Dr. rer. nat. Christopher Metter

• Resilience, Availability, and Serviceability Evaluation in Software-defined Networks. Technical Report (PhD dissertation), . Metter, Christopher. PhD dissertation. Universitiy of Würzburg, 2019, January.
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  @phdthesis{info3-dissertation-2019-1, author = {Metter, Christopher}, keywords = {sys:hidden:supervisor:phuoc.tran-gia}, month = {01}, school = {Universitiy of Würzburg}, title = {Resilience, Availability, and Serviceability Evaluation in Software-defined Networks}, year = 2019 }

  %0 Thesis %1 info3-dissertation-2019-1 %A Metter, Christopher %D 2019 %T Resilience, Availability, and Serviceability Evaluation in Software-defined Networks

• Towards an Active Probing Extension for the {ONOS} {SDN} Controller. Metter, Christopher; Burger, Valentin; Hu, Zheng; Pei, Ke; Wamser, Florian. In 2018 28th International Telecommunication Networks and Applications Conference (ITNAC) (ITNAC 2018), p. 8. Sydney, Australia, 2018.
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  Network monitoring is a complex task and is always a trade-off between granularity of information and the performance impact of the monitoring itself on the network. SDN controllers, such as the ONOS SDN controller make this challenge easier as they can supply centralized information over the whole network. In our previous work we mathematically analyzed the built-in detection mechanism of ONOS and revealed a lack of detection performance and the vulnerability of this process to jitter. These results were also verified by measurements. In this paper we present an Active Probing extension for the ONOS SDN controller that overcomes these shortcomings by emitting probing packets that are transmitted through the network. Statistics over a history of those packets allow for the detection of packet loss. The evaluation by the means of measurements proves the benefits in terms of detection performance and controller load of this application. Furthermore, our extension is able to detect jitter being present in the network and to automatically adapt the probing process to these conditions.

  @inproceedings{info3-inproceedings-2018-34, abstract = {Network monitoring is a complex task and is always a trade-off between granularity of information and the performance impact of the monitoring itself on the network. SDN controllers, such as the ONOS SDN controller make this challenge easier as they can supply centralized information over the whole network. In our previous work we mathematically analyzed the built-in detection mechanism of ONOS and revealed a lack of detection performance and the vulnerability of this process to jitter. These results were also verified by measurements. In this paper we present an Active Probing extension for the ONOS SDN controller that overcomes these shortcomings by emitting probing packets that are transmitted through the network. Statistics over a history of those packets allow for the detection of packet loss. The evaluation by the means of measurements proves the benefits in terms of detection performance and controller load of this application. Furthermore, our extension is able to detect jitter being present in the network and to automatically adapt the probing process to these conditions.}, address = {Sydney, Australia}, author = {Metter, Christopher and Burger, Valentin and Hu, Zheng and Pei, Ke and Wamser, Florian}, booktitle = {2018 28th International Telecommunication Networks and Applications Conference (ITNAC) (ITNAC 2018)}, keywords = {can}, month = 11, pages = 8, title = {Towards an Active Probing Extension for the {ONOS} {SDN} Controller}, year = 2018 }

  %0 Conference Paper %1 info3-inproceedings-2018-34 %A Metter, Christopher %A Burger, Valentin %A Hu, Zheng %A Pei, Ke %A Wamser, Florian %B 2018 28th International Telecommunication Networks and Applications Conference (ITNAC) (ITNAC 2018) %C Sydney, Australia %D 2018 %P 8 %T Towards an Active Probing Extension for the {ONOS} {SDN} Controller %X Network monitoring is a complex task and is always a trade-off between granularity of information and the performance impact of the monitoring itself on the network. SDN controllers, such as the ONOS SDN controller make this challenge easier as they can supply centralized information over the whole network. In our previous work we mathematically analyzed the built-in detection mechanism of ONOS and revealed a lack of detection performance and the vulnerability of this process to jitter. These results were also verified by measurements. In this paper we present an Active Probing extension for the ONOS SDN controller that overcomes these shortcomings by emitting probing packets that are transmitted through the network. Statistics over a history of those packets allow for the detection of packet loss. The evaluation by the means of measurements proves the benefits in terms of detection performance and controller load of this application. Furthermore, our extension is able to detect jitter being present in the network and to automatically adapt the probing process to these conditions.
• Evaluation of the Detection Capabilities of the ONOS SDN Controller. Metter, Christopher; Burger, Valentin; Hu, Zheng; Pei, Ke; Wamser, Florian. In 7th IEEE International Conference on Communications and Electronics (IEEE ICCE 2018), pp. 96–101. Hue, Vietnam, 2018.
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  The process of monitoring the network, especially for larger ones, is very complex and contains many pitfalls. For instance the balance between granularity of information and their performance impact on the network. With the help of SDN this challenge can become easier, as it offers new methods, mechanisms and opportunities. One of the current most important Open Source controllers is the ONOS SDN controller. According to its developers it is a production ready controller that offers high availability due to its logically centralized and physically distributed architecture. But, as our investigations show, it is unable to cope with hazardous network conditions such as sporadic or recurring packet loss. It either does not detect packet loss or only detects it after long time periods, failing all common network availability targets.

