This guide was originally developed for internal use by the Canadian Government, with the objective of assisting systems managers, systems designers, and programmers to reach a common understanding of the nature and purpose of the Open Systems Interconnection (OSI). A further objective was to indicate the steps which could be taken to begin migration towards systems based on OSI principles. In line with those objectives, a deliberate attempt has been made to avoid complex terminology, and to include illustrative examples based on the target audience’s experience with data processing systems.

It is unfortunate that the comprehensive list of reference material, standards, and the like relates only to that published up to and including the October 1983 Ottawa Plenary TC97/SC16 meeting of the International Standards Organization. Aside from that limitation, it must be said that the paper should come very close to meeting its objectives.

A brief history of the OSI standards is provided, followed by an introduction to the concepts of layering. The functions of each of the seven layers in the OSI model are then outlined, and a conceptual example illustrating the exchange of data between two open systems is offered.

Each of the seven layers is then examined in some detail, with reference to physical and functional characteristics, work in progress, and existing standards which are (or may become) applicable. This last aspect is considered to be invaluable, since it identifies for the reader where those standards with which he may be familiar (e.g., RS-232, X.21, X.25, and S.70) fit within the model.

The paper concludes with a set of recommendations on how users can prepare for OSI standards (e.g., use existing standards, apply OSI principles in system design). Annexes providing lists of appropriate ISO and CCITT documents, and addresses of local Canadian contacts are also included.