A recent study characterizing failures in computer networks shows that transient single element (node link) failures are the dominant failures in large communication networks like the Internet. Thus, having the routing paths globally recomputed on a failure does not pay off since the failed element recovers fairly quickly, and the recomputed routing paths need to be discarded. In this paper, we present the first distributed algorithm that computes the alternate paths required by some "proactive recovery schemes" for handling transient failures. Our algorithm computes paths that avoid a failed node, and provides an alternate path to a particular destination from an upstream neighbor of the failed node. With minor modifications, we can have the algorithm compute alternate paths that avoid a failed link as well. To the best of our knowledge all previous algorithms proposed for computing alternate paths are centralized, and need complete information of the network graph as input to the algorithm.
@cite_12: As the Internet becomes the critical information infrastructure for both personal and business applications, survivable routing protocols need to be designed that maintain the performance of those services in the presence of failures. This paper examines the survivability of interdoamin routing protocols in the presence of routing failure events, and provides a backup route aware routing protocol that performs non-stop routing in the presence of failures. We demonstrate through simulation its effectiveness in preventing packet losses during transient routing failures.
Wang and Gao's Backup Route Aware Protocol (BRAP) @cite_12 also uses some precomputed backup routes in order to handle transient single link failures. One problem central to their solution asks for the availability of reverse paths at each node. However, they do not discuss the computation of these reverse paths. As we discuss later, the alternate paths that our algorithm computes qualify as the reverse paths required by the BRAP protocol of @cite_12 .