Network Bu er Requirements of the Rate Based Control Mechanism for ABR Services

Congestion control plays an essential role in ATM networks to support di erent quality of service guarantees for a large variety of tra c types While for real time communications such as CBR and VBR services a preventive open loop congestion control mechanism is applied a reactive closed loop mechanism has been suggested for the ABR service class which was introduced aiming at data communication applications This paper presents a performance analysis of the rate based congestion control mech anism developed by the ATM Forum Using a di erential equation approach for the computation of the evolution of the allowed cell rate and the bu er content during steady state we derive closed form solutions to estimate the bu er space which must be provided in network nodes to avoid cell losses The solutions can be formulated for steady state conditions as well as for transient phases In our approach scenarios with and without priority for the resource management cells are considered From numerical examples we conclude that an appropriate setting of the control parame ters is important to achieve a reasonable performance of the rate based control mechanism In particular we are interested in limiting the required bu er size while enabling a fast reaction to changes of the available transmission capacity