Abstract: Embodiments of this application provide a packet transmission method and apparatus, and relate to the field of communication technologies. When the packet transmission method is applied, a first packet may be determined by using a first device, where packet fields of the first packet include an authentication identifier field, an authentication code field, and at least one candidate authentication field, and the authentication identifier field indicates a field that is in the at least one candidate authentication field and that corresponds to the authentication code field; and then the first packet is sent.