2.5 WAN Link Options
2.5.4 Packet-switched connections
Packet switching is a WAN switching method in which network devices share a permanent virtual circuit (PVC), which is like a point-to-point link to transport packets from a source to a destination across a carrier network, as shown in the Figure. Frame Relay, SMDS, and X.25 are all examples of packet-switched WAN technologies.

Switched networks can carry variable-size frames (packets) or fixed-size cells. The most common packet-switched network type is Frame Relay.