Content delivery to end user devices (EUD) is controlled by transmitting content portions at a controlled flow. The time for the EUD to process the data is used to control the flow. The first portion is transmitted to the EUD and the amount of time to process the first portion is noted. Threshold values to stop and start transmissions are examined prior to the transmission of each content portion. If the amount of data remaining to be processed by the EUD is below the stop transmission threshold, transmission continues with the next portion. If the amount of data remaining to be processed by the EUD is above the stop threshold, transmission is either stopped or retarded. When it is determined that the amount of data remaining to be processed by the EUD is above the start transmission threshold, transmission is started or continued.