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Failure resilience is one of the desired features of the Internet. Most of the traditional restoration architectures are based on single-failure assumption which is unrealistic. Multiple link failure models, in the form of shared-risk link groups (SRLG's) and shared risk node groups (SRNG's) are becoming critical in survivable optical network design. We classify both these form of failures under a common heading of shared-risk resource groups (SRRG) failures. In our research, we propose graph transformation techniques for tolerating multiple failures arising out of shared resource group (SRRG) failures. Diverse routing in such multi-failure scenario essentially necessitates finding out two paths between a source and a destination that are SRRG disjoint. The generalized diverse routing problem has been proved to be NP-complete. The proposed transformation techniques however provide a polynomial time solution for certain restrictive failure sets. We study how restorability can be achieved for dependent or shared risk link failures and multiple node failures and prove the validity of our approach for different network scenarios.
Date of Conference: 25-29 Oct. 2004