Maximum delivery time and hot spots in ServerNet/sup TM/ topologies

Abstract

This paper centers on analysis of the performance characteristics of ServerNet topologies, concentrating on the prediction through simulation and statistical analysis of the maximum two-way delivery time, the identification of congested links (hot spots) and tree saturation. ServerNet/sup TM/, developed by Tandem Computers Inc., is a wormhole-routed, packet-switched, point-to-point network, with special attention paid to reducing latency and to assuring reliability. ServerNet uses multiple high-speed, low-cost routers to rapidly switch data directly between data sources and destinations. Our study is based on data generated by a simulation tool. Statistical analysis and inference methods were used to process the samples generated by the simulator and to obtain estimates for the maximum two-way packet delivery time. Link usage statistics were recorded by the simulator for the purpose of performing a detailed investigation of congestion effects and hot spots. Hot spots may cause the occurrence of tree saturation in the network i.e., where an individual tree will become congested (tree saturation) while all other trees are mostly idle, which leads to significant performance degradation.