Backward Explicit Congestion Notification (FECN)

A bit set in a frame that notifies a DTE that congestion avoidance procedures should be initiated by the receiving device. As shown in Figure when a Frame Relay switch recognizes congestion in the network, it sends a BECN packet to the source router, instructing the router to reduce the rate at which it is sending packets. If the router receives any BECNs during the current time interval, it decreases the transmit rate by 25%.
Discard Eligibility (DE) Indicator
A set bit that indicates the frame may be discarded in preference to other frames if congestion occurs. When the router detects network congestion, the Frame Relay switch will drop packets with the DE bit set first. The DE bit is set on the oversubscribed traffic (that is, the traffic that was received after the CIR was met).

Frame Relay can be used as an interface to either a publicly available carrier-provided service or to a network of privately owned equipment. You deploy a public Frame Relay service by putting Frame Relay switching equipment in the central office of a telecommunications carrier. In this case, users get economic benefits from traffic-sensitive charging rates, and don't have to spend the time and effort to administer and maintain the network equipment and service.