Public switched data network

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A public switched data network (PSDN) is a network for providing data services via a system of multiple wide-area networks, similar in concept to the public switched telephone network (PSTN).[1] A PSDN may use a variety of switching technologies, including packet switching, circuit switching, and message switching.[1] A packet-switched PSDN may also be called a packet-switched data network.[2][3]

Originally the term PSDN referred only to Packet Switch Stream (PSS), an X.25-based packet-switched network, mostly used to provide leased-line connections between local area networks and the Internet using permanent virtual circuits (PVCs).[citation needed] Today, the term may refer not only to Frame Relay and Asynchronous Transfer Mode (ATM), both providing PVCs, but also to Internet Protocol (IP), GPRS, and other packet-switching techniques.

Whilst there are several technologies that are superficially similar to the PSDN, such as Integrated Services Digital Network (ISDN) and the Digital Subscriber Line (DSL) technologies, they are not examples of it.[citation needed] ISDN utilizes the PSTN circuit-switched network, and DSL uses point-to-point circuit switching communications overlaid on the PSTN local loop (copper wires), usually utilized for access to a packet-switched broadband IP network.


  1. ^ a b Bagad (2009). Telecommunication Switching Systems and Networks. Technical Publications. p. 344. ISBN 9788184315905. Retrieved 25 November 2016.
  2. ^ Hura and Singal (2001). Data and Computer Communications: Networking and Internetworking. CRC Press. p. 1168. ISBN 9780849309281. Retrieved 25 November 2016.
  3. ^ Mazda, Fraidoon (2013). Focal Illustrated Dictionary of Telecommunications. Taylor & Francis. p. 704. ISBN 9781136121029. Retrieved 25 November 2016.