Optimum Rooted Trees for Failover in Switched Networks

Loop-avoidance is essential in switched networks to avoid indefinite looping of broadcast traffic. Traditionally, spanning trees or Dijkstra trees are constructed to provide logical loop free forwarding paths on the physically meshed network to overcome this problem. Spanning tree based protocols construct a tree from a single root and incur high convergence latency on root switch failure. Dijkstra tree based protocols construct a tree from every switches and incur high operational overhead. Given the probability of simultaneous multiple switch failures is very low, we propose an approach that allows an administrator to predesignate an optimum number of roots. The advantage of this approach - the high convergence latency experienced with Spanning tree protocols and the high operational overhead and complexity of Dijkstra tree based protocols both are avoided. The new approach based on Meshed Tree Bridging provides a novel loop-avoidance system that reconverges networks quickly with very low downtime in the event of root switch failure. This is demonstrated on the Global Environment for Network Innovations (GENI) testbed against Rapid Spanning Tree Protocol - an industry accepted standard for loop-avoidance.