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一、交换方式的发展七十年代以来,计算机网络复盖面积不断扩大——远程网已横跨洲际;网络的复盖密度急速加密——本地网正犹如雨后春笋般地展开;各种新的网络技术课题纷纷涌现出来。其中发展远程计算机网的主要问题之一是通信费用高,而降低通信费用的有效方法之一是发展新交换方式,设法提高通信设备的有效利用率。计算机通信网采用的交换方式现有两种:(1)电路交换方式,(2)存储转发方式。电路交换方式是沿用电话网中交换机的工作原理。当计算机与终端相互之间需要通信时,才向交换机申请建立连接。这种方式适合远程成批作业的处理和文件传递,即电路接续时间大大小于传输时间的情况。存储转发方式类似于电报转发的工作方式。六十年代中期开始出现的分组交换技术具有连续时间短、传输误码率低并能
I. Development of exchange mode Since the 1970s, the coverage of computer network has been expanding - the remote network has crossed the intercontinental network; the coverage density of the network has been rapidly encrypted - the local network is mushroomed; the new networks Technical topics have emerged. One of the major problems in developing a remote computer network is that communication costs are high, and one of the effective ways to reduce communication costs is to develop new exchange modes and try to improve the effective utilization of communication devices. There are two kinds of exchange modes used in computer communication network: (1) circuit switching mode, (2) storage and forwarding mode. Circuit switching method is to follow the telephone network switch working principle. When the computer and the terminal need to communicate with each other, the switch is requested to establish a connection. This approach is suitable for remote batch processing operations and file transfer, that is, the circuit connection time is much less than the transmission time. Storage and forwarding methods similar to telegraph work. The packet switching technology that began to appear in the mid-1960s has the advantages of short continuous time, low transmission error rate and