Part III-1. NAME SYSTEMS AND TCP/IP NAME REGISTRATION AND NAME RESOLUTION
TCP/IP APPLICATION LAYER PROTOCOLS
The OSI Reference Model is used to describe the architecture of networking protocols and technologies and to show how they relate to one another. In the chapter describing OSI Reference Model concepts (Chapter 5), I mentioned that its seven layers could be organized into two layer groupings: the lower layers (1 through 4) and the upper layers (5 through 7). While there are certainly other ways to divide the layers, this split best reflects the different roles that the layers play in a network.
The lower layers are concerned primarily with the mechanics of formatting, encoding, and sending data over a network. These layers involve software ...