Please Whitelist This Site?

I know everyone hates ads. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. And I have a family to support, just like you. :)

If you like The TCP/IP Guide, please consider the download version. It's priced very economically and you can read all of it in a convenient format without ads.

If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. To do so, just open the Adblock menu and select "Disable on tcpipguide.com". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||tcpipguide.com^$document". Then just click OK.

Thanks for your understanding!

Sincerely, Charles Kozierok
Author and Publisher, The TCP/IP Guide


NOTE: Using software to mass-download the site degrades the server and is prohibited.
If you want to read The TCP/IP Guide offline, please consider licensing it. Thank you.

The Book is Here... and Now On Sale!

Enjoy The TCP/IP Guide? Get the complete PDF!
The TCP/IP Guide

Custom Search







Table Of Contents  The TCP/IP Guide
 9  The Open System Interconnection (OSI) Reference Model

Previous Topic/Section
Comparing the OSI Reference Model to Network Architectures and Protocol Stacks
Previous Page
Pages in Current Topic/Section
1
Next Page
OSI Reference Model Networking Layers, Sublayers and Layer Groupings
Next Topic/Section

Key OSI Reference Model Concepts

The OSI Reference Model is valuable as a tool for explaining how networks function, and for describing the relationships between different networking technologies and protocols. To accomplish this, the model relies on a number of important concepts and terms. To understand the model, then, I need to explain what these are and how they relate to the model as a whole.

In this section, I describe the key concepts that define how the OSI Reference Model works. I begin with a discussion of how the model uses layers, perhaps the single most important model concepts. I then talk about some of the notation and jargon you are likely to see used in general discussions of the model. I define in more detail what “interfaces” and “protocols” are in the context of the model. I then explain the important concept of data encapsulation and the terminology used to refer to messages in the OSI Reference Model: PDUs and SDUs. Finally, I put together most of the preceding issues by describing how the various layers work to handle the routing of messages on a theoretical basis.

Note: Many of the concepts discussed in this section are also used by many people in describing the details of various individual technologies. The best example is the word “protocol”, which is used just about everywhere to refer to just about anything. My focus here is on the conceptual definitions of such terms. However, the conceptual discussions here often also apply to real-world technologies. For example, data encapsulation is performed as data is sent between protocols and technologies at various OSI layers, pretty much as I describe it here.


Quick navigation to subsections and regular topics in this section



Previous Topic/Section
Comparing the OSI Reference Model to Network Architectures and Protocol Stacks
Previous Page
Pages in Current Topic/Section
1
Next Page
OSI Reference Model Networking Layers, Sublayers and Layer Groupings
Next Topic/Section

If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. Thanks for your support!
Donate $2
Donate $5
Donate $10
Donate $20
Donate $30
Donate: $



Home - Table Of Contents - Contact Us

The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005

© Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
Not responsible for any loss resulting from the use of this site.