Temporal characteristics of industrial networks

This issue is dedicated to the study of time in local networks, and specifically in industrial LANs. Data transmission requires different qualities of service depending on the application, but it always takes time, and different time constraints must be respected. Temporal aspects thus represent one of the important elements of quality of service. The aim of this dossier is firstly to present all the delays that make up the transmission time of a message and are responsible for delays, and then to show how performance can be assessed using a few simplified applications drawn from the real world. It does not cover the modeling of traffic by probabilistic arrival laws, nor the resolution of systems modeled by queues.

The basic principles of the OSI model are assumed. However, two boxes recall a few definitions, so that the reader doesn't have to look them up in other works. Where necessary, bibliographical references provide additional information, either of a general nature, or on a specific protocol.

This dossier is structured as follows. The first paragraph recalls a few key principles and the importance of the notion of performance in communication.

The second and third paragraphs deal respectively with the concepts of a physical channel and a logical channel, made up of several physical channels connected by intermediate stations. Performance depends to a large extent on Medium Access Control protocols, which are discussed in 4 .

Finally, a number of applications are examined in the context of a methodological approach.