The service being carried over the "wire" may be Asynchronous Transfer Mode (ATM), Frame Relay, Ethernet or time-division multiplexing (TDM) while the packet network may be Multiprotocol Label Switching (MPLS), Internet Protocol (IPv4 or IPv6), or Layer 2 Tunneling Protocol Version 3 (L2TPv3).
[1] In 2001, the Internet Engineering Task Force (IETF) set up the PWE3 working group, which was chartered to develop an architecture for service provider edge-to-edge pseudowires, and service-specific documents detailing the encapsulation techniques.
Starting from 2006, telecom operators like BellSouth, Supercomm, AT&T, and Verizon began to invest more into pseudowire technology, pointing out its advantages to Ethernet in particular.
[2] Pseudowires tie services together across multiple transport technologies, including Ethernet over SONET, WDM, GPON, DSL, and WiMax.
[4] There are now many pseudowire standards, the most important of which are IETF RFCs as well as ITU-T Recommendations: