The invention relates to a procedure for the transmission of data in variable time slots between a controller of a packet-oriented data network on the one hand and a terminal of a user of the data network on the other hand, time slots for the data transmission being assigned to a terminal following request made by the terminal and in dependence on the transmission capacity available in the data network. In order to create the possibility of enabling known data networks for the transmission of data in variable time slots to be used also for QoS applications without restriction of the functionality, it is proposed that the data transmission rate be monitored separately for each data flow of a terminal of the data network.