Optimal feedback control for ABR service in ATM

Abstract

The efficient support of data traffic over ATM networks requires congestion control, whose objectives include maximizing throughput, minimizing switch buffer requirement, and attaining a fair bandwidth allocation. With available bit rate (ABR) service in ATM, congestion control is achieved by requiring data sources to adjust their rates based on the feedback from the network. The difficulties in providing effective ABR service are caused by the burstiness of data traffic, the dynamic nature of the available bandwidth, as well as the feedback delay. Using a new design methodology described in our previous paper, we present here a congestion control algorithm that is provably stable and is optimal in the sense that it has the shortest possible transient response time. Moreover, our algorithm achieves fair bandwidth allocation among contending connections and maximizes network throughput. It also delivers good performance for switches that use a FIFO queuing discipline. Essentially, the algorithm implicitly measures the round-trip delay using resource enhancement cells, and establishes an observer (in the control theoretic sense) to control the flow of data in the network. Rigorous analysis as well as simulation results are presented to substantiate our claims.