Basic Specification for IP Fast-Reroute: Loop-free Alternates
This document describes the use of loop-free alternates to provide local protection for unicast traffic in pure IP and MPLS/LDP networks in the event of a single failure, whether link, node or shared risk link group (SRLG). The goal of this technology is to reduce the micro-looping and packet loss that happens while routers converge after a topology change due to a failure. Rapid failure repair is achieved through use of precalculated backup next-hops that are loop- free and safe to use until the distributed network convergence process completes.