Tiered-Service Fair Queueing (TSFQ): A Practical and Efficient Fair Queueing Algorithm

Abstract

A router in today's Internet has to satisfy two important properties in order to efficiently provide the Quality of Service (QoS) requested by the users. It should be fair among flows and also have low operational complexity. The packet scheduling techniques that have been proposed earlier do not have both these properties. Schedulers like Weighted Fair Queueing (WFQ) provide good fairness among flows but have high operational complexity. Schedulers like Weighted Round Robin (WRR) are efficient but provide poor fairness among flows. We propose a new packet scheduling technique, Tiered Service Fair Queueing (TSFQ), which is both fair and efficient. We achieve our goal by applying the concept of traffic quantization. A quantized network offers a small set of service levels (tiers), each with its own weight. Each flow is then mapped to one of the service levels so as to guarantee a QoS at least as good as that requested by the flow. We propose different versions of TSFQ, each with its own level of fairness. We present the complexity analysis of the TSFQ scheduler. Finally, we demonstrate through simulations on the TSFQ implementation on $ns-2$, that TSFQ provides good fairness among flows.