TCRED:一种基于DiffServ的队列管理算法

AF PHB的实现机制是DiffServ网络的重要研究课题，目前的多数实现采用了RED或类似的队列管理技术，在分析了RED及其改进算法在公平性及分组优先级等方面存在的不足后，提出了一种采用同一组RED参数对三色分组实行队列管理的TCRED算法．TCRED对不同颜色的分组分别计算平均队列长度，并考虑了分组的到达和离去对平均队长的影响，据此计算出各色分组的丢弃几率，该算法能实现分组的相对优先级，保证用户所预定的带宽，同时能实现分组优先级的平滑升级和降级，因而很好地满足了AF PHB的要求。

TCRED: A NOVEL QUEUE MANAGEMENT ALGORITHM BASED ON DIFFSERV ARCHITECTURE

Mechanisms able to provide the AF PHB in DiffServ networks constitute a significant research topic. Most of the current implementations of AF use RED or similar queue management techniques. Analyzed in this parper are some shortcomings inherent in RED and its improved algorithms in terms of fairness and packet drop precedence, and then proposed is a novel queue management algorithm named TCRED (three color random early drop) using a same suite of RED parameter to control green, yellow and red packets. TCRED calculates the average queue length of these colored packets respectively, accounting for the effect of both packet arrival and packet departure, and computes packet drop probability based on calculated average queue length. The algorithm implements relative drop precedence among different colored packets, assures the customers of their booked bandwidth, and realizes graceful upgrade and degrade of packet drop precedence; it thus well meets the requirements of AF PHB.