A network node (120), such as a packet marking node, efficiently measures the bitrates of incoming packets on a plurality of timescales (TSs). A throughput-value function (TVF) is then graphed to indicate the throughput-packet value relationship for that TVF. Then, starting from the longest TS and moving towards the shortest TS, the packet marking node determines (88) a distance between the TVFs of different TSs at the measured bitrates. To determine the packet marking, the packet marking node selects a random throughput value between 0 and the bitrate measured on the shortest TS. Depending on how the random value relates to the measured bitrates, a TVF, and the distances to add to the random value, is then selected to determine (92) a packet value (PV) with which to mark the packet. The packet marking node then marks (94) the packet according to the determined PV.