying routing system for both cases. Our performance results for various network types show that the dual marking PCN architecture leads to significantly better resource efficiency than the single marking PCN architecture.

  @article{info3-article-2008-55, abstract = {Pre-congestion notification (PCN) in IP networks uses packet metering and marking within a PCN domain to notify its egress nodes whether link-specific admissible or supportable rate thresholds have been exceeded by high priority traffic. Based on this information simple admission control and flow termination is implemented. The latter is a new flow control function and useful in case of overload through high priority traffic which can occur in spite of admission control, e.g., when traffic is rerouted in failure cases. Resilient admission control admits only so much traffic that admitted traffic can be rerouted without causing congestion on backup paths in case of a likely failures, e.g., single link failures. We propose algorithms to configure the link-specific PCN rate thresholds such that resources are utilized efficiently and fairly by competing traffic aggregates while meeting resilience constraints. This is done for the single and dual marking PCN architecture whereby the single marking case is more demanding since it requires that the supportable rate is a fixed multiple of the admissible rate on all links within a single PCN domain. Furthermore, we derive objective functions to optimize the underlying routing system for both cases. Our performance results for various network types show that the dual marking PCN architecture leads to significantly better resource efficiency than the single marking PCN architecture.}, author = {Menth, Michael and Hartmann, Matthias and Tran-Gia, Phuoc and Klein, Dominik}, journal = {it - Information Technology}, keywords = {sys:hidden:article}, month = 12, title = {Future Internet Routing: Motivation and Design Issues}, volume = {50(6)}, year = 2008 }

  %0 Journal Article %1 info3-article-2008-55 %A Menth, Michael %A Hartmann, Matthias %A Tran-Gia, Phuoc %A Klein, Dominik %D 2008 %J it - Information Technology %T Future Internet Routing: Motivation and Design Issues %V 50(6) %X Pre-congestion notification (PCN) in IP networks uses packet metering and marking within a PCN domain to notify its egress nodes whether link-specific admissible or supportable rate thresholds have been exceeded by high priority traffic. Based on this information simple admission control and flow termination is implemented. The latter is a new flow control function and useful in case of overload through high priority traffic which can occur in spite of admission control, e.g., when traffic is rerouted in failure cases. Resilient admission control admits only so much traffic that admitted traffic can be rerouted without causing congestion on backup paths in case of a likely failures, e.g., single link failures. We propose algorithms to configure the link-specific PCN rate thresholds such that resources are utilized efficiently and fairly by competing traffic aggregates while meeting resilience constraints. This is done for the single and dual marking PCN architecture whereby the single marking case is more demanding since it requires that the supportable rate is a fixed multiple of the admissible rate on all links within a single PCN domain. Furthermore, we derive objective functions to optimize the underlying routing system for both cases. Our performance results for various network types show that the dual marking PCN architecture leads to significantly better resource efficiency than the single marking PCN architecture.
• Analysis of Skype VoIP Traffic in UMTS: End-to-End QoS and QoE Measurements. Hoßfeld, Tobias; Binzenhöfer, Andreas. In Computer Networks, 52, pp. 650–666. 2008.
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  In the future Internet, multi-network services will follow a new paradigm in which the intelligence of the network control is gradually moved to the edge of the network. This impacts both the objective Quality of Service (QoS) of the end-toend connection as well as the subjective Quality of Experience (QoE) as perceived by the end user. Skype already offers such a multi-network Voice-over-IP (VoIP) telephony service today. Due to its ease of use and a high sound quality, it becomes increasingly popular in the wired Internet. UMTS operators promise to offer large data rates which should suffice to support VoIP calls in a mobile environment. However, the success of those applications strongly depends on the corresponding QoE. In this work, we analyze the theoretically achievable as well as the actually achieved quality of IP-based voice calls using Skype. This is done performing measurements in both a real UMTS network and a testbed environment. The latter is used to emulate rate control mechanisms and changing system conditions of UMTS networks. The results show in how far Skype over UMTS is able to keep pace with existing mobile telephony systems and how it reacts to different network characteristics. The investigated performance measures comprise the QoE in terms of the MOS value and the QoS in terms of network-based factors like throughput, packet interarrival times, or packet loss.

  @article{info3-article-2008-50, abstract = {In the future Internet, multi-network services will follow a new paradigm in which the intelligence of the network control is gradually moved to the edge of the network. This impacts both the objective Quality of Service (QoS) of the end-toend connection as well as the subjective Quality of Experience (QoE) as perceived by the end user. Skype already offers such a multi-network Voice-over-IP (VoIP) telephony service today. Due to its ease of use and a high sound quality, it becomes increasingly popular in the wired Internet. UMTS operators promise to offer large data rates which should suffice to support VoIP calls in a mobile environment. However, the success of those applications strongly depends on the corresponding QoE. In this work, we analyze the theoretically achievable as well as the actually achieved quality of IP-based voice calls using Skype. This is done performing measurements in both a real UMTS network and a testbed environment. The latter is used to emulate rate control mechanisms and changing system conditions of UMTS networks. The results show in how far Skype over UMTS is able to keep pace with existing mobile telephony systems and how it reacts to different network characteristics. The investigated performance measures comprise the QoE in terms of the MOS value and the QoS in terms of network-based factors like throughput, packet interarrival times, or packet loss.}, author = {Hoßfeld, Tobias and Binzenhöfer, Andreas}, journal = {Computer Networks}, keywords = {sys:hidden:article}, month = {02}, pages = {650-666}, title = {Analysis of Skype VoIP Traffic in UMTS: End-to-End QoS and QoE Measurements}, volume = 52, year = 2008 }

  %0 Journal Article %1 info3-article-2008-50 %A Hoßfeld, Tobias %A Binzenhöfer, Andreas %D 2008 %J Computer Networks %P 650-666 %T Analysis of Skype VoIP Traffic in UMTS: End-to-End QoS and QoE Measurements %V 52 %X In the future Internet, multi-network services will follow a new paradigm in which the intelligence of the network control is gradually moved to the edge of the network. This impacts both the objective Quality of Service (QoS) of the end-toend connection as well as the subjective Quality of Experience (QoE) as perceived by the end user. Skype already offers such a multi-network Voice-over-IP (VoIP) telephony service today. Due to its ease of use and a high sound quality, it becomes increasingly popular in the wired Internet. UMTS operators promise to offer large data rates which should suffice to support VoIP calls in a mobile environment. However, the success of those applications strongly depends on the corresponding QoE. In this work, we analyze the theoretically achievable as well as the actually achieved quality of IP-based voice calls using Skype. This is done performing measurements in both a real UMTS network and a testbed environment. The latter is used to emulate rate control mechanisms and changing system conditions of UMTS networks. The results show in how far Skype over UMTS is able to keep pace with existing mobile telephony systems and how it reacts to different network characteristics. The investigated performance measures comprise the QoE in terms of the MOS value and the QoS in terms of network-based factors like throughput, packet interarrival times, or packet loss.
• Efficient Simulation of Large-Scale P2P Networks. Binzenhöfer, Andreas; Hoßfeld, Tobias; Kunzmann, Gerald; Eger, Kolja. In International Journal of Computational Science and Engineering (IJCSE): Special Issue on Parallel, Distributed and Network-Based Processing. 2008.
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  @article{info3-article-2008-51, author = {Binzenhöfer, Andreas and Hoßfeld, Tobias and Kunzmann, Gerald and Eger, Kolja}, journal = {International Journal of Computational Science and Engineering (IJCSE): Special Issue on Parallel, Distributed and Network-Based Processing}, keywords = {sys:hidden:article}, month = {03}, title = {Efficient Simulation of Large-Scale P2P Networks}, year = 2008 }

