AN IMPROVED FLOW CONTROL SCHEME

Abstract

In a computer communication network, when the user's demand exceed the network capacities a phenomenon like traffic jam occurs causing excessive delay and lowering the throughput. Various flow control schemes are used to avoid it. The most common schemes being end-to-end window flow control and node-by-node or backpressure flow control scheme. Unlimited buffers are assumed in the mathematical analysis of these schemes. Nodal buffers are, however, limited in real world. The allocation of these buffers will affect the network performance characteristics such as delay, throughput and fairness. Thus at heavy loads window flow control due to buffer overflow at the nodes causes the retransmission of packets lowering throughput and Increasing delay. To improve upon this scheme we combine backpressure and window flow control and investigate its performance with respect to throughput, delay and fairness. Its performance characteristics are then compared with window flow control alone. It Is found that combination of window with backpressure is a better strategy in that (a) It provides a fair bandwidth allocation under heavy traffic load. (b) it provides nearly equal individual VC throughputs under equal loads. (c) It provides nearly same individual VC delay.