An efficient algorithm for virtual topology reconfiguration in WDM optical ring networks

Wavelength-division multiplexed (WDM) networks using wavelength routing are emerging to be the right choice for the future transport networks. In a WDM-based transport network, the optical layer provides circuit-switched lightpath services to the client layer such as IP, SONET, and ATM. The set of lightpaths in the optical layer de fines the virtual topology. Since the optical switches (cross-connects) are reconfigurable, the virtual topology can be reconfigured in accordance with the changing traffic demand pattern at the client layer in order to optimize the network performance. On the other hand, changing the virtual topology can be disruptive to the network since the traffic at each node must be buffered or re-routed while the topology is being reconfigured. In this paper, we develop a reconfiguration algorithm to reduce the cost of virtual topology reconfiguration in WDM optical ring networks. The algorithm is based on the concept of splitting and merging existing lightpaths, together with cost-benefit analysis to reduce the network reconfiguration cost. Our objective is to reduce the number of lightpaths that need to be reconfigured, while ensuring that the network congestion is low. The performance of the algorithm is verified through simulation experiments.