  %0 Journal Article %1 info3-article-2008-51 %A Binzenhöfer, Andreas %A Hoßfeld, Tobias %A Kunzmann, Gerald %A Eger, Kolja %D 2008 %J International Journal of Computational Science and Engineering (IJCSE): Special Issue on Parallel, Distributed and Network-Based Processing %T Efficient Simulation of Large-Scale P2P Networks
• Resilient Network Admission Control. Menth, Michael; Kopf, Stefan; Charzinski, Joachim; Schrodi, Karl. In Computer Networks, 52(14). 2008.
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  @article{info3-article-2008-56, author = {Menth, Michael and Kopf, Stefan and Charzinski, Joachim and Schrodi, Karl}, journal = {Computer Networks}, keywords = {sys:hidden:article}, month = 10, title = {Resilient Network Admission Control}, volume = {52(14)}, year = 2008 }

  %0 Journal Article %1 info3-article-2008-56 %A Menth, Michael %A Kopf, Stefan %A Charzinski, Joachim %A Schrodi, Karl %D 2008 %J Computer Networks %T Resilient Network Admission Control %V 52(14)

• Mechanismen zur Steuerung und Verwaltung von ATM-Netzen (Mechanisms for ATM network control and managment). Tran-Gia, Phuoc; Ritter, Michael. In Informatik Spektrum, 20, pp. 216–224. 2007.
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  @article{info3-article-1997-6, author = {Tran-Gia, Phuoc and Ritter, Michael}, journal = {Informatik Spektrum}, keywords = {sys:hidden:article}, pages = {216–224}, title = {Mechanismen zur Steuerung und Verwaltung von ATM-Netzen (Mechanisms for ATM network control and managment)}, volume = 20, year = 2007 }

  %0 Journal Article %1 info3-article-1997-6 %A Tran-Gia, Phuoc %A Ritter, Michael %D 2007 %J Informatik Spektrum %P 216--224 %T Mechanismen zur Steuerung und Verwaltung von ATM-Netzen (Mechanisms for ATM network control and managment) %V 20
• Engine control using neural networks: A new method in engine management systems. Hemberger, Hans-Hubert; Müller, Rainer; Baier, Karlheinz. In MECCANICA, 32, pp. 423–430. 2007.
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  @article{info3-article-1997-7, author = {Hemberger, Hans-Hubert and Müller, Rainer and Baier, Karlheinz}, journal = {MECCANICA}, keywords = {sys:hidden:article}, pages = {423–430}, title = {Engine control using neural networks: A new method in engine management systems}, volume = 32, year = 2007 }

  %0 Journal Article %1 info3-article-1997-7 %A Hemberger, Hans-Hubert %A Müller, Rainer %A Baier, Karlheinz %D 2007 %J MECCANICA %P 423--430 %T Engine control using neural networks: A new method in engine management systems %V 32
• Analytical Performance Evaluation of Low-Bitrate Real-Time Traffic Multiplexing in UMTS over IP-Networks. Menth, Michael. In International Journal of Interconnection Networks (JoIN), World Sientific Publishing Company, Vol. 2, No. 1. 2007.
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  @article{info3-article-2001-11, author = {Menth, Michael}, journal = {International Journal of Interconnection Networks (JoIN), World Sientific Publishing Company}, keywords = {sys:hidden:article}, title = {Analytical Performance Evaluation of Low-Bitrate Real-Time Traffic Multiplexing in UMTS over IP-Networks}, volume = {Vol. 2, No. 1}, year = 2007 }

  %0 Journal Article %1 info3-article-2001-11 %A Menth, Michael %D 2007 %J International Journal of Interconnection Networks (JoIN), World Sientific Publishing Company %T Analytical Performance Evaluation of Low-Bitrate Real-Time Traffic Multiplexing in UMTS over IP-Networks %V Vol. 2, No. 1
• Dynamic Operation in Peer-to-Peer Overlay Networks. de Meer, Hermann; Tran-Gia, Phuoc; Tutschku, Kurt. In Praxis der Informationsverarbeitung und Kommunikation - Special Issues on Peer-to-Peer Systems. 2007.
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  @article{info3-article-2003-13, author = {de Meer, Hermann and Tran-Gia, Phuoc and Tutschku, Kurt}, journal = {Praxis der Informationsverarbeitung und Kommunikation - Special Issues on Peer-to-Peer Systems}, keywords = {sys:hidden:article}, title = {Dynamic Operation in Peer-to-Peer Overlay Networks}, year = 2007 }

  %0 Journal Article %1 info3-article-2003-13 %A de Meer, Hermann %A Tran-Gia, Phuoc %A Tutschku, Kurt %D 2007 %J Praxis der Informationsverarbeitung und Kommunikation - Special Issues on Peer-to-Peer Systems %T Dynamic Operation in Peer-to-Peer Overlay Networks
• Modeling of customer retrial phenomenon in cellular mobile networks. Tran-Gia, Phuoc; Mandjes, Michael. In IEEE JSAC special issue on Personal Communication - Services, architecture and performance issues, pp. 1406–1414. 2007.
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  @article{info3-article-1997-4, author = {Tran-Gia, Phuoc and Mandjes, Michael}, journal = {IEEE JSAC special issue on Personal Communication - Services, architecture and performance issues}, keywords = {sys:hidden:article}, pages = {1406–1414}, title = {Modeling of customer retrial phenomenon in cellular mobile networks}, year = 2007 }

  %0 Journal Article %1 info3-article-1997-4 %A Tran-Gia, Phuoc %A Mandjes, Michael %D 2007 %J IEEE JSAC special issue on Personal Communication - Services, architecture and performance issues %P 1406--1414 %T Modeling of customer retrial phenomenon in cellular mobile networks
• Spatial traffic estimation and characterization for mobile communication network design. Tran-Gia, Phuoc; Tutschku, Kurt. In IEEE JSAC, 16. 2007.
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  @article{info3-article-1998-2, author = {Tran-Gia, Phuoc and Tutschku, Kurt}, journal = {IEEE JSAC}, keywords = {sys:hidden:article}, title = {Spatial traffic estimation and characterization for mobile communication network design}, volume = 16, year = 2007 }

  %0 Journal Article %1 info3-article-1998-2 %A Tran-Gia, Phuoc %A Tutschku, Kurt %D 2007 %J IEEE JSAC %T Spatial traffic estimation and characterization for mobile communication network design %V 16
• Neural adaptive ignition control. Müller, Rainer; Hemberger, Hans-Hubert. In SAE, 981057, pp. 97–102. 2007.
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  @article{info3-article-1998-3, author = {Müller, Rainer and Hemberger, Hans-Hubert}, journal = {SAE}, keywords = {sys:hidden:article}, pages = {97–102}, title = {Neural adaptive ignition control}, volume = 981057, year = 2007 }

