S112. Optionally, the first network node sends second indication information to the first system, where the second indication information includes the second cell radio network temporary identifier for the terminal device.
Optionally, the second indication information includes cell identifier information, such as a PCI or an E-UTRAN cell global identifier (E-UTRAN Cell Global Identifier), of the cell accessed by the terminal device.
Optionally, the second indication information is sent via an F1 control plane message (for example, an F1AP message). The F1 control plane message includes at least one of the following information: identification information for the terminal device at an F1 interface (for example, the identification information may be identification information for the terminal device of an F1AP DU side, or independent identification information for the terminal device at the interface), the second cell radio network temporary identifier (C-RNTI2), and the cell identifier information.
S113. The terminal device sends a first message to the first network node, where the first message includes identification information of the terminal device.
Optionally, the identification information for the terminal device is at least one of first cell radio network temporary identifier information and corresponding physical cell identifier information.