OSI model

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Sep 24th, 2008
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Hellow friends

i have realized the importance of OSI model in networking studies. even though i read a lot on the topic,i could not manage to form a clear-cut concept.

please help me to master the real functions of the seven layers of OSI model

with rgds


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compsolv Wed, 09/24/2008 - 21:45
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Getting two different network systems from different manufacturers to communicate successfully on a network would be near to impossible if there was not a blueprint to follow like the OSI model. You see, this hugely complex task is made more simple by breaking it down into manageable components and functions.

For example, it is the job of the Network layer to take care of the IP addressing of systems so they can be located on the network. It is the job of the Session layer to make sure that a communication flow can be opened and closed properly.

Breaking down the very difficult task of networking computers together into these manageable chunks is critical. It allows for standards to be developed more easily, and for the modern day, remarkable Internet to be a reality.

The OSI model also allows network engineers to troubleshoot systems more effectively. It gives us a blueprint to follow when trying to track down exactly why two systems cannot communicate. We can follow a “bottom-up” approach:

1. Is the physical layer OK? In other words, are the darn things still plugged in?

2. Is the network layer OK? In other words, do the systems have their proper IP addresses?

3. Is the application layer OK? In other words, is a firewall blocking a key application protocol that is needed like Simple Mail Transfer Protocol (SMTP)?

I sure hope this post can help you understand a very difficult topic!

Anthony J. Sequeira, CCIE #15626, CCSI #23251

Senior CCIE Instructor

[email protected]

Internetwork Expert, Inc.


Toll Free: 877-224-8987

Outside US: 775-826-4344

shafistrokes Fri, 09/26/2008 - 02:32
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thank you sir

for your brief account on OSI model

it is very helpful to me.

let me ask two more things

1.sir, could you differentiate the OSI model and TCP/IP model with reference to the real life environment.

2.it is said that DoD has designed the TCP/IP model to withstand even a nuclear war.

how can TCP/IP model survive with out physical media?

with regards


dwgray0422 Mon, 09/29/2008 - 04:24
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Medan posted a very useful chart under the TCP/IP stack heading in this forum.


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