TCP/IP Model and Terminology

Before completing this introduction to the TCP/IP model, this section examines a few remaining details of the model and some related terminology.

Comparing the Original and Modern TCP/IP Models

The original TCP/IP model defined a single layer—the link layer—below the internetwork layer. The functions defined in the original link layer can be broken into two major categories: functions related directly to the physical transmission of data and those only indirectly related to the physical transmission of data. For example, in the four steps shown in Figure 1-11, Steps 2 and 3 were specific to sending the data, but Steps 1 and 4—encapsulation and deencapsulation—were only indirectly related. This division will become ...

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