Public data network
A public data network (PDN) is a network established and operated by a telecommunications administration, or a recognized private operating agency, for the specific purpose of providing data transmission services for the public. The first network was deployed in 1972 in Spain called RETD. Public data network was the common name given to the international collection of X.25 providers whose combined network had large global coverage during the 1980s and into the 1990s, which provided infrastructure for the early Internet.
In communications, a PDN is a circuit- or packet-switched network that is available to the public and that can transmit data in digital form. A PDN provider is a company that provides access to a PDN and that provides any of X.25, frame relay, or cell relay (ATM) services. Access to a PDN generally includes a guaranteed bandwidth, known as the committed information rate (CIR). Costs for the access depend on the guaranteed rate. PDN providers differ in how they charge for temporary increases in required bandwidth (known as surges). Some use the amount of overrun; others use the surge duration.
Examples include the following experimental/public networks which came into operation in the 1970s: RETD/Iberpac in Spain was the first in 1972; RCP/Transpac in France; Telenet, Tymnet and CompuServe in the United States; EPSS/Packet Switch Stream, in the United Kingdom; EIN/Euronet in the EEC; DATAPAC in Canada; and AUSTPAC in Australia.
The International Packet Switched Service was the first commercial and international packet-switched network. It was a collaboration between British and American telecom companies that became operational in 1978.
Public switched data network
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). A PSDN may use a variety of switching technologies, including packet switching, circuit switching, and message switching. A packet-switched PSDN may also be called a packet-switched data network.
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). 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. 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.
- History of the Internet
- Public data transmission service
- National research and education network
- X.25 § History
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