Evaluation of communication protocols for star-coupled multidimensional WDM networks for multiprocessors

The relatively mature fiber optic technology, enhanced by the use of wavelength division multiplexing (WDM), provides a solution for surmounting the problems associated with copper based interconnections for multiprocessors as the CPU clock frequencies increase. In this paper we undertake a trace-driven simulation study of the performance of several fast channel access schemes for WDM channels that are appropriate for multi-dimensional interconnections for multiprocessors with thousands of nodes. We show that the protocols that employ tunable components cannot provide adequate performance unless the tuning times improve to 500 nanoseconds. The main conclusion of our study is that a simple WDM channel access protocol, called CLUSTER, based on the use of fixed-tuned optical transmitters and receivers, is the protocol of choice for building multidimensional WDM interconnections. The recent advent of single chip laser and receiver arrays for WDM links, employing fixed-tuned components, provides an added incentive for using the CLUSTER protocol for multidimensional WDM interconnections for multiprocessors.