Robust controller assignment for sdn survivability

Robustness in software defined networks (SDN) control plane is a challenging goal when a single controller is employed. Thus, distributed controllers are deployed to realize a robust, resilient and reliable software defined network. However, such a strategy can not succeed without an efficacious controller-switch assignment scheme. In addition to zero-day assignment, online re-assignment is crucial since due to network failures, the connections between controllers and switches may break off intermittently and impair the network operation. In this thesis, we propose a reactive assignment model against network failures using integer linear programming based on the load distribution of controllers. We also use a complementary strategy to monitor the network by using monitoring agents as network beacons at the edge via the flexibility of SDN. Real-time information about network connectivity and latency is provided by these agents and used in the assignment decisions. We augment our proposal with simulated annealing and random assignment approaches for switch, link and controller failures. Our proposed framework is evaluated using different types of traffic such as VoIP, video, and network gaming. Our model is also investigated using two different test scenarios to assess the contribution of monitoring agents. The experimental results show that our model gives resilience against network failures while load-awareness is an effective strategy for controller assignment.