WDM optical networks are widely viewed as the most appropriate choice for the future Internet backbone with the potential to fulfill the ever-growing demands for bandwidth. A failure in a network such as a cable cut may result in a tremendous loss of data. Therefore, network survivability, the ability for a network to continue to provide services in the event of failures, is a very important issue in WDM optical networks. This chapter introduces the principles and state-of-the-art of survivability provisioning in optical networks, in particular, in optical networks that employ wavelength division multiplexing (WDM). Concepts of survivability provisioning in optical networks such as protection and restoration, dedicated versus shared survivability, path-based, link-based, segment-based, cycle-based survivability, and so on, are covered to provide multiple classes of quality of protection against single failure, dual-failure, multiple simultaneous failures, or shared risk link group failures, in WDM mesh networks. Recent developments in survivable service provisioning are summarized, such as survivability provisioning that takes into account the connection holding-time, survivability in WDM light-trail networks and optical burst switched networks. Finally, the chapter briefly examines future research directions.
On double-link failure recovery in WDM optical networks