A real time data transmission method is used in a network in which a real time media gateway is provided to allow access to the internet backbone in addition to the usual GPRS specific gateway. The method involves changing the header in a real time data stream as it passes through the network so that it can pass directly to the real time gateway without passing through the GPRS specific gateway. This ensures that the data stream travels along a more direct route and shortens the headers used in the data stream in the process.