FECN BECN and the discard eligibility DE bit

Frame Relay uses two mechanisms to indicate congestion: Forward Explicit Congestion Notification (FECN) and Backward Explicit Congestion Notification (BECN). When a frame passes through a congested network, routers set the FECN bit in the frame’s header to 1 to indicate that congestion has been experienced. When the frame arrives at its destination, the receiver can use this information to adjust the flow of traffic.

BECN, on the other hand, is set by the receiver of a congested frame to inform the sender that congestion has been detected. If the sender receives a BECN, it can slow down the flow of traffic. The discard eligibility (DE) bit is used by Frame Relay to determine which frames should be discarded when congestion occurs. Frames with the DE bit set are more likely to be discarded than frames without it.

To control speed and discards, Frame Relay uses two mechanisms: Traffic Shaping and Congestion Management. Traffic Shaping is used to control the flow of traffic by buffering and delaying frames to conform to a specific rate. Congestion Management is used to manage congestion in the network by specifying the order in which packets should be sent and which ones should be dropped during periods of congestion. These mechanisms help to ensure that Frame Relay networks remain efficient and reliable, even under heavy traffic loads.