End-to-end flow control in interconnected local area ring networks

The authors evaluate the performance of end-to-end flow control in a system of interconnected token-ring local area networks via a backbone ring network. The analysis is based upon an existing delay approximation for a stand-alone local area network. This approximation is extended to analyze a system of interconnected local area ring networks. Local area networks are interconnected via bridges. A bridge is modeled as two queues: one queue is for the backbone ring and the other is for the individual ring or subnetwork. Average delay, throughput, and power are used as performance measures. Traffic is assumed to be balanced. Bridges are assumed to have enough buffers such that messages are not blocked. The probability of transmission errors is assumed to be negligible. Analytical results show that tighter restrictions result in poor utilization of resources although the performance in terms of delay may look very attractive. On the other hand, loose restrictions (i.e. larger window size) mean no flow control and result in performance degradation under heavy traffic conditions. Therefore, it is suggested that window size should be dynamically adjusted according to the traffic conditions in order to achieve the best performance