  %0 Journal Article %1 info3-article-1998-3 %A Müller, Rainer %A Hemberger, Hans-Hubert %D 2007 %J SAE %P 97--102 %T Neural adaptive ignition control %V 981057
• Source Traffic Modeling of Wireless Applications. Tran-Gia, Phuoc; Staehle, Dirk; Leibnitz, Kenji. In International Journal of Electronics and Communications, 55. 2007.
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  @article{info3-article-2001-9, author = {Tran-Gia, Phuoc and Staehle, Dirk and Leibnitz, Kenji}, journal = {International Journal of Electronics and Communications}, keywords = {sys:hidden:article}, title = {Source Traffic Modeling of Wireless Applications}, volume = 55, year = 2007 }

  %0 Journal Article %1 info3-article-2001-9 %A Tran-Gia, Phuoc %A Staehle, Dirk %A Leibnitz, Kenji %D 2007 %J International Journal of Electronics and Communications %T Source Traffic Modeling of Wireless Applications %V 55
• P2P-based Network and Service Operation for the Emerging Future Internet. Tutschku, Kurt. In Praxis der Informationsverarbeitung und Kommunikation - Special Issue on Current Trends in Network a, II/2007. 2007.
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  @article{info3-article-2007-41, author = {Tutschku, Kurt}, journal = {Praxis der Informationsverarbeitung und Kommunikation - Special Issue on Current Trends in Network a}, keywords = {sys:hidden:article}, title = {P2P-based Network and Service Operation for the Emerging Future Internet.}, volume = {II/2007}, year = 2007 }

  %0 Journal Article %1 info3-article-2007-41 %A Tutschku, Kurt %D 2007 %J Praxis der Informationsverarbeitung und Kommunikation - Special Issue on Current Trends in Network a %T P2P-based Network and Service Operation for the Emerging Future Internet. %V II/2007
• Discrete-time approximation of the machine interference problem with generally distributed failure, repair, and walking times. Kern, Christoph; Mittler, Manfred. In European Journal of Control, 3, pp. 254–267. 2007.
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  @article{info3-article-1997-8, author = {Kern, Christoph and Mittler, Manfred}, journal = {European Journal of Control}, keywords = {sys:hidden:article}, pages = {254–267}, title = {Discrete-time approximation of the machine interference problem with generally distributed failure, repair, and walking times}, volume = 3, year = 2007 }

  %0 Journal Article %1 info3-article-1997-8 %A Kern, Christoph %A Mittler, Manfred %D 2007 %J European Journal of Control %P 254--267 %T Discrete-time approximation of the machine interference problem with generally distributed failure, repair, and walking times %V 3
• Teletraffic Issues in Mobile Communication Network Planning. Leibnitz, Kenji; Tran-Gia, Phuoc; Tutschku, Kurt. In Telecommunication Systems, 15. 2007.
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  @article{info3-article-2000-10, author = {Leibnitz, Kenji and Tran-Gia, Phuoc and Tutschku, Kurt}, journal = {Telecommunication Systems}, keywords = {sys:hidden:article}, title = {Teletraffic Issues in Mobile Communication Network Planning}, volume = 15, year = 2007 }

  %0 Journal Article %1 info3-article-2000-10 %A Leibnitz, Kenji %A Tran-Gia, Phuoc %A Tutschku, Kurt %D 2007 %J Telecommunication Systems %T Teletraffic Issues in Mobile Communication Network Planning %V 15
• Modeling of an Online TV Recording System. Hoßfeld, Tobias; Leibnitz, Kenji; Remiche, Marie-Ange. In SIGMETRICS Performance Evaluation Review, Volume 35, Number 2. 2007.
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  Recently, new services have emerged which utilize the Internet as a delivery mechanism for multimedia content. With the advent of broadband accesses, more users are willing to download large volume content from servers, such as video files of TV shows. While some popular video services (e.g. YouTube.com) or some broadcasting companies (e.g. ABC.com) use streaming data with Flash technology, some media distributors (e.g. iTunes) offer entire TV shows for download. In this study, we investigate the performance of the German site OnlineTVRecorder.com (OTR), which acts as an online video cassette recorder (VCR) where users can program their favorite shows over a web interface and download the recorded files from a server or its mirrors. These files are offered in different file formats and can consist of several hundred megabytes up to 1GB or more depending on the length of the TV show as well as the encoding format. OTR can, thus, be seen as an example for a server-based content distribution system with large data files. However, as these server farms are often overloaded, new requests are queued when the provided download slots are full. The restriction to a maximum number of simultaneous downloads guarantees a minimal download bandwidth for each user. Additionally, the service offers premium users prioritized access to downloading. The download duration itself depends on the total capacity of the server and the number of users currently sharing this capacity. On the other hand, users who might encounter slow downloads may abort their downloading attempt if their patience is exceeded. In this paper, we discuss analytical modeling approaches which consider the impact of the user’s impatience on the performance of an OTR server with different file size distributions. The paper is organized as follows. After describing the problem and related work, we formulate simple analytical models and compare their performance in terms of download duration and success ratio. Especially, we address the question of how to properly dimension the number of simultaneous downloads at a server in order to optimize the performance of the system and to maximize the user satisfaction.

  @article{info3-article-2007-49, abstract = {Recently, new services have emerged which utilize the Internet as a delivery mechanism for multimedia content. With the advent of broadband accesses, more users are willing to download large volume content from servers, such as video files of TV shows. While some popular video services (e.g. YouTube.com) or some broadcasting companies (e.g. ABC.com) use streaming data with Flash technology, some media distributors (e.g. iTunes) offer entire TV shows for download. In this study, we investigate the performance of the German site OnlineTVRecorder.com (OTR), which acts as an online video cassette recorder (VCR) where users can program their favorite shows over a web interface and download the recorded files from a server or its mirrors. These files are offered in different file formats and can consist of several hundred megabytes up to 1GB or more depending on the length of the TV show as well as the encoding format. OTR can, thus, be seen as an example for a server-based content distribution system with large data files. However, as these server farms are often overloaded, new requests are queued when the provided download slots are full. The restriction to a maximum number of simultaneous downloads guarantees a minimal download bandwidth for each user. Additionally, the service offers premium users prioritized access to downloading. The download duration itself depends on the total capacity of the server and the number of users currently sharing this capacity. On the other hand, users who might encounter slow downloads may abort their downloading attempt if their patience is exceeded. In this paper, we discuss analytical modeling approaches which consider the impact of the user’s impatience on the performance of an OTR server with different file size distributions. The paper is organized as follows. After describing the problem and related work, we formulate simple analytical models and compare their performance in terms of download duration and success ratio. Especially, we address the question of how to properly dimension the number of simultaneous downloads at a server in order to optimize the performance of the system and to maximize the user satisfaction.}, author = {Hoßfeld, Tobias and Leibnitz, Kenji and Remiche, Marie-Ange}, journal = {SIGMETRICS Performance Evaluation Review}, keywords = {sys:hidden:article}, month = {09}, title = {Modeling of an Online TV Recording System}, volume = {Volume 35, Number 2}, year = 2007 }

