Apublic data network (PDN) is anetwork established and operated by atelecommunications administration, or a recognized private operating agency, for the specific purpose of providingdata transmission services for the public.
The first public packet switching networks wereRETD in Spain (1972), the experimentalRCP network in France (1972) andTelenet in the United States (1975). "Public data network" was the common name given to the collection ofX.25 providers, the first of which were Telenet in the U.S. andDATAPAC in Canada (both in 1976), andTranspac in France (in 1978). TheInternational Packet Switched Service (IPSS) was the first commercial and international packet-switched network (1978). The networks were interconnected withgateways usingX.75. These combined networks had large global coverage during the 1980s and into the 1990s. The networks later provided the infrastructure for the earlyInternet.
In communications, a PDN is acircuit- orpacket-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 ofX.25,Frame Relay, orcell relay (ATM) services.[1] Access to a PDN generally includes a guaranteed bandwidth, known as thecommitted 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.[2]
Apublic switched data network (PSDN) is a network for providing data services via a system of multiplewide area networks, similar in concept to thepublic switched telephone network (PSTN).[3] A PSDN may use a variety of switching technologies, includingpacket switching,circuit switching, andmessage switching.[3] A packet-switched PSDN may also be called a packet-switched data network.[4][5]
Originally the term PSDN referred only toPacket Switch Stream (PSS), anX.25-based packet-switched network in the United Kingdom, mostly used to provide leased-line connections betweenlocal area networks and the Internet usingpermanent virtual circuits (PVCs).[6] Today, the term may refer not only to Frame Relay andAsynchronous Transfer Mode (ATM), both providing PVCs, but also toInternet Protocol (IP),GPRS, and otherpacket-switching techniques.
Whilst there are several technologies that are superficially similar to the PSDN, such asIntegrated Services Digital Network (ISDN) and thedigital subscriber line (DSL) technologies, they are not examples of it.[7] ISDN utilizes the PSTN circuit-switched network, and DSL uses point-to-pointcircuit switching communications overlaid on the PSTN local loop (copper wires), usually utilized for access to a packet-switched broadband IP network.
Apublic data transmission service is adata transmission service that is established and operated by atelecommunicationadministration, or a recognized private operating agency, and uses apublic data network. A public data transmission service may includeCircuit Switched Data,packet-switched, andleased line data transmission.
Public packet switching networks came into operation in the 1970s. The first wereRETD in Spain, in 1972;[8] the experimentalRCP in France, also in 1972;[9]Telenet in the United States, which began operation with proprietary protocols in 1975;EIN in theEEC in 1976; andEPSS in the United Kingdom in 1976 (in development since 1969).[10]
Telenet adoptedX.25 protocols shortly after they were published in 1976 whileDATAPAC in Canada was the first public data network specifically designed for X.25, also in 1976.[11] Many other PDNs adopted X.25 when they came into operation, includingTranspac in France in 1978,Euronet in the EEC in 1979,Packet Switch Stream in the United Kingdom in 1980, andAUSTPAC in Australia in 1982.Iberpac in Spain adopted X.25 in the 1980s.Tymnet andCompuServe in the United States also adopted X.25.
TheInternational Packet Switched Service (IPSS) was the first commercial and international packet-switched network. It was a collaboration between British and American telecom companies that became operational in 1978.[12][11][13]
TheSITA Data Transport Network for airlines adopted X.25 in 1981, becoming the world's most extensive packet-switching network.[14][15][16]
The networks were interconnected withgateways usingX.75. These combined networks had large global coverage during the 1980s and into the 1990s.[17][18][19]
Over time, other packet-switching technologies, includingFrame Relay (FR) andAsynchronous Transfer Mode (ATM) gradually replaced X.25.[20]
Many of these networks later adoptedTCP/IP and provided the infrastructure for the earlyInternet.[21][22]
The Spanish, dark horses, were the first people to have a public network. They'd got a bank network which they craftily turned into a public network overnight, and beat everybody to the post.
Two main approaches to internetworking have come into existence based upon the virtual circuit and the datagram services. The vast majority of the work on interconnecting networks falls into one of these two approaches: The CCITT X.75 Recommendation; The DoD Internet Protocol (IP).
{{cite book}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
This article incorporatespublic domain material fromFederal Standard 1037C.General Services Administration. Archived fromthe original on 2022-01-22.