1. Reference model

1.1 Reference model levels

The reference model was developed in the 1980s and still serves as a benchmark for understanding the place of the various functions required to build a network. In fact, this reference model has evolved considerably, even though very few official documents reflect these changes. First, we'll review the various definitions of the layers of this architecture, then we'll indicate the changes that need to be taken into account in the new vision of this reference model.

The classic architecture is illustrated in figure 1 . It is a seven-layer model.

The physical layer is complex: it describes, via numerous standards,...