On the cascading failures of multi-controllers in Software Defined Networks

In this paper, a potential threat to reliability of Software Defined Networking (SDN) is disclosed: the cascading failures of controllers. Current SDN designs have widely utilized multiple controllers and the load of a failed controller can be redistributed to the other controllers. However, simply utilizing multiple controllers cannot protect SDN networks from a single point of failure: the load of the controllers which carry the load of the failed controller can exceed the capacity of them, and then cascading failures of controllers will happen. In this article, at first we propose a model for such failures and present simulation results based on the model. Strategies for initial load balance and load redistribution after failure are designed to prevent such failures. The simulation result shows the strategies can significantly increase the resistance of SDN networks to cascading failures.