关键词: 服务质量, 区分服务, 调度算法, 公平性, 网络延迟

Abstract: Through the analysis of four kinds of priority queues and the priority scheduling algorithm in DiffServ system，the dynamic priority scheduling algorithm is obtained which can be used to solve the fairness problem that occurs when IP blocks are being forwarded.The following problem，however，is the delay phenomenon at the same time.After determining the more precise criterion of delay threshold and the concrete method of realization，find that with the dynamic priority scheduling algorithm，forwarding IP blocks dose not exceed the delay threshold.From the simulations，with the algorithm，it can provide the QoS guarantee that four kinds of priority queues are forwarded fairly.

Key words: Quality of Service（QoS）, DiffServ, scheduling algorithm, fairness, network delay