A system includes an ingress node, an egress node, and one or more intermediate nodes. A path is formed from the ingress node to the egress node via the one or more intermediate nodes, where the path carries label distribution protocol (LDP) packets of an LDP traffic flow. One of the intermediate nodes detects traffic congestion, modifies one of the LDP packets to include an indicator of the traffic congestion, and sends the modified LDP packet towards the egress node. The egress node receives the modified LDP packet and notifies the ingress node of the traffic congestion in response to identifying the indicator of the traffic congestion within the modified LDP packet.