  %0 Journal Article %1 info3-article-2007-49 %A Hoßfeld, Tobias %A Leibnitz, Kenji %A Remiche, Marie-Ange %D 2007 %J SIGMETRICS Performance Evaluation Review %T Modeling of an Online TV Recording System %V Volume 35, Number 2 %X Recently, new services have emerged which utilize the Internet as a delivery mechanism for multimedia content. With the advent of broadband accesses, more users are willing to download large volume content from servers, such as video files of TV shows. While some popular video services (e.g. YouTube.com) or some broadcasting companies (e.g. ABC.com) use streaming data with Flash technology, some media distributors (e.g. iTunes) offer entire TV shows for download. In this study, we investigate the performance of the German site OnlineTVRecorder.com (OTR), which acts as an online video cassette recorder (VCR) where users can program their favorite shows over a web interface and download the recorded files from a server or its mirrors. These files are offered in different file formats and can consist of several hundred megabytes up to 1GB or more depending on the length of the TV show as well as the encoding format. OTR can, thus, be seen as an example for a server-based content distribution system with large data files. However, as these server farms are often overloaded, new requests are queued when the provided download slots are full. The restriction to a maximum number of simultaneous downloads guarantees a minimal download bandwidth for each user. Additionally, the service offers premium users prioritized access to downloading. The download duration itself depends on the total capacity of the server and the number of users currently sharing this capacity. On the other hand, users who might encounter slow downloads may abort their downloading attempt if their patience is exceeded. In this paper, we discuss analytical modeling approaches which consider the impact of the user’s impatience on the performance of an OTR server with different file size distributions. The paper is organized as follows. After describing the problem and related work, we formulate simple analytical models and compare their performance in terms of download duration and success ratio. Especially, we address the question of how to properly dimension the number of simultaneous downloads at a server in order to optimize the performance of the system and to maximize the user satisfaction.
• Linear algorithm solving the travelling salesman optimization problem. Tran-Gia, Phuoc; Fritsch, Thomas; Gihr, Ottmar. In IBM Technical Disclosure Bulletin, 37(06B):265. 2007.
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  @article{info3-article-1994-20, author = {Tran-Gia, Phuoc and Fritsch, Thomas and Gihr, Ottmar}, journal = {IBM Technical Disclosure Bulletin}, keywords = {sys:hidden:article}, title = {Linear algorithm solving the travelling salesman optimization problem}, volume = {37(06B):265}, year = 2007 }

  %0 Journal Article %1 info3-article-1994-20 %A Tran-Gia, Phuoc %A Fritsch, Thomas %A Gihr, Ottmar %D 2007 %J IBM Technical Disclosure Bulletin %T Linear algorithm solving the travelling salesman optimization problem %V 37(06B):265
• Improving Experience-Based Admission Control through Traffic Type Awareness. Milbrandt, Jens; Menth, Michael; Junker, Jan. In Journal of Networks (JNW), Vol. 2, No.2. 2007.
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  @article{info3-article-2007-40, author = {Milbrandt, Jens and Menth, Michael and Junker, Jan}, journal = {Journal of Networks (JNW)}, keywords = {sys:hidden:article}, month = {05}, title = {Improving Experience-Based Admission Control through Traffic Type Awareness}, volume = {Vol. 2, No.2}, year = 2007 }

  %0 Journal Article %1 info3-article-2007-40 %A Milbrandt, Jens %A Menth, Michael %A Junker, Jan %D 2007 %J Journal of Networks (JNW) %T Improving Experience-Based Admission Control through Traffic Type Awareness %V Vol. 2, No.2
• QoS of Internet Access with GPRS. Staehle, Dirk; Leibnitz, Kenji; Tsipotis, Konstantin. In Wireless Networks, 9, pp. 213–222. 2007.
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  @article{info3-article-2003-12, author = {Staehle, Dirk and Leibnitz, Kenji and Tsipotis, Konstantin}, journal = {Wireless Networks}, keywords = {sys:hidden:article}, pages = {213–222}, title = {QoS of Internet Access with GPRS}, volume = 9, year = 2007 }

  %0 Journal Article %1 info3-article-2003-12 %A Staehle, Dirk %A Leibnitz, Kenji %A Tsipotis, Konstantin %D 2007 %J Wireless Networks %P 213--222 %T QoS of Internet Access with GPRS %V 9
• Throughput Performance of the BEA WebLogic JMS Server. Henjes, Robert; Menth, Michael; Himmler, Valentin. In International Transactions on Systems Science and Applications, Volume 3, Number 3. 2007.
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  @article{info3-article-2007-53, author = {Henjes, Robert and Menth, Michael and Himmler, Valentin}, journal = {International Transactions on Systems Science and Applications}, keywords = {sys:hidden:article}, month = 10, title = {Throughput Performance of the BEA WebLogic JMS Server}, volume = {Volume 3, Number 3}, year = 2007 }

  %0 Journal Article %1 info3-article-2007-53 %A Henjes, Robert %A Menth, Michael %A Himmler, Valentin %D 2007 %J International Transactions on Systems Science and Applications %T Throughput Performance of the BEA WebLogic JMS Server %V Volume 3, Number 3
• Design and Analysis of a Scalable Algorithm to Monitor Chord-based P2P Systems at Runtime. Binzenhöfer, Andreas; Kunzmann, Gerald; Henjes, Robert. In Concurrency and Computation: Practice and Experience - Special Issue on HotP2P 06. 2007.
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  @article{info3-article-2007-42, author = {Binzenhöfer, Andreas and Kunzmann, Gerald and Henjes, Robert}, journal = {Concurrency and Computation: Practice and Experience - Special Issue on HotP2P 06}, keywords = {sys:hidden:article}, month = {08}, title = {Design and Analysis of a Scalable Algorithm to Monitor Chord-based P2P Systems at Runtime}, year = 2007 }

  %0 Journal Article %1 info3-article-2007-42 %A Binzenhöfer, Andreas %A Kunzmann, Gerald %A Henjes, Robert %D 2007 %J Concurrency and Computation: Practice and Experience - Special Issue on HotP2P 06 %T Design and Analysis of a Scalable Algorithm to Monitor Chord-based P2P Systems at Runtime
• A Note on Source Models for Speech Traffic. Menth, Michael; Binzenhöfer, Andreas; Mühleck, Stefan. In Performance Evaluation Review: Special Issue on PERFORMANCE 2007 Posters, 35(3). 2007.
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  @article{info3-article-2007-52, author = {Menth, Michael and Binzenhöfer, Andreas and Mühleck, Stefan}, journal = {Performance Evaluation Review: Special Issue on PERFORMANCE 2007 Posters}, keywords = {sys:hidden:article}, month = 12, title = {A Note on Source Models for Speech Traffic}, volume = {35(3)}, year = 2007 }

