Bandwidth allocation in fair distributed queue (FDQ) networks

Fair distributed queue (FDQ) is a high speed metropolitan area network proposed by Kabatepe (1992). FDQ has fair throughput, and delay characteristics and is a highly scalable protocol in that its performance is little affected by growing networks sizes, and/or transmission speeds. While FDQ allocates equal bandwidth to all active nodes, the authors focus on dividing the capacity arbitrarily among the active nodes. Under heavy load, this would result in nodes achieving throughput rates equal to their allocated bandwidths. Under normal load conditions, they aim to provide equal quality of service to the nodes in terms of message delay, if their arrival rates turn out to be equal to their allocated bandwidths. They present the bandwidth allocation FDQ (BA-FDQ) protocol which achieves this objective subject to propagation delays. The delay characteristics of BA-FDQ are compared via simulation with FDQ, DQDB and DQDB with BWB under symmetric load (an important special case in the absence of known arrival rates). They also consider arbitrary bandwidth allocations and study the delay characteristics of BA-FDQ by simulation. The studies show that BA-FDQ makes the mean message delays of individual nodes close to each other as intended for transmissions on one of the buses