一.前言计算中心在计算机方面的投资,到目前为止,已有相当的规模。但这都是在不同历史时期,根据不同的应用目的,而分别引进的。其机型包括大、中、小各种不同类型的计算机8套,从不同厂家购进的工作站十几套,微型机几十台。进货时期不同,供货厂商不同,操作系统五花八门。这就使我们面临一个多厂商、异机种、异种网互联的难题。也是当今网络技术研究关注的焦点,是计算中心局域网研究和实施的关键技术之一。这一问题的解决对保护已有投资,以最少的再投资,使我们现有的计算机互联成网起了决定性作用。从而使人们工作更加愉快、快速、有效且方便。为此从92年初开始进行中心局网的研究与开发,经过两年的试验研究和两次实 I. Foreword The computer center’s investment in computing has so far reached a considerable size. However, these are introduced separately in different historical periods according to different purposes of application. Its models include large, medium and small 8 sets of different types of computers, workstations purchased from different manufacturers more than 10 sets, dozens of micro-computer. Different purchase time, different vendors, operating system variety. This makes us face a multi-vendor, heterogeneous, heterogeneous network interconnection problem. It is also the focus of research on network technology today and one of the key technologies in the research and implementation of computing center LAN. The solution to this problem has played a decisive role in protecting the existing investments and interconnecting our existing computers with minimal reinvestment. So that people work happier, fast, effective and convenient. To this end from the beginning of 92 central office network research and development, after two years of experimental research and two real