Summary

This chapter provided a simple tutorial of the OSI Reference Model. The OSI Model was developed by the ISO in 1984 and is considered the primary architectural model for internetwork communications.

The seven layers of the OSI Model are divided into two categories: the upper layers and the lower layers. The upper layers (Layers 5 7) deal with user-data and application issues, which are implemented in client software only. The lower layers (Layers 1 4) are implemented in both hardware and software, and they handle data transport across the internetwork. The process by which data is handled layer-to-layer through the OSI Model is referred to as data encapsulation.