Full integration of satellite technology in future terrestrial infrastructures requires support for high-quality broadband bi-directional communications. Research efforts in the field of satellite communications are currently oriented in the study of QoS-aware solutions for DVB-S and DVB-RCS, which allowed seamless deployment in the Internet. In this paper the QoS architecture designed in the framework of the SATIP6 project, sponsored within the 5th EU Research Programme Framework, is presented. This is organized into two main modules, the traffic control and bandwidth on demand (BoD) module, whose aim are to provide for differentiated service of conveyed IP flows and efficient utilization of uplink bandwidth respectively. Experimental results obtained through Opnet simulations are reported and discussed to assess the effectiveness of the designed solution in terms of both service differentiation and efficient utilization of satellite resources.