Performance of ABR flow control in ATM networks

A good flow control scheme is crucial for the proper functioning of the available bit rate (ABR) service in asynchronous transfer mode (ATM) networks. To this end, the ABR flow control scheme has been developed by the ATM Forum. In this scheme, resource management (RM) cells are used to carry network feedback to the ABR sources. The ABR sources use the feedback information to adjust their source rates. We examine the response of the congestion control mechanism using a simulation method. It has been found that the flow control scheme is able to achieve low cell loss under extreme traffic conditions, and high link bandwidth utilisation is possible under stable conditions. It has also been found that the feedback to the sources may be inadequate for high bandwidth utilisation under changing network conditions. We propose that the maximum rate of the out-of-rate RM cells be increased, the destination be allowed to generate backward RM cells indicating available bandwidth, and congestion information be modified only in the backward RM cells.