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随着我国改革开放的不断深入,经济迅猛发展,通信的信息量骤增,各行各业对邮电通信提出了更高的要求。非话业务大量涌现,特别是分组交换、VSAT、可视图文、电子数据交换(EDI)、会议电视、电子信箱(E—MAIL)等一批新业务的涌现,使非话业务向多元化迅速发展。但以 X.25为基础的分组交换网难以满足日益增长的计算机之间或计算机与终端之间的通信,以及基于话音、图形和视频的多媒体通信的要求。于是人们
With the deepening of China’s reform and opening up, the rapid economic development, the rapid increase in the amount of information for communications, all walks of life put forward higher requirements for post and telecommunications. The emergence of a large number of non-speech services, especially the emergence of new services such as packet switching, VSAT, videotex, electronic data interchange (EDI), conference television and E-mail, Rapid development. However, X.25-based packet-switched networks can not meet the growing demand for communication between computers or computers and terminals, as well as voice, graphics and video-based multimedia communications. So people