A method and apparatus is disclosed for differentiating service in a data network which supports a plurality of service classes, by implementing a pricing strategy such that revenue for the ISP in non-busy hours in increased. An edge router assigns a predetermined packet service class value, which is either an artificial packet loss probability or an artificial packet delay, to each one of an associated plurality of service classes, of packets in a data stream, the predetermined packet service class value decreasing with the increasing importance degree of each of its associated plurality of service classes. The packets are delayed or dropped according to the predetermined packet service class value and according to a load on the data network.