This paper addresses the problem of configuring active queue management systems (e.g. WRED and RIO) for service level specifications in Internetworks. In particular, we focus on Assured Forwarding (AF) for non-responsive flows in Differentiated Services networks. The difficulty is to determine the correct queue level thresholds that will result in correct drop rates for various AF precedence levels under any combination of offered loads. A new active queue management scheme based on a control algorithm is proposed that senses not only queue levels but also rates of queue levels changes and per flow bit rates to converge automatically to an optimal set of transmit fractions. The scheme has been implemented and tested on a network processor. Results show that the new active queue management scheme protects assured aggregated flow rates during periods of congestion. For non-responsive traffic the buffer occupancy level remains low during 250 offered load.