Supporting Multipoint Connections in Multi-Hop WDM Optical Networks

It is widely recognized that the multi-hop strategy is the preferred scheme in WDM networks employing slow tuning optical transmitters (and/or receivers) and having relatively static traffic matrices. The essential idea is to tune the transmitters and/or receivers in the network so that an optimal configuration, which minimizes the number of hops that most of the traffic needs to make, is obtained. Earlier work in this area has concentrated on “skewed” traffic matrices consisting of point-to-point connections. We show that the problem is different when multipoint traffic, which is becoming increasingly important, is introduced. We present a heuristic algorithm for the optimal placement of nodes to satisfy traffic matrices that have multipoint connections. Two logical topologies, the bidirectional linear chain and the bidirectional ring, are the target topologies considered. They are evaluated with respect to three traffic models based on fixed, uniform, and geometric distribution of the number of destinations. Monte-Carlo simulation results for this algorithm are obtained for a large number of connections and are compared with the performance of the random placement algorithm. For the latter case, both simulation and analytical results, based on the theory of order statistics, are shown. The results demonstrate that the algorithm leads to substantial savings for node placement in both topologies.