CompTIA Network+® Study Guide

2.2. The OSI Reference Model

One of the greatest functions of the OSI specifications is to assist in data transfer between disparate hosts—meaning, for example, that they enable you to transfer data between a Unix host and a PC or a Mac.

The OSI model isn't a physical model, though. Rather, it's a set of guidelines that application developers can use to create and implement applications that run on a network. It also provides a framework for creating and implementing networking standards, devices, and internetworking schemes. The OSI model has seven layers:

• Application (Layer 7)

• Presentation (Layer 6)

• Session (Layer 5)

• Transport (Layer 4)

• Network (Layer 3)

• Data Link (Layer 2)

• Physical (Layer 1)

Figure 2.1 shows a summary of the functions defined at ...