  %0 Journal Article %1 info3-article-2007-52 %A Menth, Michael %A Binzenhöfer, Andreas %A Mühleck, Stefan %D 2007 %J Performance Evaluation Review: Special Issue on PERFORMANCE 2007 Posters %T A Note on Source Models for Speech Traffic %V 35(3)
• Methods for Performance Improvement of Kademlia-based Overlay Networks. Binzenhöfer, Andreas; Schnabel, Holger; Tran-Gia, Phuoc. In it - Information Technology (Methods and Applications of Informatics and Information Technology), 46. 2007.
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  @article{info3-article-2007-45, author = {Binzenhöfer, Andreas and Schnabel, Holger and Tran-Gia, Phuoc}, journal = {it - Information Technology (Methods and Applications of Informatics and Information Technology)}, keywords = {sys:hidden:article}, month = {05}, title = {Methods for Performance Improvement of Kademlia-based Overlay Networks}, volume = 46, year = 2007 }

  %0 Journal Article %1 info3-article-2007-45 %A Binzenhöfer, Andreas %A Schnabel, Holger %A Tran-Gia, Phuoc %D 2007 %J it - Information Technology (Methods and Applications of Informatics and Information Technology) %T Methods for Performance Improvement of Kademlia-based Overlay Networks %V 46
• Efficiency of PCN-Based Network Admission Control with Flow Termination. Menth, Michael. In Praxis der Informationsverarbeitung und Kommunikation (PIK), 30(2). 2007.
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  @article{info3-article-2007-46, author = {Menth, Michael}, journal = {Praxis der Informationsverarbeitung und Kommunikation (PIK)}, keywords = {sys:hidden:article}, month = {04}, title = {Efficiency of PCN-Based Network Admission Control with Flow Termination}, volume = {30(2)}, year = 2007 }

  %0 Journal Article %1 info3-article-2007-46 %A Menth, Michael %D 2007 %J Praxis der Informationsverarbeitung und Kommunikation (PIK) %T Efficiency of PCN-Based Network Admission Control with Flow Termination %V 30(2)
• Experience-Based Admission Control in the Presence of Traffic Changes. Milbrandt, Jens; Menth, Michael; Junker, Jan. In Journal of Communications (JCM), Vol. 2, No.1. 2007.
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  @article{info3-article-2007-39, author = {Milbrandt, Jens and Menth, Michael and Junker, Jan}, journal = {Journal of Communications (JCM)}, keywords = {sys:hidden:article}, month = {01}, title = {Experience-Based Admission Control in the Presence of Traffic Changes}, volume = {Vol. 2, No.1}, year = 2007 }

  %0 Journal Article %1 info3-article-2007-39 %A Milbrandt, Jens %A Menth, Michael %A Junker, Jan %D 2007 %J Journal of Communications (JCM) %T Experience-Based Admission Control in the Presence of Traffic Changes %V Vol. 2, No.1
• Modelling and Performance of Inter-Processor Messaging in Distributed Systems. Tran-Gia, Phuoc; Jans, Herbert; Manfield, David. In Performance Evaluation, 7. 2007.
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  @article{info3-article-1987-34, author = {Tran-Gia, Phuoc and Jans, Herbert and Manfield, David}, journal = {Performance Evaluation}, keywords = {sys:hidden:article}, title = {Modelling and Performance of Inter-Processor Messaging in Distributed Systems}, volume = 7, year = 2007 }

  %0 Journal Article %1 info3-article-1987-34 %A Tran-Gia, Phuoc %A Jans, Herbert %A Manfield, David %D 2007 %J Performance Evaluation %T Modelling and Performance of Inter-Processor Messaging in Distributed Systems %V 7
• Fluctuations in Bipolar Affective Illnes. Tran-Gia, Phuoc; Kniffki, Klaus-D.; Braun, Christian; Klusch, Andreas. In Fractal Reviews in the Natural and Applied Sciences. 2007.
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  @article{info3-article-1995-37, author = {Tran-Gia, Phuoc and Kniffki, Klaus-D. and Braun, Christian and Klusch, Andreas}, journal = {Fractal Reviews in the Natural and Applied Sciences}, keywords = {sys:hidden:article}, title = {Fluctuations in Bipolar Affective Illnes}, year = 2007 }

  %0 Journal Article %1 info3-article-1995-37 %A Tran-Gia, Phuoc %A Kniffki, Klaus-D. %A Braun, Christian %A Klusch, Andreas %D 2007 %J Fractal Reviews in the Natural and Applied Sciences %T Fluctuations in Bipolar Affective Illnes

• Capacity Overprovisioning for Networks with Resilience Requirements. Menth, Michael; Martin, Rüdiger; Charzinski, Joachim. In ACM SIGCOMM Computer Communication Review (CCR), 36(4). 2006.
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  @article{info3-article-2006-48, author = {Menth, Michael and Martin, Rüdiger and Charzinski, Joachim}, journal = {ACM SIGCOMM Computer Communication Review (CCR)}, keywords = {sys:hidden:article}, month = 10, title = {Capacity Overprovisioning for Networks with Resilience Requirements}, volume = {36(4)}, year = 2006 }

  %0 Journal Article %1 info3-article-2006-48 %A Menth, Michael %A Martin, Rüdiger %A Charzinski, Joachim %D 2006 %J ACM SIGCOMM Computer Communication Review (CCR) %T Capacity Overprovisioning for Networks with Resilience Requirements %V 36(4)
• Throughput Performance of Popular JMS Servers. Menth, Michael; Henjes, Robert; Gehrsitz, Sebastian; Zepfel, Christian. In ACM SIGMETRICS Performance Evaluation Review (PER), 34(1). 2006.
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  @article{info3-article-2006-47, author = {Menth, Michael and Henjes, Robert and Gehrsitz, Sebastian and Zepfel, Christian}, journal = {ACM SIGMETRICS Performance Evaluation Review (PER)}, keywords = {sys:hidden:article}, month = {06}, title = {Throughput Performance of Popular JMS Servers}, volume = {34(1)}, year = 2006 }

  %0 Journal Article %1 info3-article-2006-47 %A Menth, Michael %A Henjes, Robert %A Gehrsitz, Sebastian %A Zepfel, Christian %D 2006 %J ACM SIGMETRICS Performance Evaluation Review (PER) %T Throughput Performance of Popular JMS Servers %V 34(1)
• Service differentiation with MEDF scheduling in TCP/IP networks. Menth, Michael; Martin, Rüdiger. In Computer Communications Journal, Volume 29, Issue 7. 2006.
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  @article{info3-article-2006-38, author = {Menth, Michael and Martin, Rüdiger}, journal = {Computer Communications Journal}, keywords = {sys:hidden:article}, month = {04}, title = {Service differentiation with MEDF scheduling in TCP/IP networks}, volume = {Volume 29, Issue 7}, year = 2006 }

  %0 Journal Article %1 info3-article-2006-38 %A Menth, Michael %A Martin, Rüdiger %D 2006 %J Computer Communications Journal %T Service differentiation with MEDF scheduling in TCP/IP networks %V Volume 29, Issue 7

• Editorial ETT Special Issue on P2P Networking and P2P Services. Tutschku, Kurt; de Meer, Hermann; Andersen, Frank-Uwe; Kawashima, Konosuke. In European Transactions on Telecommunications, 6. 2004.
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  @article{info3-article-2004-30, author = {Tutschku, Kurt and de Meer, Hermann and Andersen, Frank-Uwe and Kawashima, Konosuke}, journal = {European Transactions on Telecommunications}, keywords = {sys:hidden:article}, month = 11, title = {Editorial ETT Special Issue on P2P Networking and P2P Services}, volume = 6, year = 2004 }

