Fast Failover with Hierarchical Disjoint Paths in SDN

When a link failure occurs in Software Defined Networking, a typical response is from controller's intervention once the Link Failure Event is triggered. Then the controller usually recalculates the possible alternative route and sets new flow rules on the affected SDN switches. However, the latency could lead to packet drop, if the route is not restored in time. Here, we propose a new method that utilizes the fast failover mechanism of group table to simulate distributed depth-first-search (DFS) with SDN switches without the intervention of controller after the related rules are installed. Based on Menger's Theorem, we can find a set of disjoint backup routes, if the topology possesses enough connectivity. With the backup routes, the controller can set up fast failover group tables with buckets watching the links appearing in the backup routes. We can properly arrange the order of the buckets in each switch, such that the switches together can simulate depth-first search for a backup route. According to our experiments, our method significantly reduces the communication between the SDN switch and the controller.