On Resolving Network View Inconsistencies in SDN Control Plane

Software Defined Networking (SDN) is a new networking paradigm which decouples control plane from the forwarding plane. Even though the control plane is assumed to be logically centralized, multiple physical controllers are essential to handle the issues such as fault tolerance and load balancing, especially in wireless networks. However, the physical constraints restrict the control plane to have a global network view among the controllers, which leads to the generation of inconsistent flowrules and, thereby, a flow-deadlock. In this paper, we identify the inconsistencies resulting from controller mismatch in a flow-path and resolve them using packet in relay mechanism through eastwest interface. We modify Optimized Link State Routing (OLSR) protocol to advertise the switch information to controllers. The performance of our scheme is tested using a wireless mesh network test-bed consisting of static and mobile nodes. The results show that our scheme provides delivery ratio greater than 0.8 in the presence of network view inconsistencies at the controller nodes, with a slight increase in controller response time.