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一、前言为研究、开发和建设市域计算机网络,(以下简称“市域网”)。异机种计算机互连课题就是“市域网”第一阶段的课题。日立M-240D主机接口硬、软件从一九八七年五月开始研制,到一九八八年年底为止已基本实现项目规定的主要技术指标,即能相互传送文件、进行会话和远程访问等,实现了三个计算机系统相互间直接通信的功能。“市域网”第一阶段的系统建设目标是实现江苏省计算中心的HITAC M-240D、东南大学(原南京工学院)的HONEYWELL DPS-8/49和南京航空学院的IBM-4341等异机种计算机系统直接互连的用户资源子网。第一阶段拓扑结构设计如图一所示。全网本着ISO7498——开放系统互连基本参考模式进行构造。下三层按照OSI与CCITT的对应关系,基本采用X.25物理级、链路级
I. Preface To research, develop and construct a computer network in the urban area (hereinafter referred to as “Metropolitan Area Network”). Different types of computer interconnection subject is the first phase of the “local area network.” Hitachi M-240D host interface hardware and software from the beginning of May 1987 to develop until the end of 1988 has basically achieved the project’s main technical indicators that can transfer files to each other, for sessions and remote access, etc. , To achieve the three computer systems communicate directly with each other. The goal of system construction in the first phase of “Metropolitan Area Network” is to realize HITAC M-240D in Jiangsu Computing Center, HONEYWELL DPS-8/49 in Southeast University (formerly Nanjing Institute of Technology), and IBM-4341 in Nanjing Aeronautical Institute Computer Resources Directly interconnected user resource subnet. The first stage topology design shown in Figure one. The whole network with ISO7498 - Open Systems Interconnection basic reference structure to construct. The next three layers according to the corresponding relationship between OSI and CCITT, the basic use of X.25 physical level, link-level