In this paper researcher analyse the performance of a queue management policy on a network switch, which receives two classes of traffic with different quality requirements in terms of delays and losses. It is shown how the state probabilities of this system can be obtained recursively, and from them the average delays of both types of traffic, as well as their loss rates. All these quantities are involved in calculating the performance of the system through an objective function that represents a weighting of the cost caused by the delays produced in priority traffic (in real time) and the losses caused by non-priority traffic (in non-real time).