Dr. rer. nat. David Hock

• Accurate Live Visualization of Packet Delays, Inter-Arrival Times, and Burstiness for Real-Time Networks. Grigorjew, Alexej; Geißler, Stefan; Ziegler, Maximilian; Schumann, Lukas Kilian; Diederich, Philip; Hock, David; Hoßfeld, Tobias; Kellerer, Wolfgang. In International Conference on Networked Systems 2023 (NetSys). 2023.
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  In this demonstration, a live delay and traffic volume visualization is presented. It is created with consumer off-the-shelf components, provides sub-microsecond accuracy, and provides sufficient performance for line rate measurements without sampling. The tool can help to accelerate the development and operation of real-time networks.

  @inproceedings{info3-inproceedings-2023-14, abstract = {In this demonstration, a live delay and traffic volume visualization is presented. It is created with consumer off-the-shelf components, provides sub-microsecond accuracy, and provides sufficient performance for line rate measurements without sampling. The tool can help to accelerate the development and operation of real-time networks.}, author = {Grigorjew, Alexej and Geißler, Stefan and Ziegler, Maximilian and Schumann, Lukas Kilian and Diederich, Philip and Hock, David and Hoßfeld, Tobias and Kellerer, Wolfgang}, booktitle = {International Conference on Networked Systems 2023 (NetSys)}, keywords = {kosinu5}, month = {09}, title = {Accurate Live Visualization of Packet Delays, Inter-Arrival Times, and Burstiness for Real-Time Networks}, year = 2023 }

  %0 Conference Paper %1 info3-inproceedings-2023-14 %A Grigorjew, Alexej %A Geißler, Stefan %A Ziegler, Maximilian %A Schumann, Lukas Kilian %A Diederich, Philip %A Hock, David %A Hoßfeld, Tobias %A Kellerer, Wolfgang %B International Conference on Networked Systems 2023 (NetSys) %D 2023 %T Accurate Live Visualization of Packet Delays, Inter-Arrival Times, and Burstiness for Real-Time Networks %X In this demonstration, a live delay and traffic volume visualization is presented. It is created with consumer off-the-shelf components, provides sub-microsecond accuracy, and provides sufficient performance for line rate measurements without sampling. The tool can help to accelerate the development and operation of real-time networks.

• Integrating Network Management Information into the SDN Control Plane. Lange, Stanislav; Reinhart, Lorenz; Zinner, Thomas; Hock, David; Gray, Nicholas; Tran-Gia, Phuoc. In IEEE/IFIP Network Operations and Management Symposium (NOMS). 2018.
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  With software defined networking (SDN), operators benefit from a higher flexibility, cost efficiency, as well as programmability of their networks. Since modern networks are comprised of a multitude of heterogeneous devices and also include non-SDN legacy devices, network management systems (NMSs) are often used in order to monitor and configure the network. Although both, the SDN controller and the NMS, have a centralized view of the network, they operate at different time scales and deal with information at different levels of granularity. In this work, we investigate the impact on the network performance when an NMS regularly provides information to an SDN controller. To this end, we design, implement, and compare three interaction mechanisms based on the ONOS controller. These represent different trade-offs regarding the complexity of the resulting system and its performance. In addition to the default ONOS controller, we develop two extended versions. One performs hash-based load balancing on equal cost paths while the other utilizes external NMS information via ONOS's intent and annotation framework to optimize control plane decisions. In addition to evaluations that show a significant performance improvement when using the optimized controllers, we present a parameter study that highlights the performance impact of network characteristics like the flow interarrival time, the flow duration, and the number of active flows.

  @inproceedings{info3-inproceedings-2018-10, abstract = {With software defined networking (SDN), operators benefit from a higher flexibility, cost efficiency, as well as programmability of their networks. Since modern networks are comprised of a multitude of heterogeneous devices and also include non-SDN legacy devices, network management systems (NMSs) are often used in order to monitor and configure the network. Although both, the SDN controller and the NMS, have a centralized view of the network, they operate at different time scales and deal with information at different levels of granularity. In this work, we investigate the impact on the network performance when an NMS regularly provides information to an SDN controller. To this end, we design, implement, and compare three interaction mechanisms based on the ONOS controller. These represent different trade-offs regarding the complexity of the resulting system and its performance. In addition to the default ONOS controller, we develop two extended versions. One performs hash-based load balancing on equal cost paths while the other utilizes external NMS information via ONOS's intent and annotation framework to optimize control plane decisions. In addition to evaluations that show a significant performance improvement when using the optimized controllers, we present a parameter study that highlights the performance impact of network characteristics like the flow interarrival time, the flow duration, and the number of active flows.}, author = {Lange, Stanislav and Reinhart, Lorenz and Zinner, Thomas and Hock, David and Gray, Nicholas and Tran-Gia, Phuoc}, booktitle = {IEEE/IFIP Network Operations and Management Symposium (NOMS)}, keywords = {sdnperf}, month = {04}, title = {Integrating Network Management Information into the SDN Control Plane}, year = 2018 }

  %0 Conference Paper %1 info3-inproceedings-2018-10 %A Lange, Stanislav %A Reinhart, Lorenz %A Zinner, Thomas %A Hock, David %A Gray, Nicholas %A Tran-Gia, Phuoc %B IEEE/IFIP Network Operations and Management Symposium (NOMS) %D 2018 %T Integrating Network Management Information into the SDN Control Plane %X With software defined networking (SDN), operators benefit from a higher flexibility, cost efficiency, as well as programmability of their networks. Since modern networks are comprised of a multitude of heterogeneous devices and also include non-SDN legacy devices, network management systems (NMSs) are often used in order to monitor and configure the network. Although both, the SDN controller and the NMS, have a centralized view of the network, they operate at different time scales and deal with information at different levels of granularity. In this work, we investigate the impact on the network performance when an NMS regularly provides information to an SDN controller. To this end, we design, implement, and compare three interaction mechanisms based on the ONOS controller. These represent different trade-offs regarding the complexity of the resulting system and its performance. In addition to the default ONOS controller, we develop two extended versions. One performs hash-based load balancing on equal cost paths while the other utilizes external NMS information via ONOS's intent and annotation framework to optimize control plane decisions. In addition to evaluations that show a significant performance improvement when using the optimized controllers, we present a parameter study that highlights the performance impact of network characteristics like the flow interarrival time, the flow duration, and the number of active flows.
• Evaluation of a Distributed Control Plane for Managing Heterogeneous SDN-enabled and Legacy Networks. Gray, Nicholas; Lange, Stanislav; Zinner, Thomas; Pfaff, Benedikt; Hock, David. In 7th International Conference on Communications and Electronics (ICCE). Hue, Vietnam, 2018.
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  With the increasing number of devices, protocols and applications, today’s networks are becoming more and more complex. Hence, Software-defined Networking (SDN) tries to ad- dress this issue by separating the data from the control plane and by providing centralized interfaces for network configuration. As legacy devices cannot be replaced instantly due to high costs, both network segments have to be operated in coexistence with defined joints at their edges. To ensure a smooth operation, both controlling instances of these segments are required to exchange information. In this work, we design and implement a data model for storing the information needed to keep the controller and a Network Management System (NMS) synchronized, which are responsible for configuring the SDN-enabled network and the legacy devices respectively. For this, we implement and evaluate a total of three different synchronization strategies by the example of an SDN-based Bring Your Own Device (BYOD) use case. Index Terms—SDN, NMS, Management, Integration, Hetero- geneous Networks, Distributed Control Plane.

  @inproceedings{info3-inproceedings-2018-33, abstract = {With the increasing number of devices, protocols and applications, today’s networks are becoming more and more complex. Hence, Software-defined Networking (SDN) tries to ad- dress this issue by separating the data from the control plane and by providing centralized interfaces for network configuration. As legacy devices cannot be replaced instantly due to high costs, both network segments have to be operated in coexistence with defined joints at their edges. To ensure a smooth operation, both controlling instances of these segments are required to exchange information. In this work, we design and implement a data model for storing the information needed to keep the controller and a Network Management System (NMS) synchronized, which are responsible for configuring the SDN-enabled network and the legacy devices respectively. For this, we implement and evaluate a total of three different synchronization strategies by the example of an SDN-based Bring Your Own Device (BYOD) use case. Index Terms—SDN, NMS, Management, Integration, Hetero- geneous Networks, Distributed Control Plane.}, address = {Hue, Vietnam}, author = {Gray, Nicholas and Lange, Stanislav and Zinner, Thomas and Pfaff, Benedikt and Hock, David}, booktitle = {7th International Conference on Communications and Electronics (ICCE)}, keywords = {sardine}, month = {07}, title = {Evaluation of a Distributed Control Plane for Managing Heterogeneous SDN-enabled and Legacy Networks}, year = 2018 }

  %0 Conference Paper %1 info3-inproceedings-2018-33 %A Gray, Nicholas %A Lange, Stanislav %A Zinner, Thomas %A Pfaff, Benedikt %A Hock, David %B 7th International Conference on Communications and Electronics (ICCE) %C Hue, Vietnam %D 2018 %T Evaluation of a Distributed Control Plane for Managing Heterogeneous SDN-enabled and Legacy Networks %X With the increasing number of devices, protocols and applications, today’s networks are becoming more and more complex. Hence, Software-defined Networking (SDN) tries to ad- dress this issue by separating the data from the control plane and by providing centralized interfaces for network configuration. As legacy devices cannot be replaced instantly due to high costs, both network segments have to be operated in coexistence with defined joints at their edges. To ensure a smooth operation, both controlling instances of these segments are required to exchange information. In this work, we design and implement a data model for storing the information needed to keep the controller and a Network Management System (NMS) synchronized, which are responsible for configuring the SDN-enabled network and the legacy devices respectively. For this, we implement and evaluate a total of three different synchronization strategies by the example of an SDN-based Bring Your Own Device (BYOD) use case. Index Terms—SDN, NMS, Management, Integration, Hetero- geneous Networks, Distributed Control Plane.

• Performance Evaluation of Selective Flow Monitoring in the ONOS Controller. Nguyen-Ngoc, Anh; Lange, Stanislav; Zinner, Thomas; Seufert, Michael; Tran-Gia, Phuoc; Aerts, Nieke; Hock, David. In 4th International Workshop on Management of SDN and NFV Systems (ManSDN/NFV). Tokio, Japan, 2017.
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  One of the benefits when network operators adopt the Software Defined Networking (SDN) paradigm is the ability to monitor the traffic in the network without an additional network management system. Usually, SDN controllers utilize OpenFlow statistics messages in order to regularly gather information about all flows in the network. However, using the same polling interval for all flows does not take into account the heterogeneity of real world traffic and thus results in an imbalance between monitoring accuracy and control plane overhead. In particular, frequent querying results in a high resource consumption at the controller. This work proposes a Selective Flow Monitoring (SFM) mechanism that allows administrators to classify flows according to their individual requirements in terms of monitoring frequency, e.g., less frequent polling of elephant flows and frequent polling of QoS sensitive VoIP connections. We compare the performance of the SFM mechanism with the default monitoring scheme in a testbed featuring the Open Network Operating System (ONOS) controller. In this context, the CPU utilization of the controller is used as performance indicator. After identifying relevant influence factors like the number of flows and switches in the network, we investigate the viability of the approaches in different scenarios. Finally, we provide guidelines regarding their choice.

