The present invention relates to a marking determining method and a related device for determining a packet marking of packets of an incoming packet-flow, in order to keep the packets in conformance with a traffic policy. The determining is based on an actual value of a traffic reservation parameter, while the traffic reservation parameter is a measure of available network resources dedicated to packets of said incoming packet-flow having a pre-assigned priority. The determining further is based on the pre-assigned priority of the packets of the incoming packet flow. The marking method a first steps of holding a threshold value for the traffic reservation parameter, while the threshold value is lying between a minimum and a maximum value of the traffic reservation parameter. A second step is the metering the actual value of the traffic reservation parameter and a last step of determining the packet marking of the packets only based on the actual value of the traffic reservation parameter if the actual value of the traffic reservation parameter exceeds the threshold value for the traffic reservation parameter.