  @inproceedings{info3-inproceedings-2018-22, abstract = {The process of monitoring the network, especially for larger ones, is very complex and contains many pitfalls. For instance the balance between granularity of information and their performance impact on the network. With the help of SDN this challenge can become easier, as it offers new methods, mechanisms and opportunities. One of the current most important Open Source controllers is the ONOS SDN controller. According to its developers it is a production ready controller that offers high availability due to its logically centralized and physically distributed architecture. But, as our investigations show, it is unable to cope with hazardous network conditions such as sporadic or recurring packet loss. It either does not detect packet loss or only detects it after long time periods, failing all common network availability targets.}, address = {Hue, Vietnam}, author = {Metter, Christopher and Burger, Valentin and Hu, Zheng and Pei, Ke and Wamser, Florian}, booktitle = {7th IEEE International Conference on Communications and Electronics (IEEE ICCE 2018)}, keywords = {can}, month = {07}, pages = {96 - 101}, title = {Evaluation of the Detection Capabilities of the ONOS SDN Controller}, year = 2018 }

  %0 Conference Paper %1 info3-inproceedings-2018-22 %A Metter, Christopher %A Burger, Valentin %A Hu, Zheng %A Pei, Ke %A Wamser, Florian %B 7th IEEE International Conference on Communications and Electronics (IEEE ICCE 2018) %C Hue, Vietnam %D 2018 %P 96 - 101 %T Evaluation of the Detection Capabilities of the ONOS SDN Controller %X The process of monitoring the network, especially for larger ones, is very complex and contains many pitfalls. For instance the balance between granularity of information and their performance impact on the network. With the help of SDN this challenge can become easier, as it offers new methods, mechanisms and opportunities. One of the current most important Open Source controllers is the ONOS SDN controller. According to its developers it is a production ready controller that offers high availability due to its logically centralized and physically distributed architecture. But, as our investigations show, it is unable to cope with hazardous network conditions such as sporadic or recurring packet loss. It either does not detect packet loss or only detects it after long time periods, failing all common network availability targets.

• Performance Assessment of Cloud Migrations from Network and Application Point of View. Iffländer, Lukas; Wamser, Florian; Metter, Christopher; Tran-Gia, Phuoc; Kounev, Samuel. In Proceedings of 9th EAI International Conference on Mobile Networks and Management (MONAMI 2017). Melbourne, Australia, 2017.
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  @inproceedings{info3-inproceedings-2017-22, address = {Melbourne, Australia}, author = {Iffländer, Lukas and Wamser, Florian and Metter, Christopher and Tran-Gia, Phuoc and Kounev, Samuel}, booktitle = {Proceedings of 9th EAI International Conference on Mobile Networks and Management (MONAMI 2017)}, keywords = {can}, month = 12, title = {Performance Assessment of Cloud Migrations from Network and Application Point of View}, year = 2017 }

