Toward Improved Path Programmability Recovery for Software-Defined WANs under Multiple Controller Failures

Enabling path programmability is an essential feature of Software-Defined Networking (SDN). During controller failures in Software-Defined Wide Area Networks (SD-WANs), a resilient design should maintain path programmability for offline flows, which were controlled by the failed controllers. Existing solutions can only partially recover the path programmability rooted in two problems: 1) the implicit preferable recovering flows with long paths and 2) the sub-optimal remapping strategy in the coarse-grained switch level. In this paper, we propose ProgrammabilityGuardian to recover the path programmability of offline flows while maintaining low communication overhead. These goals are achieved through the fine-grained flow-level mappings enabled by existing SDN techniques. ProgrammabilityGuardian configures the flow-controller mappings to recover offline flows with a similar path programmability, maximize the total programmability of the offline flows, and minimize the total communication overhead for controlling these recovered flows. Simulation results of different controller failure scenarios under two different topologies show that ProgrammabilityGuardian recovers offline flows with a balanced path programmability, improves the total programmability of the recovered flows up to 68% and 70%, and reduces the communication overhead by 96% and 99%, compared with the baseline algorithm.