Lehrstuhl für Informatik III

    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.

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