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数据通信网主要完成数据传输与交换任务，并为广域网和城域网提供网络互连技术。按ＯＳＩ－ＲＭ七层协议分析，数据通信网提供的是低３层功能，即网络层、链路层、物理层的功能。目前的数据通信网主要有分组交换网、帧中继（ＦＲ）网、ＤＤＮ网、ＡＴＭ网。Ｎ－ＩＳＤＮ网等。
Data communications network to complete the main data transmission and exchange tasks, and WAN and MAN provide network interconnection technology. According to the analysis of OSI-RM seven-layer protocol, the data communication network provides the functions of the lower layer 3, that is, the network layer, the link layer and the physical layer. The current data communications networks are mainly packet-switched network, Frame Relay (FR) network, DDN network, ATM network. N-ISDN network and so on.