网络设计chap9-lkjv3.pptVIP

网络规划与设计Chapter 9 WANs 网络规划与设计第九章　广域网 Chapter 9 WANs 9.1 Introduction This chapter introduces the various protocols and technologies used in wide-area network (WAN) environments. 9.2 WAN Technology Overview WAN technologies function at the three lowest layers of the OSI reference model: the physical layer, the data link layer, and the network layer. Fig. 9-1 第九章 广域网 9.1 简介 本章主要介绍在广域网(WAN)环境中应用的多种协议和技术 9.2 广域网技术概况 广域网技术主要体现在OSI参考模型的下3层：物理层，数据链路层和网络层. 如图9-1 9.2.1 WAN Services three main types of WAN services: Call setup—Sets up and clears calls between telephone users, is also called signaling. The most commonly used call setup is Signaling System 7 (SS7), which uses telephone control messages and signals between the source and destination along the way to the called destination. PSTN uses this service. Time-division multiplexing (TDM)—Basic telephone service and ISDN use TDM circuits. Frame Relay 9.2.1 广域网服务 广域网提供的服务可分为三种主要类型: 呼叫建立(Call setup)—也称为信令，在电话用户之间建立和清除呼叫。最常用的呼叫建立是七号信号系统(SS7), 它使用从呼叫方到被呼叫方的电话控制信息和信令. PSTN 就使用这种服务. 时分多路复用(TDM)—普通电话和ISDN都使用TDM电路 帧中继(Frame Delay) Telephone and data services are connected from the building point of presence (POP) to the WAN providers central office (CO). 9.2.2 WAN Service Providers the main parts（部件） of WAN services: -fig 9-3 Customer premises equipment (CPE, 用户室内设备)—located on the subscriber’s premises. Includes both devices owned by the subscriber and devices leased to the subscriber by the service provider. Demarcation (or demarc,分界)—Often occurs at the POP of a building. Local loop (or “last-mile”)—Cabling (usually copper wiring) that extends from the demarc into central office. CO switch—A switching facility that provides the nearest distance to point of presence. Toll network (长途网络） 通过电信连接点(POP)和广域网供应商的中心局(CO)之间建立的连接获得电话和数据服务 9.2.2 广域网服务提供商 广域网提供的服务有以下主要部件: -如图 9-3 用户室内设备(CPE， Customer premises equipment)—位于用户终端的设备. 包括属于用户的设备和服务供应商租用给用户的设备. 分界(demarcation,或者demarc)—通常位于建筑物的 POP处. 本地环路(local loop,或者“last-mile”)—从分界