Hybrid topology for multicast support in constrained WDM networks

Supporting multicast at WDM layer is an important requirement for high bandwidth multicast applications emerging in IP over WDM optical networks. Light-splitting technique has been proposed to provide light-trees, i.e., multicast trees in an optical layer. Many recent studies have been focused to efficiently build and configure light-trees without existing light-paths for unicast traffic into consideration. In this paper we identify and explore the optimal design problem of multicast configuration for realistic and constrained WDM networks. In such a network, both unicast and multicast are supported, and WDM switches have limited light splitting capability. Using wavelength sharing among traffic demands of unicast and multicast, we build a hybrid virtual topology which exploits both light-trees and light-paths. By optimizing WDM resources in addition to resource sharing with unicast, we truly maximize the WDM layer capability and efficiently support multicast traffic demands. We validate the efficiency of our approach with extensive simulations.