Enhancing of available bit rate traffic management schemes in ATM networks

Abstract

The rate-based flow control for available bit rate (ABR) services in asynchronous transfer mode (ATM) networks is presented. A closed control loop between the source and the destination is performed to implement flow control for ABR services. The source sends resource management (RM) cells with the data cells to be used to indicate the sending station's current transmission rate and the higher rate it would like to use. Based on this information the available cell rate (ACR) which the network can afford is calculated. This is performed in three different ways known as explicit forward congestion identification (EFCI), relative rate marking (RRM) and explicit proportional rate control algorithm (EPRCA). In this paper the combination of the three different schemes is considered. A general formula for evaluating ACR value is given when two network conditions are considered, namely heavy load and moderate load. The new ACR value is calculated based on a feedback acknowledgement from the bottleneck switch. This acknowledgement suggests a new ACR value namely explicit rate (ER)-a rate that the congested switch can afford. A computer simulation is performed to examine the performance of a network consisting of two ATM switches applying the previously mentioned control schemes. High performance is achieved when using the explicit rate (ER) determined by the congested switch.