A New Approach in Scheduling for Differentiated Services Networks

In previous decades, the Internet has moved from a limited low bandwidth network to a sophisticated infrastructure supporting many new applications such as video conferencing and Internet telephony. These applications have diverse QoS requirements. Support of QoS in such a packet-switched network requires a broad range of functions, such as priority mechanisms, scheduling disciplines, traffic shaping schemes, QoS signaling, and routing algorithms. One of the most important parameters in QoS is the delay of packets. The absolute guarantee model and the proportional service model are two methods to guarantee the delay. In the absolute guarantee model, a fixed maximum service delay for each class needs to be enforced. In the proportional service model, a fixed ratio between the delays seen by the different service classes can be enforced. To reach the delay constraints, routers allocate the rates of classes by scheduling algorithms.