Dynamic multithreshold rate control mechanisms for supporting ABR traffic in ATM networks

Existing feedback-based rate control schemes supporting the available bit rate (ABR) service in ATM networks mostly employ a single static buffer threshold at each switching node as the forewarning of congestion. We first propose a continuous-based adaptive rate control mechanism, which employs, logically, an infinite number of thresholds. Each node periodically determines the precise permitted rate of immediate upstream nodes based on a simple fluid model aimed at satisfying both loss-free and starvation-free criteria. The scheme achieves high utilization and low (zero) cell-loss probability under highly bursty (deterministic) traffic, but at the expense of a drastic increase in signalling overhead due to frequent adjustment of permitted rates. To reduce overhead, we further propose a so-called stepwise-based rate control mechanism adopting a limited number of movable thresholds, referred to as the threshold set. The threshold set shifts up (down) reflecting the increase (decrease) in departure rates. Compared to continuous-based control via simulation, stepwise-based control is shown to be efficient and accurate using a reasonably low number of thresholds. Moreover, we also display simulation results, which demonstrate that the stepwise-based mechanism outperforms existing single-static-threshold-based schemes in terms of cell-loss probability and link utilization.