Multicast traffic in multi-hop lightwave networks: performance analysis and an argument for channel sharing

A local lightwave network can be constructed by employing two-way fibers to connect nodes in a passive-star physical topology, and the available optical bandwidth may be effectively accessed by the nodal transmitters and receivers at electronic rates using wavelength division multiplexing (WDM). The number of channels, w, in a WDM network is limited by technology and is usually less than the number of nodes, N, in the network. Channel sharing, achievable via time-division-multiplexing, may be used to construct practical multi-hop networks under this limitation. Multicasting-the ability to transmit information from a single source node to multiple destination nodes-is becoming an important requirement in high-performance networks. Multicasting, if improperly implemented, can be bandwidth-abusive. Channel sharing is one approach towards efficient management of multicast traffic. We develop a general modeling procedure for the analysis of both unicast (point-to-point) and multicast (point-to-multipoint) traffic in shared-channel, multi-hop WDM networks. The analysis is comprehensive in that it considers all components of delay that packets in the network experience-namely, synchronization, queueing, transmission, and propagation. The results show that, in the presence of multicast traffic, WDM networks with w<N channels may actually perform better than if w=N channels are used