Supporting best-effort traffic with fair service curve

While packet fair queuing (PFQ) algorithms can provide per-flow end-to-end delay guarantees for real-time traffic or protection among competing best-effort traffic, they 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. When used for real-time traffic, this can result in network under-utilization. The second and less well known limitation is that, when used for best-effort traffic, PFQ algorithms favor throughput-oriented applications such as FTP over delay-sensitive bursty applications such as WWW, and telnet. This is due to the memory-less instantaneous fairness property of PFQ algorithms. 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.