Congestion Detection Methods and Their Impact on the Performance of the Abr Flow Control Mechanism

The support of the ABR service category is a key feature for future ATM networks to allow an economical transmission of applications with vague requirements for throughput and delay. The idea behind the ABR service is to convey feedback information about the network congestion status from the network elements to the end systems in order to dynamically adapt the transmission rates of the ABR sources to changing network conditions. The performance of the ABR ow c o n trol mechanism strongly depends on the congestion detection scheme used by the network elements. Until now only the number of cells queued in the switch buuers has been considered to investigate performance issues of the ABR ow control mechanism. In this paper, we discuss and compare the performance of three easy-to-implement congestion detection schemes for ATM switches supporting the ABR service category. Simple and accurate formulae to estimate the minimum and maximum numberof cells queued in the switch buuers are derived.