Origin of the OSI Model

By stretch | Friday, May 28, 2010 at 1:27 a.m. UTC

As ubiquitous as the OSI model is in the world of network engineering, it occurred to me recently that I could not recall seeing a standard document defining the model referenced even once in all of the books I've read. Odd. A little digging turned up a formal definition of the model in the form of ITU recommendation X.200, available for free in PDF format.

The document is, as one would expect from an international standards body, extremely dry. But there are a few interesting sections worth reading through. Section 5.2, Principles of Layering, describes the sequential structure of the layers and how each was developed to interface only with the layers directly above and/or below it. Annex A provides a brief discussion of how the layers were chosen. The meat of the standard, a technical definition of each of the seven layers, is found in section 7.

About the Author

Jeremy Stretch is a network engineer living in the Raleigh-Durham, North Carolina area. He is known for his blog and cheat sheets here at Packet Life. You can reach him by email or follow him on Twitter.

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Tim (guest)
May 28, 2010 at 10:24 p.m. UTC

This OSI model is far cooler, although less useful for troubleshooting. I think I found this with Netscape Navigator 1.0 using my first SLIP or PPP connection...........

Anyone else old enough to remember those days? :)

ayman (guest)
May 30, 2010 at 6:25 p.m. UTC

stretch you are the best!!!,it's exactly what I'm looking for.... many thanks

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