It is often necessary to fairly allocate bandwidth among services with different requirements in high-speed packet switching circuits while meeting their QoS parameters.When queues of such services are multiplexed to a single output link

a variety of traffic scheduling algorithms are used for this purpose.Weighted Fair Queuing（WFQ） is a commonly used scheduling algorithm

which can not only ensure fairness

but also provide good delay performance.This paper discusses the basic principle of WFQ in detail.