01数通原理参考教材卷一交换广域网和路由

特性描述 局域网与城域网接入 目 录

目 录

1 以太网 ........................................................................................................................................... 1-1

1.1 以太网的起源 .............................................................................................................................................. 1-2 1.2 以太网的物理层 .......................................................................................................................................... 1-2 1.2.1 以太网的线缆标准简介 ..................................................................................................................... 1-2 1.2.2 CSMA/CD ........................................................................................................................................... 1-4 1.2.3 最小帧长与最大传输距离 ................................................................................................................. 1-5 1.2.4 以太网的双工模式 ............................................................................................................................. 1-5 1.2.5 以太网的自动协商 ............................................................................................................................. 1-6 1.2.6 HUB ..................................................................................................................................................... 1-7 1.3 以太网的数据链路层 .................................................................................................................................. 1-9 1.3.1 以太网链路层的分层结构 ................................................................................................................. 1-9 1.3.2 MAC子层 ........................................................................................................................................... 1-9 1.3.3 以太网帧结构 ................................................................................................................................... 1-11 1.3.4 LLC子层 ........................................................................................................................................... 1-13 1.3.5 以太网交换机 ................................................................................................................................... 1-13 1.4 以太网的发展 ............................................................................................................................................ 1-15 1.4.1 共享式以太网 ................................................................................................................................... 1-15 1.4.2 交换式以太网 ................................................................................................................................... 1-15 1.4.3 1000M以太网和10G以太网 .......................................................................................................... 1-16 1.5 以太网的应用 ............................................................................................................................................ 1-17 1.5.1 计算机互连....................................................................................................................................... 1-17 1.5.2 高速网络设备之间互连 ................................................................................................................... 1-17 1.5.3 城域网中用户接入的手段 ............................................................................................................... 1-17 1.6 参考资料清单 ............................................................................................................................................ 1-17

2 VLAN .......................................................................................................................................... 2-19

2.1 VLAN简介 ................................................................................................................................................. 2-20 2.1.1 VLAN的引入.................................................................................................................................... 2-20 2.1.2 VLAN的划分.................................................................................................................................... 2-22 2.1.3 VLAN帧格式.................................................................................................................................... 2-23 2.1.4 VLAN的基本概念 ............................................................................................................................ 2-24

文档版本 01 (2006-12-08) 华为技术有限公司 i

1 以太网 特性描述 局域网与城域网接入

2.2 VLAN内通信过程 ..................................................................................................................................... 2-26 2.2.1 VLAN基本通信原理 ........................................................................................................................ 2-26 2.2.2 VLAN跨越交换机通信原理 ............................................................................................................ 2-27 2.3 VLAN间通信原理 ..................................................................................................................................... 2-29 2.3.1 二层交换机＋路由器 ....................................................................................................................... 2-29 2.3.2 三层交换机....................................................................................................................................... 2-29 2.4 VLAN Aggregation ..................................................................................................................................... 2-30 2.4.1 VLAN aggregation原理 .................................................................................................................... 2-30 2.4.2 VLAN aggregation的优点 ................................................................................................................ 2-31 2.5 VLAN Stacking ........................................................................................................................................... 2-31 2.6 VLAN Mapping .......................................................................................................................................... 2-31 2.7 VLAN Damping .......................................................................................................................................... 2-32 2.8 VLAN的应用 ............................................................................................................................................. 2-33 2.8.1 基于端口的VLAN划分 .................................................................................................................. 2-33 2.8.2 VLAN Trunk的应用 ......................................................................................................................... 2-33 2.8.3 VLAN间互通应用 ............................................................................................................................ 2-34 2.8.4 VLAN Aggregation的应用 ............................................................................................................... 2-35 2.9 参考资料清单 ............................................................................................................................................ 2-36

3 MSTP .......................................................................................................................................... 3-37

3.1 MSTP的引入 ............................................................................................................................................. 3-38 3.1.1 STP..................................................................................................................................................... 3-38 3.1.2 RSTP .................................................................................................................................................. 3-38 3.1.3 MSTP ................................................................................................................................................. 3-39 3.1.4 三种生成树协议的比较 ................................................................................................................... 3-40 3.2 MSTP的基本概念 ..................................................................................................................................... 3-41 3.2.1 MSTP的网络层次 ............................................................................................................................ 3-41 3.2.2 MSTP网络 ........................................................................................................................................ 3-42 3.2.3 MST Region ....................................................................................................................................... 3-43 3.2.4 MSTI .................................................................................................................................................. 3-45 3.2.5 端口角色 .......................................................................................................................................... 3-45 3.2.6 端口状态 .......................................................................................................................................... 3-48 3.3 MSTP报文格式 ......................................................................................................................................... 3-48 3.4 MSTP的拓扑计算 ..................................................................................................................................... 3-52 3.4.1 优先级向量....................................................................................................................................... 3-52 3.4.2 CIST的计算 ...................................................................................................................................... 3-54 3.4.3 MSTI的计算 ..................................................................................................................................... 3-54 3.4.4 生成树算法实现 ............................................................................................................................... 3-54 3.4.5 MSTP对拓扑变化的处理 ................................................................................................................ 3-55 3.5 MSTP的快速收敛机制 ............................................................................................................................. 3-55 3.5.1 Proposal/Agreement机制 .................................................................................................................. 3-55

ii 华为技术有限公司 文档版本 01 (2006-12-08)

