Page 38 - M. Abrahim Thesis

Chapter (2) Network Fundamental and Layered Network Architecture

To illustrate further, imagine a world at war, crisscrossed by different kinds of
connections, including wires, microwaves, optical fibers, and satellite links. Then imagine that
information/data (in the form of packets) must flow, regardless of the condition of any particular
node or network on the internetwork (which, in this case, might have been destroyed by the
war). The DoD wants its packets to get through every time, under any conditions, from any one
point to any other point. This very difficult design problem brought about the creation of the
TCP/IP model, which has since become the standard on which the Internet has grown.

When reading about the TCP/IP model layers, remember the original intent of the
Internet; it helps explain why certain things are as they are. The TCP/IP model, as shown in Table
2-1, has four layers:

• The application layer
• The transport layer

• The Internet layer

• The network access layer

Table 2-1 shown a difference between OSI and TCP/IP Layer Model

It is important to note that some of the layers in the TCP/IP model have the same names
as layers in the OSI model. However, do not confuse the layers of the two models. Even with the
same name, most the layers have the same functions in each model, but some do not, as shown
in Table 2-1.

https://www.youtube.com/watch?v=byrH3myfCcc&t=22s

2.8.1 Encapsulation De-Encapsulation Process

All communications on a network originate at a source and are sent to a destination. The
information that is sent on a network is called data or data packets. If one computer (Host A)
wants to send data to another computer (Host B), the data must first be packaged by a process
called encapsulation.

https://www.youtube.com/watch?v=xeAe7kyejiI&t=47s

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