The fair distributed queue protocol for high speed networking

Abstract

Advances in fiber optic technology now allow networks to opeozate at transmission rates greater than one gigabit per second (1Gb/s). The increase in network perfonnance promises the potential for supporting applications that require high bandwidth, low latency and predictable performance. However, the benefits to the transfer of bits node-to-node are limited. Latencies inside the nodes in the form of pocessiog delays and access delays remain the two "bottlenecks" that restrict end-to-end performance. Here, we address the second bottleneck. We consider a very efficient protocol called Fair Distributed Queue (FDQ), suitable for very high speed networts over lang distances. It uses the fiber optic medium and utilizes the full channel capacity indepmdent of the network length, the transmission speed and the number of nodes. Hence, it offers the high bandwidth required by future networks. FDQ's topology and certain other features are related to DQDB. However, it does not suffer from the asymmetry problems usociated with DQDB. The DQDB protocol has recently been accepted as the IEEE 802.6 Standard for metropolitan area networks (MANs). The purpose of this sbort paper is to summarize some of the results from, especially regarding high bandwidth implementations. We show that FDQ has lower average delay results under Poisson load than both DQDB and DQDB with BWB. Also, its worst-case delay performance for messages (assuming messages require a multiple number of slots to be transmitted) is significantly better than DQDB with or without BWB. Thus, it meets low latency requirements in addition to high bandwidth. FDQ's scalability properties allow its total length to extend over 100 Ian and transmission rates well above 1 Gb/s. This eliminates the upward mobility problems faced by current network protocols, including DQDB.