Secondary Controller Mapping for Reliable Control Traffic Forwarding in SDN

In SDN, to enable resilience each switch can be mapped to multiple controllers (e.g., primary, secondary) and distribute the control traffic among them. The SDN controllers for each switch need to be chosen in a manner that does not compromise on network response time, while taking controller reliability into consideration. Given the switch-primary controller mapping, the objective of our work is to find an optimal switch-secondary controller mapping and control traffic distribution such that the reliability of mapped controllers is maximized. We mathematically model controller reliability, formulate and solve the optimization problem with the above objective. We implement a switch-controller mapping approach in SDN, wherein we map each switch to two active controllers and distribute the flow-setup requests (control traffic) between them. We implement our approach using Floodlight controllers and Mininet, and show that it improves reliability of mapping and achieves better recovery time upon controller failure by up to 27.3% as compared to the traditional master-slave setup.