Layered protocol architecture: basic concepts

Data transmission protocols are those that enable two entities to communicate via a telecommunications network. A protocol is a set of rules that must be respected so that these two entities can exchange information. These rules can be as simple as the coding technique used to recognize a character, or as complex as the protocols used to route blocks of information from one end of the network to the other.

Standardization has a considerable impact on protocols. For communication to take place, both ends must use the same rules. Protocols must therefore either be standardized by international bodies (ISO, ITU-T...), or be recognized as "de facto standards". The best example of a de facto standard is, of course, the Internet Protocol (IP). There are also so-called "proprietary" protocols, developed and used by IT companies for their own specific architecture, but this solution is now disappearing.

In this article, we focus on the formalism of data transmission protocols. The study of the main data transmission protocols is the subject of a second article.