What is OSI?

• Because it's an important part of the history of computer networks. It's also something you're likely to get asked about in job interviews, which is where it really matters...
   
  
• It's a genuine International Standard (ISO/IEC IS 7498:1993) of the International Organisation for Standardisation and International Electrotechnical Committee(ISO/IEC)
   
  
  • Mechanism: working draft --> committee draft --> draft IS --> IS, with ballots at each stage.
  
   
  
• Was adopted (in part) as the definitive standard for network architectures by most western governments: GOSIP
   
  
  • National policy to mandate an OSI subset (or profile) for government systems, discontinued in 1994/5.
  
   
  
• Huge and complicated, never fully implemented anywhere (see GOSIP, as above) although some portions are commercially available.
   
  
• Has had some influence on the Internet community: some upper layer OSI protocols (eg X.500, X.509, ASN.1) have been adopted in the Internet.