TCP/IP and the DoD Model
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Host-to-Host layer
Internet layer
Network Access layer
Figure 3.1 shows a comparison of the DoD model and the OSI reference
model. As you can see, the two are similar in concept, but each has a different
number of layers with different names.
F I G U R E 3 . 1
The DoD and OSI models
When talking about the different protocols in the IP stack, the layers of the OSI
and DoD models are interchangeable. In other words, the Internet layer and
the Network layer describe the same thing, as do the Host-to-Host layer
and the Transport layer.
A vast array of protocols combine at the DoD model's
Process/Appli-
cation layer
to integrate the various activities and duties spanning the
focus of the OSI's corresponding top three layers (Application, Presenta-
tion, and Session). We'll be looking closely at those protocols in the next
part of this chapter. The Process/Application layer defines protocols for
node-to-node application communication and also controls user-interface
specifications.
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