Voice Over IP

THE INTERNET LAYERED ARCHITECTURE

Many of the concepts in this book are explained with the layered protocol concept. This section provides a brief review of the Internet layers and Chapter 2 gives more detailed information.

Figure 1-10 a reviews the Internet protocol suite layers. With some exceptions, the Open Systems Interconnection (OSI) Model layer 6 is not used. Layer 5 is not used at all.

The physical and data link layers are (as a general rule) also not defined. The philosophy is to rely on existing physical and data link systems. One notable exception to this practice is at the data link layer, where the Internet task forces have defined the Point-to-Point Protocol (PPP).

For the newcomer, here is a summary of the functions of the layers: ...