1. A method of managing data traffic in a communications network, the method comprising: selecting, by a processing circuit of an edge node in the communications network, a penalty indicator in dependence upon a level of traffic determined for a subscriber associated with a packet being sent through the communications network, the penalty indicator comprising a services-differentiation indicator and representing a per-hop behavior to be applied subsequently to the packet associated with the subscriber, and wherein the per-hop behavior represented by the applied penalty indicator is adapted to allow bandwidth borrowing between subscribers associated with different respective levels of traffic; and applying, by the processing circuit, the penalty indicator to the packet so as to thereby manage traffic associated with the subscriber.