text: what is header and trailer in network? in data link layer it have header and trailer...(in network) a data packet consists of three elements. the first element is a header, which contains the information needed to get the packet from the source to the destination, and the second element is a data area, which contains the information of the user who caused the creation of the packet. the third element of packet is a trailer, which often contains techniques ensuring that errors do not occur during transmission.