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) traac service category for ATM. In this paper, 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 nite Quasi-Birth-Death (QBD) process. Due to the peculiar block tri-diagonol nature of its generator, eecient 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 exibility to study the eeect of several additional factors such as asynchronous feedback, two-level control and explicit rate notiication in the presence of underlying high-priority traac. This study brings to light the trade-oos 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 eeect on its performance. These time scales are associated with the feedback delay, the durations of active/idle periods of traac sources and the time scales of the underlying high-priority traac. We also examine the eeect of the time scales on the convergence time for the transient queueing system.