  %0 Conference Paper %1 info3-inproceedings-2017-22 %A Iffländer, Lukas %A Wamser, Florian %A Metter, Christopher %A Tran-Gia, Phuoc %A Kounev, Samuel %B Proceedings of 9th EAI International Conference on Mobile Networks and Management (MONAMI 2017) %C Melbourne, Australia %D 2017 %T Performance Assessment of Cloud Migrations from Network and Application Point of View
• Analytical Model for SDN Signaling Traffic and Flow Table Occupancy and its Application for Various Types of Traffic. Metter, Christopher; Seufert, Michael; Wamser, Florian; Zinner, Thomas; Tran-Gia, Phuoc. In IEEE Transactions on Network and Service Management, 14(3), pp. 603–615. 2017.
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  Software Defined Networking (SDN) has emerged as a promising networking paradigm overcoming various drawbacks of current communication networks. The control and data plane of switching devices is decoupled and control functions are centralized at the network controller. In SDN, each new flow introduces additional signaling traffic between the switch and the controller. Based on this traffic, rules are created in the flow table of the switch, which specify the forwarding behavior. To avoid table overflows, unused entries are removed after a predefined time-out period. Given a specific traffic mix, the choice of this time-out period affects the trade-off between signaling rate and table occupancy. As a result, network operators have to adjust this parameter to enable a smooth and efficient network operation. Due to the complexity of this problem caused by the various traffic flows in a network, a suitable abstraction is necessary in order to derive valid parameter values in time. The contribution of this work is threefold. Firstly, we formulate a simple analytical model that allows optimizing the network performance with respect to the table occupancy and the signaling rate. Secondly, we validate the model by means of simulation. Thirdly, we illustrate the impact of the time-out period on the signaling traffic and the flow table occupancy for different data-plane traffic mixes and characteristics. This includes scenarios with single application instances, as well as multiple application instances of different application types in an SDN-enabled network.

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

  %0 Journal Article %1 info3-article-2017-5 %A Metter, Christopher %A Seufert, Michael %A Wamser, Florian %A Zinner, Thomas %A Tran-Gia, Phuoc %D 2017 %J IEEE Transactions on Network and Service Management %N 3 %P 603-615 %T Analytical Model for SDN Signaling Traffic and Flow Table Occupancy and its Application for Various Types of Traffic %V 14 %X Software Defined Networking (SDN) has emerged as a promising networking paradigm overcoming various drawbacks of current communication networks. The control and data plane of switching devices is decoupled and control functions are centralized at the network controller. In SDN, each new flow introduces additional signaling traffic between the switch and the controller. Based on this traffic, rules are created in the flow table of the switch, which specify the forwarding behavior. To avoid table overflows, unused entries are removed after a predefined time-out period. Given a specific traffic mix, the choice of this time-out period affects the trade-off between signaling rate and table occupancy. As a result, network operators have to adjust this parameter to enable a smooth and efficient network operation. Due to the complexity of this problem caused by the various traffic flows in a network, a suitable abstraction is necessary in order to derive valid parameter values in time. The contribution of this work is threefold. Firstly, we formulate a simple analytical model that allows optimizing the network performance with respect to the table occupancy and the signaling rate. Secondly, we validate the model by means of simulation. Thirdly, we illustrate the impact of the time-out period on the signaling traffic and the flow table occupancy for different data-plane traffic mixes and characteristics. This includes scenarios with single application instances, as well as multiple application instances of different application types in an SDN-enabled network.

• Analytic Model for SDN Controller Traffic and Switch Table Occupancy. Metter, Christopher; Seufert, Michael; Wamser, Florian; Zinner, Thomas; Tran-Gia, Phuoc. In 12th International Conference on Network and Service Management (CNSM). Best Paper Award, Montreal, Canada, 2016.
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  Software Defined Networking (SDN) is a major paradigm in the field of current communication networks. SDN is used as the basis of many new networks although few performance models are available in the literature, and the majority of performance evaluations are based primarily on practical measurements. To fill this gap, we develop an analytical model to assess SDN control plane traffic as well as the occupancy of the flow table of an SDN switch. The contribution of this work is the formulation of the model for the performance-decisive parameters control-plane traffic and flow table occupancy and the application of the model for different data plane traffic characteristics. In the end, there is a discussion about the setting of time-out values for storing flow entries in the switch flow table depending on the traffic characteristics in the data plane. The trade-off between the signaling traffic in the control plane and the occupancy of the flow table is discussed in order to minimize both.

