A constrained multipath traffic engineering scheme for MPLS networks

A traffic engineering problem consists of setting up paths between the edge nodes of the network to meet traffic demands while optimizing the network performance. It is known that total traffic throughput in a network, hence the resource utilization, can be maximized if the traffic demand is split over multiple paths. However, the problem formulation and practical algorithms, which calculate the paths and the traffic split ratio taking the route constraints or policies into consideration, have not been much touched. This paper proposes practical algorithms that find near optimal paths satisfying the given traffic demand under constraints such as maximum hop count, and preferred or not-preferred node/link list. The mixed integer programming formulation also calculates the traffic split ratio for the multiple paths. The problems are solved with the split ratio of continuous or discrete values. However, the split ratio solved with discrete values (0.1, 0.2 etc.) are more suitable for easy implementation at the network nodes. The proposed algorithms are applied to the multiprotocol label switching (MPLS) that permits explicit path setup. The paths and split ratio are calculated off-line, and passed to MPLS edge routers for explicit label-switched path (LSP) setup. The proposed schemes are tested in a large-scale fictitious backbone network. The experiment results show that the proposed algorithms are fast and superior to the conventional shortest path algorithm in terms of maximum link utilization, total traffic volume, and number of required LSPs.