Controller placement in software defined networks: A Comprehensive survey

Abstract

Software defined networking (SDN) offers centralized network management and effective resource utilization by offloading the intelligent control plane, responsible for routing and signaling, of network devices to one or more external entities known as controllers. It also allows us to experiment with new ideas and deploy applications in the existing network through programmability of the control plane. The number and placement of controllers in the network influences several aspects such as performance metrics, availability, fault tolerance, convergence time and state distribution options. Therefore, the problem of determining the number and placement of controllers and switch to controller mapping, widely known as the controller placement problem, is one of the problems that needs more attention. This review presents a comprehensive overview of recent literature on the controller placement strategies in SDN. The existing literature on the controller placement problem is analyzed across six aspects: target network environment, traffic characteristics, controller characteristics, solution approach, reliability of network elements, and different optimization objective(s). We mainly focus our discussion on controller placement approaches based on optimization objectives such as latency, connectivity, cost, load, energy, QoS, control plane overhead or a combination of these objectives.