Jean Philippe Vasseur

Local Detection and Recovery from Multi-Failure Patterns in MPLS-TE Networks

MPLS Fast Reroute advocates local protection mechanisms to rapidly reroute traffic onto pre-computed and signaled bypass tunnels. When the network is subject to multiple element failures, it becomes challenging to handle all the possible failure scenarios, for they are more disruptive and may require many more bypass tunnels to be dealt with. The objective of this paper is to adapt the MPLS local recovery schemes to deal with multi-failure scenarios, while retaining as much as possible the simplicity and the fast failure detection feature of current (single failure) local recovery mechanisms. This objective is achieved by optimally grouping failure patterns into clusters and minimizing the overall additional network resources - i.e., bypass tunnels and bidirectional forwarding detection sessions - while yielding full recovery from such failure patterns.

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.