Analytical Model for SDN Signaling Traffic and Flow Table Occupancy and Its Application for Various Types of Traffic

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 tradeoff 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 paper is threefold. First, we formulate a simple analytical model that allows optimizing the network performance with respect to the table occupancy and the signaling rate. Second, we validate the model by means of simulation. Third, 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.