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4 ISDN用户—网络接口的协议 ISDN协议包括用户—网络接口通信协议和网络内部通信协议。因ISDN业务的多样化,使ISDN的协议比一般通信网复杂。而且用户信息和控制信令分别在不同的信道中传送,所以用户信息和控制信令将遵守不同的协议。这里主要介绍用户—网络接口协议中的几个主要问题。4.1 用户—网络接口的分层功能 ISDN用户—网络接口协议根据OSI开放系统互连参考模型可分为3层:第1层是物理层,它包括基本速率接口和一次群速率接口;第2层是数据
4 ISDN user-network interface protocol ISDN protocol includes user-network interface communication protocol and network internal communication protocol. Due to the diversification of ISDN services, the ISDN protocol is more complicated than the general communication network. Moreover, user information and control signaling are respectively transmitted in different channels, so user information and control signaling will comply with different protocols. Here mainly introduces the user - network interface protocol in several major issues. 4.1 User-Network Interface Hierarchical Features The ISDN User-Network Interface Protocol can be divided into three layers according to the OSI Open Systems Interconnection Reference Model: Layer 1 is a physical layer that includes a basic rate interface and a group-rate interface; Layer 2 Is the data