A method of controlling the rate of traffic flow through an Iub interface of a Radio Network Controller is described. The method includes obtaining a licensed rate, which defines the maximum throughput permitted through the Iub interface, at the Radio Network Controller. The rate of traffic flow through the Iub interface and all Iu interfaces of the Radio Network Controller is measured, and the extent to which packet switched traffic flow through the Iub interface exceeds the licensed rate identified. If the packet switched traffic flow through the Iub interface exceeds the licensed rate, packets are dropped from traffic flow through the Iub interface to reduce the traffic flow to the licensed rate.