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OSI
Layers Model
Introduction
During the early years of our modern computer era, very few
standards and protocols existed between various
manufacturers. However, as time went on and computer
technology continued to improve and become more widespread,
it became apparent that standards would be necessary to
ensure compatibility.
This was especially true with regard to networks, and
networking technology. Since the main purpose of a network
is to share information, a standard that governs how this
information is formatted, transmitted, received and verified
would make it possible for information to be shared openly,
even when dealing with dissimilar networks.
This need for a standard means of implementing open
communications led the ISO and ANSI to develop the
seven-layer network communications model known as Open
Systems Interconnect. By providing guidelines regarding the
way network equipment should be manufactured and how network
operating systems communicate on a network, the OSI model
became the common link that allows data to be transmitted
and exchanged reliably. Although it does not actually
perform any functions or do any of the actual work, the OSI
model defines the way things should be done by the software
and hardware on a network so that communications can take
place between two computers or nodes.
In
this way, the OSI model provides a universal set of rules
that make it possible for various manufacturers and
developers to create software and hardware that is
compatible with each other. This makes for organized
communications. As I thought about this, I related it to the
freeways that connect the various states of the mainland
U.S.
Because all of these freeways were constructed with the same
set of standards regarding the width of each lane, the
proper side that a person should drive on, the speed at
which they should travel, and so on, people can comfortably
drive across the country in an organized and efficient
manner and car manufacturers are able to design cars within
these guidelines as well.
On
the other hand, if each state had devised its own set of
rules, each differing from the other, not only would there
be a lot more chaos on the roads, but also car manufacturers
would have a hard time designing vehicles that would be
compatible with each state's roads. To me, this illustrates
the importance of the OSI model with respect to network
communications. Not only is it the foundation for all
network communications today, but also because it is such a
fundamental part of these communications, it becomes very
apparent to me that it is very important for a network
technician to understand the OSI model in full detail.
The
OSI model is made up of the following layers: the physical,
data link, network, transport, session, presentation and
application. Together, these seven layers are collectively
referred to as a stack. As a node receives data, each layer
starting with the physical layer extracts the various
portions of the packet and this process works its way up to
the application layer. When data is sent, it begins at the
application layer and travels down to the physical layer.
The information is pushed to the next layer of the stack by
means of commands called primitives. Each layer uses a peer
protocol to encode the information, which ensures that the
same layer on the receiving node will be able to understand
the information.
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