Although practically every networking book on the market today discusses the Open System Interconnection (OSI) model, its importance should not be taken for granted. For this reason, the OSI model will be discussed here as it pertains to local-area networks (LANs) and wide-area networks (WANs).
The OSI reference model describes how information from a user or client application in one host or computer moves through an internetwork to an application on another host. The OSI model is a conceptual model composed of seven layers, each specifying particular network functions (see Figure 1-1).
Figure 1-1. OSI Reference Model
The OSI model was developed by the International Organization ...