This switched data transmission system, particularly for use in avionics applications, of the type comprising a plurality of electronic devices and equipment units adapted for transmitting discrete messages over a transmission network, and in which each of the devices and equipment units is connected to a network switch, the switches being connected to each other by means of data transmission links so as to form a physical topology of a loop network, each message being associated with information regarding data flow priority in the network comprising of functional priority information, is characterized in that each message is also associated with information regarding temporal priority of data flow in the network.