A mechanism is provided to resolve the Iub transport network congestion efficiently for HSDPA by dynamic adjustment of the transmit window of the RLC. The RLC protocol is extended with congestion control functionality. The Iub TN and Uu congestion detection method in the Node-B (120) signals the congestion to the RNC (110), and this congestion indication is used by RLC to react on the congestion situation. In the RNC (110), the transmission window of the RLC is adjusted to control the flow rate. When congestion is detected, the RLC transmission window size is decreased. When there is no congestion, then the RLC transmission window size is increased automatically. Different types of congestion are distinguished and are handled in different ways. Alternatively, congestion control is achieved without any modification in the RLC layer from the existing standard. Here, RLC STATUS PDUs are used to change the RLC transmission window size.