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本文讨论了用X.25作为节点机之间接口的方法,并给出了在此方法下网络内部虚电路的形式、流量控制、阻塞控制的原则等。这样一个协议可以用于中、小型远程专用网络,并能够方便地与公用数据网相连。 本文用CCITT建议的SDL语言以形式化描述的方法来设计该协议。文中给出了SDL中进程、外部输入输出信号、内部输入输出信号与协议中逻辑信道、到达分组、逻辑信道间交互作用之间的对应关系,且以简例示出了以SDL描述该协议的一般方法。最后,对于用SDL来描述分组交换的数据通信系统,做了简要的评价。
This paper discusses the method of using X.25 as the interface between nodes, and gives the principle of virtual circuit, flow control and congestion control in this method. Such an agreement can be used for medium and small remote private networks, and can easily connect with the public data network. This paper uses the CCITT proposed SDL language to formally describe the protocol to design this protocol. In this paper, the corresponding relationship between process, external input and output signals, internal input and output signals and the logical channels, arriving packets and logical channels in the SDL is given, and the SDL is used to describe the protocol in general method. Finally, a brief review of the data communication system using SDL to describe packet switching is made.