A method for specifying the quality of service in a transmission of data packets between a service entity (AF1) and a user equipment over a mobile network is described. The mobile network comprises a core network node (SGSN1) and an access node (NB1, RNC1) which are adapted to control the handling of data packets sent between the service entity (AF1) and the user equipment (UE1). A plurality of service classes relating to the quality of service are preconfigured and a selected service class is selected from said plurality for the transmission. A first transmission context (PDP1) is established between the core network node and the user equipment (UE1), said first transmission context being associated with a first set of attributes for defining a first quality of service for the exchange of the data packets with the user equipment in the transmission.; Furthermore, a second transmission context (RAB1, RB1) is established between the access node (NB1, RNC1) and the user equipment (UE1),said second transmission context being associated with a second set of attributes for defining a second quality of service for the exchange of the data packets with the user equipment in the transmission. The selected service class determines the first set of attributes by a first unique mapping function performed in the core network node and the selected service class determines the second set of attributes by a second unique mapping function performed in the access node. A corresponding mobile network, control device and computer program are also described.