3. Reference model (IEEE 802)

Computer networks are based on the seven-layer OSI (Open System Interconnection) reference model defined by the ISO (International Standard Organization). In this model, each layer has a specific function and relies on the services of the layer immediately below. Let's take a brief look at the functionalities of these different layers:

• Layer 1, or the physical layer, adapts computer binary data to the physical transmission medium;

• Layer 2, or the link layer, ensures reliable transmission of information. Data is grouped into frames. The range of a frame is that of the physical medium on which it is transmitted;

• Layer 3, or the network layer, enables access to any equipment on the network. This layer overcomes frame range limitations. This layer introduces the notion of address,...