中国钟学我术大草 信息网给与协议 UKIVERIITY OF SCIENCE AND TECHNOLOOY OF CHINA ATM: 虚电路 ·Why VPI+VCI Private network ATM Backbone 11H ◆ nn wwwm Private network Private network Use VPI for switching Use VCI to ID connection in backbone Within private network信息网络与协议 ATM：虚电路 • Why VPI+VCI