WANs use the OSI reference model layered approach to encapsulation,
just as LANs do, but they are mainly focused on the physical and data
link layers. WAN standards typically describe both physical-layer
delivery methods and data link-layer requirements, including
addressing, flow control and encapsulation. WAN standards are defined
and managed by a number of recognized authorities, including the
following agencies:
- International Telecommunication Union-Telecommunication
Standardization Sector (ITU-T), formerly the Consultative
Committee for International Telegraph and Telephone (CCITT)
- International Organization for Standardization (ISO)
- Internet Engineering Task Force
(IETF)
- Electronic Industries Association (EIA)
- Telecommunications Industries Association (TIA)
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