Different Names for WAN Link

Leased circuit

In telco lingo, when you pick up the phone and make a voice call, the telco sets up a temporary circuit. When a customer pays money to have a permanently up circuit between two sites, the telco considers the circuit to be leased.

Leased line

The term "leased" is used for the same reasons as for leased circuit. The term "line" refers to the fact that the service is supposed to always be working, so it's like a cable, or a line, between the two sites.

Point-to-point link

The term "point-to-point" refers to the fact that exactly two end points exist on the circuit. The term "link" refers to the way the two end points are linked together so that they can communicate.

WAN link

The term "link" is used for the same reasons as in point-to-point link. The term "WAN" just refers to the link being used for wide-area networking at a relatively long distance.

Serial link

The term "serial" refers to the fact that the routers use serial interfaces on each end of the link.

4-wire circuit

The "4-wire" part refers to the number of wires in the cable between each CO and each site; a telco often uses the term "circuit" to refer to a communication path between two customer devices.

Serial link

A WAN link connects to serial interfaces on routers, hence the name "serial link."