Leased line

A leased line is a private telecommunications circuit between two or more locations provided according to a commercial contract. It is sometimes also known as a private circuit, and as a data line in the UK. Typically, leased lines are used by businesses to connect geographically distant offices. Unlike traditional telephone lines in the public switched telephone network (PSTN) leased lines are generally not switched circuits, and therefore do not have an associated telephone number. Each side of the line is permanently connected, always active and dedicated to the other. Leased lines can be used for telephone, Internet, or other data communication services. Some are ringdown services, and some connect to a private branch exchange (PBX) or network router. The primary factors affecting the recurring lease fees are the distance between end stations and the bandwidth of the circuit. Since the connection does not carry third-party communications, the carrier can assure a specified level of quality. An Internet leased line is a premium Internet connectivity product, normally delivered over fiber, which provides uncontended, symmetrical bandwidth with full-duplex traffic. It is also known as an Ethernet leased line, dedicated line, data circuit or private line. Leased line services (or private line services) became digital in the 1970s with the conversion of the Bell backbone network from analog to digital circuits. This allowed AT&T to offer Dataphone Digital Services (later re-branded digital data services) that started the deployment of ISDN and T1 lines to customer premises to connect. Leased lines were used to connect mainframe computers with terminals and remote sites, via IBM's Systems Network Architecture (created in 1974) or DEC's DECnet (created in 1975). With the extension of digital services in the 1980s, leased lines were used to connect customer premises to Frame Relay or ATM networks. Access data rates increased from the original T1 option with maximum transmission speed of 1.544 Mbit/s up to T3 circuits.