Leased line

The primary factors affecting the recurring lease fees are the distance between end stations and the bandwidth of the circuit.

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.

In the 1990s, with the advances of the Internet, leased lines were also used to connect customer premises to ISP point of presence whilst the following decade saw a convergence of the aforementioned services (frame relay, ATM, Internet for businesses) with the MPLS integrated offerings.

Terminating a leased line with two PBX allowed customers to by-pass PSTN for inter-site telephony.

This allowed the customers to manage their own dial plan (and to use short extensions for internal telephone number) as well as to make significant savings if enough voice traffic was carried across the line (especially when the savings on the telephone bill exceeded the fixed cost of the leased line).

Thus, a number of telecommunication companies added ATM, Frame-relay or ISDN offerings to their services portfolio.

Then came the Internet (in the mid-1990s) and since then the most common application for leased line is to connect a customer to its ISP point of presence.

The NTE will terminate the circuit and provide the requested presentation most frequently X.21 however higher speed interfaces are available such as G.703 or 10BASE-T.

Local telephone companies also may provide CDA (Circuito Diretto Analogico), that are plain copper dry pair between two buildings, without any line termination: in the past (pre-2002) a full analog base band was provided, giving an option to customer to deploy xDSL technology between sites: nowadays everything is limited at 4 kHz of bearer channel, so the service is just a POTS connection without any setup channel.

Some internet service providers have therefore developed alternative products that aim to deliver leased-line type services (carrier Ethernet-based, zero contention, guaranteed availability), with more moderate bandwidth, over the standard UK national broadband network.