Louis Nyerges


A subset of the Recommendation X.25 protocol is implemented on a two node network. Each node accepts and translates data from the user in a sequential fashion into the appropriate protocol structure for transmission to another node. Each node has the capability of full duplex operation. The hardware is built around a Motorola M6800 microprocessor employing a minimum of 4096 words of random access memory and two asynchronous ports: one for communication with the user and the other for communication with the network. The software on each node contains the protocol programs and a multitasking monitor which is used to buffer the data bytes between the protocol software and the two communication ports. The multitasking monitor is also used to time slice among the seven tasks which implement the protocol structure. This paper illustrates in some detail the structure of Recommendation X.25. The subset of the packet types which are implemented is also examined. Finally, a scenario of the procedure for information exchange between one user and another is discussed in detail.

Library of Congress Subject Headings

Motorola M6800 series (Computers); Data transmission systems; Packet switching (Data transmission); Computer networks

Publication Date


Document Type


Department, Program, or Center

Computer Science (GCCIS)


Czernikowski, Roy


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