Dynamic Routing and Wavelength Assignment with Backward Reservation in Wavelength-routed Multifiber WDM Networks

In wavelength-routed WDM networks, blocking probability of lightpath establishments is generally high due to coarse granularity and wavelength continuity constraint. Therefore, blocking of lightpath establishments is one of crucial issues which must be resolved. Multifiber environments reduce blocking probability of lightpath establishments because each link consists of multiple fibers and multifiber links can be viewed as limited-range wavelength conversion. Blocking probability can be further reduced by an appropriate routing and wavelength assignment (RWA) scheme. This paper proposes a dynamic RWA scheme using signaling of backward reservation for wavelength-routed multifiber WDM networks. In the proposed scheme, information on link state is collected by signaling of backward reservation along multiple routes between a sender node and a receiver node whenever a new lightpath-setup request arrives. Then the proposed scheme selects a combination of a route and a wavelength at the receiver node based on the collected information in such a way that it avoids the generation of bottleneck links and the depletion of a specific wavelength. Through simulation experiments, we show that the proposed scheme efficiently reduces blocking probability of lightpath establishments in multifiber WDM networks.