Syngress - Eleventh Hour Network+ Exam N10-004 Study Guide (11 ...

How to Use the OSI Model in Troubleshooting 163
IMPORTANCE OF NETWORK DOCUMENTATION
After you’ve done all of the necessary troubleshooting to solve a problem, documenting
your troubleshooting activities is vitally important. It helps you to
stay organized and perform those steps methodically. Also, when the same thing
occurs again, you will be well prepared.
HOW TO USE THE OSI MODEL IN
TROUBLESHOOTING
The OSI model fits into an overall troubleshooting strategy. Depending on the
layer that you begin your troubleshooting, different techniques may be required
to determine the root cause of the issue. The following are some of the purposes
behind having a networking model:
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It provides a standard to utilize and reference, thereby helping to isolate
network issues to specific layers of a protocol stack.
It allows to identify the types of components that may be involved in an
issue, thus helping in troubleshooting the problem.
Open standards enable the consumer to patronize multiple vendors.
Vendors produce products that can be used in various networks, including
those that started out using a different vendor’s products.
The layered approach provides a logical division of responsibility, where
each layer handles only the functions that are specific to that layer.
Since the networking protocols are typically divided into layers, troubleshooting
is easier because you are better able to narrow down the source of
the problem to a specific layer.
Reviewing the OSI Model
The OSI model consists of seven layers, and when one computer communicates
with another one, data at the sending computer is passed from one layer to the
next until the final layer puts it out onto the network cable. At the receiving end, it
travels back up in reverse order. Although the data travels down the layers on one
side and up the layers on the other, the logical communication link is between
each layer and its matching counterpart, as shown in Figure 10.1.
As the data goes down through the layers, it is encapsulated or enclosed within
a larger unit as each layer adds its own header information. When it reaches
the receiving computer, the process occurs in reverse; the information is passed
upward through each layer, and as it does so, the encapsulation information is
evaluated and then stripped off one layer at a time.
Establishing a Troubleshooting Strategy
The most important thing that you can do when troubleshooting is to be
organized and methodical in your approach to solving problems.