Adaptive congestion control schemes for ATM LANs

Abstract

New congestion control schemes using the adaptive rate control for ATM LANs are presented. It is preferable for hosts in LANs to be able to send bursts at the same speed as the interface link speed in a lightly loaded condition, and as the network load increases, to reduce their traffic rate adaptively in order to avoid network congestion. The authors propose to apply such a rate control concept for two different traffic classes in the ATM LANs. For the first traffic class requiring no bandwidth reservation, i.e. a best effort service class, a combination of the end-to-end adaptive peak rate control with the link-by-link backpressure control is proposed. For the second traffic class, requiring the bandwidth reservation for the burst transmission, i.e. a guaranteed burst service class, a combination of the adaptive peak rate control with the fast bandwidth reservation (FRP) is proposed. It is shown through simulations that, in the first class traffic, cell loss is avoided by the backpressure, while the unfairness problems caused by the backpressure in a heavy load situation are resolved with the adaptive rate control. In the second class traffic, the network throughput characteristics are shown to be improved in the heavily loaded situations, owing to the fact that the adaptive rate control reduces the bandwidth reservation blocking probability. >