Supporting Best-Effort Traffic with Fair Service Curve
CARNEGIE-MELLON UNIV PITTSBURGH PA SCHOOL OF COMPUTER SCIENCE
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Packet Fair Queueing PFQ algorithms are the most popular and well studied scheduling algorithms for integrated services networks for two reasons 1 With reservation, they can provide per-flow end-to-end delay guarantees for real-time traffic flows. 2 Without the reservation, they can provide protection among competing best-effort flows while allowing dynamic bandwidth sharing. However, PFQ algorithms have two important limitations. The first one is that, since only one parameter a weight is used to allocate resource for each flow, there is a coupling between delay and bandwidth allocation. This can result in network under-utilization when real-time flows have diverse delay and bandwidth requirements. The second and less well known limitation is that, due to the instantaneous fairness property of PFQ algorithms, when used for best-effort service, PFQ algorithms favor continuously- backlogged throughput-oriented applications such as FTP over bursty applications such as WWW and telnet. In a previous study, we proposed the Fair Service Curve FSC algorithm which enables more flexible delay and bandwidth allocation for real-time traffic through the use of non-linear service curves. In this paper, we show that, when used for best-effort traffic, FSC can improve performance of delay-sensitive bursty applications without negatively affecting the performance of throughput-oriented applications.
- Computer Systems