This application provides a packet transmission method that includes: receiving from a first session management network element, a first message including an address of a first terminal device and an identifier of a first user plane network element servicing the first terminal device; receiving from a second session management network element, a second message including an address of a second terminal device and an identifier of a second user plane network element servicing the second terminal device; determining, that the first terminal device and the second terminal device belong to a same local area network group; sending to the first session management network element the identifier of the second user plane network element and the address of the second terminal device; and sending to the second session management network element the identifier of the first user plane network element and the address of the first terminal device.