On-demand optimization of label switched paths in MPLS networks

Multiprotocol Label Switching (MPLS) technology provides efficient means for controlling the traffic of IP backbone networks and thus, offers performance superior to that of traditional Interior Gateway Protocol (IGP) based packet forwarding. However, computation of explicit paths yielding optimal network performance is a difficult task; several different strategies can be thought of. In this paper we propose a novel approach for the optimal routing of new label switched paths (LSPs). Our method is based on the idea that we allow the re-routing of an already established LSP when there is no other way to route the new one. Our optimization algorithm is based on an Integer Linear Programming (ILP) formulation of the problem. We show by numerical evaluation that our method significantly improves the success probability of setting up new LSPs by extending the widely known Constrained Shortest Path First (CSPF) algorithm with the ILP-based re-routing function. Although the task itself is NP-hard, our heuristic method provides efficient solution in practical cases. The proposed algorithm is aimed to be implemented primarily in a network operation center. However, with the restriction that only LSPs starting from the optimizing Label Edge Routers can be rerouted, the algorithm can be implemented directly in edge routers themselves in a distributed fashion.