A dynamic backup reservation scheme for wavelength assignment in WSONs

For the Destination Initialed Reservation (DIR) in Wavelength Switched Optical Networks (WSONs) using the distributed wavelength assignment scheme, the establishment of a lightpath might be blocked because of the contention for the same lambda between two or more concurrent requests traversing the same links, although there might be enough available lambda resource. In order to reduce the blocking caused by contention, a Dynamic Backup-reservation-based Wavelength Assignment (DBWA) scheme has been proposed in this paper. Considering that it is not an advisable way to reserve additional wavelength when the resource is lacking and that a lightpath with more physical hops has the higher probability to collide with others, a threshold which refers to the number of available lambdas and the physical hops for a lightpath, is defined to decide whether to reserve a backup wavelength or not. Simulation results show that, by setting a proper value for the threshold, DBWA can reduce the blockings caused by contention efficiently thus performs much better in total blocking probability than the two traditional schemes.