  @inproceedings{info3-inproceedings-2017-20, abstract = {One of the benefits when network operators adopt the Software Defined Networking (SDN) paradigm is the ability to monitor the traffic in the network without an additional network management system. Usually, SDN controllers utilize OpenFlow statistics messages in order to regularly gather information about all flows in the network. However, using the same polling interval for all flows does not take into account the heterogeneity of real world traffic and thus results in an imbalance between monitoring accuracy and control plane overhead. In particular, frequent querying results in a high resource consumption at the controller. This work proposes a Selective Flow Monitoring (SFM) mechanism that allows administrators to classify flows according to their individual requirements in terms of monitoring frequency, e.g., less frequent polling of elephant flows and frequent polling of QoS sensitive VoIP connections. We compare the performance of the SFM mechanism with the default monitoring scheme in a testbed featuring the Open Network Operating System (ONOS) controller. In this context, the CPU utilization of the controller is used as performance indicator. After identifying relevant influence factors like the number of flows and switches in the network, we investigate the viability of the approaches in different scenarios. Finally, we provide guidelines regarding their choice.}, address = {Tokio, Japan}, author = {Nguyen-Ngoc, Anh and Lange, Stanislav and Zinner, Thomas and Seufert, Michael and Tran-Gia, Phuoc and Aerts, Nieke and Hock, David}, booktitle = {4th International Workshop on Management of SDN and NFV Systems (ManSDN/NFV)}, keywords = {sys:hidden:inproceedings}, month = 11, title = {Performance Evaluation of Selective Flow Monitoring in the ONOS Controller}, year = 2017 }

  %0 Conference Paper %1 info3-inproceedings-2017-20 %A Nguyen-Ngoc, Anh %A Lange, Stanislav %A Zinner, Thomas %A Seufert, Michael %A Tran-Gia, Phuoc %A Aerts, Nieke %A Hock, David %B 4th International Workshop on Management of SDN and NFV Systems (ManSDN/NFV) %C Tokio, Japan %D 2017 %T Performance Evaluation of Selective Flow Monitoring in the ONOS Controller %X One of the benefits when network operators adopt the Software Defined Networking (SDN) paradigm is the ability to monitor the traffic in the network without an additional network management system. Usually, SDN controllers utilize OpenFlow statistics messages in order to regularly gather information about all flows in the network. However, using the same polling interval for all flows does not take into account the heterogeneity of real world traffic and thus results in an imbalance between monitoring accuracy and control plane overhead. In particular, frequent querying results in a high resource consumption at the controller. This work proposes a Selective Flow Monitoring (SFM) mechanism that allows administrators to classify flows according to their individual requirements in terms of monitoring frequency, e.g., less frequent polling of elephant flows and frequent polling of QoS sensitive VoIP connections. We compare the performance of the SFM mechanism with the default monitoring scheme in a testbed featuring the Open Network Operating System (ONOS) controller. In this context, the CPU utilization of the controller is used as performance indicator. After identifying relevant influence factors like the number of flows and switches in the network, we investigate the viability of the approaches in different scenarios. Finally, we provide guidelines regarding their choice.
• SDN/NFV-enabled Security Architecture for Fine-grained Policy Enforcement and Threat Mitigation for Enterprise Networks. Pfaff, Benedikt; Scherer, Johann; Hock, David; Gray, Nicholas; Zinner, Thomas; Tran-Gia, Phuoc; Durner, Raphael; Kellerer, Wolfgang; Lorenz, Claas. 2017, August.
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  Network Functions Visualization (NFV) replaces physical middleboxes with software instances running network functions in cloud environments. To support this new paradigm, it is necessary to port the code basis from highly specialized hardware devices to virtual machines running on COTS hardware. In order to fully exploit the inherent capabilities of cloud environments it is further necessary to redesign the software to support a large amount of distributed, cooperating function instances instead of single, isolated and monolithic instances. This development can be observed for network functions like stateful firewalling. Until now, available software firewalls lack support for active/active operation in clustered environments, which hinders horizontal scalability. This is due to the fact that the required synchronization of connection states among the cluster's instances is an impediment that still has to be resolved. Therefore, this work investigates different synchronization strategies and mechanisms, which allow to share connection states among the cluster to maintain scalability and high-availability.

  @misc{info3-demo-2017-3, abstract = {Network Functions Visualization (NFV) replaces physical middleboxes with software instances running network functions in cloud environments. To support this new paradigm, it is necessary to port the code basis from highly specialized hardware devices to virtual machines running on COTS hardware. In order to fully exploit the inherent capabilities of cloud environments it is further necessary to redesign the software to support a large amount of distributed, cooperating function instances instead of single, isolated and monolithic instances. This development can be observed for network functions like stateful firewalling. Until now, available software firewalls lack support for active/active operation in clustered environments, which hinders horizontal scalability. This is due to the fact that the required synchronization of connection states among the cluster's instances is an impediment that still has to be resolved. Therefore, this work investigates different synchronization strategies and mechanisms, which allow to share connection states among the cluster to maintain scalability and high-availability.}, author = {Pfaff, Benedikt and Scherer, Johann and Hock, David and Gray, Nicholas and Zinner, Thomas and Tran-Gia, Phuoc and Durner, Raphael and Kellerer, Wolfgang and Lorenz, Claas}, booktitle = {In Proceedings of the SIGCOMM Posters and Demos}, keywords = {sardine}, month = {08}, title = {SDN/NFV-enabled Security Architecture for Fine-grained Policy Enforcement and Threat Mitigation for Enterprise Networks}, year = 2017 }

  %0 Generic %1 info3-demo-2017-3 %A Pfaff, Benedikt %A Scherer, Johann %A Hock, David %A Gray, Nicholas %A Zinner, Thomas %A Tran-Gia, Phuoc %A Durner, Raphael %A Kellerer, Wolfgang %A Lorenz, Claas %B In Proceedings of the SIGCOMM Posters and Demos %D 2017 %T SDN/NFV-enabled Security Architecture for Fine-grained Policy Enforcement and Threat Mitigation for Enterprise Networks %X Network Functions Visualization (NFV) replaces physical middleboxes with software instances running network functions in cloud environments. To support this new paradigm, it is necessary to port the code basis from highly specialized hardware devices to virtual machines running on COTS hardware. In order to fully exploit the inherent capabilities of cloud environments it is further necessary to redesign the software to support a large amount of distributed, cooperating function instances instead of single, isolated and monolithic instances. This development can be observed for network functions like stateful firewalling. Until now, available software firewalls lack support for active/active operation in clustered environments, which hinders horizontal scalability. This is due to the fact that the required synchronization of connection states among the cluster's instances is an impediment that still has to be resolved. Therefore, this work investigates different synchronization strategies and mechanisms, which allow to share connection states among the cluster to maintain scalability and high-availability.
• 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.

• Green Wireless Energy Efficiency in Wireless Networks. Bernardo, Vitor; Braun, Torsten; Curado, Marilia; Fiedler, Markus; Hock, David; Hossmann, Theus; Hummel, Karin A.; Hurni, Philipp; Ickin, Selim; Jamakovic, Almerima; Nadjm-Tehrani, Simin; Ahn Trinh, Tuan; Jon Vergara, Ekhiotz; Wamser, Florian; Zinner, Thomas. In Large-scale Distributed Systems and Energy Efficiency: A Holistic View, J.-M. Pierson (ed.). John Wiley & Sons, Ltd, 2015.
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  Summary Wireless networks have become more and more popular because of ease of installation, ease of access, and support of smart terminals and gadgets on the move. In the overall life cycle of providing green wireless technology, from production to operation and, finally, removal, this chapter focuses on the operation phase and summarizes insights in energy consumption of major technologies. The chapter also focuses on the edge of the network, comprising network access points (APs) and mobile user devices. It discusses particularities of most important wireless networking technologies: wireless access networks including 3G/LTE and wireless mesh networks (WMNs); wireless sensor networks (WSNs); and ad-hoc and opportunistic networks. Concerning energy efficiency, the chapter discusses challenges in access, wireless sensor, and ad-hoc and opportunistic networks.

  @incollection{info3-incollection-2014-23, abstract = {Summary Wireless networks have become more and more popular because of ease of installation, ease of access, and support of smart terminals and gadgets on the move. In the overall life cycle of providing green wireless technology, from production to operation and, finally, removal, this chapter focuses on the operation phase and summarizes insights in energy consumption of major technologies. The chapter also focuses on the edge of the network, comprising network access points (APs) and mobile user devices. It discusses particularities of most important wireless networking technologies: wireless access networks including 3G/LTE and wireless mesh networks (WMNs); wireless sensor networks (WSNs); and ad-hoc and opportunistic networks. Concerning energy efficiency, the chapter discusses challenges in access, wireless sensor, and ad-hoc and opportunistic networks.}, author = {Bernardo, Vitor and Braun, Torsten and Curado, Marilia and Fiedler, Markus and Hock, David and Hossmann, Theus and Hummel, Karin A. and Hurni, Philipp and Ickin, Selim and Jamakovic, Almerima and Nadjm-Tehrani, Simin and Ahn Trinh, Tuan and Jon Vergara, Ekhiotz and Wamser, Florian and Zinner, Thomas}, booktitle = {Large-scale Distributed Systems and Energy Efficiency: A Holistic View}, editor = {Pierson, Jean-Marc}, keywords = {myown}, month = {03}, publisher = {John Wiley & Sons, Ltd}, title = {Green Wireless Energy Efficiency in Wireless Networks}, year = 2015 }

  %0 Book Section %1 info3-incollection-2014-23 %A Bernardo, Vitor %A Braun, Torsten %A Curado, Marilia %A Fiedler, Markus %A Hock, David %A Hossmann, Theus %A Hummel, Karin A. %A Hurni, Philipp %A Ickin, Selim %A Jamakovic, Almerima %A Nadjm-Tehrani, Simin %A Ahn Trinh, Tuan %A Jon Vergara, Ekhiotz %A Wamser, Florian %A Zinner, Thomas %B Large-scale Distributed Systems and Energy Efficiency: A Holistic View %D 2015 %E Pierson, Jean-Marc %I John Wiley & Sons, Ltd %T Green Wireless Energy Efficiency in Wireless Networks %X Summary Wireless networks have become more and more popular because of ease of installation, ease of access, and support of smart terminals and gadgets on the move. In the overall life cycle of providing green wireless technology, from production to operation and, finally, removal, this chapter focuses on the operation phase and summarizes insights in energy consumption of major technologies. The chapter also focuses on the edge of the network, comprising network access points (APs) and mobile user devices. It discusses particularities of most important wireless networking technologies: wireless access networks including 3G/LTE and wireless mesh networks (WMNs); wireless sensor networks (WSNs); and ad-hoc and opportunistic networks. Concerning energy efficiency, the chapter discusses challenges in access, wireless sensor, and ad-hoc and opportunistic networks.
• 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).

