Reliable Routing in MPLS Networks

Explicit routing and the pre-allocation of network resources are essential to achieve absolute end-to-end QoS guarantees in networks. MPLS (MultProtocol Label Switching) provides a good platform to implement explicit routing and also supports pre-establishment of multiple explicit routes for a source-destination pair. We show that MPLS can achieve reliable explicit routing, by deploying maximally-disjoint, precalculated alternate paths. To obtain the appropriate alternate paths, common edges shared among paths have to be considered, as well as path lengths (end-to-end delays), during path calculations. Three alternate path-finding algorithms have been developed for this purpose. Simulation results show that our alternate path-finding algorithms are effective in improving reliability of explicit routing. In addition, all calculated paths respect QoS latency constraints. Finally, we note that switching to a precalculated alternate path is much faster than determining a new path (e.g. by executing a shortest path algorithm), so failure recovery time is much improved.