in scenarios where the quality of service is negotiated through a signalling layer whereas the services are actually carried through a bearer layer , application functions at the signalling layer are not always aware of how quality of service is individually accomplished at the bearer layer on a service basis . the invention provides a method and devices whereby events are detected on a service data flow basis at a detection device in the bearer layer and notified towards an application device in the signalling layer via a control device between the signalling and the bearer layer . the list of events to be notified is obtainable at the control device from the application device and is included in quality of service related rules , along with service data flow filters . this quality of service related rules are provided to the detection device for inspecting individual service data flows in order to detect and notify the indicated events .