A guaranteed forwarding service for Differentiated Service architecture

This paper presents an assured forwarding service for Differentiated Service architecture computer networks. In DiffServ, traffic flows are grouped into different classes such that the higher priority traffics have lower loss rate and delay as compared to lower priority traffics. We introduce two feedback controllers that guarantee the quality of service (QoS) for different classes of service. In each class, QoS is defined as the queuing delay and the amounts of loss rates in the queue. The internal loop controls the delay associated to each class. By controlling the output bit rate of each link, we can adjust the delay while maximizing the link utilization. The proposed controller can be called a Nonlinear Deadbeat Controller since the error dynamics are all canceled out. The external loop is also added to control the loss rate associated to each class. The controller uses the amount of overflow in the buffer to determine the amount of packets each class has to drop such that the loss specifications are also met. The stability of the closed-loop system is also shown. Simulation results are given to demonstrate the enhanced performance of the system utilizing the proposed controller.