• Analysis and Optimization of Resilient Routing in Core Communication Networks. Hock, David. 2014, April.
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  @phdthesis{info3-dissertation-2014-37, author = {Hock, David}, keywords = {sys:hidden:dissertation}, month = {04}, title = {Analysis and Optimization of Resilient Routing in Core Communication Networks}, year = 2014 }

  %0 Thesis %1 info3-dissertation-2014-37 %A Hock, David %D 2014 %T Analysis and Optimization of Resilient Routing in Core Communication Networks
• POCO-PLC: Enabling Dynamic Pareto-Optimal Resilient Controller Placement in SDN Networks. Hock, David; Hartmann, Matthias; Gebert, Steffen; Zinner, Thomas; Tran-Gia, Phuoc. Toronto, Canada, 2014, April.
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  @misc{info3-software-2014-19, address = {Toronto, Canada}, author = {Hock, David and Hartmann, Matthias and Gebert, Steffen and Zinner, Thomas and Tran-Gia, Phuoc}, booktitle = {Computer Communications Workshops (INFOCOM WKSHPS)}, keywords = {poco}, month = {04}, title = {POCO-PLC: Enabling Dynamic Pareto-Optimal Resilient Controller Placement in SDN Networks}, year = 2014 }

  %0 Generic %1 info3-software-2014-19 %A Hock, David %A Hartmann, Matthias %A Gebert, Steffen %A Zinner, Thomas %A Tran-Gia, Phuoc %B Computer Communications Workshops (INFOCOM WKSHPS) %C Toronto, Canada %D 2014 %T POCO-PLC: Enabling Dynamic Pareto-Optimal Resilient Controller Placement in SDN Networks
• Social Network Analysis in the Enterprise: Challenges and Opportunities. Burger, Valentin; Hock, David; Scholtes, Ingo; Hoßfeld, Tobias; Garcia, David; Seufert, Michael. In Socioinformatics - The Social Impact of Interactions between Humans and IT, K. Zweig, W. Neuser, V. Pipek, M. Rohde, I. Scholtes (eds.). Springer International Publishing, 2014.
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  Enterprise social software tools are increasingly being used to support the communication and collaboration between employees, as well as to facilitate the collaborative organisation of information and knowledge within companies. Not only do these tools help to develop and maintain an efficient social organisation, they also produce massive amounts of fine-grained data on collaborations, communication and other forms of social relationships within an enterprise. In this chapter, we argue that the availability of these data provides unique opportunities to monitor and analyse social structures and their impact on the success and performance of individuals, teams, communities and organisations. We further review methods from the planning, design and optimisation of telecommunication networks and discuss challenges arising when wanting to apply them to optimise the structure of enterprise social networks.

  @incollection{info3-incollection-2014-24, abstract = {Enterprise social software tools are increasingly being used to support the communication and collaboration between employees, as well as to facilitate the collaborative organisation of information and knowledge within companies. Not only do these tools help to develop and maintain an efficient social organisation, they also produce massive amounts of fine-grained data on collaborations, communication and other forms of social relationships within an enterprise. In this chapter, we argue that the availability of these data provides unique opportunities to monitor and analyse social structures and their impact on the success and performance of individuals, teams, communities and organisations. We further review methods from the planning, design and optimisation of telecommunication networks and discuss challenges arising when wanting to apply them to optimise the structure of enterprise social networks.}, author = {Burger, Valentin and Hock, David and Scholtes, Ingo and Hoßfeld, Tobias and Garcia, David and Seufert, Michael}, booktitle = {Socioinformatics - The Social Impact of Interactions between Humans and IT}, editor = {Zweig, Katharina and Neuser, Wolfgang and Pipek, Volkmar and Rohde, Markus and Scholtes, Ingo}, keywords = {myown}, month = {08}, publisher = {Springer International Publishing}, title = {Social Network Analysis in the Enterprise: Challenges and Opportunities}, year = 2014 }

  %0 Book Section %1 info3-incollection-2014-24 %A Burger, Valentin %A Hock, David %A Scholtes, Ingo %A Hoßfeld, Tobias %A Garcia, David %A Seufert, Michael %B Socioinformatics - The Social Impact of Interactions between Humans and IT %D 2014 %E Zweig, Katharina %E Neuser, Wolfgang %E Pipek, Volkmar %E Rohde, Markus %E Scholtes, Ingo %I Springer International Publishing %T Social Network Analysis in the Enterprise: Challenges and Opportunities %X Enterprise social software tools are increasingly being used to support the communication and collaboration between employees, as well as to facilitate the collaborative organisation of information and knowledge within companies. Not only do these tools help to develop and maintain an efficient social organisation, they also produce massive amounts of fine-grained data on collaborations, communication and other forms of social relationships within an enterprise. In this chapter, we argue that the availability of these data provides unique opportunities to monitor and analyse social structures and their impact on the success and performance of individuals, teams, communities and organisations. We further review methods from the planning, design and optimisation of telecommunication networks and discuss challenges arising when wanting to apply them to optimise the structure of enterprise social networks.
• POCO: A Framework for the Pareto-Optimal Resilient Controller Placement in SDN-based Core Networks. Hock, David; Gebert, Steffen; Hartmann, Matthias; Zinner, Thomas; Tran-Gia, Phuoc. Krakow, Poland, 2014, May.
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  @misc{info3-software-2014-18, address = {Krakow, Poland}, author = {Hock, David and Gebert, Steffen and Hartmann, Matthias and Zinner, Thomas and Tran-Gia, Phuoc}, booktitle = {IEEE NOMS}, keywords = {poco}, month = {05}, title = {POCO: A Framework for the Pareto-Optimal Resilient Controller Placement in SDN-based Core Networks}, year = 2014 }

  %0 Generic %1 info3-software-2014-18 %A Hock, David %A Gebert, Steffen %A Hartmann, Matthias %A Zinner, Thomas %A Tran-Gia, Phuoc %B IEEE NOMS %C Krakow, Poland %D 2014 %T POCO: A Framework for the Pareto-Optimal Resilient Controller Placement in SDN-based Core Networks
• Including Energy Efficiency Aspects in Multi-Layer Optical Network Design. Gebert, Steffen; Hock, David; Hartmann, Matthias; Spoerhase, Joachim; Zinner, Thomas; Tran-Gia, Phuoc. In 5th International Conference on Communications and Electronics (ICCE 2014). Da Nang, Vietnam, 2014.
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  This paper investigates the influence of the network planning process on a higher energy-awareness of optical multi-layer core networks. In particular, we propose to remove redundant links in the network, and to route corresponding network traffic on other links. Based on the reduced network topology, we compute the required network equipment for realistic traffic demands using a network planning tool. Due to the lack of an accurate model for operational expenditures and energy consumption, we choose the link length as cost function. We show the applicability of our idea and demonstrate the energy saving potential using realistic network topologies.

  @inproceedings{info3-inproceedings-2014-492, abstract = {This paper investigates the influence of the network planning process on a higher energy-awareness of optical multi-layer core networks. In particular, we propose to remove redundant links in the network, and to route corresponding network traffic on other links. Based on the reduced network topology, we compute the required network equipment for realistic traffic demands using a network planning tool. Due to the lack of an accurate model for operational expenditures and energy consumption, we choose the link length as cost function. We show the applicability of our idea and demonstrate the energy saving potential using realistic network topologies.}, address = {Da Nang, Vietnam}, author = {Gebert, Steffen and Hock, David and Hartmann, Matthias and Spoerhase, Joachim and Zinner, Thomas and Tran-Gia, Phuoc}, booktitle = {5th International Conference on Communications and Electronics (ICCE 2014)}, keywords = {saser-siegfried}, month = {07}, title = {Including Energy Efficiency Aspects in Multi-Layer Optical Network Design}, year = 2014 }

  %0 Conference Paper %1 info3-inproceedings-2014-492 %A Gebert, Steffen %A Hock, David %A Hartmann, Matthias %A Spoerhase, Joachim %A Zinner, Thomas %A Tran-Gia, Phuoc %B 5th International Conference on Communications and Electronics (ICCE 2014) %C Da Nang, Vietnam %D 2014 %T Including Energy Efficiency Aspects in Multi-Layer Optical Network Design %X This paper investigates the influence of the network planning process on a higher energy-awareness of optical multi-layer core networks. In particular, we propose to remove redundant links in the network, and to route corresponding network traffic on other links. Based on the reduced network topology, we compute the required network equipment for realistic traffic demands using a network planning tool. Due to the lack of an accurate model for operational expenditures and energy consumption, we choose the link length as cost function. We show the applicability of our idea and demonstrate the energy saving potential using realistic network topologies.
• Demonstrating the Optimal Placement of Virtualized Cellular Network Functions in Case of Large Crowd Events. Gebert, Steffen; Hock, David; Zinner, Thomas; Tran-Gia, Phuoc; Hoffmann, Marco; Jarschel, Michael; Schmidt, Ernst-Dieter; Braun, Ralf-Peter; Banse, Christian; Koepsel, Andreas. 2014, August.
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  @misc{info3-software-2014-21, author = {Gebert, Steffen and Hock, David and Zinner, Thomas and Tran-Gia, Phuoc and Hoffmann, Marco and Jarschel, Michael and Schmidt, Ernst-Dieter and Braun, Ralf-Peter and Banse, Christian and Koepsel, Andreas}, booktitle = {SIGCOMM}, keywords = {sys:hidden:software}, month = {08}, title = {Demonstrating the Optimal Placement of Virtualized Cellular Network Functions in Case of Large Crowd Events}, year = 2014 }

  %0 Generic %1 info3-software-2014-21 %A Gebert, Steffen %A Hock, David %A Zinner, Thomas %A Tran-Gia, Phuoc %A Hoffmann, Marco %A Jarschel, Michael %A Schmidt, Ernst-Dieter %A Braun, Ralf-Peter %A Banse, Christian %A Koepsel, Andreas %B SIGCOMM %D 2014 %T Demonstrating the Optimal Placement of Virtualized Cellular Network Functions in Case of Large Crowd Events

