In order to select a synchronization signal higher in accuracy, thereby increasing the accuracy of the time synchronization, it is provided a network node for transferring data in a network, comprising: a network interface having a plurality of ports; a transfer control module; a time synchronizing module; a fluctuation measurement module; and a clock. The time synchronization module uses a received time synchronization packet to synchronize the clock. The fluctuation measurement module determines an accuracy of a time contained in the received time synchronization packet based on a result of comparison between the time contained in the received time synchronization packet and a time of the clock.