Method for monitoring a network for anomalies

A method for monitoring a network for anomalies, the network provided for data transmission and having a plurality of devices connected to one another overfixedly prescribed signal transmission paths, which comprises the steps of:

• assigning one of the devices to be a master device having a counter and a trigger apparatus, and by said master device a prescribed signal feature of a signal transmitted via the network is acquired;
• reading, upon acquisition of the prescribed signal feature, a master counter state of the counter of the master device, corresponding to a time of the acquisition;
• determining via an evaluation apparatus, under predetermined anomaly-free conditions, a setpoint value of at least one network-specific parameter defined by a physical property of the network, wherein a frequency difference between a frequency of a clock generator of an actual source device, from which the signal was transmitted, and a clock generator of the master device, coupled to the counter of the master device, forms the network-specific parameter;
• determining a respective actual value of the at least one network-specific parameter by the evaluation apparatus from a difference between a read master counter state and a further counter state;
• indicating an anomaly if a predetermined deviation criterion between the respective actual value and the setpoint value is met;
• additionally acquiring a second prescribed signal feature of the signal by the trigger apparatus of the master device;
• reading a second master counter state, corresponding to a time of an acquisition of the second prescribed signal feature, wherein the actual value of the frequency difference is determined on a basis of a difference between the master counter state and the second master counter state and taking into account a prescribed data transmission rate and/or network clock frequency used in the network and/or a communication protocol used in the network and/or a type of modulation used in the network;
• calculating a relative frequency deviation as
• Δfrel=ΔCX/ΔCXMM,
• wherein
• ΔCX indicates a number of cycles awaited by the actual source device between the transmission of the first and second prescribed signal features;
• and
• ΔCXMM indicates the difference between the master counter state and the second master counter state.