At one time, most vendors agreed to support OSI in one form or another, but OSI was too loosely defined and proprietary standards were too entrenched. Except for the OSI-compliant X.400 and X.500 e-mail and directory standards, which are widely used, what was once thought to become the universal communications standard now serves as the teaching model for all other protocols.

Most of the functionality in the OSI model exists in all communications systems, although two or three OSI layers may be incorporated into one.

OSI is also referred to as the OSI Reference Model or just the OSI Model.

See a breakdown of the seven OSI layers in the Quick Reference section of Webopedia.

Also see "The OSI Reference Model — Understanding Layers" in Webopedia's "Did You Know..." section.

(2) Abbreviation for the Open Source Initiative.

ISO OSI standards page
This site lists OSI standards by reference number. Look here to find out which standard you need, but you can't download it - the standards must be purchased from the ISO.

OSI: The Network Layer
This page, from Cisco Systems, provides an illustrated overview of OSI with information on OSI network-layer services and protocols, routing protocols, and a description of Cisco's OSI implementation.

Understanding OSI
Provides chapters of a book that explains why OSI is the shape it is and offers critical examination of the OSI approach to specifying rules for computer communication (computer protocols).

EnterpriseNetworkingPlanet
EnterpriseNetworkingPlanet provides practical advice and news for running and managing an enterprise network. In-depth articles and news cover topics such as network management, network monitoring, servers, communications, Internet telephony, operating systems, and much more.

Open Networks Today
Networking news moves at a fast pace, and Open Networks Today lets you keep up with it. Open Networks Today offers its readers the ability to control how news is presented through customizing content filters, discussions, and news feed links.

PracticallyNetworked.com
PracticallyNetworked.com provides easy-to-understand help for small-network builders. The site contains how-to information for setting up and debugging home-office and small-business networks. Users can also find extensive troubleshooting information, tips on getting applications to work through firewalls, product reviews on network hardware and software, and more.

PracticallyNetworked.com Discussion Forums
If network connections, sharing computers, router problems or other networking issues are bogging you down, then the PracticallyNetworked.com discussion forum is the place to be. Here you'll find help and support for all your network-related problems.

Webopedia's Quick Reference Section
Use this Webopedia reference section for information on common Internet and computer facts and occurrences.

Webopedia's Tech Support Area
Read the descriptions of each tech support Web site below, and choose the one that best suits your needs. We offer these links to help users get the tech support they need.