Deutsch Intern
    Lehrstuhl für Informatik III

    Networking and SDN

    We deal in projects with the topic of Access Networks and Software-Defined Networking (SDN). In particular we consider availability, reliability and serviceability for data center and WAN networks.

    An extended version of our paper "Analytic Model for SDN Controller Traffic and Switch Table Occupancy" will be published in the next issue of the IEEE Transactions on Network and Service Management.



    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.


    Our Paper "Analytic Model for SDN Controller Traffic and Switch Table Occupancy" will be in the proceedings of the CNSM 2016 in Montreal.



    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 to minimize both.


    SDN-RAS²: Kick-off


    Our new Project "SDN-RAS²" has been started today. This project focuses on Fast failure Detection in Software-Defined Networks and is a successor to our "SDN-RAS" project. We are looking forward to continue the cooperation with our partner.


    For this analysis, we consider a single SDN switch, which is connected to a reactive SDN controller. Multiple TCP flows are active in the network, thus, packet streams arrive at the SDN switch and have to be forwarded. In the beginning the SDN switch has no knowledge how to handle any arriving packet. When the first packet of a TCP flow arrives, the SDN switch has a flow table miss and asks the SDN controller how to handle the new flow.


    Our goal is to mathematically model the request rate at the SDN controller and the occupancy of the SDN switch flow table. Based on this analysis, we are able to trade-off controller traffic and table size, and gain insights into effective overload control.


    Current Projects

    SDN-RAS2 (Fast Failure Detection in Software-Defined Networks)

    In systems design, a fail-fast system is one which immediately reports at its interface any condition that is likely to indicate a failure. Such designs often check the system's state at several points in an operation, so any failures can be detected early.

    The objective of the project is the study and analysis of fast fault detection and localization techniques for SDN.

    SDN-RAS (SDN - Reliabilty, Availabilty & Serviceability Challenges)

    The project focuses on the identification and analysis of the top reliability, availability and serviceability challenges of current SDN mechanisms, protocols, and architectures. 

    Related Research Areas

    Research Area: Access Networks

    Study on Wifi Offloading: WiFi Offloading is a current trend to cope with the demands of mobile users and the load on cellular networks. It allows providers to handle the traffic in well-dimensioned fixed networks and thereby save costs. In addition, end users can benefit from higher throughput and avoid exceeding their data plan.

    Application Aware Networking: Application-aware resource management is the approach to tailor access networks to have characteristics beneficial for the running applications and services. This is achieved through the monitoring and integration of key performance indicators from the application layer within the network resource management.

    Research Area: Network Functions Virtualization - Research on Performance Evaluation

    Network Function Virtualization (NFV) has become an emerge network technology in recent years. It has received a noticeable interest of not only researchers, network providers but also a huge market. NFV aims to reduce significantly the Capital Expenses (CAPEX) and Operating Expenses (OPEX) by leveraging virtualization technology to consolidate network functions running on equipment onto high volume commodity servers.

    Considering this field of study, we are interested in the NFV architecture and its components. For example, the NFV infrastructure requires optimized methods to dynamically allocate virtual resources for VNFs. On the other hand, NFV management and orchestration needs a VNF manager/placement engine to instantiate the VNFs in network with regard to energy saving, less traffic utilization, etc. On the top of the architecture, the VNFs must perform at least as efficient as the legacy functions. We are focusing on evaluating the VNF performance in comparison with a legacy function. Other topics may relate to the trade-off between hardware utilization and the performance of VNFs and traffic modeling for virtual network functions chaining.



    Projects SDN-RAS & SDN-RAS²

    • Metter, C., Seufert, M., Wamser, F., Zinner, T., Tran-Gia, P.: Analytical Model for SDN Signaling Traffic and Flow Table Occupancy and its Application for Various Types of Traffic. IEEE Transactions on Network and Service Management. 14, 603-615 (2017).
    • Metter, C., Seufert, M., Wamser, F., Zinner, T., Tran-Gia, P.: Analytic Model for SDN Controller Traffic and Switch Table Occupancy. 12th International Conference on Network and Service Management (CNSM). , Best Paper Award, Montreal, Canada (2016).

    Student projects and theses

    • Metter, C., Seufert, M., Wamser, F., Zinner, T., Tran-Gia, P.: Analytical Model for SDN Signaling Traffic and Flow Table Occupancy and its Application for Various Types of Traffic. IEEE Transactions on Network and Service Management. 14, 603-615 (2017).
    • Bott, L.: Implementing Backup Paths and Recovery Strategies in an SDN controlled by ONOS, (2017).
    • Knapp, T.: Extending the Monitoring Features of ONOS, (2017).
    • Supervisor: Metter, C.: Towards OFCProbe 2.0, (2017).
    • Abd El Hai, S.: Measuring the Applicability of the Analytic Model for SDN Controller Traffic and Switch Table Occupancy, (2017).
    • Knapp, T.: Assessment of the ONOS SDN Controller in Case of Network Errors, (2016).
    • Rachor, C.: Testbed-based RAS Evaluation in SDN using ONOS, (2015).
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    Lehrstuhl für Informatik III (Kommunikationsnetze)
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    Phone: +49 931 31-86631

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