Identifying Models for Implementing QoS参考.ppt

Introduction to IP QoS Identifying Models for Implementing QoS QoS Models Best-Effort Model Internet was initially based on a best-effort packet delivery service.Internet 即是一个基于尽力而为型的网络. Best-effort is the default mode for all traffic.对于所有的流量尽力而为是一种默认的QoS模型. There is no differentiation among types of traffic.不区分不同的流量类型. Best-effort model is similar to using standard mail—It will get there when it gets there.尽力而为模型类似于发送邮件,邮局平等地对待所有信件. Benefits and Drawbacksof the Best-Effort Model Benefits:优点: Highly scalable较高的可扩展性 No special mechanisms required不需要特殊机制(简单性) Drawbacks:缺点: No service guarantees缺乏服务保证 No service differentiation缺乏区分服务 IntServ Model Introduction of IntServ model (RFC 1633) was driven by real-time applications, such as remote video and conferencing.RFC1633描述了集成服务模型的QoS,主要是用于实时性应用,比如远程视频和会议. IntServ end-to-end model ensures guaranteed delivery and predictable behavior of the network for applications.集成端到端服务模型是一种可预测的服务等级 Resource Reservation Protocol (RSVP) is used as a signaling protocol.IntServ使用资源预留协议作为其信令协议. The requested QoS parameters are then linked to a packet stream.只有当QoS参数被正确的识别时RSVP才能为其预留带宽确保QoS的实现. End-to-end streams are not established if the required QoS parameters are not available.如果必需的QoS参数不是有效的话,哪么端到端的流的连接是无法建立的. IntServ Model (Cont.) Provides multiple service levels能够提供多种服务等级的QoS模型 Requests specific kind of service from the network before sending data传输数据前必须向网络请求,而且所请求的资源必须被释放. Uses RSVP to reserve resources for specified QoS parameters详细的QoS参数用于RSVP为流进行资源预留. Intelligent queuing mechanisms required to provide resource reservation in terms of: Guaranteed rate保证速率 Controlled load (low delay, high throughput)负载受控(低延时,高吞吐量) IntServ Functions IntServ requires several functions on routers and switches along the path:需要网络路径中的路由器交换机上启用以下功能: Admission control接纳控制:如果无法在不影响现有应用的情况下请求资源,哪么则被拒绝. Classification分类:为数据包进行分类识别,才能为数据包提供正确的网络服务. Policing监管:测量和监控应用不超过它们的所定的资源使用量. Queuing队列:处理和转发数据包的同时能容纳的一定数量. Scheduling调度:总与队列联动