An overlay-based congestion management mechanism for assured forwarding in differentiated services (DiffServ) network is presented in this paper. In the proposed scheme, a control packet is sent from the ingress to the egress router every fixed time interval. The ingress router employs a simple additive increase and explicitly decrease algorithm to adjust the aggregate's sending rate according to the QoS (quality of services) information reflected from the egress routers. For the performance evaluation of the proposed scheme, the simulation of the (proportional) fairness of aggregates traffic and packet loss ratio is presented.