Signal route selector and method of signal routing

A signal route selector for routing a signal between a source and a destination over one of a plurality of alternative routes comprises a response monitor for determining whether transmissions between the source and destination succeed or fail on a selected route. A record of the successes and failures for the routes is maintained and a determination is made of the probability that a transmission will succeed on any route. A route for a transmission is selected according to the probabilities of success for the alternative routes.