The Shared Risk Link Group (SRLG) concept introduced in [IPO-FRM] and extended in [CCAMP-SRG] is considered as one of the most important criteria concerning the constraint-based path computation of optical channel routes. By applying the SRLG disjointness criteria to the constraint-based path computation, one can select a route taking into account both resource and logical structure disjointness. That implies a lower probability of simultaneous optical channel failure.
This document describes the various physical and logical resource types considered in the SRLG concept. The proposed method focuses on the inference of SRLG information between the network physical and logical layers. 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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