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一、引言 计算机网络到现在已经历了三代的发展:第一代是60年代为共享,当时昂贵的计算机硬件资源(小型机、大型机)而发展起来的面向终端的联机系统;第二代是70年代为大范围共享信息资源而发展起来的以通信子网为中心的分组交换网,如ARPANET;第三代计算机网络是为实现更大范围异种网络互连而发展起来的遵循开放系统互连标准(OSI、TCP/IP等)大规模互连网络,其典型代表就是因特网(Internet)。 经过仅仅三代、40年的发展,计算机网络就发展成为今天因特网的模样。这令许多预测专家们大跌眼镜,更令世
I. INTRODUCTION Computer network has now gone through three generations of development: the first generation is the terminal oriented online system developed in the 1960s for sharing and then expensive computer hardware resources (minicomputers, mainframes); the second generation is In the 1970s, packet-switched networks such as ARPANET, which were developed for large-scale sharing of information resources, centered on communication subnets. Third-generation computer networks were developed to achieve a wider range of heterogeneous network interconnections and follow the Open Systems Interconnection Standard (OSI, TCP / IP, etc.) large-scale interconnection network, the typical representative of the Internet (Internet). After just three generations and 40 years of development, the computer network has become the appearance of today’s Internet. This makes many forecasting experts surprise, but also to the world