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Pre-Compute an Alternate To be used in event of a single failure to protect IP and/or LDP traffic until SPF has converged. Idea of IGP Fast-Reroute discussed previously IETF Routing Area Meeting Nov 2003 Cengiz Alaettinoglu & Alex Zinin Expired draft (draft-kini-traf-restore-nsp-00.txt ) R5 R2 R3 R6 R1 Time3 R4 10 10 2 1 1 1 2 2 Non-Primary neighbor N is loop-free with regard to a source S and a destination D if D!S(N,D) = Dopt(N,D) < Dopt(N,S) + Dopt(S,D) Safe and Simple local decision but insufficient Loop-Free alternatives in real networks Multiple links to primary neighbor give alternate to primary neighbor (no node protection) |