Performance analysis of rate based feedback control for ATM networks

Closed-loop input rate regulation schemes have come to play an important role in the transport of the available bit rate (ABR) traffic service category for ATM. We present a numerical approach to the performance study of a delayed feedback system with one congested node and multiple connections. This approach consists in modeling the feedback system as a finite quasi-birth-death (QBD) process. Due to the peculiar block tri-diagonal nature of its generator, efficient techniques exist for its steady-state and transient solutions. Using these techniques, we examine a simple parsimonious feedback system for issues such as throughput/loss performance, fairness and stability. Our approach has the flexibility to study the effect of several additional factors such as asynchronous feedback, two-level control and explicit rate notification in the presence of underlying high-priority traffic. This study brings to light the trade-offs between system performance and the complexity of the feedback scheme. Our study shows that the time scales of correlation of the feedback system have a dominant effect on its performance. These time scales are associated with the feedback delay, the durations of active/idle periods of traffic sources and the time scales of the underlying high-priority traffic. We also examine the effect of the time scales on the convergence time for the transient queueing system.