Frame Relay is a packet-switched(with low overhead),connection-oriented,WAN service.
Frame Relay uses a subset of the high-level data link control(HDLC) protocol called Link Access Procedure for Frame Relay(LAPF).
Frames carry data between user devices called data terminal equipment (DTE), and the data communications equipment (DCE) at the edge of the WAN.
Frame Relay is often used to interconnect LANs. When this is the case, a router on each LAN will be the DTE.
Developed for use in ISDN networks, however, it used widely in a variety of private and public networks which are not ISDN.