Fault tolerant mechanisms for SDN controllers

Software-Defined Networking (SDN) enables decoupling of the data plane from the control plane on network devices. This approach differs from the traditional networking architecture where both planes reside on the same network device. SDN offers flexibility, centralized control, reduced complexity and a dramatic decrease in network systems and equipment costs. OpenFlow (OF) is a widely used protocol for establishing communication between the control and data planes for SDN. Reliance on a single controller might not be feasible since the controller is a single point-of-failure (SPOF) in the network. In this paper, we propose to approach the issue of fault-tolerance by using a slave controller architecture with local mechanisms of virtual controller redundancy and synchronization between the controllers. Our prototype implementation enables the network to cope with control plane crashes in the controllers without changing the OF protocol between controllers and switches.