The effects of congestion on performance in interconnected high-speed local networks are investigated. The system studied uses network adapters as gateways to connect distributed local networks through a high-performance network link. Throughput measurements were determined by simulations of various combinations of link speeds, gateway buffering capacities, and local network traffic loads. The performance effects of several high-speed, local-network, bus-access protocols are investigated. Simulation model parameters are based on measurements of HYPERchannel networks.>

In this paper we consider HYPERchannel adapter local networks, the most oft used approach to realizing very high speed (50 Mbit/s transmission rates) local networks. We first describe the channel selection, channel access, and virtual circuit protocols used in HYPERchannel networks. Next, to characterize adapter network performance we present and interpret a series of measurements obtained from an adapter testbed network. From these measurements we are able to characterize the effects of various adapter protocol parameter settings, and hence recommend settings to avoid certain possible anomalous performance behavior and achieve desired effects.