A public data network (PDN) is a network established and operated by a

telecommunications Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of ...

administration, or a recognized private operating agency, for the specific purpose of providing

data transmission Data communication, including data transmission and data reception, is the transfer of data, signal transmission, transmitted and received over a Point-to-point (telecommunications), point-to-point or point-to-multipoint communication chann ...

services for the public. The first public packet switching networks were RETD in Spain (1972), the experimental RCP network in France (1972) and Telenet in the United States (1975). "Public data network" was the common name given to the collection of

X.25 X.25 is an ITU-T standard protocol suite for Packet switched network, packet-switched data communication in wide area network, wide area networks (WAN). It was originally defined by the CCITT, International Telegraph and Telephone Consultative Co ...

providers, the first of which were Telenet in the U.S. and DATAPAC in Canada (both in 1976), and Transpac in France (in 1978). The

International Packet Switched Service The International Packet Switched Service (IPSS) was the first international and commercial packet switching network. It was created in 1978 by a collaboration between Britain's Post Office Telecommunications, and the United States' Western Union ...

(IPSS) was the first commercial and international packet-switched network (1978). The networks were interconnected with gateways using X.75. These combined networks had large global coverage during the 1980s and into the 1990s. The networks later provided the infrastructure for the early

Internet The Internet (or internet) is the Global network, global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a internetworking, network of networks ...

Description

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

Frame Relay Frame Relay (FR) is a standardized wide area network (WAN) technology that specifies the Physical layer, physical and data link layers of digital telecommunications channels using a packet switching methodology. Frame Relay was originally devel ...

, 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.

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 The public switched telephone network (PSTN) is the aggregate of the world's telephone networks that are operated by national, regional, or local telephony operators. It provides infrastructure and services for public telephony. The PSTN consists o ...

(PSTN). A PSDN may use a variety of switching technologies, including

packet switching In telecommunications, packet switching is a method of grouping Data (computing), data into short messages in fixed format, i.e. ''network packet, packets,'' that are transmitted over a digital Telecommunications network, network. Packets consi ...

, 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

-based packet-switched network in the United Kingdom, mostly used to provide leased-line connections between

local area network A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, campus, or building, and has its network equipment and interconnects locally managed. LANs facilitate the distribution of da ...

s and the Internet using permanent virtual circuits (PVCs). Today, the term may refer not only to Frame Relay and

Asynchronous Transfer Mode Asynchronous Transfer Mode (ATM) is a telecommunications standard defined by the American National Standards Institute and International Telecommunication Union Telecommunication Standardization Sector (ITU-T, formerly CCITT) for digital trans ...

(ATM), both providing PVCs, but also to

Internet Protocol The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet. IP ...

(IP),

GPRS General Packet Radio Service (GPRS), also called 2.5G, is a mobile data standard on the 2G cellular communication network's Global System for Mobile Communications, global system for mobile communications (GSM). Networks and mobile devices wit ...

, and other packet-switching techniques. Whilst there are several technologies that are superficially similar to the PSDN, such as

Integrated Services Digital Network Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the digitalised circuits of the public switched telephone network. ...

(ISDN) and the

digital subscriber line Digital subscriber line (DSL; originally digital subscriber loop) is a family of technologies that are used to transmit digital data over telephone lines. In telecommunications marketing, the term DSL is widely understood to mean asymmetric dig ...

(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.

Public data transmission service

A public data transmission service is a

service that is established and operated by a

telecommunication Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of ...

administration Administration may refer to: Management of organizations * Management, the act of directing people towards accomplishing a goal: the process of dealing with or controlling things or people. ** Administrative assistant, traditionally known as a se ...

, or a recognized private operating agency, and uses a ''public data network''. A public data transmission service may include Circuit Switched Data, packet-switched, and leased line data transmission.

History

Public packet switching networks came into operation in the 1970s. The first were RETD in Spain, in 1972; the experimental RCP in France, also in 1972; Telenet in the United States, which began operation with proprietary protocols in 1975; EIN in the

EEC The European Economic Community (EEC) was a regional organisation created by the Treaty of Rome of 1957,Today the largely rewritten treaty continues in force as the ''Treaty on the functioning of the European Union'', as renamed by the Lisbo ...

in 1976; and EPSS in the United Kingdom in 1976 (in development since 1969). Telenet adopted

protocols shortly after they were published in 1976 while DATAPAC in Canada was the first public data network specifically designed for X.25, also in 1976. Many other PDNs adopted X.25 when they came into operation, including Transpac in France in 1978, Euronet in the EEC in 1979, Packet Switch Stream in the United Kingdom in 1980, and AUSTPAC in Australia in 1982. Iberpac in Spain adopted X.25 in the 1980s. Tymnet and

CompuServe CompuServe, Inc. (CompuServe Information Service, Inc., also known by its initialism CIS or later CSi) was an American Internet company that provided the first major commercial online service provider, online service. It opened in 1969 as a times ...

in the United States also adopted X.25. The

(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. The

SITA Sita (; ), also known as Siya, Jānaki and Maithili, is a Hindu goddess and the female protagonist of the Hindu epic ''Ramayana''. Sita is the consort of Rama, the avatar of god Vishnu, and is regarded as an avatar of goddess Lakshmi. She is t ...

Data Transport Network for airlines adopted X.25 in 1981, becoming the world's most extensive packet-switching network. The networks were interconnected with gateways using X.75. These combined networks had large global coverage during the 1980s and into the 1990s. Over time, other packet-switching technologies, including

(FR) and

(ATM) gradually replaced X.25. Many of these networks later adopted

TCP/IP The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suite are ...

and provided the infrastructure for the early

References

Sources