The proportional differentiated services model has been gaining attention in recent years. Many effective algorithms have been proposed to provide delay and packet loss differentiated services to different traffic classes according to their pre-defined constraints.
In this article, we propose three novel QoS mechanisms to enhance the control of class-based QoS. First, we introduce a Scheduling to Dropping feedback mechanism, which is called SDF model. The main usage of the SDF is to provide dynamic trade-off between different basic QoS metrics. SDF provide differentiated services based on both proportionality constraints and absolute constraints. We also introduces an additional feature called Adaptive Safety margin (ASM). Usually, The Earlier Due Date (EDD)  employs a fixed safety margin to pre-assign more bandwith for time-critical traffics. ASM can adaptively changes this margin according to the queuing length or packet head-drop rate of the time-critical traffics when the congestion happened. By employing ASM with SDF model, it is found that the total packet drop can greatly be reduced.
Finally, we introduce two sorting methods, called one-sort and complete-sort scheme, for the queuing systems in the end-to-end QoS environment. By sorting the order of the packets in the queue based on their deadlines, we can reduce the probability of end-to-end deadline violation.