Protocols for rapid restoration in WDM optical networks

Wavelength division multiplexing (WDM) networks have become a viable solution to meet the increasing bandwidth demand. These networks carry messages in the optical domain at data rates of several gigabits per second. Such high data rates make it necessary for using efficient restoration protocols in an event of a failure. This paper addresses the issue of dynamic path-based restoration in WDM optical networks. Dynamic restoration protocols can be used for restoring unprotected paths, that is, paths that do not reserve backup paths in advance. Our objective is to develop protocols that ensure rapid recovery while keeping the restoration ratio high. We develop two distributed dynamic restoration protocols called disjoint path-wavelength grouping (PWG) protocol and disjoint weighted PWG protocol. Those protocols group all the candidate backup paths of the failed paths into path-disjoint groups before assigning wavelengths to them. This allows the failed paths to search different sets of wavelengths on various candidate backup paths in parallel without any reservation conflicts. Also, it does not require any reservation retries, thus resulting in rapid restoration. The grouping method attempts to restore increased number of failed paths by allowing increased number of wavelengths to be searched on a path. We also consider the problem of prioritizing the paths where high-priority paths have better chances of recovery than the low-priority paths. The effectiveness of the proposed protocols is verified through extensive simulation results.