Abstract: A network traffic management system and method for a relay-based communications network such as Frame Mode Bearer Service (FMBS) in which terminals (A and B) are linked by nodes (N) through which calls are routed, consists of setting a Recovery Needed flag at a node on detection of incorrect transmission of a frame or congestion at a node which discards the frame. The destination terminal (B) is notified by transmitting a null frame giving rise to a negative acknowledgement (NAK) received at the source terminal (A). The discarded frame is retransmitted with a Recovery flag set. At the node (N) the Recovery flag is detected and the frame is transmitted toward the destination terminal in the normal way. If the Recovery flag is not set and the Recovery Needed flag is set the frame is discarded. In this way, the rest of the network is not burdened with the transmission of frames that will be discarded by the destination terminal in any event until the discarded frame is correctly received.