AR2C2: Actively replicated controllers for SDN resilient control plane

Software Defined Networking (SDN) is a promising architectural approach based on a programmatic separation of the control and data planes. For high availability purposes, logically centralized SDN controllers follow a distributed implementation. While controller role features in the OpenFlow protocol allow switches to communicate with multiple controllers, these mechanisms alone are not sufficient to guarantee a resilient control plane, leaving the actual implementation as open challenge for SDN designers. This paper explores OpenFlow roles for the design of resilient SDN control plane and proposes AR2C2 as an actively replicated multi-controller strategy. As proof of concept, AR2C2 is implemented based on the Ryu controller and relying on OpenReplica to ensure consistent state among the distributed controllers. Our prototype is experimentally evaluated using real commodity switches and Mininet emulated environment. Results of the measured times to recover from failures for different workloads shed some light on the practical trade-offs on replication overhead and latency as a step forward towards SDN resiliency.