Dynamic max rate control algorithm for available bit rate service in ATM networks

The ATM Forum has adopted rate-based congestion control as the standard for available bit rate (ABR) services. In order to achieve fairness, it is necessary that the rate-based control schemes use intelligent marking, i.e., notify congestion only to selected connections. For these schemes to perform well, the central issue is to guarantee that the marking threshold is a good estimate of the fair share of the available bandwidth to which each connection is supposed to converge. In the existing schemes, such as the enhanced proportional rate control algorithm (EPRCA), this approximation does not always hold, for example due to bottlenecked connections, transient behaviors, safety parameters in the algorithms, or incorrect rate information from the sources. In this paper, we propose a new algorithm for the switch behavior, called the dynamic max rate control algorithm (DMRCA), which distinguishes itself from the existing schemes in that it uses a marking threshold which is a function of the degree of congestion at the switch and the maximum rate of all active connections. We show that this threshold is always an accurate estimate of the fair share, and thus the new algorithm outperforms the existing schemes, achieving fairness in all situations. The new scheme can be implemented with low complexity, and is fully compatible with the existing ATM standard.