A routing switch (1) includes an input (4a) for receiving serial packets from a source node in a computer network, a plurality of outputs (6a...6n), switch circuitry (10) for selectively interconnecting said input to a selected one of said outputs and header reading circuitry (22) for reading the header portion of a packet received at the input prior to receiving all of the packet. The switch also has a random header generator (28) which produces header portions generated at random which are then read by the header reading circuitry. The header reading circuitry is coupled to the switch circuitry (10) to connect to said input one of said outputs in dependence on said random header. The random header portion is then discarded at the routing switch identified thereby to reveal the original header. There is also provided a computer network, having a plurality of computer devices and at least one routing switch, and a method of routing messages through such a network.