Decentralized local backup LSP calculation with efficient bandwidth sharing

The protection of virtual circuits (label switched paths, LSPs) in (G)MPLS (generalized multi-protocol label switching) networks is discussed. The proposed algorithm is designed to protect traffic with strong delay requirements such as EF (expedited forwarding) ordered aggregates in a DiffServ domain. For this type of application end-to-end recovery schemes are usually considered to be far too slow. Local, fast-rerouting is the only solution which can compete with restoration times offered by SONET self-healing ring. However local restoration has a cost in terms of extra bandwidth consumed for the backup paths. The scheme thus includes a sophisticated resource aggregation mechanism based on the concepts of backup-backup aggregation and backup-primary aggregation. The path selection algorithm is also designed to efficiently reduce the resource usage. Moreover, when considering LSPs at different preemption levels, the proposed algorithm is able to correctly calculate the amount of bandwidth that can be preempted despite the sharing of resource. It was shown that the approach, though local, could compete with the state-of-the-art end-to-end recovery schemes in terms of resource reservation. The major contribution of the scheme, the backup-primary aggregation, was then also used in the context of end-to-end recovery and improved its performance substantially.