目 录1 、前 言....................................................62 、系统概述与需求...........................................72.1 系统建设的必要性.......................................72.2 系统建设概况...........................................72.3 总体需求...............................................72.4 建网目的...............................................83 、局域网技术现状分析与技术概述.............................93.1 网络技术选择.........................................103.2 网络设备的系统结构...................................103.3 虚拟专用网络(VPN)....................................113.4 路由功能.............................................113.5 容错功能.............................................113.6 网络管理.............................................114 、网络方案概述............................................124.1 网络设计思想..........................................124.2 网络逻辑结构..........................................145 、网络实现................................................155.1 系统需求..............................................155.2 网络实现技术..........................................155.2.1 主干网............................................155.2.2 各子网设计........................................165.2.3 远程服务..........................................165.2.4 与外部网络的连接..................................165.2.5 网络物理拓扑结构..................................175.3 外连方式..............................................175.3.1 PSTN(电话拨号)....................................185.3.2 ISDN(综合业务数据网)..............................185.3.3 DDN(数字数据网)...................................205.3.4 X.25(公共分组数据交换网)..........................215.3.5 帧中继............................................225.4 网络设备选择..........................................235.4.1 交换机............................................235.4.2 路由器..............................................
