Patent ID: 7733786

Claim:
A computer implemented method for performing a constrained shortest path first (CSPF) computation of a label switched path (LSP) from a first network element in a Multiprotocol Label Switching (MPLS) network acting as a source of the LSP to a second network element in the MPLS network acting as a destination of the LSP based on one or more traffic engineering constraints, wherein the MPLS network includes a plurality of other network elements acting as intermediaries between the source and the destination providing a plurality of paths between the source and destination, comprising: storing a representation of the MPLS network's topology including a set of one or more link characteristics for each link in the MPLS network in a traffic engineering data structure, wherein each link connects two of the network elements; receiving a first request to compute the LSP, the request including a set of one or more links to be excluded from the LSP; setting an exclusion bit for each link that is to be excluded; during calculation of the first request, for each network element that is not the destination, determining whether the exclusion bit is set for the link to each neighboring network element, and disregarding each link from the calculation whose corresponding exclusion bit is set; receiving a second request to re-optimize bandwidth of the LSP, the second request including a minimum bandwidth constraint; for each of the links of the LSP, setting a re-optimization bit, and storing a value of allocated bandwidth for the link; and during calculation of the second request, for each network element that is not the destination, determining whether the re-optimization bit is set for the link to each neighboring network element, and if the re-optimization bit is set, adding the value of allocated bandwidth of the link to the link's current available bandwidth to form a re-optimization comparison value, and comparing the re-optimization comparison value with the minimum bandwidth constraint.