How RTT between the control and data plane on a SDN network impacts on the perceived performance

With the increasing complexity of modern communications networks, Software Defined Networking (SDN) has been proposed as an approach that can solve a variety of real network management problems. The separation between the control plane and the data plane within SDN brings the flexibility which can aid network operators to reduce complexity, cost, and improve the user experience. In this paper, we analyse the impact of the location of the control plane with respect to the data plane on the perceived performance of traffic flows through an SDN network. Our experimental results indicate that the distance between the control plane and data plane has significant impacts on the perceived performance as seen by users of the network. These include a large decrease in throughput for small TCP transfers, and a significant amount of packet re-ordering and continual transmission delay for real-time VoIP-like flows.