Congestion-aware local reroute for fast failure recovery in software-defined networks

Although a restoration approach derives a reroute path when failure occurs and greatly reduces forwarding rules in switches compared with a protection approach, software-defined networks (SDNs) induce a long failure recovery process because of frequent flow operations between the SDN controller and switches. Accordingly, it is indispensable to design a new resilience approach to balance failure recovery time and forwarding rule occupation. To this end, we leverage flexible flow aggregation in fast reroute to solve this problem. In the proposed approach, each disrupted traffic flow is reassigned to a local reroute path for the purpose of congestion avoidance. Thus, all traffic flows assigned to the same local reroute path are aggregated into a new 'big' flow, and the number of reconfigured forwarding rules in the restoration process is greatly reduced. We first formulate this problem as an integer linear programming model, then design an efficient heuristic named the 'congestion-aware local fast reroute' (CALFR). Extensive emulation results show that CALFR enables fast recovery while avoiding link congestion in the post-recovery network.