With reference to the first possible implementation of the twelfth aspect, in a second possible implementation of the twelfth aspect, the transceiver module is further configured to send a seventh message to a third network node, where the seventh message includes the identification information of the terminal device, and the identification information of the terminal device is used by the first network node to retrieve context information of the terminal device that is stored at the first network node, or the seventh message includes context information of the terminal device, and the third network node is a user plane node of the first system.
With reference to any one of the twelfth aspect, or the first or the second possible implementation of the twelfth aspect, in a third possible implementation of the twelfth aspect, the first network node includes at least one of a Radio Link Control protocol layer function, a Media Access Control layer function, a physical layer function, and a Radio Resource Control layer function; and/or the first system includes at least one of a Packet Data Convergence Protocol layer function, a Service Data Adaptation Protocol layer function, and a Radio Resource Control layer function.