In computer networking and telecommunications, a pseudowire (or pseudo-wire) is an emulation of a point-to-point connection over a packet-switching network (PSN).

The pseudowire emulates the operation of a "transparent wire" carrying the service, but it is realized that this emulation will rarely be perfect. The service being carried over the "wire" may be Asynchronous Transfer Mode

Asynchronous Transfer Mode

Asynchronous Transfer Mode is a standard switching technique designed to unify telecommunication and computer networks. It uses asynchronous time-division multiplexing, and it encodes data into small, fixed-sized cells. This differs from approaches such as the Internet Protocol or Ethernet that...

 (ATM), Frame Relay

Frame relay

Frame Relay is a standardized wide area network technology that specifies the physical and logical link layers of digital telecommunications channels using a packet switching methodology...

, Ethernet

Ethernet

Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....

 or Time-division multiplexing

Time-division multiplexing

Time-division multiplexing is a type of digital multiplexing in which two or more bit streams or signals are transferred apparently simultaneously as sub-channels in one communication channel, but are physically taking turns on the channel. The time domain is divided into several recurrent...

 (TDM) while the packet network may be Multi-protocol label switching (MPLS), Internet Protocol

Internet Protocol

The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...

 (IPv4

IPv4

Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and the first version of the protocol to be widely deployed. Together with IPv6, it is at the core of standards-based internetworking methods of the Internet...

 or IPv6

IPv6

Internet Protocol version 6 is a version of the Internet Protocol . It is designed to succeed the Internet Protocol version 4...

), or Layer 2 Tunneling Protocol Version 3

L2TPv3

Layer 2 Tunneling Protocol Version 3 is an IETF standard related to L2TP that can be used as an alternative protocol to Multiprotocol Label Switching for encapsulation of multiprotocol Layer 2 communications traffic over IP networks...

 (L2TPv3).

The first pseudowire specifications were the Martini draft

Martini draft

The Martini drafts are contributions made to the IETF's PWE3 working group by Luca Martini of Cisco Systems and a number of other authors...

 for ATM pseudowires, and the TDMoIP

TDMoIP

In computer networking and telecommunications, TDM over IP is the emulation of time-division multiplexing over a packet switched network . TDM refers to a T1, E1, T3, or E3 signal, while the PSN is based either on IP or MPLS or on raw Ethernet...

 draft for transport of E1/T1 over IP.

In 2001, the Internet Engineering Task Force

Internet Engineering Task Force

The Internet Engineering Task Force develops and promotes Internet standards, cooperating closely with the W3C and ISO/IEC standards bodies and dealing in particular with standards of the TCP/IP and Internet protocol suite...

 (IETF) set up the PWE3

PWE3

In 2001, the IETF set up the pseudowire emulation edge to edge working group, and this group was given the acronym PWE3...

 working group, which was chartered to develop an architecture for service provider edge-to-edge pseudowires, and service-specific documents detailing the encapsulation

Encapsulation (networking)

In computer networking, encapsulation is a method of designing modular communication protocols in which logically separate functions in the network are abstracted from their underlying structures by inclusion or information hiding within higher level objects....

 techniques. Other standardization forums, including the International Telecommunication Union

International Telecommunication Union

The International Telecommunication Union is the specialized agency of the United Nations which is responsible for information and communication technologies...

(ITU) and the MFA Forum, are also active in producing standards and implementation agreements for pseudowires.