WAN operations focus primarily on the physical layer (OSI Layer 1) and the data link layer (OSI Layer 2). WAN access standards typically describe both physical layer delivery methods and data link layer requirements, including physical addressing, flow control, and encapsulation.
WAN access standards are defined and managed by a number of recognized authorities, including the:
- Telecommunication Industry Association and the Electronic Industries Alliance (TIA/EIA)
- International Organization for Standardization (ISO)
- Institute of Electrical and Electronics Engineers (IEEE)
Layer 1 protocols describe how to provide electrical, mechanical, operational, and functional connections to the services of a communications service provider.
Layer 2 protocols define how data is encapsulated for transmission toward a remote location, and the mechanisms for transferring the resulting frames. A variety of different technologies are used, such as the Point-to-Point Protocol (PPP), Frame Relay, and ATM. Some of these protocols use the same basic framing or a subset of the High-Level Data Link Control (HDLC) mechanism.
Most WAN links are point-to-point. For this reason, the address field in the Layer 2 frame is usually not used.