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在协议选择方面,开放系统互连层次标准中,对于 OSI 七层里的每一层的许多选择,均已引起了不少混乱和困难。为了选择一套适用于异种局部网络互连的互操作协议集,本文对每一层面向连接和无连接所提供服务需求,进行了深入地分析。这种选择主要取决于所采用的是面向连接还是无连接的互连策略。这两种不同的观点已对局部网络仿形带来两种可能的方案:方案1——TP4—IP—LLC1(无连接网络服务)和方案2——TP1—X.25PLP—LLC1(面向连接的网络服务)。基于对这两种局部网络仿式正反两方面的详细分析表明:方案1较之方案2更为有效和通用,因而是一种较好的局部网络互连途径。这也符合 MAP、TOP 以及其它的国际标准网络协议的基本原则。
In terms of protocol selection, many of the options for each layer of OSI’s seven layers have caused a lot of confusion and difficulty in the standard of open system interconnection level. In order to select a set of interoperability protocols that are suitable for heterogeneous local area network interconnection, this article provides an in-depth analysis of the service requirements for each layer for both connected and disconnected. This choice depends mainly on the connection-oriented or connectionless interconnect strategy used. These two different views have led to two possible scenarios for local network profiling: Scenario 1 - TP4-IP-LLC1 (Connectionless Network Services) and Scenario 2 - TP1-X.25PLP-LLC1 Network service). Based on a detailed analysis of both the positive and negative aspects of the two local networks, Scheme 1 is more effective and versatile than scheme 2 and is therefore a better route for local network interconnection. This is also in line with the basic principles of MAP, TOP and other international standard network protocols.