An efficient operation of modern network services in packet networks is often conditional on complex quality-of-service (QoS) support. Because of its relative simplicity the mechanism of Differentiated Services (DiffServ) has recently come to be the most widely used QoS support technology in IP networks. One of the biggest disadvantages of this mechanism is the inability to cooperate with end-stations and end-user applications. This paper introduces a solution which allows end-stations to automatically retrieve DiffServ-related information from a network. As a result, end-users can control traffic policing in the DiffServ domain provided the predefined traffic conditions are not violated.