一种区分服务模型及其在三层交换机的实现

服务质量（QoS）是用来定义网络给不同形式的流量提供不同级别的服务保障的能力.当前服务质量的体系结构和模型有多种,本文参照RFC2474、RFC2475 标准,提出了一种新的服务质量-区分服务（Diffserv）应用模型,该模型包括：流量的分类器、计量器、标记（或重标记）器、丢弃器和调度器等模块, 其中对于核心模块-调度器, 提出基于最大延迟的加权轮转调度（WRR-MBD）算法,同时给出区分服务模型在3 层以太网交换机的实现方法.通过网络测试分析仪对3 层交换机QoS 性能进行测试,得出在WRR 调度策略下,不同优先级数据包的丢失率基本按所设置的权重比例进行分配,从而避免了严格优先级（SP）调度存在的低优先级队列“饥饿”的现象.

Implementation of a new Diffserv model based on 3-layer switch

Quality of Service（QoS） is used to define different forms of network traffic to providedifferent levels of service assurance capabilities. The models and architectures of QoS fall into severaltypes. A new type of application model of QoS-Differentiated service（Diffserv） application model isproposed according to the standard of RFC2474 and RFC2475. This model is composed of sub-modulessuch as classifier, meter, marker（remarker）, dropper and scheduler etc. Meanwhile, the algorithm ofWeighted Round Robin with Max Bounded Delay（WRR-MBD） of scheduler is proposed and analyzed indetail. Finally, the implementation of Diffserv based on 3-layer switch is described. Through a networkanalyzer to test QoS of 3-layer switch, it is concluded that in WRR scheduling policy, the loss rate ofpackets with different priorities is basically allocated according to the ratio of weight, which avoids lowpriority queues “hunger” existing in strict priority scheduling policy.