A DELAY ANALYSIS OF FDQ (FAIR-DISTRIBUTED-QUEUE) AND DQDB NETWORKS

A delay analysis of FDQ (Fair Distributed Queue) and DQDB (with and wi thout the BWB mechanism) is presented, A network of two active nodes w ith a large separation of nodes is considered in each case. Under the common set of assumptions of single buffer nodes, geometric arrivals a nd the packet size of one segment, the mean delay at each node is obta ined using limited independence assumptions. Results from the analyses are compared to simulation results. The analyses are shown to be quit e accurate for low to moderate loads and they only require the solutio n of polynomial equations, The mean delays at both stations under FDQ with equal arrival rates are shown to be almost equal. DQDB and DQDB w ith BWB have increasingly asymmetric mean delays with higher arrival r ates. For a dual bus implementation, the mean delay at the upstream st ation is less than that at the downstream station for all three protoc ols. FDQ has the smallest difference between the two stations' delay r esults and DQDB has the highest in this case. (C) 1998 Elsevier Scienc e B.V. All rights reserved.