Low-Complexity Master Controller Assignment in Distributed SDN Controller Environments

In a large-scale distributed software-defined networking environment, a switch is connected to multiple controllers for resiliency while assigned with one master controller, and only the master controller can install flow rules. Due to such permissions, the flow setup latency can be affected significantly depending on the master controller assignment and thus how to assign the master controller is a prominent issue. In this paper, we formulate a master controller assignment problem to minimize the average flow setup latency with consideration of the number of assigned master controllers along a path. A low-complexity master assignment (LCMA) algorithm is devised to solve the problem in a practical manner. Extensive simulation results over real-world network topologies demonstrate that LCMA achieves near-optimal performance and outperforms the existing assignment scheme in terms of the average flow setup latency under various settings.