Cisco Networking Essentials

Introducing the Layers of the OSI Model

There are seven layers in the OSI model; each layer plays a role in creating a package of data along with critical information describing the data. This package will be sent from one device to another device, where it will be taken apart and read. This process is called encapsulation and de-encapsulation and will be explained more fully in the last section of this chapter.

First, the role of each layer must be understood to grasp the encapsulation process. Let's explore each layer and its job in the process. Notice in Figure 2.1 that the functions discussed in the three top layers of the OSI model are condensed into the Application layer of the TCP/IP model, and the functions of the two bottom layers of ...