Sub-graph routing : a novel fault-tolerant architecture for shared-risk link group failures in WDM optical networks

Failure resilience is one the desired features of the Internet. Multiple link failure models, in the form of shared-risk link group (SRLG) failures, are becoming critical in survivable optical network design. Most of the traditional restoration schemes are based on the single-failure assumption which is unrealistic. In our research, we propose a novel survivability approach that can tolerate multiple failures arising out of SRLG situations. Each network has a set of sub-graphs that can be created by removing each of the links in the network and, in addition, removing all of the links of a SRLG. Connections in the newly proposed strategy are accepted if they can be routed in all the sub-graphs, and are protected against all single link and SRLG failures. We also study how restorability can be achieved for node failures and analyze the performance of our approaches for different network topologies. Our proposed restoration architecture requires the storage of network state information corresponding to each of the possible failure scenarios defined by the subgraphs. This restoration model is novel and can be implemented in current WDM backbone networks.