Metaheuristic algorithms for capacitated controller placement in software defined networks considering failure resilience

Software-defined networking (SDN) has revolutionized network architectures by decoupling the control plane from the data plane. An intriguing challenge within this paradigm is the strategic placement of controllers and the allocation of switches to optimize network performance and resilience. In the event of a controller failure, the switches are disconnected from the controller until they are reassigned to other active controllers possessing sufficient spare capacity. The reassignment could lead to a significant rise in propagation latency. This correspondence presents a mathematical model for capacitated controller placement, strategically designed to anticipate failures and prevent a substantial increase in worst-case latency and disconnections. The aim is to minimize the worst-case latency between switches and their backup controllers and among the controllers. Four metaheuristic algorithms are proposed including, an enhanced genetic algorithm (CCPCFR-EGA), particle swarm optimization (CCPCFR-PSO), a hybrid particle swarm optimization and simulated annealing algorithm (CCPCFR-HPSOSA), and a grey wolf optimization algorithm (CCPCFR-GWO). These algorithms are compared with a simulated annealing method and an optimal method. Evaluation conducted on four network datasets demonstrates that the proposed metaheuristic methods are faster than the optimal method. The experimental outcome indicates that CCPCFR-HPSOSA and CCPCFR-GWO outperform the other methods, consistently providing near-optimal solutions. However, CCPCFR-GWO is preferred over CCPCFR-HPSOSA due to its faster execution time. Specifically, CCPCFR-GWO achieves an average speed-up of 3.9 over the optimal for smaller networks and an average speed-up of 31.78 for larger networks, while still producing near-optimal solutions.