特性描述 局域网与城域网接入 目 录

3.5.2 根端口快速切换机制 ....................................................................................................................... 3-56 3.5.3 边缘端口 .......................................................................................................................................... 3-56 3.6 MSTP的保护功能 ..................................................................................................................................... 3-56 3.6.1 BPDU保护 ........................................................................................................................................ 3-57 3.6.2 Root保护 ........................................................................................................................................... 3-57 3.6.3 环路保护 .......................................................................................................................................... 3-57 3.7 BPDU TUNNEL ......................................................................................................................................... 3-57 3.8 MSTP的应用 ............................................................................................................................................. 3-58 3.8.1 MSTP的典型应用 ............................................................................................................................ 3-59 3.8.2 BPDU TUNNEL的应用 ................................................................................................................... 3-59 3.9 参考资料清单 ............................................................................................................................................ 3-60

4 PPP和MP .................................................................................................................................. 4-60

4.1 PPP和MP简介 ......................................................................................................................................... 4-62 4.1.1 PPP的引入 ........................................................................................................................................ 4-62 4.1.2 PPP的简介 ........................................................................................................................................ 4-63 4.1.3 PPP的基本构架 ................................................................................................................................ 4-63 4.1.4 PPP报文格式 .................................................................................................................................... 4-64 4.1.5 MP简介 ............................................................................................................................................. 4-67 4.2 PPP的运行过程 ......................................................................................................................................... 4-67 4.2.1 PPP的协商过程 ................................................................................................................................ 4-68 4.2.2 PPP的PAP验证协议 ....................................................................................................................... 4-70 4.2.3 PPP的CHAP验证协议 ................................................................................................................... 4-74 4.3 PPP的报文压缩 ......................................................................................................................................... 4-79 4.4 MP的实现方式 .......................................................................................................................................... 4-79 4.4.1 MP-group ........................................................................................................................................... 4-79 4.4.2 虚拟接口模板VT（Virtual-Template） ......................................................................................... 4-79 4.5 MP的协商过程 .......................................................................................................................................... 4-80 4.6 参考资料清单 ............................................................................................................................................ 4-80

5 PPPoE .......................................................................................................................................... 5-81

5.1 PPPoE简介 ................................................................................................................................................. 5-82 5.1.1 PPPoE的引入 ................................................................................................................................... 5-82 5.1.2 PPPoE简介 ....................................................................................................................................... 5-82 5.1.3 PPPoE的数据帧 ............................................................................................................................... 5-83 5.2 Discovery阶段 ........................................................................................................................................... 5-84 5.2.1 Discovery阶段简介 .......................................................................................................................... 5-84 5.2.2 PADI数据包 ...................................................................................................................................... 5-89 5.2.3 PADO数据包 .................................................................................................................................... 5-89 5.2.4 PADR数据包 .................................................................................................................................... 5-90 5.2.5 PADS数据包 ..................................................................................................................................... 5-90

文档版本 01 (2006-12-08) 华为技术有限公司 iii

1 以太网 特性描述 局域网与城域网接入

5.2.6 PADT数据包 .................................................................................................................................... 5-90 5.3 PPP会话阶段 ............................................................................................................................................. 5-91 5.4 PPPoE注意事项 ......................................................................................................................................... 5-91 5.4.1 LCP方面 ........................................................................................................................................... 5-92 5.4.2 安全方面 .......................................................................................................................................... 5-92 5.4.3 其它方面 .......................................................................................................................................... 5-92 5.5 PPPoE的应用 ............................................................................................................................................. 5-93 5.6 参考资料清单 ............................................................................................................................................ 5-93

6 HDLC .......................................................................................................................................... 6-94

