Local recovery solutions from multi-link failures in MPLS-TE networks with probable failure patterns

MPLS-TE (traffic engineering) fast reroute proposes a local protection mechanism to reroute protected TE LSPs (label switched paths) quickly onto precomputed and signaled bypass tunnels. The paper explores the case of multiple network element failure scenarios. The undesired complexity inherent in the multiple failure scenario originates from the fact that those failure scenarios are more disruptive, and may require multiple bypass tunnels to cope with them. The paper adapts the MPLS local recovery schemes to multi-failure scenarios, while controlling the number of bypass tunnels that are required. This is achieved by mapping multi-failure scenarios onto probable failure patterns (PFPs). PFPs are characterized by their probability (or frequency) of occurrence during the network lifetime. A number of bypass tunnels is then computed to cope effectively with the PFPs according to their frequency or probability of occurrence. It is shown that by properly choosing how the PFPs are grouped, and how the corresponding bypass tunnels are computed, it is possible to trade the required number of bypass tunnels for their average length and outage probability, i.e., the probability that the local recovery scheme cannot cope with the occurrence of a multi-failure pattern.