Network buffer requirements of the rate-based control mechanism for ABR services

In ATM networks congestion control plays an essential role in supporting different quality of service guarantees for a large variety of traffic 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 mechanism developed by the ATM Forum. Using a differential equation approach for the computation of the evolution of the allowed cell rate and the buffer content during the steady state, we derive closed-form expressions to estimate the maximum buffer lengths. These expressions 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 parameters is important achieving a reasonable performance of the rate-based control mechanism. In particular, we are interested in limiting the required buffer size while enabling a fast reaction to changes of the available transmission capacity