The invention relates to methods and apparatus for controlling traffic congestion of communication traffic in a communication network. The network includes a first node which is operable to receive communication traffic in the form of data from one of more sending nodes and to pass that data to one or more receiving nodes. The method includes monitoring the possible output data rate of the first node and detecting if the possible output data rate becomes smaller than a maximum data rate value and responsive to that monitoring step performing congestion control whereby the data throughput of a flow of data through the first node is decreased.