The Shared Risk Link Group (SRLG) concept introduced in [IPO-Frame] is considered as one of the most important criteria concerning the constrained-based path computation of optical channel routes. By applying the SRLG criteria to the constrained-based path computation, one can select a route taking into account physical resource and logical structure disjointness that implies a lower probability of simultaneous lightpath failure. This contribution describes the various physical and logical resource types considered in the SRLG concept. The proposed model focuses on the inference of SRLG information between the network physical layers as well as logical structures such as geographical locations. The main applications of the proposed model are the related Constraint-based Shortest Path First (CSPF) algorithm for optical channel path computation and the reduction of the SRLG information flooded through traffic engineering extensions of the IGP routing protocols (such as OSPF and IS-IS).
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