IP/LDP Local Protection
Avici Systems
This document defines an architecture and selection process for providing local protection for IP unicast and/or LDP traffic in the event of a single link or node failure until the router has converged. When computing the primary next-hop for a prefix, a router S also determines an alternate next-hop which can be used if the primary next-hop fails. The alternate can be either a loop-free alternate, which goes to a neighbor whose shortest path to the prefix does not go back through the router S, or a U-turn alternate, which goes to a neighbor whose primary next-hop to the prefix is the router S, and which has itself a loop-free node-protecting alternate, which thus does not go through router S to reach the destination prefix.