Dynamic Multicasting in WDM Optical Unicast Networks for Bandwidth-Intensive Applications

Traditionally in wavelength division multiplexed (WDM) networks, multicasting is accomplished by splitting the signals all-optically, thereby establishing a tree of lightpaths (light-tree) from the source to every destination. To provision for this functionality in a Multicast-Incapable environment, in which the switches are not capable of directing an incoming signal to more than one output interface, one must implement a logical multicast overlay to the underlying optical layer. A naive method of accomplishing this is by creating a set of unicast lightpaths from the source to each destination of the multicast request. However, for large multicast groups, this leads to a poor utilization of the network resources. To alleviate this problem, we present two multicast Steiner tree overlay alternatives: Multicast with Drop At Member Node (DAMN), in which a lightpath may only terminate at member nodes of the multicast request, and Multicast with Drop At Any Node (DAAN), in which lightpaths may terminate at any node in the physical topology. We consider a dynamic traffic model, and propose efficient heuristics to solve the DAMN and DAAN problems with a goal of minimizing the total number of wavelengths required to satisfy the request. Moreover, we present a simple heuristic to approximate the baseline unicast approach (naive method). Our results demonstrate that at various loads, both the DAMN and DAAN reduce wavelength consumption by 42 - 60% over the naive unicast approach in realistic networks.