Evaluating the controller capacity in software defined networking

The flow-based OpenFlow architecture decouples the control plane and data plane, and it has involved great evolution towards traditional networks. A particular important issue in OpenFlow architecture is controller capacity, which can be defined as the number of switches a controller can manage. In this paper, we model the flow set-up requests from switches to controller as a batch arrival process M^k/M /1. Further, we analyze the controller performance with queuing theory, and derive the expression of average flow service time. Under the circumstance of a limited flow set-up time, the number of switches is determined, this provides a method to evaluate the controller capacity. Moreover, we extend the scene of a single controller to multiple controllers. All of these results are meaningful to large scale OpenFlow network deployment in the future.