• OC²E²AN: Optimized Control Center for Experience Enhancements in Access Networks. Hock, David; Wamser, Florian; Seufert, Michael; Pries, Rastin; Tran-Gia, Phuoc. Stuttgart, Germany, 2013, March.
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  @misc{info3-software-2013-17, address = {Stuttgart, Germany}, author = {Hock, David and Wamser, Florian and Seufert, Michael and Pries, Rastin and Tran-Gia, Phuoc}, keywords = {sys:hidden:software}, month = {03}, title = {OC²E²AN: Optimized Control Center for Experience Enhancements in Access Networks}, year = 2013 }

  %0 Generic %1 info3-software-2013-17 %A Hock, David %A Wamser, Florian %A Seufert, Michael %A Pries, Rastin %A Tran-Gia, Phuoc %C Stuttgart, Germany %D 2013 %T OC²E²AN: Optimized Control Center for Experience Enhancements in Access Networks
• 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.
• 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
• Pareto-Optimal Resilient Controller Placement in SDN-based Core Networks. Hock, David; Hartmann, Matthias; Gebert, Steffen; Jarschel, Michael; Zinner, Thomas; Tran-Gia, Phuoc. In 25th International Teletraffic Congress (ITC). Shanghai, China, 2013.
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  With the introduction of Software Defined Networking (SDN), the concept of an external and optionally centralized network control plane, i.e. controller, is drawing the attention of researchers and industry. A particularly important task in the SDN context is the placement of such external resources in the network. In this paper, we discuss important aspects of the controller placement problem with a focus on SDN-based core networks, including different types of resilience and failure tolerance. When several performance and resilience metrics are considered, there is usually no single best controller placement solution, but a trade-off between these metrics. We introduce our framework for resilient Pareto-based Optimal COntroller-placement (POCO) that provides the operator of a network with all Pareto-optimal placements. The ideas and mechanisms are illustrated using the Internet2 OS3E topology and further evaluated on more than 140 topologies of the Topology Zoo. In particular, our findings reveal that for most of the topologies more than 20% of all nodes need to be controllers to assure a continuous connection of all nodes to one of the controllers in any arbitrary double link or node failure scenario.

  @inproceedings{info3-inproceedings-2013-466, abstract = {With the introduction of Software Defined Networking (SDN), the concept of an external and optionally centralized network control plane, i.e. controller, is drawing the attention of researchers and industry. A particularly important task in the SDN context is the placement of such external resources in the network. In this paper, we discuss important aspects of the controller placement problem with a focus on SDN-based core networks, including different types of resilience and failure tolerance. When several performance and resilience metrics are considered, there is usually no single best controller placement solution, but a trade-off between these metrics. We introduce our framework for resilient Pareto-based Optimal COntroller-placement (POCO) that provides the operator of a network with all Pareto-optimal placements. The ideas and mechanisms are illustrated using the Internet2 OS3E topology and further evaluated on more than 140 topologies of the Topology Zoo. In particular, our findings reveal that for most of the topologies more than 20% of all nodes need to be controllers to assure a continuous connection of all nodes to one of the controllers in any arbitrary double link or node failure scenario.}, address = {Shanghai, China}, author = {Hock, David and Hartmann, Matthias and Gebert, Steffen and Jarschel, Michael and Zinner, Thomas and Tran-Gia, Phuoc}, booktitle = {25th International Teletraffic Congress (ITC)}, keywords = {poco}, month = {09}, title = {Pareto-Optimal Resilient Controller Placement in SDN-based Core Networks}, year = 2013 }

  %0 Conference Paper %1 info3-inproceedings-2013-466 %A Hock, David %A Hartmann, Matthias %A Gebert, Steffen %A Jarschel, Michael %A Zinner, Thomas %A Tran-Gia, Phuoc %B 25th International Teletraffic Congress (ITC) %C Shanghai, China %D 2013 %T Pareto-Optimal Resilient Controller Placement in SDN-based Core Networks %X With the introduction of Software Defined Networking (SDN), the concept of an external and optionally centralized network control plane, i.e. controller, is drawing the attention of researchers and industry. A particularly important task in the SDN context is the placement of such external resources in the network. In this paper, we discuss important aspects of the controller placement problem with a focus on SDN-based core networks, including different types of resilience and failure tolerance. When several performance and resilience metrics are considered, there is usually no single best controller placement solution, but a trade-off between these metrics. We introduce our framework for resilient Pareto-based Optimal COntroller-placement (POCO) that provides the operator of a network with all Pareto-optimal placements. The ideas and mechanisms are illustrated using the Internet2 OS3E topology and further evaluated on more than 140 topologies of the Topology Zoo. In particular, our findings reveal that for most of the topologies more than 20% of all nodes need to be controllers to assure a continuous connection of all nodes to one of the controllers in any arbitrary double link or node failure scenario.
• 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.
• Demonstrating the Benefit of Joint Application and Network Control Within a Wireless Access Network. Wamser, Florian; Hock, David; Seufert, Michael; Zinner, Thomas; Tran-Gia, Phuoc. Turin, Italy, 2013, April.
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  @misc{info3-software-2013-16, address = {Turin, Italy}, author = {Wamser, Florian and Hock, David and Seufert, Michael and Zinner, Thomas and Tran-Gia, Phuoc}, booktitle = {2013 IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS)}, keywords = {sys:hidden:software}, month = {04}, title = {Demonstrating the Benefit of Joint Application and Network Control Within a Wireless Access Network}, year = 2013 }

  %0 Generic %1 info3-software-2013-16 %A Wamser, Florian %A Hock, David %A Seufert, Michael %A Zinner, Thomas %A Tran-Gia, Phuoc %B 2013 IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS) %C Turin, Italy %D 2013 %T Demonstrating the Benefit of Joint Application and Network Control Within a Wireless Access Network
• Resilience in Enterprise Social Networks. Burger, Valentin; Hoßfeld, Tobias; Garcia, David; Seufert, Michael; Scholtes, Ingo; Hock, David. In Workshop Sozioinformatik 2013. Koblenz, Germany, 2013.
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  The goal of human resource management is to ensure an effective company environment. Crucial for a good corporate culture is a comfortable atmosphere and positive social relationships between the employees. The interactions of the people and groups working in the company define their relationships and are reflected in the company's social network. Projections of such networks are Enterprise Social Networks which are more and more integrated in companies. These social networks can be a powerful tool to analyse the structure of a company and indicate potential problems. This extended abstract poses research questions to identify and quantify mechanisms that have an impact on the social network of a company to ensure resilience. To address these questions we make assumptions based on real-world observations for a subsequent model.

  @inproceedings{info3-inproceedings-2013-473, abstract = {The goal of human resource management is to ensure an effective company environment. Crucial for a good corporate culture is a comfortable atmosphere and positive social relationships between the employees. The interactions of the people and groups working in the company define their relationships and are reflected in the company's social network. Projections of such networks are Enterprise Social Networks which are more and more integrated in companies. These social networks can be a powerful tool to analyse the structure of a company and indicate potential problems. This extended abstract poses research questions to identify and quantify mechanisms that have an impact on the social network of a company to ensure resilience. To address these questions we make assumptions based on real-world observations for a subsequent model.}, address = {Koblenz, Germany}, author = {Burger, Valentin and Hoßfeld, Tobias and Garcia, David and Seufert, Michael and Scholtes, Ingo and Hock, David}, booktitle = {Workshop Sozioinformatik 2013}, keywords = {sys:hidden:inproceedings}, month = {09}, title = {Resilience in Enterprise Social Networks}, year = 2013 }

  %0 Conference Paper %1 info3-inproceedings-2013-473 %A Burger, Valentin %A Hoßfeld, Tobias %A Garcia, David %A Seufert, Michael %A Scholtes, Ingo %A Hock, David %B Workshop Sozioinformatik 2013 %C Koblenz, Germany %D 2013 %T Resilience in Enterprise Social Networks %X The goal of human resource management is to ensure an effective company environment. Crucial for a good corporate culture is a comfortable atmosphere and positive social relationships between the employees. The interactions of the people and groups working in the company define their relationships and are reflected in the company's social network. Projections of such networks are Enterprise Social Networks which are more and more integrated in companies. These social networks can be a powerful tool to analyse the structure of a company and indicate potential problems. This extended abstract poses research questions to identify and quantify mechanisms that have an impact on the social network of a company to ensure resilience. To address these questions we make assumptions based on real-world observations for a subsequent model.
• 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

• Evaluating the Trade-Off Between Energy-Efficiency and QoE in Wireless Mesh Networks. Hock, David; Bernardo, Vitor; Zinner, Thomas; Wamser, Florian; Hummel, Karin A.; Curado, Marilia; Pries, Rastin; Braun, Torsten; Tran-Gia, Phuoc. In 4th International Conference on Communications and Electronics (ICCE 12). Hué, Vietnam, 2012.
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  @inproceedings{info3-inproceedings-2012-447, address = {Hué, Vietnam}, author = {Hock, David and Bernardo, Vitor and Zinner, Thomas and Wamser, Florian and Hummel, Karin A. and Curado, Marilia and Pries, Rastin and Braun, Torsten and Tran-Gia, Phuoc}, booktitle = {4th International Conference on Communications and Electronics (ICCE 12)}, keywords = {sys:hidden:inproceedings}, month = {08}, title = {Evaluating the Trade-Off Between Energy-Efficiency and QoE in Wireless Mesh Networks}, year = 2012 }

  %0 Conference Paper %1 info3-inproceedings-2012-447 %A Hock, David %A Bernardo, Vitor %A Zinner, Thomas %A Wamser, Florian %A Hummel, Karin A. %A Curado, Marilia %A Pries, Rastin %A Braun, Torsten %A Tran-Gia, Phuoc %B 4th International Conference on Communications and Electronics (ICCE 12) %C Hué, Vietnam %D 2012 %T Evaluating the Trade-Off Between Energy-Efficiency and QoE in Wireless Mesh Networks
• Performance Optimization in Access Networks Using a Combined Control Strategy. Wamser, Florian; Hock, David; Seufert, Michael; Pries, Rastin; Tran-Gia, Phuoc. Würzburg, Germany, 2012, July.
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  @misc{info3-software-2012-11, address = {Würzburg, Germany}, author = {Wamser, Florian and Hock, David and Seufert, Michael and Pries, Rastin and Tran-Gia, Phuoc}, keywords = {sys:hidden:software}, month = {07}, title = {Performance Optimization in Access Networks Using a Combined Control Strategy}, year = 2012 }

