The SDN Control Plane Challenge for Minimum Control traffic: Distributed or Centralized?

Software Defined Networking (SDN) decouples the control and data planes and moves the control logic to the SDN controllers. The traffic in the control plane is either related to the interconnection of the controllers or to the connectivity between the SDN switches and the controllers. The controller placement affects the total control traffic. Multiple distributed controllers increase the inter-controller traffic, while few concentrated controllers increase the controller to switch traffic. We model the problem of determining the optimal controller placement for minimum control traffic. We further discuss the complexity of the optimization problem, and devise a heuristic algorithm for its solution. Our simulations and testhed experimentation reveal close to optimal performance of the presented heuristic algorithm.