A method including a network device receives a plurality of fragments of an Ethernet frame, where the plurality of fragments include an initial fragment and a first fragment, and the initial fragment includes a destination media access control (MAC) address field, in response to an error that occurs in the Ethernet frame, changes the first fragment to a second fragment, where the second fragment includes second type indication information (TII) and second to-be-transmitted data (TBTD), the second TII indicates that a type of the second TBTD is a control character, a value of first TBTD is different from a value of the second TBTD, and the second TBTD indicates that an error occurs in the Ethernet frame, and the network device sends the second fragment to a destination device.