  @inproceedings{info3-inproceedings-2016-17, abstract = {Software Defined Networking (SDN) is a major paradigm in the field of current communication networks. SDN is used as the basis of many new networks although few performance models are available in the literature, and the majority of performance evaluations are based primarily on practical measurements. To fill this gap, we develop an analytical model to assess SDN control plane traffic as well as the occupancy of the flow table of an SDN switch. The contribution of this work is the formulation of the model for the performance-decisive parameters control-plane traffic and flow table occupancy and the application of the model for different data plane traffic characteristics. In the end, there is a discussion about the setting of time-out values for storing flow entries in the switch flow table depending on the traffic characteristics in the data plane. The trade-off between the signaling traffic in the control plane and the occupancy of the flow table is discussed in order to minimize both.}, address = {Best Paper Award, Montreal, Canada}, author = {Metter, Christopher and Seufert, Michael and Wamser, Florian and Zinner, Thomas and Tran-Gia, Phuoc}, booktitle = {12th International Conference on Network and Service Management (CNSM)}, keywords = {can}, month = 10, title = {Analytic Model for SDN Controller Traffic and Switch Table Occupancy}, year = 2016 }

  %0 Conference Paper %1 info3-inproceedings-2016-17 %A Metter, Christopher %A Seufert, Michael %A Wamser, Florian %A Zinner, Thomas %A Tran-Gia, Phuoc %B 12th International Conference on Network and Service Management (CNSM) %C Best Paper Award, Montreal, Canada %D 2016 %T Analytic Model for SDN Controller Traffic and Switch Table Occupancy %X Software Defined Networking (SDN) is a major paradigm in the field of current communication networks. SDN is used as the basis of many new networks although few performance models are available in the literature, and the majority of performance evaluations are based primarily on practical measurements. To fill this gap, we develop an analytical model to assess SDN control plane traffic as well as the occupancy of the flow table of an SDN switch. The contribution of this work is the formulation of the model for the performance-decisive parameters control-plane traffic and flow table occupancy and the application of the model for different data plane traffic characteristics. In the end, there is a discussion about the setting of time-out values for storing flow entries in the switch flow table depending on the traffic characteristics in the data plane. The trade-off between the signaling traffic in the control plane and the occupancy of the flow table is discussed in order to minimize both.

• Investigating the Impact of Network Topology on the Processing Times of SDN Controllers. Metter, Christopher; Gebert, Steffen; Lange, Stanislav; Zinner, Thomas; Tran-Gia, Phuoc; Jarschel, Michael. In Seventh IFIP/IEEE International Workshop on Management of the Future Internet. Ottawa, Canada, 2015.
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  Software Defined Networking (SDN) introduces the concept of logically-centralized controllers in charge of managing the forwarding behavior of network elements. The new possibilities enabled through the centralization of control logic come with a certain risk: The controller might become a performance bottleneck. Therefore, ensuring sufficient controller performance is one of the crucial tasks prior to a successful SDN deployment. Furthermore, fine-grained traffic engineering, e.g., to achieve higher link utilization, results in a higher frequency of requests that are sent to the controller, which leads to an increased controller load. It is therefore important to analyze the capabilities of SDN controllers prior to deployment. This paper investigates two software implementations, the OpenDaylight and Ryu controllers. The control message throughput of different controllers has been studied several times already; however, it is not yet known what influence the number and topology of connected switches have. This paper investigates this influence in detail for a fat-tree data center topology and a WAN topology as well as 261 topologies with varying characteristics from the Internet Topology Zoo.

  @inproceedings{info3-inproceedings-2015-510, abstract = {Software Defined Networking (SDN) introduces the concept of logically-centralized controllers in charge of managing the forwarding behavior of network elements. The new possibilities enabled through the centralization of control logic come with a certain risk: The controller might become a performance bottleneck. Therefore, ensuring sufficient controller performance is one of the crucial tasks prior to a successful SDN deployment. Furthermore, fine-grained traffic engineering, e.g., to achieve higher link utilization, results in a higher frequency of requests that are sent to the controller, which leads to an increased controller load. It is therefore important to analyze the capabilities of SDN controllers prior to deployment. This paper investigates two software implementations, the OpenDaylight and Ryu controllers. The control message throughput of different controllers has been studied several times already; however, it is not yet known what influence the number and topology of connected switches have. This paper investigates this influence in detail for a fat-tree data center topology and a WAN topology as well as 261 topologies with varying characteristics from the Internet Topology Zoo.}, address = {Ottawa, Canada}, author = {Metter, Christopher and Gebert, Steffen and Lange, Stanislav and Zinner, Thomas and Tran-Gia, Phuoc and Jarschel, Michael}, booktitle = {Seventh IFIP/IEEE International Workshop on Management of the Future Internet}, keywords = {saser-siegfried}, month = {05}, title = {Investigating the Impact of Network Topology on the Processing Times of SDN Controllers}, year = 2015 }

