Cost-effective implementation of multicasting in wavelength-routed networks

Multicasting in the optical domain has been recently shown to provide subst antial savings in terms of the network-wide average packet hop distance and the total number of transceivers in the network, Current proposed multicas ting architectures [e.g., Splitter-and-Delivery (SaD)] employ power splitti ng mechanisms which have the side effect of high fabrication cost due to th e large number of splitters and the need for optical amplifiers. We propose a low-cost novel architecture called Tap-and-Continue (TaC) for realizing multicasting, This architecture provides a natural evolution from current u nicast cross-connects and is based on tapping devices. We prove that any mu lticasting session can be feasibly realized in networks employing only TaC cross-connects, and the problem of finding the optimal multiple-destination minimum cost trail in such networks is NP-complete, Therefore, we develop a 4-approximation algorithm for multiple-destination routing. Simulation re sults demonstrate that the TaC cross-connect provides a realistic, cost-eff ective approach for implementing multicasting with negligible blocking degr adation especially in multifiber networks.