Modern WAN standards are defined and managed by a number of recognized authorities including the following:
TIA/EIA - Telecommunications Industry Association and Electronic Industries Alliance
ISO - International Organization for Standardization
IEEE - Institute of Electrical and Electronics Engineers
WANs in the OSI Model
Most WAN standards focus on the physical layer and the data link layer.
Layer 1 Protocols
Synchronous Digital Hierarchy (SDH)
Synchronous Optical Networking (SONET)
Dense Wavelength Division Multiplexing (DWDM)
Layer 2 Protocols
Broadband (i.e., DSL and Cable)
Wireless
Ethernet WAN (Metro Ethernet)
Multiprotocol Label Switching (MPLS)
Point-to-Point Protocol (PPP) (less used)
High-Level Data Link Control (HDLC) (less used)
Frame Relay (legacy)
Asynchronous Transfer Mode (ATM) (legacy)