  %0 Journal Article %1 info3-article-2004-30 %A Tutschku, Kurt %A de Meer, Hermann %A Andersen, Frank-Uwe %A Kawashima, Konosuke %D 2004 %J European Transactions on Telecommunications %T Editorial ETT Special Issue on P2P Networking and P2P Services %V 6

• Nonlinear time series analysis of combustion-pressure data for neural network training with the concept of a mutual information (to be published). Heister, Frank; Fröhlich, M. In SAE Journal of Automobile Engineering. 2001.
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  @article{info3-article-2000-1, author = {Heister, Frank and Fröhlich, M}, journal = {SAE Journal of Automobile Engineering}, keywords = {sys:hidden:article}, title = {Nonlinear time series analysis of combustion-pressure data for neural network training with the concept of a mutual information (to be published)}, year = 2001 }

  %0 Journal Article %1 info3-article-2000-1 %A Heister, Frank %A Fröhlich, M %D 2001 %J SAE Journal of Automobile Engineering %T Nonlinear time series analysis of combustion-pressure data for neural network training with the concept of a mutual information (to be published)

• Simple and efficient models for variable bit rate MPEG video traffic. Rose, Oliver. In Performance Evaluation, 30, pp. 69–85. 1997.
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  @article{info3-article-1997-5, author = {Rose, Oliver}, journal = {Performance Evaluation}, keywords = {sys:hidden:article}, pages = {69–85}, title = {Simple and efficient models for variable bit rate MPEG video traffic}, volume = 30, year = 1997 }

  %0 Journal Article %1 info3-article-1997-5 %A Rose, Oliver %D 1997 %J Performance Evaluation %P 69--85 %T Simple and efficient models for variable bit rate MPEG video traffic %V 30
• Temporal fluctuations in biorhythms: expression of self-organized criticality?. Mandel, Wolfgang; Kniffki, Klaus-D.; Tran-Gia, Phuoc. In Fractals, 1, pp. 380–387. 1997.
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  @article{info3-article-1993-28, author = {Mandel, Wolfgang and Kniffki, Klaus-D. and Tran-Gia, Phuoc}, journal = {Fractals}, keywords = {sys:hidden:article}, pages = {380–387}, title = {Temporal fluctuations in biorhythms: expression of self-organized criticality?}, volume = 1, year = 1997 }

  %0 Journal Article %1 info3-article-1993-28 %A Mandel, Wolfgang %A Kniffki, Klaus-D. %A Tran-Gia, Phuoc %D 1997 %J Fractals %P 380--387 %T Temporal fluctuations in biorhythms: expression of self-organized criticality? %V 1

• Cell loss analysis of broadband switching systems carrying VBR video traffic. Rose, Oliver; Frater, Michael R. In Telecommunication Systems, 4, pp. 319–338. 1995.
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  @article{info3-article-1995-18, author = {Rose, Oliver and Frater, Michael R}, journal = {Telecommunication Systems}, keywords = {sys:hidden:article}, pages = {319–338}, title = {Cell loss analysis of broadband switching systems carrying VBR video traffic}, volume = 4, year = 1995 }

  %0 Journal Article %1 info3-article-1995-18 %A Rose, Oliver %A Frater, Michael R %D 1995 %J Telecommunication Systems %P 319--338 %T Cell loss analysis of broadband switching systems carrying VBR video traffic %V 4

• Discrete-time analysis of cell spacing in ATM systems. Tran-Gia, Phuoc; Hübner, Frank. In Telecommunications Systems, 3, pp. 379–395. 1994.
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  @article{info3-article-1995-19, author = {Tran-Gia, Phuoc and Hübner, Frank}, journal = {Telecommunications Systems}, keywords = {sys:hidden:article}, pages = {379–395}, title = {Discrete-time analysis of cell spacing in ATM systems}, volume = 3, year = 1994 }

  %0 Journal Article %1 info3-article-1995-19 %A Tran-Gia, Phuoc %A Hübner, Frank %D 1994 %J Telecommunications Systems %P 379--395 %T Discrete-time analysis of cell spacing in ATM systems %V 3
• Cellular mobile communication design using self-organizing feature maps. Fritsch, Thomas. In Neural Networks in Telecommunications, B. Yuhas and N. Ansari, editors, Kuwer, boston, pp. 211–232. 1994.
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  @article{info3-article-1994-21, author = {Fritsch, Thomas}, journal = {Neural Networks in Telecommunications, B. Yuhas and N. Ansari, editors, Kuwer, boston}, keywords = {sys:hidden:article}, pages = {211–232}, title = {Cellular mobile communication design using self-organizing feature maps}, year = 1994 }

  %0 Journal Article %1 info3-article-1994-21 %A Fritsch, Thomas %D 1994 %J Neural Networks in Telecommunications, B. Yuhas and N. Ansari, editors, Kuwer, boston %P 211--232 %T Cellular mobile communication design using self-organizing feature maps
• Discrete-time analysis of usage parameter control functions in ATM systems. Tran-Gia, Phuoc. In Architecture and protocols for high-speed networks, O. Spaniol, A.Danthine, and W.Effelsberg, editor, chapter 7, pp. 111-1. 1994.
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  @article{info3-article-1994-22, author = {Tran-Gia, Phuoc}, journal = {Architecture and protocols for high-speed networks, O. Spaniol, A.Danthine, and W.Effelsberg, editor}, keywords = {sys:hidden:article}, month = 10, title = {Discrete-time analysis of usage parameter control functions in ATM systems}, volume = {chapter 7, pp. 111-1}, year = 1994 }

  %0 Journal Article %1 info3-article-1994-22 %A Tran-Gia, Phuoc %D 1994 %J Architecture and protocols for high-speed networks, O. Spaniol, A.Danthine, and W.Effelsberg, editor %T Discrete-time analysis of usage parameter control functions in ATM systems %V chapter 7, pp. 111-1
• Structure and performance of neural nets in broadband system admission control. Gropp, Oliver; Tran-Gia, Phuoc. In Neural networks in Telecommunications, B. Yuhas and N. Ansari, editors, Kluwer, Boston, chapter 7, pp. 127-1. 1994.
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  @article{info3-article-1994-24, author = {Gropp, Oliver and Tran-Gia, Phuoc}, journal = {Neural networks in Telecommunications, B. Yuhas and N. Ansari, editors, Kluwer, Boston}, keywords = {sys:hidden:article}, month = {01}, title = {Structure and performance of neural nets in broadband system admission control}, volume = {chapter 7, pp. 127-1}, year = 1994 }

  %0 Journal Article %1 info3-article-1994-24 %A Gropp, Oliver %A Tran-Gia, Phuoc %D 1994 %J Neural networks in Telecommunications, B. Yuhas and N. Ansari, editors, Kluwer, Boston %T Structure and performance of neural nets in broadband system admission control %V chapter 7, pp. 127-1
• Multi-rate models for dimensioning and performance evaluation of ATM networks. Tran-Gia, Phuoc; Ritter, Michael. In Interim report, Cooperation in the Field of Science and Technical Research COST 242. 1994.
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  @article{info3-article-1994-23, author = {Tran-Gia, Phuoc and Ritter, Michael}, journal = {Interim report, Cooperation in the Field of Science and Technical Research COST 242}, keywords = {sys:hidden:article}, month = {06}, title = {Multi-rate models for dimensioning and performance evaluation of ATM networks}, year = 1994 }

