A distributed LSP mechanism to reduce spare bandwidth in MPLS networks

Abstract

We propose a new label switched path (LSP) mechanism, called the distributed LSP (D-LSP) mechanism, for multiprotocol label switching (MPLS) networks. In the proposed D-LSP mechanism, traffic belonging to a forwarding equivalent class (FEC) is partitioned into several sub-classes and is distributed to the corresponding sub-LSPs, each of which is set up on a different node-disjoint route connecting the traffic source and destination node pair. To protect service, a D-LSP reserves the spare bandwidth of which the amount is equal to the amount of the working bandwidth of one sub-LSP and thus the total amount of spare bandwidth in a network can be reduced. The traffic partitioning of the D-LSP mechanism may decrease the statistical multiplexing gain obtained by aggregating IP packet flows into an LSP, as compared to that of the conventional MPLS networks. Sub-LSP and backup LSP assignment algorithms are proposed and the effect of D-LSP mechanism on the required amount of spare bandwidth is evaluated by numeric analysis and is compared with a conventional LSP mechanism. The results show that there is a trade-off between the reduction of spare bandwidth and the degradation of statistical multiplexing gain.