The ongoing challenge of supporting high performance communications, real-time critical and secure applications leads to a shift from traditional IP networks towards a more intelligent, end-to-end, service-aware network paradigm. Further networks have to i) be more content or application-aware; ii) provide dynamic features for service creation; iii) observe and enforce network-wide policies; and finally iv) enable control from the network provider to the end-user. This paper presents the technical aspects of a policy based auditing system for a QoS-enabled network. The goal is to define the architecture of policy-based network QoS control and to develop and implement a prototype to evaluate this architecture.