TCAM-aware Local Rerouting for Fast and Efficient Failure Recovery in Software Defined Networks

In Software Defined Networks (SDNs), a reactive approach for failure recovery involves the centralized SDN controller which incurs long delay leading to packet losses. While a proactive approach enables fast failure recovery, it poses a new challenge concerning the number of additional forwarding rules required at every switch traversed by a flow on the primary and backup paths. These forwarding rules are stored in Ternary Content Addressable Memory (TCAM) which is limited in size and can hold only a few thousands of rules at a switch since it is expensive and power hungry. In this paper, we develop and analyze two proactive local rerouting algorithms namely Forward Local Rerouting (FLR) and Backward Local Rerouting (BLR) to compute backup paths for a primary path. By rerouting the failed traffic from the point of failure, local rerouting enables fast recovery. The proposed FLR and BLR algorithms choose backup paths so as to reduce the number of forwarding table entries with improved sharing of forwarding rules at the switches along the primary and backup paths. We evaluate the proposed algorithms through simulations on different topologies. The results show that the proposed algorithms reduce the average number of additional rules required to protect a flow by up to 75% compared to the existing approaches which do not take into account the limited size of TCAM. The results also show that the proposed algorithms are effective in terms of backup bandwidth sharing efficiency.