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 constraint criteria to the constrained-based path computation, one can select a route taking into account 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 related to the Constraint-based Shortest Path First (CSPF) algorithm for optical channel route computation and the aggregation of the SRLG information flooded throughout traffic engineering extensions of the IGP routing protocols (such as OSPF and IS-IS).
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