A QoS packet/burst scheduler for broadband networks

Abstract

Prevailing weight-based scheduling algorithms advocate static or coarse-grained simplification of timestamp computation, resulting in performance bottleneck and unnecessary downgrade under heavy and normal computation loads, respectively. Our goal is to design a scheduler that enables quantitative trade-off balance between performance and complexity. In this paper, we propose a Stepwise QoS Scheduler (SQS), enabling packet to burst scheduling under normal to heavy computation loads, based on a new notion of window. Window sizes of unity and greater than one correspond to packet and burst scheduling, respectively. SQS exerts simple FIFO service within the window and guarantees stepwise weight-proportional service at the window boundary. As a result, quantitative trade-off balance can be facilitated via the adjustment of the window size. We further formally specify the SQS service guarantee for a flow by a stepwise service curve, which is a function of W and theta(min) - the least-upper-bound delay incurred by the first packet of the busy period of the flow. Finally, we demonstrate through experimental results that, by applying a small window (W less than or equal to 10), SQS outperforms Weighted Fair Queueing (WFQ) and performs as superior as Worst-case Fair Weighted Fair Queueing (WF(2)Q) with respect to throughput fairness, mean delay, and worst-case delay fairness.