Identification of priority faults in a transport network

A first aspect of the invention provides a system for prioritising faults in a transport network comprising network elements arranged to transport data signals comprising respective overhead data and payload data. The system comprises one or more first network elements arranged to include in said overhead data a priority indicator indicating the relative importance of the respective payload data. The system further includes one or more second network elements arranged to examine the respective priority indicator of data signals in respect of which a fault is detected. Detected faults are prioritised using the respective value of the priority indicator and hence on the relative importance of the information carried by the faulty signal.