Using Multiple Topologies for IP-only Protection Against Network Failures: A Routing Performance Perspective

IP networks have to carry increasingly more mission critical traffic where outages even of very short duration are undesirable or in some cases unacceptable. Traffic disruptions occur when the topology of the network changes either due to failures or reconfiguration. In connectionless networks current methods for protecting traffic from network failures rely on tunneling mechanisms for directing traffic around the failed resources and forwarding it to its destination avoiding loops. Recently, IP-only traffic recovery has been explored to avoid the high configuration complexity of the explicit tunneling approaches. In this work we present mechanisms for achieving recovery from failures of a single link or node using only IP forwarding mechanisms and an emerging feature of intra-domain routing, multi-topology forwarding. Using the multi-topology approach we build a small number of recovery topologies that are used to route traffic when failures occur. Through detailed and realistic performance evaluation we show that the multi-topology based approach has low computational, storage and forwarding overhead. In particular we focus on how traffic is routed after a failure and we present a heuristic method for optimizing the routing performance of multi-topology recovery. We show that this approach outperforms other IP based recovery methods and its performance can be close to that of an unrealistic optimal failure routing policy as well as to that of a computationally expensive brute force approach which explicitly optimizes the link weights of each recovery topology.