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随着经济的发展和社会的进步,计算机网络为人们提供了不受地域限制的直接、广泛的联系,实现了真正的资源共享,计算机网络在金融、政府、企业中发挥着越来越重要的作用,联网的方式也从原来的模拟专线、X.25逐步过渡到数字专线 DDN、帧中继 FR 及综合数字业务网 ISDN,其中数字专线DDN 以其通信质量高,性能可靠占据了相当一部分市场份额。DDN 通信线路在实际应用中一般提供点对点的服务,典型连接方式如下:
With economic development and social progress, computer networks provide people with direct and broad links without geographical restrictions and real sharing of resources. Computer networks play an increasingly important role in finance, government and enterprises Function, networked way from the original analog leased line, X.25 gradually transition to the digital line DDN, FR and ISDN ISDN, digital line DDN with its high-quality communications, reliable performance occupy a considerable part of the market Share. DDN communication line generally provides point-to-point service in practical application. The typical connection mode is as follows: