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 public packet switching network, RETD, was deployed in 1972 in Spain. "Public data network" was the common name given to the collection of X.25 providers, the first of which was DATAPAC in 1976. The International Packet Switched Service became the first commercial and international packet-switched network in 1978. Their combined networks had large global coverage during the 1980s and into the 1990s. These networks later provided the 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. Experimental packet switching networks preceded the first public data networks which came into operation in the 1970s. Early examples include: RETD/Iberpac in Spain, which was the first PDN 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, which was the first PDN to use X.25; 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. These networks later adopted TCP/IP and provided the infrastructure for the early Internet.