  %0 Generic %1 info3-software-2012-11 %A Wamser, Florian %A Hock, David %A Seufert, Michael %A Pries, Rastin %A Tran-Gia, Phuoc %C Würzburg, Germany %D 2012 %T Performance Optimization in Access Networks Using a Combined Control Strategy
• Performance Optimization in Access Networks Using a Combined Control Strategy. Wamser, Florian; Hock, David; Seufert, Michael; Pries, Rastin; Tran-Gia, Phuoc. In 12th Würzburg Workshop on IP: ITG Workshop ’Visions of Future Generation Networks’ (Euroview). Würzburg, Germany, 2012.
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  @inproceedings{info3-inproceedings-2012-454, address = {Würzburg, Germany}, author = {Wamser, Florian and Hock, David and Seufert, Michael and Pries, Rastin and Tran-Gia, Phuoc}, booktitle = {12th Würzburg Workshop on IP: ITG Workshop 'Visions of Future Generation Networks' (Euroview)}, keywords = {sys:hidden:inproceedings}, month = {07}, title = {Performance Optimization in Access Networks Using a Combined Control Strategy}, year = 2012 }

  %0 Conference Paper %1 info3-inproceedings-2012-454 %A Wamser, Florian %A Hock, David %A Seufert, Michael %A Pries, Rastin %A Tran-Gia, Phuoc %B 12th Würzburg Workshop on IP: ITG Workshop 'Visions of Future Generation Networks' (Euroview) %C Würzburg, Germany %D 2012 %T Performance Optimization in Access Networks Using a Combined Control Strategy
• Application and Quality of Experience Aware Resource Management in Wireless Access Networks. Wamser, Florian; Hock, David; Seufert, Michael; Pries, Rastin; Tran-Gia, Phuoc. Würzburg, Germany, 2012, March.
  • [ BibTeX ]
  • [ EndNote ]
  @misc{info3-poster-2012-34, address = {Würzburg, Germany}, author = {Wamser, Florian and Hock, David and Seufert, Michael and Pries, Rastin and Tran-Gia, Phuoc}, booktitle = {EuroNF Summer School Modeling and Analysis of Novel Mechanisms in Future Internet Applications}, keywords = {sys:hidden:poster}, month = {03}, title = {Application and Quality of Experience Aware Resource Management in Wireless Access Networks}, year = 2012 }

  %0 Generic %1 info3-poster-2012-34 %A Wamser, Florian %A Hock, David %A Seufert, Michael %A Pries, Rastin %A Tran-Gia, Phuoc %B EuroNF Summer School Modeling and Analysis of Novel Mechanisms in Future Internet Applications %C Würzburg, Germany %D 2012 %T Application and Quality of Experience Aware Resource Management in Wireless Access Networks
• Combined Control for QoE Optimization in Access Networks. Hock, David; Wamser, Florian. G-Lab Statusmeeting, Seminaris CampusHotel, Berlin, 2012, February 14.
  • [ BibTeX ]
  • [ EndNote ]
  @presentation{info3-talk-2012-442, address = {G-Lab Statusmeeting, Seminaris CampusHotel, Berlin}, author = {Hock, David and Wamser, Florian}, keywords = {sys:hidden:presentation}, month = {02}, title = {Combined Control for QoE Optimization in Access Networks}, year = 2012 }

  %0 Generic %1 info3-talk-2012-442 %A Hock, David %A Wamser, Florian %C G-Lab Statusmeeting, Seminaris CampusHotel, Berlin %D 2012 %T Combined Control for QoE Optimization in Access Networks

• 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.
  • [ Abstract ]
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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.
• 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 1st European Teletraffic Seminar (ETS). Poznan, Poland, 2011.
  • [ BibTeX ]
  • [ EndNote ]
  @inproceedings{info3-inproceedings-2011-408, address = {Poznan, Poland}, author = {Żukowski, Cezary and Tomaszewski, Artur and Pióro, Michał and Hock, David and Hartmann, Matthias and Menth, Michael}, booktitle = {1st European Teletraffic Seminar (ETS)}, keywords = {sys:hidden:inproceedings}, month = {02}, title = {Compact node-link formulations for the optimal single path MPLS Fast Reroute layout}, year = 2011 }

  %0 Conference Paper %1 info3-inproceedings-2011-408 %A Żukowski, Cezary %A Tomaszewski, Artur %A Pióro, Michał %A Hock, David %A Hartmann, Matthias %A Menth, Michael %B 1st European Teletraffic Seminar (ETS) %C Poznan, Poland %D 2011 %T Compact node-link formulations for the optimal single path MPLS Fast Reroute layout
• ResiLyzer: Ein Werkzeug zur Analyse der Ausfallsicherheit in paketvermittelten Kommunikationsnetzen. Hock, David; Hartmann, Matthias; Schwartz, Christian; Menth, Michael. Kiel, Germany, 2011, March.
  • [ BibTeX ]
  • [ EndNote ]
  @misc{info3-software-2011-4, address = {Kiel, Germany}, author = {Hock, David and Hartmann, Matthias and Schwartz, Christian and Menth, Michael}, booktitle = {PIK-Praxis der Informationsverarbeitung und Kommunikation}, keywords = {sys:hidden:software}, month = {03}, title = {ResiLyzer: Ein Werkzeug zur Analyse der Ausfallsicherheit in paketvermittelten Kommunikationsnetzen}, year = 2011 }

  %0 Generic %1 info3-software-2011-4 %A Hock, David %A Hartmann, Matthias %A Schwartz, Christian %A Menth, Michael %B PIK-Praxis der Informationsverarbeitung und Kommunikation %C Kiel, Germany %D 2011 %T ResiLyzer: Ein Werkzeug zur Analyse der Ausfallsicherheit in paketvermittelten Kommunikationsnetzen
• Loop-Free Convergence using Ordered FIB Updates: Analysis and Routing Optimization. Hock, David. 8th International Workshop on the Design of Reliable Communication Networks (DRCN), Krakow, Poland, 2011, October 12.
  • [ BibTeX ]
  • [ EndNote ]
  @presentation{info3-talk-2011-444, address = {8th International Workshop on the Design of Reliable Communication Networks (DRCN), Krakow, Poland}, author = {Hock, David}, keywords = {sys:hidden:presentation}, month = 10, title = {Loop-Free Convergence using Ordered FIB Updates: Analysis and Routing Optimization.}, year = 2011 }

  %0 Generic %1 info3-talk-2011-444 %A Hock, David %C 8th International Workshop on the Design of Reliable Communication Networks (DRCN), Krakow, Poland %D 2011 %T Loop-Free Convergence using Ordered FIB Updates: Analysis and Routing Optimization.
• ToMaTo - a network experimentation tool. Schwerdel, Dennis; Hock, David; Günther, Daniel; Reuther, Bernd; Müller, Paul; Tran-Gia, Phuoc. In 7th International ICST Conference on Testbeds and Research Infrastructures for the Development of Networks and Communities (TridentCom 2011). Shanghai, China, 2011.
  • [ BibTeX ]
  • [ EndNote ]
  @inproceedings{info3-inproceedings-2011-409, address = {Shanghai, China}, author = {Schwerdel, Dennis and Hock, David and Günther, Daniel and Reuther, Bernd and Müller, Paul and Tran-Gia, Phuoc}, booktitle = {7th International ICST Conference on Testbeds and Research Infrastructures for the Development of Networks and Communities (TridentCom 2011)}, keywords = {sys:hidden:inproceedings}, month = {04}, title = {ToMaTo - a network experimentation tool}, year = 2011 }

  %0 Conference Paper %1 info3-inproceedings-2011-409 %A Schwerdel, Dennis %A Hock, David %A Günther, Daniel %A Reuther, Bernd %A Müller, Paul %A Tran-Gia, Phuoc %B 7th International ICST Conference on Testbeds and Research Infrastructures for the Development of Networks and Communities (TridentCom 2011) %C Shanghai, China %D 2011 %T ToMaTo - a network experimentation tool
• 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.
  • [ Abstract ]
  • [ BibTeX ]
  • [ EndNote ]
  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.
• Loop-Free Convergence using Ordered FIB Updates: Analysis and Routing Optimization. Hock, David; Hartmann, Matthias; Neubert, Tim; Menth, Michael. In 8th International Workshop on the Design of Reliable Communication Networks (DRCN). Krakow, Poland, 2011.
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  @inproceedings{info3-inproceedings-2011-420, address = {Krakow, Poland}, author = {Hock, David and Hartmann, Matthias and Neubert, Tim and Menth, Michael}, booktitle = {8th International Workshop on the Design of Reliable Communication Networks (DRCN)}, keywords = {sys:hidden:inproceedings}, month = 10, title = {Loop-Free Convergence using Ordered FIB Updates: Analysis and Routing Optimization}, year = 2011 }

  %0 Conference Paper %1 info3-inproceedings-2011-420 %A Hock, David %A Hartmann, Matthias %A Neubert, Tim %A Menth, Michael %B 8th International Workshop on the Design of Reliable Communication Networks (DRCN) %C Krakow, Poland %D 2011 %T Loop-Free Convergence using Ordered FIB Updates: Analysis and Routing Optimization
• 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.
  • [ BibTeX ]
  • [ EndNote ]
  @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

• Optimizing Unique Shortest Paths for Resilient Routing and Fast Reroute in IP-Based Networks. Hock, David; Hartmann, Matthias; Menth, Michael; Schwartz, Christian. In IEEE/IFIP Network Operations and Management Symposium (NOMS). Osaka, Japan, 2010.
  • [ Abstract ]
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  Intradomain routing in IP networks follows shortest paths according to administrative link costs. When several equalcost shortest paths exist, routers that use equal-cost multipath (ECMP) distribute the traffic over all of them. To produce singleshortest path (SSP) routing, a selection mechanism (tie-breaker) chooses just one of the equal-cost paths. Tie-breakers are poorly standardized and use information that may change over time, which makes SSP routing unpredictable. Therefore, link costs producing unique shortest paths (USP) are preferred. In this paper, we show that optimized SSP routing can lead to significantly higher link utilization than expected in case of non-deterministic tie-breakers. We investigate the impact of the allowed link cost range on the general availability of USP routing. We use a heuristic algorithm to generate link costs for USP routing and to minimize the maximum link utilization in networks with and without failures. Fast reroute (FRR) mechanisms can repair failures faster than conventional IP rerouting by pre-computing shortest backup paths around failed network elements. However, when multiple equal-cost paths exist, the backup path layout is unpredictable. We adapt our heuristic to optimize USP routing for IP-FRR using not-via addresses and MPLS-FRR with facility and oneto- one backup. Finally, we compare the performance of USP with various other routing schemes using realistic Rocketfuel topologies.

