Sub-graph routing: A generalized fault-tolerant strategy for link failures in WDM optical networks

Single- and multiple-link failure resilience are of critical importance in survivable wavelength division multiplexed (WDM) optical network design. Networks are not made up simply of logical links, but also of links that are physically routed together or share a common node. Links that share a common physical duct are known in literature as shared risk link groups (SRLGs), and their impact on network design is widely studied.This paper presents a complete survivability approach for WDM optical network design known as sub-graph fault tolerance. Sub-graphs are created by removing any combination of components in the network to accommodate specific fault scenarios. Connections in the network are accepted if they can be routed in all predetermined sub-graphs. In this manner, protection against 100% of all multiple- and single-link failure scenarios designated by the designer is achieved, and heuristic best-effort protection is provided against subsequent or simultaneous link failures for which the network is not specifically designed.