High-Performance Optical Local and Metropolitan Area Networks: Enhancements of FDDI and IEEE 802.6 DQDB.

The Fiber Distributed Data Interface (FDDI) and the IEEE 802. 6 Distributed Queueing Dual Bus (DQDB) are emerging standards for high-speed (45 - 150 Mb/s) local and metropolitan area networks. In this memorandum, we describe several ways to build on these emerging standards to significantly increase the achievable throughput and lower the end-to-end delay. Without increasing the number of transceivers or their rate, substantial throughput increases are obtained by a highly-concurrent logical interconnection pattern of user nodes, and the end- to-end delay is decreased by the use of more efficient media- access techniques. The most promising architecture is a multi- connected ring having only two transmitters and two receivers per node, where each node needs to handle or process only a small fraction of the network traffic. In one example, we describe a 24-node, distributed, packet-switched network, with only two 100 Mb/s transmitters and two 100 Mb/s receivers per node, that has a throughput of 1.5 Gb/s - fifteen times the 100 Mb/s throughput of FDDI. Such a system has the potential to be a follow-on standard to FDDI (or IEEE 802.6) or to provide an AT&T-proprietary high-performance LAN/MAN that can interwork with standard systems.