  %0 Journal Article %1 info3-article-1994-23 %A Tran-Gia, Phuoc %A Ritter, Michael %D 1994 %J Interim report, Cooperation in the Field of Science and Technical Research COST 242 %T Multi-rate models for dimensioning and performance evaluation of ATM networks

• Das DQDB-Zugriffsprotokoll in Hochgeschwindigkeitsnetzen und der IEEE-Standard 802.6. Stock, Thomas; Tran-Gia, Phuoc; Dittmann, Rainer. In Informatik-Spektrum, 16, pp. 143–158. 1993.
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  @article{info3-article-1993-25, author = {Stock, Thomas and Tran-Gia, Phuoc and Dittmann, Rainer}, journal = {Informatik-Spektrum}, keywords = {sys:hidden:article}, month = {06}, pages = {143–158}, title = {Das DQDB-Zugriffsprotokoll in Hochgeschwindigkeitsnetzen und der IEEE-Standard 802.6}, volume = 16, year = 1993 }

  %0 Journal Article %1 info3-article-1993-25 %A Stock, Thomas %A Tran-Gia, Phuoc %A Dittmann, Rainer %D 1993 %J Informatik-Spektrum %P 143--158 %T Das DQDB-Zugriffsprotokoll in Hochgeschwindigkeitsnetzen und der IEEE-Standard 802.6 %V 16
• Performance of a finite-capacity asynchronous multiplexer with modulated input. Tran-Gia, Phuoc; Hübner, Frank. In Telecommunication systems: Modeling, Analysis, Design and Management, 1, pp. 263–278. 1993.
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  @article{info3-article-1993-14, author = {Tran-Gia, Phuoc and Hübner, Frank}, journal = {Telecommunication systems: Modeling, Analysis, Design and Management}, keywords = {sys:hidden:article}, pages = {263–278}, title = {Performance of a finite-capacity asynchronous multiplexer with modulated input}, volume = 1, year = 1993 }

  %0 Journal Article %1 info3-article-1993-14 %A Tran-Gia, Phuoc %A Hübner, Frank %D 1993 %J Telecommunication systems: Modeling, Analysis, Design and Management %P 263--278 %T Performance of a finite-capacity asynchronous multiplexer with modulated input %V 1
• Artificial neural net applications in telecommunication systems. Tran-Gia, Phuoc; Fritsch, Thomas; Mittler, Manfred. In Neural Computing & Applications, 1, pp. 124–146. 1993.
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  @article{info3-article-1993-26, author = {Tran-Gia, Phuoc and Fritsch, Thomas and Mittler, Manfred}, journal = {Neural Computing & Applications}, keywords = {sys:hidden:article}, pages = {124–146}, title = {Artificial neural net applications in telecommunication systems}, volume = 1, year = 1993 }

  %0 Journal Article %1 info3-article-1993-26 %A Tran-Gia, Phuoc %A Fritsch, Thomas %A Mittler, Manfred %D 1993 %J Neural Computing & Applications %P 124--146 %T Artificial neural net applications in telecommunication systems %V 1
• A batch service system operating in a pull production line. Gold, Hermann; Tran-Gia, Phuoc; Grob, Heidrun. In Archiv für Elektronik und Übertragungstechnik, 47, pp. 379–385. 1993.
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  @article{info3-article-1993-29, author = {Gold, Hermann and Tran-Gia, Phuoc and Grob, Heidrun}, journal = {Archiv für Elektronik und Übertragungstechnik}, keywords = {sys:hidden:article}, pages = {379–385}, title = {A batch service system operating in a pull production line}, volume = 47, year = 1993 }

  %0 Journal Article %1 info3-article-1993-29 %A Gold, Hermann %A Tran-Gia, Phuoc %A Grob, Heidrun %D 1993 %J Archiv für Elektronik und Übertragungstechnik %P 379--385 %T A batch service system operating in a pull production line %V 47
• Performance analysis of a batch service queue arising out of manufacturing system modelling. Gold, Hermann; Tran-Gia, Phuoc. In Queueing Systems, 14, pp. 413–426. 1993.
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  @article{info3-article-1993-27, author = {Gold, Hermann and Tran-Gia, Phuoc}, journal = {Queueing Systems}, keywords = {sys:hidden:article}, pages = {413–426}, title = {Performance analysis of a batch service queue arising out of manufacturing system modelling}, volume = 14, year = 1993 }

  %0 Journal Article %1 info3-article-1993-27 %A Gold, Hermann %A Tran-Gia, Phuoc %D 1993 %J Queueing Systems %P 413--426 %T Performance analysis of a batch service queue arising out of manufacturing system modelling %V 14

• A discrete-time analysis of the cyclic reservation multiple access protocol. Dittmann, Rainer; Tran-Gia, Phuoc. In Performance Evaluation, 16, pp. 263–278. 1992.
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  @article{info3-article-1992-15, author = {Dittmann, Rainer and Tran-Gia, Phuoc}, journal = {Performance Evaluation}, keywords = {sys:hidden:article}, pages = {263–278}, title = {A discrete-time analysis of the cyclic reservation multiple access protocol}, volume = 16, year = 1992 }

  %0 Journal Article %1 info3-article-1992-15 %A Dittmann, Rainer %A Tran-Gia, Phuoc %D 1992 %J Performance Evaluation %P 263--278 %T A discrete-time analysis of the cyclic reservation multiple access protocol %V 16
• Analytische Modellbildung von Fertigungssystemen - Eine Fallstudie. Gihr, Ottmar; Gold, Hermann; Tran-Gia, Phuoc. In Informatik als Produktionsfaktor. 1992.
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  @article{info3-article-1992-31, author = {Gihr, Ottmar and Gold, Hermann and Tran-Gia, Phuoc}, journal = {Informatik als Produktionsfaktor}, keywords = {sys:hidden:article}, title = {Analytische Modellbildung von Fertigungssystemen - Eine Fallstudie}, year = 1992 }

  %0 Journal Article %1 info3-article-1992-31 %A Gihr, Ottmar %A Gold, Hermann %A Tran-Gia, Phuoc %D 1992 %J Informatik als Produktionsfaktor %T Analytische Modellbildung von Fertigungssystemen - Eine Fallstudie
• Analysis of polling systems with general input process and finite capacity. Tran-Gia, Phuoc. In IEEE Transactions on Communications, Vol. 40, No. 2, pp. 1992.
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  @article{info3-article-1992-16, author = {Tran-Gia, Phuoc}, journal = {IEEE Transactions on Communications}, keywords = {sys:hidden:article}, title = {Analysis of polling systems with general input process and finite capacity}, volume = {Vol. 40, No. 2, pp.}, year = 1992 }

  %0 Journal Article %1 info3-article-1992-16 %A Tran-Gia, Phuoc %D 1992 %J IEEE Transactions on Communications %T Analysis of polling systems with general input process and finite capacity %V Vol. 40, No. 2, pp.

