leased line

Definition of leased line in The Network Encyclopedia.

What is Leased Line?

Also called a dedicated line, a telecommunications service provided to businesses by telcos and long distance carriers that provides a permanent direct connection between two geographically separate local area networks (LANs).

Leased lines are dedicated circuits that the telco reserves for the exclusive use of the customer. They are permanently available, always active, and secure, and they have a consistent quality of service (QoS) and a flat monthly fee. However, they are very expensive compared to dial-up lines, and businesses rarely use their full bandwidth capabilities except in short bursts.

Leased lines are a form of point-to-point connection. Your LAN is connected by bridges, routers, modems, and terminal adapters to the telco’s central office (CO), which sets up dedicated switches to connect you to the destination LAN. The presence of dedicated switches is what makes leased lines so expensive. You would use a leased line to connect a Microsoft Exchange server to the Internet, for example. Since the leased line is always on, there is no connection delay when users try to access the server for their e-mail.

Leased lines are available in 56 Kbps, T1, T3, and higher speeds. They are used mainly for connecting customer premises to the telco CO. The charge for a leased line is based on both bandwidth and distance; leased lines are usually leased for a base monthly cost, and sometimes incur an extra monthly charge proportional to the traffic carried on the line.

Graphic L-3. Leased line.


The opposite of a leased or dedicated line is a dial-up line or switched line.