In this paper, a novel active queue management scheme is proposed to employ in the routers that deal with both the best-effort traffic flows and multimedia traffic flows. Most of the available active queue management schemes consider only TCP flows, which results in unexpected congestion when it deals with multimedia flows. The queue size and packet receiving rate are the common parameters to calculate the marking probability in the queue. The use of Round Trip Time (RTT) in the process of marking probability calculation has the advantages over other approaches. We discuss the applicability of our approach when the framework in our earlier paper is used for rate adaptation in multimedia flows. With the use of RTT in packet marking probability calculations, we can assure rate reduction in both best-effort and multimedia flows before a queue gets exhausted. The most influential feature of the proposed approach is that it can work with the existing systems. The soundness of the proposed approach is inferred from the simulation results.