29
Chapter 3:
Understanding Networking
between the theory and actual practice in most networks. Still, the OSI model offers
an excellent way to understand and visualize how computers network to each other,
and it is required knowledge for anyone active in the field of networking. Just about all
employers expect networking professionals to be knowledgeable about the OSI model,
and it comes up on most networking certification tests. This might be a very dry topic,
but it's important to learn!
The OSI model defines a basic framework for how modern networks operate.
It separates the methods and protocols needed for a network connection into seven
different layers. Each higher layer relies on services provided by a lower layer. If you
were to think about a desktop computer in this way, its hardware would be the lowest
layer, and the operating system drivers--the next-higher layer--would rely on the
lowest layer to do their job. The operating system itself, the next-higher layer, would
rely on both of the lower layers working properly. This continues all the way up to the
point at which an application presents data to you on the computer screen. Figure 3-3
shows the seven layers of the OSI model.
NOTE
The OSI model is sometimes called the seven-layer model. It was developed by the
International Standards Organization (ISO) in 1983 and is documented as Standard 7498.
Figure 3-3.
The seven layers of the OSI model
Application
Presentation
Session
Transport
Network
Data-link
Physical
Summary :
29 Chapter 3: Understanding Networking between the theory and actual practice in most networks. Still, the OSI model offers an excellent way to understand and visualize how computers network to each other, and it is required knowledge for anyone active in the field of networking.
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