A method to perform a cycle synchronization between interconnected sub-networks, in which a reference node connected to one of the sub-networks transmits a respective cycle time information to cycle masters of all other sub-networks at recurring time instants, and the cycle masters of all other sub-networks adjust their cycle time accordingly. An adjustment of the cycle time within a cycle master is performed by determining a first time interval (t1, t1′) in-between two receptions of cycle time information from the reference node with an own clock, determining a second time interval (t2, t2′) in-between two corresponding transmissions of cycle time information from the reference node on basis of the received cycle time information, comparing the first time interval (t1, t1′) and the second time interval (t2, t2′), and adjusting the own cycle length according to the comparison result.