1.前言现有的高速公路骨干通信网大多采用的都是SDH设备,使用的是TDM技术,具有良好的网络自愈保护功能,非常适合传输电路交换的传统话音业务。现有的光通信网络的容量已经很大,在相当多的地方用于传统业务已经过剩,部分容量处于闲置状况。另外一方面,随着IP技术的飞速发展和IP业 1. Preface Most of the existing highway backbone communication networks use SDH equipment, which uses TDM technology and has good self-healing network protection function. It is very suitable for transmitting traditional voice services with circuit switching. The capacity of the existing optical communication network is already very large. There are quite a few places where the traditional services are over-used and part of the capacity is idle. On the other hand, with the rapid development of IP technology and IP industry