Abstract   Today’s IP networks must be able to serve many applications with different needs and goals and the traditional best effort approach is not sufficient to provide the various degrees of Quality of Service (QoS) required by these heterogeneous applications. In previous work, we have proposed a user-centric QoS management scheme within a game theoretic framework. In this paper, our goal is to model user behavior and to study the relationship between network performance, user satisfaction and choice of service class. Our results show that our user behavior model is realistic in the context of a user-controlled QoS: users can obtain a satisfactory service by choosing their service classes themselves. Their satisfaction is higher when they can choose their service classes dynamically rather than with a static allocation. The model also points out the importance of user actions on network stability.