Controller Placements for Optimizing Switch-to-Controller and Inter-controller Communication Latency in Software Defined Networks

The logically centralized control plane in large-scale SDN networks consists of multiple controllers, and the controllers communicate with each other to keep a consistent view of the network status. Inconsistent controllers or controllers failing to maintain the network state in time may severely degrade the network performance. However, most of the existing research focuses on the switch-to-controller communication latency by ignoring the communication latency between the controllers. In this paper, we formulate a novel multi-objective SDN controller placement problem with the objectives to minimize both the switch-to-controller and the inter-controller communication latency. We propose an efficient Multi-Objective Controller Placement (MOCP) algorithm. Algorithm MOCP generates the new controller placement solutions with crossover and mutation operations. The switches are assigned to the controllers with the greedy strategy initially, and then mapped to the other controllers via the local search strategy. Our simulation results show that algorithm MOCP can effectively reduce the latency between the controllers and from the switches to controllers simultaneously.