Frame Relay
The frame relay protocol is similar in purpose to X.25 but was created as an improvement. Frame relay operates at transmission rates of 56 kbps to 45 mbps.
Frame relay relies on higher level protocols to do error checking and flow control so it is more efficient than X.25. It has largely replaced X.25 in the US.
Frame relay is based on digital lines and usually operates over T1 (copper) and T3 (fiber) lines. It is the fastest WAN protocol described in this chapter.
Frame relay defines the connection between the CPE (customer premises equipment) which is usually a router and the telecommunications provider's local access switching equipment (frame relay switch).