Failure protected shortest paths in GMPLS networks

A link, which is protected at a lower layer, appears as perfectly reliable at an upper layer. In this case global path protection does not require that the active and backup path to be strictly link-disjoint. These paths need only to be failure-disjoint, that is they can share resilient links. Moreover, the distribution of Shared Risk Link Group (SRLG) information allows the calculation of two SRLG failure-disjoint paths. Sometimes it is not possible to obtain a pair of paths that is fully disjoint. In this case one may accept a pair of paths which are maximally SRLG-disjoint. In this work two algorithms for solving the min-min SRLG failure-disjoint routing problem, which are based on two already known algorithms for SRLG diverse routing, are presented. They calculate pairs of paths, which may share links that are protected at lower layers, but are SRLG-disjoint in the remaining unprotected links. A modified version of each of those algorithms is also proposed for solving the maximally SRLG-disjoint path problem in a network with protected links. These algorithms can be applied in the context of resilient routing in GMPLS networks. Experimental results, using a reference network, show the effectiveness of the algorithms.