A data flow control method for managing the flow of media data from a sending node to a receiving node over a communication network, the receiving node capable of playing said media data, wherein the data transmitted to the receiving node is a sequence of data segments encoded at a plurality of different data rates, and wherein the data flow control method is implemented by the receiving node for controlling the flow of said data from the sending node to the receiving node, the method further comprising: identifying a condition of the communication network between said sending and receiving nodes; identifying a condition of the data buffer at the receiving node; and adjusting the media data flow through said communication network based on the identified condition of the communication network and the identified condition of the receiving node.