  @inproceedings{info3-inproceedings-2010-363, abstract = {Intradomain routing in IP networks follows shortest paths according to administrative link costs. When several equalcost shortest paths exist, routers that use equal-cost multipath (ECMP) distribute the traffic over all of them. To produce singleshortest path (SSP) routing, a selection mechanism (tie-breaker) chooses just one of the equal-cost paths. Tie-breakers are poorly standardized and use information that may change over time, which makes SSP routing unpredictable. Therefore, link costs producing unique shortest paths (USP) are preferred. In this paper, we show that optimized SSP routing can lead to significantly higher link utilization than expected in case of non-deterministic tie-breakers. We investigate the impact of the allowed link cost range on the general availability of USP routing. We use a heuristic algorithm to generate link costs for USP routing and to minimize the maximum link utilization in networks with and without failures. Fast reroute (FRR) mechanisms can repair failures faster than conventional IP rerouting by pre-computing shortest backup paths around failed network elements. However, when multiple equal-cost paths exist, the backup path layout is unpredictable. We adapt our heuristic to optimize USP routing for IP-FRR using not-via addresses and MPLS-FRR with facility and oneto- one backup. Finally, we compare the performance of USP with various other routing schemes using realistic Rocketfuel topologies.}, address = {Osaka, Japan}, author = {Hock, David and Hartmann, Matthias and Menth, Michael and Schwartz, Christian}, booktitle = {IEEE/IFIP Network Operations and Management Symposium (NOMS)}, keywords = {sys:hidden:inproceedings}, month = {04}, title = {Optimizing Unique Shortest Paths for Resilient Routing and Fast Reroute in IP-Based Networks}, year = 2010 }

  %0 Conference Paper %1 info3-inproceedings-2010-363 %A Hock, David %A Hartmann, Matthias %A Menth, Michael %A Schwartz, Christian %B IEEE/IFIP Network Operations and Management Symposium (NOMS) %C Osaka, Japan %D 2010 %T Optimizing Unique Shortest Paths for Resilient Routing and Fast Reroute in IP-Based Networks %X Intradomain routing in IP networks follows shortest paths according to administrative link costs. When several equalcost shortest paths exist, routers that use equal-cost multipath (ECMP) distribute the traffic over all of them. To produce singleshortest path (SSP) routing, a selection mechanism (tie-breaker) chooses just one of the equal-cost paths. Tie-breakers are poorly standardized and use information that may change over time, which makes SSP routing unpredictable. Therefore, link costs producing unique shortest paths (USP) are preferred. In this paper, we show that optimized SSP routing can lead to significantly higher link utilization than expected in case of non-deterministic tie-breakers. We investigate the impact of the allowed link cost range on the general availability of USP routing. We use a heuristic algorithm to generate link costs for USP routing and to minimize the maximum link utilization in networks with and without failures. Fast reroute (FRR) mechanisms can repair failures faster than conventional IP rerouting by pre-computing shortest backup paths around failed network elements. However, when multiple equal-cost paths exist, the backup path layout is unpredictable. We adapt our heuristic to optimize USP routing for IP-FRR using not-via addresses and MPLS-FRR with facility and oneto- one backup. Finally, we compare the performance of USP with various other routing schemes using realistic Rocketfuel topologies.
• 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.
  • [ BibTeX ]
  • [ EndNote ]
  @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
• ResiLyzer: A Tool for Resilience Analysis in Packet-Switched Communication Networks. Hock, David; Menth, Michael; Hartmann, Matthias; Schwartz, Christian; Stezenbach, David. In 15th International GI/ITG Conference on Measurement, Modelling and Evaluation of Computing Systems and Dependability and Fault Tolerance (MMB & DFT 2010). Essen, Germany, 2010.
  • [ Abstract ]
  • [ BibTeX ]
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  We present a tool for the analysis of fault-tolerance in packet-switched communication networks. Network elements like links or routers can fail or unexpected traffic surges may occur. They lead to service disruptions and degradations. Our tool quantifies these risks and presents a comprehensive digest of the results. We explain the core idea of the analysis and illustrate the tool.

  @inproceedings{info3-inproceedings-2010-365, abstract = {We present a tool for the analysis of fault-tolerance in packet-switched communication networks. Network elements like links or routers can fail or unexpected traffic surges may occur. They lead to service disruptions and degradations. Our tool quantifies these risks and presents a comprehensive digest of the results. We explain the core idea of the analysis and illustrate the tool.}, address = {Essen, Germany}, author = {Hock, David and Menth, Michael and Hartmann, Matthias and Schwartz, Christian and Stezenbach, David}, booktitle = {15th International GI/ITG Conference on Measurement, Modelling and Evaluation of Computing Systems and Dependability and Fault Tolerance (MMB & DFT 2010)}, keywords = {sys:hidden:inproceedings}, month = {03}, title = {ResiLyzer: A Tool for Resilience Analysis in Packet-Switched Communication Networks}, year = 2010 }

  %0 Conference Paper %1 info3-inproceedings-2010-365 %A Hock, David %A Menth, Michael %A Hartmann, Matthias %A Schwartz, Christian %A Stezenbach, David %B 15th International GI/ITG Conference on Measurement, Modelling and Evaluation of Computing Systems and Dependability and Fault Tolerance (MMB & DFT 2010) %C Essen, Germany %D 2010 %T ResiLyzer: A Tool for Resilience Analysis in Packet-Switched Communication Networks %X We present a tool for the analysis of fault-tolerance in packet-switched communication networks. Network elements like links or routers can fail or unexpected traffic surges may occur. They lead to service disruptions and degradations. Our tool quantifies these risks and presents a comprehensive digest of the results. We explain the core idea of the analysis and illustrate the tool.
• ResiLyzer: A Tool for Resilience Analysis in Packet-Switched Communication Networks. Hock, David. 15th International GI/ITG Conference on Measurement, Modelling and Evaluation of Computing Systems and Dependability and Fault Tolerance (MMB & DFT 2010), Essen, Germany, 2010, March 16.
  • [ BibTeX ]
  • [ EndNote ]
  @presentation{info3-talk-2010-365, address = {15th International GI/ITG Conference on Measurement, Modelling and Evaluation of Computing Systems and Dependability and Fault Tolerance (MMB & DFT 2010), Essen, Germany}, author = {Hock, David}, keywords = {sys:hidden:presentation}, month = {03}, title = {ResiLyzer: A Tool for Resilience Analysis in Packet-Switched Communication Networks}, year = 2010 }

  %0 Generic %1 info3-talk-2010-365 %A Hock, David %C 15th International GI/ITG Conference on Measurement, Modelling and Evaluation of Computing Systems and Dependability and Fault Tolerance (MMB & DFT 2010), Essen, Germany %D 2010 %T ResiLyzer: A Tool for Resilience Analysis in Packet-Switched Communication Networks
• Effectiveness of Link Cost Optimization for IP Rerouting and IP Fast Reroute. Hock, David; Hartmann, Matthias; Schwartz, Christian; Menth, Michael. In 15th International GI/ITG Conference on Measurement, Modelling and Evaluation of Computing Systems and Dependability and Fault Tolerance (MMB & DFT 2010). Essen, Germany, 2010.
  • [ Abstract ]
  • [ BibTeX ]
  • [ EndNote ]
  • [ Download ]
  In this paper, we bring together resilience analysis and routing optimization for IP-based intra-domain networks. When link, node, or multiple failures occur, traffic is rerouted which increases the link load on backup paths and possibly causes congestion. Resilience analysis detects the risk of overload situations a priori based on a large set of most likely failure scenarios. To counteract, the routing can be optimized and configured that such bottlenecks are avoided at least for a smaller set of failure scenarios. In this paper, we demonstrate the effectiveness of this routing optimization in IP networks. We use resilience analysis with suitable aggregate views on relative link loads. Furthermore, we compare conventional IP rerouting with IP fast reroute (IP-FRR) and show that IP-FRR can also significantly profit from routing optimization. This paper reviews major parts of previous publications and presents a new method to visualize and compare the resilience of different routing schemes.

  @inproceedings{info3-inproceedings-2010-364, abstract = {In this paper, we bring together resilience analysis and routing optimization for IP-based intra-domain networks. When link, node, or multiple failures occur, traffic is rerouted which increases the link load on backup paths and possibly causes congestion. Resilience analysis detects the risk of overload situations a priori based on a large set of most likely failure scenarios. To counteract, the routing can be optimized and configured that such bottlenecks are avoided at least for a smaller set of failure scenarios. In this paper, we demonstrate the effectiveness of this routing optimization in IP networks. We use resilience analysis with suitable aggregate views on relative link loads. Furthermore, we compare conventional IP rerouting with IP fast reroute (IP-FRR) and show that IP-FRR can also significantly profit from routing optimization. This paper reviews major parts of previous publications and presents a new method to visualize and compare the resilience of different routing schemes.}, address = {Essen, Germany}, author = {Hock, David and Hartmann, Matthias and Schwartz, Christian and Menth, Michael}, booktitle = {15th International GI/ITG Conference on Measurement, Modelling and Evaluation of Computing Systems and Dependability and Fault Tolerance (MMB & DFT 2010)}, keywords = {sys:hidden:inproceedings}, month = {03}, title = {Effectiveness of Link Cost Optimization for IP Rerouting and IP Fast Reroute}, year = 2010 }

  %0 Conference Paper %1 info3-inproceedings-2010-364 %A Hock, David %A Hartmann, Matthias %A Schwartz, Christian %A Menth, Michael %B 15th International GI/ITG Conference on Measurement, Modelling and Evaluation of Computing Systems and Dependability and Fault Tolerance (MMB & DFT 2010) %C Essen, Germany %D 2010 %T Effectiveness of Link Cost Optimization for IP Rerouting and IP Fast Reroute %X In this paper, we bring together resilience analysis and routing optimization for IP-based intra-domain networks. When link, node, or multiple failures occur, traffic is rerouted which increases the link load on backup paths and possibly causes congestion. Resilience analysis detects the risk of overload situations a priori based on a large set of most likely failure scenarios. To counteract, the routing can be optimized and configured that such bottlenecks are avoided at least for a smaller set of failure scenarios. In this paper, we demonstrate the effectiveness of this routing optimization in IP networks. We use resilience analysis with suitable aggregate views on relative link loads. Furthermore, we compare conventional IP rerouting with IP fast reroute (IP-FRR) and show that IP-FRR can also significantly profit from routing optimization. This paper reviews major parts of previous publications and presents a new method to visualize and compare the resilience of different routing schemes.
• Optimizing Unique Shortest Paths for Resilient Routing and Fast Reroute in IP-Based Networks. Hock, David. IEEE/IFIP Network Operations and Management Symposium (NOMS), Osaka, Japan, 2010, April 20.
  • [ BibTeX ]
  • [ EndNote ]
  @presentation{info3-talk-2010-383, address = {IEEE/IFIP Network Operations and Management Symposium (NOMS), Osaka, Japan}, author = {Hock, David}, keywords = {sys:hidden:presentation}, month = {04}, title = {Optimizing Unique Shortest Paths for Resilient Routing and Fast Reroute in IP-Based Networks.}, year = 2010 }

