The invention relates to a method and a system for transferring timing messages in a digital data transfer system. In a solution according to the invention a timing message is transferred (101, 102, 103) within control data carried in a protocol data unit. The timing message is dependent on a transmission moment of the protocol data unit from a network element of the digital data transfer system. The control data is a synchronization status message (Ethernet-SSM) carried in an Ethernet-frame. Therefore, the number of such protocol data units that are dedicated only for timing purposes can be reduced.