<title>New methods for more effective use of bandwidth in MPLS networks with fast rerouting</title>

Abstract

Multi-protocol label switching (MPLS) technology is useful for IP Virtual Private Networks (IP-VPNs), guaranteeing bandwidth in IP (Internet Procotol) networks, and carrying out traffic engineering with explicit routing. The advantage of MPLS is its high capability to achieve of reliable networks when used with Fast Rerouting. However, Fast Rerouting requires a lot of network resources. This is because, for the rapid recovery of end-to-end communications after dtectoin of failures, secondary LSPs must already have been reserved as detours in case there are failures on primary node-of-node links. The sharing of bandwith among secondary LSPs is thus significant as a way of reducing the usage of network resources when Fast Rerouting is applied.In this paper, we propose a new routing algorithm in which bandwidth is shared among the secondary LSPs for multiple primary LSPs. This algorithm produces efficient network-level LSP designs. Three approaches to the dynamical changing of Open Shortest Path First (OSPF) link-cost metrics are applied in the algorithm. Each approach improves efficiency in the sharing of LSPs. The approaches are (1) the broader distribution of primary LSPs to reduce the need for detours in cases of single failures, (2) the concentration of secondary LSPs on links to increase the possibilities for bandwidth sharing, and (3) the distribution of secondary LSPs that cater to a certain failure, thus increasing the numbers of detouring LSPs which are independent of each other on the respective links. The scheme provides a slight improvement over the results of the conventional Dijkstra-algorithm calculation which is used in conventional OSPF. The proposed algorithms are applied with various network models that have been proposed in IETF Internet drafts, e.g., Haskin, to egress, and Next-Next-Hop; the results are evaluated on the basis of parameters that indicate the consumption of network resources, including the numbers of labels per node, usage of the network's bandwidth capacity, and round-trip times for the secondary LSPs. Application of algorithm (1) led to a 10% lower total LSP cost of the network than the result for the conventional form of bandwidth sharing, i.e., for sharing among the secondary LSPs of a single primary LSP.