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Chapter 1
Internetworking
The OSI Layers
Basically, the International Organization for Standardization (ISO) is pretty
much the Emily Post of the network protocol world. Just like Ms. Post, who
wrote the book setting the standards--or protocols--for human social inter-
action, the ISO developed the OSI reference model as the precedent and
guide for an open network protocol set. Defining the etiquette of communi-
cation models, it remains today the most popular means of comparison for
protocol suites.
The OSI reference model has seven layers:
Application layer
Presentation layer
Session layer
Transport layer
Network layer
Data Link layer
Physical layer
Figure 1.4 shows the functions defined at each layer of the OSI model.
With this in hand, we can now move on to explore each layer's function
in detail.
F I G U R E 1 . 4
Layer functions
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