1. A control device for specifying a quality of service in a transmission of data packets between a service entity and a user equipment over a mobile network comprising a core network node and an access node which are adapted to control the handling of data packets sent between the service entity and the user equipment, control device, wherein the control device stores in a memory a defined number of service classes relating to the quality of service; the control device further comprises a processing unit adapted to select a service class from said defined number of service classes for the transmission, the processing unit is further adapted to receive a second set of attributes, wherein the second set of attributes specifies the selected service class, and determine, by a first unique mapping function, the first set of attributes according to the selected service class, and the control device is adapted to establish a first transmission context between the core network and the user equipment, wherein the first transmission context is associated with the 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.