  %0 Generic %1 info3-talk-2010-383 %A Hock, David %C IEEE/IFIP Network Operations and Management Symposium (NOMS), Osaka, Japan %D 2010 %T Optimizing Unique Shortest Paths for Resilient Routing and Fast Reroute in IP-Based Networks.
• A Policy-Based Vertical Handover System. Technical Report (471), . Pries, Rastin; Staehle, Dirk; Hock, David; Hirth, Matthias. University of Wuerzburg, 2010.
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  @techreport{info3-techreport-2010-251, author = {Pries, Rastin and Staehle, Dirk and Hock, David and Hirth, Matthias}, institution = {University of Wuerzburg}, keywords = {sys:hidden:techreport}, month = {05}, number = 471, title = {A Policy-Based Vertical Handover System}, year = 2010 }

  %0 Report %1 info3-techreport-2010-251 %A Pries, Rastin %A Staehle, Dirk %A Hock, David %A Hirth, Matthias %D 2010 %N 471 %T A Policy-Based Vertical Handover System
• FIRMS - Demonstration of a Mapping System for Loc/ID Split Internet Routing in G-Lab. Hartmann, Matthias; Hock, David; Höfling, Michael; Neubert, Tim; Menth, Michael. Würzburg, Germany, 2010, July.
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  @misc{info3-software-2010-12, address = {Würzburg, Germany}, author = {Hartmann, Matthias and Hock, David and Höfling, Michael and Neubert, Tim and Menth, Michael}, keywords = {sys:hidden:software}, month = {07}, title = {FIRMS - Demonstration of a Mapping System for Loc/ID Split Internet Routing in G-Lab}, year = 2010 }

  %0 Generic %1 info3-software-2010-12 %A Hartmann, Matthias %A Hock, David %A Höfling, Michael %A Neubert, Tim %A Menth, Michael %C Würzburg, Germany %D 2010 %T FIRMS - Demonstration of a Mapping System for Loc/ID Split Internet Routing in G-Lab
• ASP7 - Experimental Facility Statistical Evaluations. Henjes, Robert; Hock, David; Schwerdel, Dennis; Müller, Paul; Tran-Gia, Phuoc. 2010, August.
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  @misc{info3-poster-2010-25, author = {Henjes, Robert and Hock, David and Schwerdel, Dennis and Müller, Paul and Tran-Gia, Phuoc}, booktitle = {10th Würzburg Workshop on IP: Joint ITG, ITC, and Euro-NF Workshop "Visions of Future Generation Networks" (EuroView2010)}, keywords = {sys:hidden:poster}, month = {08}, title = {ASP7 - Experimental Facility Statistical Evaluations}, year = 2010 }

  %0 Generic %1 info3-poster-2010-25 %A Henjes, Robert %A Hock, David %A Schwerdel, Dennis %A Müller, Paul %A Tran-Gia, Phuoc %B 10th Würzburg Workshop on IP: Joint ITG, ITC, and Euro-NF Workshop "Visions of Future Generation Networks" (EuroView2010) %D 2010 %T ASP7 - Experimental Facility Statistical Evaluations
• Optimized IP-Based vs. Explicit Paths for One-to-One Backup in MPLS Fast Reroute. Pióro, Michał; Tomaszewski, Artur; Żukowski, Cezary; Hock, David; Hartmann, Matthias; Menth, Michael. In 14th International Telecommunications Network Strategy and Planning Symposium (NETWORKS 2010), Best Paper Award. Warsaw, Poland, 2010.
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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 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.

  @inproceedings{info3-inproceedings-2010-389, 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 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.}, address = {Warsaw, Poland}, author = {Pióro, Michał and Tomaszewski, Artur and Żukowski, Cezary and Hock, David and Hartmann, Matthias and Menth, Michael}, booktitle = {14th International Telecommunications Network Strategy and Planning Symposium (NETWORKS 2010), Best Paper Award}, keywords = {sys:hidden:inproceedings}, month = {09}, title = {Optimized IP-Based vs. Explicit Paths for One-to-One Backup in MPLS Fast Reroute}, year = 2010 }

  %0 Conference Paper %1 info3-inproceedings-2010-389 %A Pióro, Michał %A Tomaszewski, Artur %A Żukowski, Cezary %A Hock, David %A Hartmann, Matthias %A Menth, Michael %B 14th International Telecommunications Network Strategy and Planning Symposium (NETWORKS 2010), Best Paper Award %C Warsaw, Poland %D 2010 %T Optimized IP-Based vs. Explicit Paths for One-to-One Backup in MPLS Fast Reroute %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 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.

• Erzeugung und Optimierung eindeutiger kürzester Pfade für ausfallsicheres IP Routing und Fast Reroute. Hock, David. ITG Fachgruppe 5.2.1 Workshop Optimierungsverfahren, IKR Stuttgart, Germany, 2009, November 13.
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  @presentation{info3-talk-2009-359, address = {ITG Fachgruppe 5.2.1 Workshop Optimierungsverfahren, IKR Stuttgart, Germany}, author = {Hock, David}, keywords = {sys:hidden:presentation}, month = 11, title = {Erzeugung und Optimierung eindeutiger kürzester Pfade für ausfallsicheres IP Routing und Fast Reroute}, year = 2009 }

  %0 Generic %1 info3-talk-2009-359 %A Hock, David %C ITG Fachgruppe 5.2.1 Workshop Optimierungsverfahren, IKR Stuttgart, Germany %D 2009 %T Erzeugung und Optimierung eindeutiger kürzester Pfade für ausfallsicheres IP Routing und Fast Reroute
• Measurement of BitTorrent Swarms and their AS Topologies. Technical Report (464), . Hoßfeld, Tobias; Hock, David; Oechsner, Simon; Lehrieder, Frank; Despotovic, Zoran; Kellerer, Wolfgang; Michel, Maximilian. University of Wuerzburg, 2009.
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  @techreport{info3-techreport-2009-246, author = {Hoßfeld, Tobias and Hock, David and Oechsner, Simon and Lehrieder, Frank and Despotovic, Zoran and Kellerer, Wolfgang and Michel, Maximilian}, institution = {University of Wuerzburg}, keywords = {sys:hidden:techreport}, month = 11, number = 464, title = {Measurement of BitTorrent Swarms and their AS Topologies}, year = 2009 }

  %0 Report %1 info3-techreport-2009-246 %A Hoßfeld, Tobias %A Hock, David %A Oechsner, Simon %A Lehrieder, Frank %A Despotovic, Zoran %A Kellerer, Wolfgang %A Michel, Maximilian %D 2009 %N 464 %T Measurement of BitTorrent Swarms and their AS Topologies
• Objective Functions for Optimization of Resilient and Non-Resilient IP Routing. Hartmann, Matthias; Hock, David; Menth, Michael; Schwartz, Christian. In 7th International Workshop on the Design of Reliable Communication Networks (DRCN). Washington, D.C., USA, 2009.
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  Intradomain routing in IP networks follows leastcost paths according to administrative link costs. Routing optimization modifies these values to minimize an objective function for a network with given link capacities and traffic matrix. An example for an objective function is the maximum utilization of all links under failure-free conditions or also after rerouting in case of network failures. Many papers have provided heuristic algorithms for routing optimization using different objective functions, but the investigation and comparison of various objective functions has not attracted much attention so far. In this work we present several objective functions for resilient IP routing. We also propose a new combined optimization approach which can simultaneously optimize different objective functions with almost no additional computation effort and describe new techniques to minimize overall computation time. The different objective functions and combinations thereof are then analyzed and compared experimentally.

  @inproceedings{info3-inproceedings-2009-358, abstract = {Intradomain routing in IP networks follows leastcost paths according to administrative link costs. Routing optimization modifies these values to minimize an objective function for a network with given link capacities and traffic matrix. An example for an objective function is the maximum utilization of all links under failure-free conditions or also after rerouting in case of network failures. Many papers have provided heuristic algorithms for routing optimization using different objective functions, but the investigation and comparison of various objective functions has not attracted much attention so far. In this work we present several objective functions for resilient IP routing. We also propose a new combined optimization approach which can simultaneously optimize different objective functions with almost no additional computation effort and describe new techniques to minimize overall computation time. The different objective functions and combinations thereof are then analyzed and compared experimentally.}, address = {Washington, D.C., USA}, author = {Hartmann, Matthias and Hock, David and Menth, Michael and Schwartz, Christian}, booktitle = {7th International Workshop on the Design of Reliable Communication Networks (DRCN)}, keywords = {sys:hidden:inproceedings}, month = 10, title = {Objective Functions for Optimization of Resilient and Non-Resilient IP Routing}, year = 2009 }

  %0 Conference Paper %1 info3-inproceedings-2009-358 %A Hartmann, Matthias %A Hock, David %A Menth, Michael %A Schwartz, Christian %B 7th International Workshop on the Design of Reliable Communication Networks (DRCN) %C Washington, D.C., USA %D 2009 %T Objective Functions for Optimization of Resilient and Non-Resilient IP Routing %X Intradomain routing in IP networks follows leastcost paths according to administrative link costs. Routing optimization modifies these values to minimize an objective function for a network with given link capacities and traffic matrix. An example for an objective function is the maximum utilization of all links under failure-free conditions or also after rerouting in case of network failures. Many papers have provided heuristic algorithms for routing optimization using different objective functions, but the investigation and comparison of various objective functions has not attracted much attention so far. In this work we present several objective functions for resilient IP routing. We also propose a new combined optimization approach which can simultaneously optimize different objective functions with almost no additional computation effort and describe new techniques to minimize overall computation time. The different objective functions and combinations thereof are then analyzed and compared experimentally.
• On QoE Provisioning for VoIP in IEEE 802.11 Mesh Networks. Hock, David. Second EuroNF Plenary Meeting, University of Kaiserslautern, Germany, 2009, June 4.
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  @presentation{info3-talk-2009-339, address = {Second EuroNF Plenary Meeting, University of Kaiserslautern, Germany}, author = {Hock, David}, keywords = {sys:hidden:presentation}, month = {06}, title = {On QoE Provisioning for VoIP in IEEE 802.11 Mesh Networks}, year = 2009 }

  %0 Generic %1 info3-talk-2009-339 %A Hock, David %C Second EuroNF Plenary Meeting, University of Kaiserslautern, Germany %D 2009 %T On QoE Provisioning for VoIP in IEEE 802.11 Mesh Networks

• QoS Provisioning in WLAN Mesh Networks Using Dynamic Bandwidth Control. Hock, David; Bayer, Nico; Pries, Rastin; Siebert, Matthias; Staehle, Dirk; Rakocevic, Veselin; Xu, Bangnan. In European Wireless 2008, p. 7. Prague, Czech Republic, 2008.
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  WLAN, based on the IEEE 802.11 standard has been extensively studied since its release. In addition to infrastructure access to WLAN, mesh networks currently attract a lot of attention. This comes from the envisioned advantages of wireless mesh networks, such as cheap installation costs, extended coverage, robustness, easy maintenance, and self-configuration possibilities. In this paper we focus on Quality of Service support for multimedia applications in WLAN-based mesh networks. Therefore, a dynamic bandwidth control mechanism is implemented on the network layer and the results show that high prioritized traffic can be protected from disturbing best effort traffic.