  %0 Conference Paper %1 info3-inproceedings-2015-510 %A Metter, Christopher %A Gebert, Steffen %A Lange, Stanislav %A Zinner, Thomas %A Tran-Gia, Phuoc %A Jarschel, Michael %B Seventh IFIP/IEEE International Workshop on Management of the Future Internet %C Ottawa, Canada %D 2015 %T Investigating the Impact of Network Topology on the Processing Times of SDN Controllers %X Software Defined Networking (SDN) introduces the concept of logically-centralized controllers in charge of managing the forwarding behavior of network elements. The new possibilities enabled through the centralization of control logic come with a certain risk: The controller might become a performance bottleneck. Therefore, ensuring sufficient controller performance is one of the crucial tasks prior to a successful SDN deployment. Furthermore, fine-grained traffic engineering, e.g., to achieve higher link utilization, results in a higher frequency of requests that are sent to the controller, which leads to an increased controller load. It is therefore important to analyze the capabilities of SDN controllers prior to deployment. This paper investigates two software implementations, the OpenDaylight and Ryu controllers. The control message throughput of different controllers has been studied several times already; however, it is not yet known what influence the number and topology of connected switches have. This paper investigates this influence in detail for a fat-tree data center topology and a WAN topology as well as 261 topologies with varying characteristics from the Internet Topology Zoo.

• OFCProbe: A Platform-Independent Tool for OpenFlow Controller Analysis. Jarschel, Michael; Metter, Christopher; Zinner, Thomas; Gebert, Steffen; Tran-Gia, Phuoc. In 5th IEEE International Conference on Communications and Electronics (IEEE ICCE 2014). Da Nang, Vietnam, 2014.
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  Controller performance and behavior are key to the operation of an SDN network. Therefore, choosing the right controller implementation and corresponding set of applications is essential. In order to facilitate this decision we previously introduced a tool for controller performance analysis called ”OFCBenchmark”. In this paper, we present ”OFCProbe” a platform-independent and extended re-design of our original approach. We describe the new architecture and explain the implemented features. Finally, we provide some sample results to illustrate the kind of investigations that can be performed using the tool.

  @inproceedings{info3-inproceedings-2014-496, abstract = {Controller performance and behavior are key to the operation of an SDN network. Therefore, choosing the right controller implementation and corresponding set of applications is essential. In order to facilitate this decision we previously introduced a tool for controller performance analysis called ”OFCBenchmark”. In this paper, we present ”OFCProbe” a platform-independent and extended re-design of our original approach. We describe the new architecture and explain the implemented features. Finally, we provide some sample results to illustrate the kind of investigations that can be performed using the tool.}, address = {Da Nang, Vietnam}, author = {Jarschel, Michael and Metter, Christopher and Zinner, Thomas and Gebert, Steffen and Tran-Gia, Phuoc}, booktitle = {5th IEEE International Conference on Communications and Electronics (IEEE ICCE 2014)}, keywords = {saser-siegfried}, month = {08}, title = {OFCProbe: A Platform-Independent Tool for OpenFlow Controller Analysis}, year = 2014 }

  %0 Conference Paper %1 info3-inproceedings-2014-496 %A Jarschel, Michael %A Metter, Christopher %A Zinner, Thomas %A Gebert, Steffen %A Tran-Gia, Phuoc %B 5th IEEE International Conference on Communications and Electronics (IEEE ICCE 2014) %C Da Nang, Vietnam %D 2014 %T OFCProbe: A Platform-Independent Tool for OpenFlow Controller Analysis %X Controller performance and behavior are key to the operation of an SDN network. Therefore, choosing the right controller implementation and corresponding set of applications is essential. In order to facilitate this decision we previously introduced a tool for controller performance analysis called ”OFCBenchmark”. In this paper, we present ”OFCProbe” a platform-independent and extended re-design of our original approach. We describe the new architecture and explain the implemented features. Finally, we provide some sample results to illustrate the kind of investigations that can be performed using the tool.