6.1 HDLC简介 ................................................................................................................................................. 6-95 6.1.1 数据链路控制协议 ........................................................................................................................... 6-95 6.1.2 HDLC的引入 .................................................................................................................................... 6-95 6.1.3 HDLC的特点 .................................................................................................................................... 6-96 6.2 HDLC的操作方式 ..................................................................................................................................... 6-96 6.2.1 HDLC操作方式简介 ........................................................................................................................ 6-96 6.2.2 HDLC常用的操作方式 .................................................................................................................... 6-97 6.3 HDLC的帧格式 ......................................................................................................................................... 6-98 6.4 HDLC的帧类型 ......................................................................................................................................... 6-99 6.4.1 控制字段帧格式 ............................................................................................................................. 6-100 6.4.2 信息帧 ............................................................................................................................................ 6-100 6.4.3 监控帧 ............................................................................................................................................ 6-100 6.4.4 无编号帧 ........................................................................................................................................ 6-101 6.5 HDLC的应用特点 ................................................................................................................................... 6-101 6.5.1 应用场合 ........................................................................................................................................ 6-102 6.5.2 传输效率 ........................................................................................................................................ 6-102 6.5.3 传输可靠性..................................................................................................................................... 6-102 6.5.4 数据透明性..................................................................................................................................... 6-102 6.5.5 信息传输格式 ................................................................................................................................. 6-102 6.5.6 链路控制 ........................................................................................................................................ 6-102 6.6 参考资料清单 .......................................................................................................................................... 6-102

7 帧中继 ....................................................................................................................................... 7-103

7.1 帧中继简介 .............................................................................................................................................. 7-104 7.1.1 帧中继的引入 ................................................................................................................................. 7-104 7.1.2 帧中继协议简介 ............................................................................................................................. 7-106 7.1.3 帧中继基本概念 ............................................................................................................................. 7-107 7.1.4 MFR ................................................................................................................................................. 7-110 7.2 帧中继在路由器协议栈中的位置 .......................................................................................................... 7-111 7.2.1 帧中继在整个软件体系结构中的位置 ......................................................................................... 7-111 7.2.2 帧中继软件结构 ............................................................................................................................. 7-111

iv 华为技术有限公司 文档版本 01 (2006-12-08)

特性描述 局域网与城域网接入 目 录

7.3 帧中继帧格式 .......................................................................................................................................... 7-113 7.4 帧中继LMI协议 .................................................................................................................................... 7-115 7.4.1 LMI协议简介 ................................................................................................................................. 7-115 7.4.2 Q.933附录A ................................................................................................................................... 7-115 7.5 InARP协议介绍 ....................................................................................................................................... 7-119 7.6 帧中继子接口 .......................................................................................................................................... 7-121 7.6.1 帧中继子接口的引入 ..................................................................................................................... 7-121 7.6.2 帧中继子接口的简介 ..................................................................................................................... 7-122 7.7 帧中继接入 .............................................................................................................................................. 7-122 7.8 帧中继PVC交换 .................................................................................................................................... 7-123 7.9 帧中继交换PVC备份 ............................................................................................................................ 7-124 7.9.1 帧中继交换PVC备份的应用 ....................................................................................................... 7-124 7.9.2 帧中继交换PVC备份的实现 ....................................................................................................... 7-124 7.10 帧中继压缩 ............................................................................................................................................ 7-125 7.10.1 FRF.9压缩 ..................................................................................................................................... 7-126 7.10.2 帧中继IP头压缩 ......................................................................................................................... 7-127 7.11 帧中继QoS ............................................................................................................................................ 7-127 7.12 多链路帧中继捆绑（MFR）................................................................................................................ 7-129 7.13 参考资料清单 ........................................................................................................................................ 7-130

8 ATM .......................................................................................................................................... 8-131

8.1 ATM简介 ................................................................................................................................................. 8-132 8.1.1 传统的交换技术 ............................................................................................................................. 8-132 8.1.2 ATM协议简介 ................................................................................................................................ 8-133 8.1.3 ATM的特点 .................................................................................................................................... 8-133 8.1.4 ATM的发展和现状 ........................................................................................................................ 8-135 8.2 ATM层次结构.......................................................................................................................................... 8-135 8.3 ATM物理层.............................................................................................................................................. 8-136 8.3.1 物理介质子层 ................................................................................................................................. 8-137 8.3.2 传输汇聚子层 ................................................................................................................................. 8-142 8.4 ATM层 ..................................................................................................................................................... 8-142 8.4.1 ATM层的基本功能 ........................................................................................................................ 8-143 8.4.2 ATM虚链路 .................................................................................................................................... 8-143 8.4.3 VPI/VCI ........................................................................................................................................... 8-144 8.4.4 ATM信元的转发 ............................................................................................................................ 8-145 8.4.5 ATM信元头格式 ............................................................................................................................ 8-145 8.4.6 ATM的网络接口 ............................................................................................................................ 8-147 8.4.7 ATM OAM ....................................................................................................................................... 8-148 8.5 ATM适配层.............................................................................................................................................. 8-149 8.5.1 AAL的层次和作用 ......................................................................................................................... 8-149

文档版本 01 (2006-12-08) 华为技术有限公司 v