A new hybrid rerouting scheme in WDM all-optical networks under dynamic traffic

In WDM all-optical networks, the wavelength continuity constraint along with the wavelength clash constraint, lead to poorer network performances when dealing with the lightpath provisioning problem. The impact of these constraints is especially severe when traffic demands are unpredictable and characterized by random arrivals and departures. To improve the network utilization efficiency, either wavelength conversion or lightpath rerouting can be used. Since, in the foreseeable future, wavelength conversion is expected to remain an expensive technology, traffic rerouting is an attractive alternative solution to improve the network throughput conditioned by the aforementioned constraints. In this paper we propose to employ hybrid rerouting, to improve the network utilization efficiency considering a dynamic traffic model. Hybrid lightpath rerouting combines passive rerouting and active rerouting. Our proposed algorithm, namely, Sequential Routing with Hybrid Lightpath Rerouting algorithm (SeqRwHLR) establishes the traffic demands sequentially, that is demand by demand at arrival dates. When an incoming traffic demand cannot be set up in the absence of path-free wavelengths between its source and destination nodes, the SeqRwHLR algorithm performs passive rerouting procedure aiming hopefully at freeing a path-free wavelength to service the new traffic demand. Furthermore, our proposed algorithm dynamically reroutes some already established lightpaths from longer paths to vacant shorter ones so as to reduce the network resources consumption. This should hopefully lead to a better performances. The performances of the proposed algorithm are demonstrated to be promising through simulation results.