SDH网的同步层功能

The synchronization layer function of the SDH network

本文从原子结构的角度，对SDH网的两个同步层：网络同步层（NS）和同步分配层功能进行定义，同时也对与之相关的传送层的部分功能进行定义。从网络的角度，分析了同步网的组成及其分层，给出了同步网时钟传递的参考链路，描述了同步法则，规定了与网同步及定时有关的原子功能构件，以及SDH网元如何参与网络的同步。结合我国的具体情况，选择了适合我国应用的同步处理规范。

We analyze the composition and layering structure of the synchronization network from the network view point, give the reference link of the clock transporting of the synchronization network, describe the rule on synchronization. It specifies the atomic function building blocks related with the network synchronization and timing,and how the SDH network elements take part in the synchronization of the network. It defines the atomic functions that are part of the two synchronization layers, the Synchronization Distribution (SD) layer and the Network Synchronization (NS) layer from atomic structure view point. It also defines some atomic function, part of the Transport layer, which are related with synchronization. We select the Synchronization Status Messages (SSM) Specifications suitable for applications in China based on the situations in our country.