  @inproceedings{info3-inproceedings-2008-316, abstract = {WLAN, based on the IEEE 802.11 standard has been extensively studied since its release. In addition to infrastructure access to WLAN, mesh networks currently attract a lot of attention. This comes from the envisioned advantages of wireless mesh networks, such as cheap installation costs, extended coverage, robustness, easy maintenance, and self-configuration possibilities. In this paper we focus on Quality of Service support for multimedia applications in WLAN-based mesh networks. Therefore, a dynamic bandwidth control mechanism is implemented on the network layer and the results show that high prioritized traffic can be protected from disturbing best effort traffic.}, address = {Prague, Czech Republic}, author = {Hock, David and Bayer, Nico and Pries, Rastin and Siebert, Matthias and Staehle, Dirk and Rakocevic, Veselin and Xu, Bangnan}, booktitle = {European Wireless 2008}, keywords = {sys:hidden:inproceedings}, month = {06}, pages = 7, title = {QoS Provisioning in WLAN Mesh Networks Using Dynamic Bandwidth Control}, year = 2008 }

  %0 Conference Paper %1 info3-inproceedings-2008-316 %A Hock, David %A Bayer, Nico %A Pries, Rastin %A Siebert, Matthias %A Staehle, Dirk %A Rakocevic, Veselin %A Xu, Bangnan %B European Wireless 2008 %C Prague, Czech Republic %D 2008 %P 7 %T QoS Provisioning in WLAN Mesh Networks Using Dynamic Bandwidth Control %X WLAN, based on the IEEE 802.11 standard has been extensively studied since its release. In addition to infrastructure access to WLAN, mesh networks currently attract a lot of attention. This comes from the envisioned advantages of wireless mesh networks, such as cheap installation costs, extended coverage, robustness, easy maintenance, and self-configuration possibilities. In this paper we focus on Quality of Service support for multimedia applications in WLAN-based mesh networks. Therefore, a dynamic bandwidth control mechanism is implemented on the network layer and the results show that high prioritized traffic can be protected from disturbing best effort traffic.
• Testing the IQX Hypothesis for Exponential Interdependency between QoS and QoE of Voice Codecs iLBC and G.711. Hoßfeld, Tobias; Hock, David; Tran-Gia, Phuoc; Tutschku, Kurt; Fiedler, Markus. In 18th ITC Specialist Seminar on Quality of Experience. Karlskrona, Sweden, 2008.
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  @inproceedings{info3-inproceedings-2008-318, address = {Karlskrona, Sweden}, author = {Hoßfeld, Tobias and Hock, David and Tran-Gia, Phuoc and Tutschku, Kurt and Fiedler, Markus}, booktitle = {18th ITC Specialist Seminar on Quality of Experience}, keywords = {sys:hidden:inproceedings}, month = {05}, title = {Testing the IQX Hypothesis for Exponential Interdependency between QoS and QoE of Voice Codecs iLBC and G.711}, year = 2008 }

  %0 Conference Paper %1 info3-inproceedings-2008-318 %A Hoßfeld, Tobias %A Hock, David %A Tran-Gia, Phuoc %A Tutschku, Kurt %A Fiedler, Markus %B 18th ITC Specialist Seminar on Quality of Experience %C Karlskrona, Sweden %D 2008 %T Testing the IQX Hypothesis for Exponential Interdependency between QoS and QoE of Voice Codecs iLBC and G.711
• Dynamic Bandwidth Control in Wireless Mesh Networks: A Quality of Experience based Approach. Pries, Rastin; Hock, David; Bayer, Nico; Siebert, Matthias; Staehle, Dirk; Rakocevic, Veselin; Xu, Bangnan; Tran-Gia, Phuoc. In 18th ITC Specialist Seminar on Quality of Experience. Karlskrona, Sweden, 2008.
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  Wireless Mesh Networks (WMNs) are gaining an increasingly important role in next generation wireless networks. Due to their advantages over other wireless and wired networks, WMNs are undergoing rapid progress and are supposed to deliver wireless services for a large variety of applications. Especially real-time applications such as voice over IP make high demands on wireless mesh networks. A small change of the Quality-of-Service (QoS) metrics like packet loss, delay, and jitter have a significant impact on the Quality-of-Experience (QoE), a subjective measure from the user perspective of the overall value of the provided service or application. In this paper, we present a dynamic bandwidth control mechanism which measures the current situation in the network and adapts the bandwidth in order to ensure a high QoE level. The mechanism is implemented in a Wireless LAN mesh testbed and the results show that real-time applications are successfully protected from disturbing best effort traffic flows.

  @inproceedings{info3-inproceedings-2008-317, abstract = {Wireless Mesh Networks (WMNs) are gaining an increasingly important role in next generation wireless networks. Due to their advantages over other wireless and wired networks, WMNs are undergoing rapid progress and are supposed to deliver wireless services for a large variety of applications. Especially real-time applications such as voice over IP make high demands on wireless mesh networks. A small change of the Quality-of-Service (QoS) metrics like packet loss, delay, and jitter have a significant impact on the Quality-of-Experience (QoE), a subjective measure from the user perspective of the overall value of the provided service or application. In this paper, we present a dynamic bandwidth control mechanism which measures the current situation in the network and adapts the bandwidth in order to ensure a high QoE level. The mechanism is implemented in a Wireless LAN mesh testbed and the results show that real-time applications are successfully protected from disturbing best effort traffic flows.}, address = {Karlskrona, Sweden}, author = {Pries, Rastin and Hock, David and Bayer, Nico and Siebert, Matthias and Staehle, Dirk and Rakocevic, Veselin and Xu, Bangnan and Tran-Gia, Phuoc}, booktitle = {18th ITC Specialist Seminar on Quality of Experience}, keywords = {sys:hidden:inproceedings}, month = {05}, title = {Dynamic Bandwidth Control in Wireless Mesh Networks: A Quality of Experience based Approach}, year = 2008 }

  %0 Conference Paper %1 info3-inproceedings-2008-317 %A Pries, Rastin %A Hock, David %A Bayer, Nico %A Siebert, Matthias %A Staehle, Dirk %A Rakocevic, Veselin %A Xu, Bangnan %A Tran-Gia, Phuoc %B 18th ITC Specialist Seminar on Quality of Experience %C Karlskrona, Sweden %D 2008 %T Dynamic Bandwidth Control in Wireless Mesh Networks: A Quality of Experience based Approach %X Wireless Mesh Networks (WMNs) are gaining an increasingly important role in next generation wireless networks. Due to their advantages over other wireless and wired networks, WMNs are undergoing rapid progress and are supposed to deliver wireless services for a large variety of applications. Especially real-time applications such as voice over IP make high demands on wireless mesh networks. A small change of the Quality-of-Service (QoS) metrics like packet loss, delay, and jitter have a significant impact on the Quality-of-Experience (QoE), a subjective measure from the user perspective of the overall value of the provided service or application. In this paper, we present a dynamic bandwidth control mechanism which measures the current situation in the network and adapts the bandwidth in order to ensure a high QoE level. The mechanism is implemented in a Wireless LAN mesh testbed and the results show that real-time applications are successfully protected from disturbing best effort traffic flows.
• VoIP performance in MeshBed - a Wireless Mesh Network Testbed. Bayer, Nico; Hock, David; Roos, Andreas; Siebert, Matthias; Xu, Bangnan; Rakocevic, Veselin; Habermann, Joachim. In In Proceedings of the 67th IEEE Vehicular Technology Conference (VTC) Spring 2008. Marina Bay, Singapore, 2008.
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  @inproceedings{info3-inproceedings-2008-345, address = {Marina Bay, Singapore}, author = {Bayer, Nico and Hock, David and Roos, Andreas and Siebert, Matthias and Xu, Bangnan and Rakocevic, Veselin and Habermann, Joachim}, booktitle = {In Proceedings of the 67th IEEE Vehicular Technology Conference (VTC) Spring 2008}, keywords = {sys:hidden:inproceedings}, month = {05}, title = {VoIP performance in MeshBed - a Wireless Mesh Network Testbed}, year = 2008 }

  %0 Conference Paper %1 info3-inproceedings-2008-345 %A Bayer, Nico %A Hock, David %A Roos, Andreas %A Siebert, Matthias %A Xu, Bangnan %A Rakocevic, Veselin %A Habermann, Joachim %B In Proceedings of the 67th IEEE Vehicular Technology Conference (VTC) Spring 2008 %C Marina Bay, Singapore %D 2008 %T VoIP performance in MeshBed - a Wireless Mesh Network Testbed
• Testing the IQX Hypothesis for Exponential Interdependency between QoS and QoE of Voice Codecs iLBC and G.711. Technical Report (442), . Hoßfeld, Tobias; Hock, David; Tran-Gia, Phuoc; Tutschku, Kurt; Fiedler, Markus. University of Wuerzburg, 2008.
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  @techreport{info3-techreport-2008-229, author = {Hoßfeld, Tobias and Hock, David and Tran-Gia, Phuoc and Tutschku, Kurt and Fiedler, Markus}, institution = {University of Wuerzburg}, keywords = {sys:hidden:techreport}, month = {03}, number = 442, title = {Testing the IQX Hypothesis for Exponential Interdependency between QoS and QoE of Voice Codecs iLBC and G.711}, year = 2008 }

  %0 Report %1 info3-techreport-2008-229 %A Hoßfeld, Tobias %A Hock, David %A Tran-Gia, Phuoc %A Tutschku, Kurt %A Fiedler, Markus %D 2008 %N 442 %T Testing the IQX Hypothesis for Exponential Interdependency between QoS and QoE of Voice Codecs iLBC and G.711