• Approximate performance analysis of the DQDB access protocol. Tran-Gia, Phuoc; Stock, Thomas. In Computer Network and ISDN Systems, 20, pp. 231–240. 1990.
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  @article{info3-article-1990-17, author = {Tran-Gia, Phuoc and Stock, Thomas}, journal = {Computer Network and ISDN Systems}, keywords = {sys:hidden:article}, pages = {231–240}, title = {Approximate performance analysis of the DQDB access protocol}, volume = 20, year = 1990 }

  %0 Journal Article %1 info3-article-1990-17 %A Tran-Gia, Phuoc %A Stock, Thomas %D 1990 %J Computer Network and ISDN Systems %P 231--240 %T Approximate performance analysis of the DQDB access protocol %V 20

• A Class of Renewal Interrupted Poisson Processes and Applications to Queueing Systems. Tran-Gia, Phuoc. In Zeitschrift für Operations Research, vol. 32. 1988.
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  @article{info3-article-1988-33, author = {Tran-Gia, Phuoc}, journal = {Zeitschrift für Operations Research}, keywords = {sys:hidden:article}, title = {A Class of Renewal Interrupted Poisson Processes and Applications to Queueing Systems}, volume = {vol. 32}, year = 1988 }

  %0 Journal Article %1 info3-article-1988-33 %A Tran-Gia, Phuoc %D 1988 %J Zeitschrift für Operations Research %T A Class of Renewal Interrupted Poisson Processes and Applications to Queueing Systems %V vol. 32
• Performance Analysis of Finite Capacity Polling Systems with Nonexhaustive Service. Tran-Gia, Phuoc; Raith, Thomas. In Perfomance Evaluation, vol. 9. 1988.
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  @article{info3-article-1988-32, author = {Tran-Gia, Phuoc and Raith, Thomas}, journal = {Perfomance Evaluation}, keywords = {sys:hidden:article}, title = {Performance Analysis of Finite Capacity Polling Systems with Nonexhaustive Service}, volume = {vol. 9}, year = 1988 }

  %0 Journal Article %1 info3-article-1988-32 %A Tran-Gia, Phuoc %A Raith, Thomas %D 1988 %J Perfomance Evaluation %T Performance Analysis of Finite Capacity Polling Systems with Nonexhaustive Service %V vol. 9

• Dependency of Service Time on Waiting Time in Switching Systems - A Queueing Analysis with Aspects of Overload Control. Tran-Gia, Phuoc; Van Hoorn, Michiel H. In IEEE Transactions on Communications, 34. 1986.
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  @article{info3-article-1986-35, author = {Tran-Gia, Phuoc and Van Hoorn, Michiel H.}, journal = {IEEE Transactions on Communications}, keywords = {sys:hidden:article}, title = {Dependency of Service Time on Waiting Time in Switching Systems - A Queueing Analysis with Aspects of Overload Control}, volume = 34, year = 1986 }

  %0 Journal Article %1 info3-article-1986-35 %A Tran-Gia, Phuoc %A Van Hoorn, Michiel H. %D 1986 %J IEEE Transactions on Communications %T Dependency of Service Time on Waiting Time in Switching Systems - A Queueing Analysis with Aspects of Overload Control %V 34

• Delay Analysis of Clock-Driven Message Transfer in Distributed Processing Systems. Tran-Gia, Phuoc; Jans, Herbert. In Archiv für Elektronik und Übertragungstechnik, 39, pp. 285–292. 1985.
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  In modern computer and communication systems the system of control is distributed among a number of individual devices or processors operating in modes of function or load sharing. Communication between distributed control units via an interconnection network is often organized in the form of message interchanging according to message transfer mechanism. In this paper, a performance analysis is given for the commonly used clock-driven messaging protocol, for which a two-level queueing system is developed and investigated. The analysis is done using a two-dimensional imbedded Markov chain, for which the calculation is done in conjunction with a dimension reducing choice of regression points. Numerical results for dimensioning purposes are given for message delay characteristics under different traffic conditions, clock intervals, and buffer sizes. The results can be used to optimize the messaging delay for the class of clock-driven message transfer mechanisms. Finally, the distribution function of the queueing delay is derived for the first-in first-out message transfer discipline.

  @article{info3-article-1985-121, abstract = {In modern computer and communication systems the system of control is distributed among a number of individual devices or processors operating in modes of function or load sharing. Communication between distributed control units via an interconnection network is often organized in the form of message interchanging according to message transfer mechanism. In this paper, a performance analysis is given for the commonly used clock-driven messaging protocol, for which a two-level queueing system is developed and investigated. The analysis is done using a two-dimensional imbedded Markov chain, for which the calculation is done in conjunction with a dimension reducing choice of regression points. Numerical results for dimensioning purposes are given for message delay characteristics under different traffic conditions, clock intervals, and buffer sizes. The results can be used to optimize the messaging delay for the class of clock-driven message transfer mechanisms. Finally, the distribution function of the queueing delay is derived for the first-in first-out message transfer discipline.}, author = {Tran-Gia, Phuoc and Jans, Herbert}, journal = {Archiv für Elektronik und Übertragungstechnik}, keywords = {sys:hidden:article}, pages = {285-292}, title = {Delay Analysis of Clock-Driven Message Transfer in Distributed Processing Systems}, volume = 39, year = 1985 }

  %0 Journal Article %1 info3-article-1985-121 %A Tran-Gia, Phuoc %A Jans, Herbert %D 1985 %J Archiv für Elektronik und Übertragungstechnik %P 285-292 %T Delay Analysis of Clock-Driven Message Transfer in Distributed Processing Systems %V 39 %X In modern computer and communication systems the system of control is distributed among a number of individual devices or processors operating in modes of function or load sharing. Communication between distributed control units via an interconnection network is often organized in the form of message interchanging according to message transfer mechanism. In this paper, a performance analysis is given for the commonly used clock-driven messaging protocol, for which a two-level queueing system is developed and investigated. The analysis is done using a two-dimensional imbedded Markov chain, for which the calculation is done in conjunction with a dimension reducing choice of regression points. Numerical results for dimensioning purposes are given for message delay characteristics under different traffic conditions, clock intervals, and buffer sizes. The results can be used to optimize the messaging delay for the class of clock-driven message transfer mechanisms. Finally, the distribution function of the queueing delay is derived for the first-in first-out message transfer discipline.

• Analysis of a Storage System with Batch Input Arising out of Message Packetisation. Tran-Gia, Phuoc; Manfield, David. In IEEE Transactions on Communications, 30. 1982.
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  @article{info3-article-1982-36, author = {Tran-Gia, Phuoc and Manfield, David}, journal = {IEEE Transactions on Communications}, keywords = {sys:hidden:article}, title = {Analysis of a Storage System with Batch Input Arising out of Message Packetisation}, volume = 30, year = 1982 }

  %0 Journal Article %1 info3-article-1982-36 %A Tran-Gia, Phuoc %A Manfield, David %D 1982 %J IEEE Transactions on Communications %T Analysis of a Storage System with Batch Input Arising out of Message Packetisation %V 30