A service class for a transmission of data packets between a service entity and a user equipment is selected from a plurality of service classes. A first transmission context is established between a core network node and the user equipment, and is associated with a first set of attributes for defining a first quality of service for the transmission. Furthermore, a second transmission context is established between an access node and the user equipment, and is associated with a second set of attributes for defining a second quality of service for 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.