When permanent dedicated connections are required, a point-to-point link is used to provide a pre-established WAN communications path from the customer premises to the provider network. Point-to-point lines are usually leased from a service provider and are called leased lines.

Leased lines have existed since the early 1950s and for this reason, are referred to by different names such as leased circuits, serial link, serial line, point-to-point link, and T1/E1 or T3/E3 lines. The term leased line refers to the fact that the organization pays a monthly lease fee to a service provider to use the line. Leased lines are available in different capacities and are generally priced based on the bandwidth required and the distance between the two connected points.

In North America, service providers use the T-carrier system to define the digital transmission capability of a serial copper media link, while Europe uses the E-carrier system, as shown in the figure. For instance, a T1 link supports 1.544 Mb/s, an E1 supports 2.048 Mb/s, a T3 supports 43.7 Mb/s, and an E3 connection supports 34.368 Mb/s. Optical Carrier (OC) transmission rates are used to define the digital transmitting capacity of a fiber optic network.

The advantages of leased lines include:

The disadvantages of leased lines include:

The Layer 2 protocol is usually HDLC or PPP.