Best Effort Shared Risk Link Group (SRLG) Failure Protection in WDM Networks

With the increase of size and number of shared risk link groups (SRLGs), capacity efficiency of shared-path protection becomes much poorer due to SRLG-disjoint constraints and blocking probability becomes much higher due to severe traps. As a result, 100% SRLG failure protection is no longer a practical protection scheme. To solve this problem, we present a new protection scheme called best effort SRLG failure protection, in which we try to provide SRLG-disjoint backup path by choosing the backup path sharing the least number of SRLGs with the working path, so as to make the impact of SRLG failures as low as possible and accept as many as possible connection requests. 100% SRLG failure protection becomes a special case of best effort SRLG failure protection when the working path and backup path share zero SRLG. We propose a heuristic to find the best effort SRLG-disjoint backup path under dynamic traffic. The best effort SRLG failure protection scheme tries to make a trade-off between blocking probability and survivability. Analytical and simulation results show, compared with 100% SRLG failure protection, the proposed scheme offers much better capacity efficiency and much lower blocking probability while keeping survivability as high as possible.