Optimal Feedback Control for ABR Service in ATM

The e cient support of data tra c over ATM networks requires congestion control, whose objectives include maximizing throughput, minimizing switch bu er 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 di culties in providing e ective ABR service are caused by the burstiness of data tra c, 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 management cells, and establishes an observer (in the control theoretic sense) to control the ow of data in the network. Rigorous analysis as well as simulation results are presented to substantiate our claims.