Toward a Flexible Design of SDN Dynamic Control Plane: An Online Optimization Approach

With a centralized control over the forwarding devices and the embedded flows, Software Defined Networking promises to increase the flexibility of communication networks. Meanwhile, a dynamic control plane would adapt itself in a timely manner to sustain flow setup performance in the face of traffic variations. Such adaptation depends on a careful decision of the controller placement, which is challenging because we need to consider two contradictory objectives, namely the cost of operating the control plane and the cost of its adaptation. In this work, we model the problem of operating the control plane as a multi-period offline optimization problem to minimize the total cost induced by the flow setup performance and the control plane adaptation. We leverage the lookahead control scheme and decompose the intractable offline problem into smaller instances, which are solved in an online fashion efficiently with an algorithm based on simulated annealing. We perform extensive simulations on real world topologies and show that our proposed algorithm can reduce the total cost by up to 20% compared with the reference algorithms. Further, we analyze the need of frequent control plane adaptation, and compare different control plane design choices according to a novel flexibility measure.