On the placement of controllers in software-Defined-WAN using meta-heuristic approach

Software Defined Networks (SDN) is a popular modern network technology that decouples the control logic from the underlying hardware devices. The control logic has implemented as a software entity that resides in a server called controller. In a Software-Defined Wide Area Network (SDWAN) with n nodes; deploying k number of controllers (k < n) is one of the challenging issue. Due to some internal or external factors, when the primary path between switch to controller fails, it severely interrupt the networks' availability. In this regard, the proposed approach provides a seamless backup mechanism against single link failure with minimum communication delay based on the survivability model. In order to obtain an efficient solution, we have considered controller placement problem (CPP) as a multi-objective combinatorial optimization problem and solve it using two population-based meta-heuristic techniques such as: Particle Swarm Optimization (PSO) and FireFly Algorithm (FFA). For CPP, three metrics have been considered: (a) controller to switch latency, (b) inter-controller latency and (c) multi-path connectivity between the switch and controller. The performance of the algorithms is evaluated on a set of publicly available network topologies in order to obtain the optimum number of controllers, and controller positions. Then we present Average Delay Rise (ADR) metric to measure the increased delay due to the failure of the primary path. By comparing the performance of our scheme to competing scheme, it was found that our proposed scheme effectively improves the survivability of the control path and the performance of the network as well.