Communication method and communication apparatus

1 . A communication method applied to a second access network device or a chip in the second access network device, the communication method comprising:

receiving a first message from a first access network device, the first message indicating whether a first state of a multicast broadcast service (MBS) session is activated or deactivated;

sending a first acknowledgment message corresponding to the first message to the first access network device;

wherein after the receiving the first message from the first access network device, the communication method further comprises:

sending a second message to a core network device, the second message requests establishing a user plane tunnel corresponding to the MBS session; and

receiving a second acknowledgment message corresponding to the second message from the core network device, wherein the second acknowledgment message indicates whether a second state of the MBS session is activated or deactivated.

2 . The communication method according to claim 1 , wherein:

the first message comprises first state information, and the first state information indicates whether the first state is activated or deactivated; or

the first message indicates whether the first state is activated or deactivated based on whether the first state information is or is not comprised within the first message.

3 . The communication method according to claim 1 , wherein the first message is a handover request message, and the first acknowledgment message is a handover request acknowledgment message.

4 . The communication method according to claim 1 , wherein the first state is a state of the MBS session before a terminal device is handed over, the second state is a state of the MBS session after the terminal device is handed over, and the MBS is an MBS that the terminal device is interested in or is receiving.

5 . The communication method according to claim 1 , wherein after the receiving the first message from the first access network device, the communication method further comprises:

determining that a state of the MBS session is the second state.

6 . The communication method according to claim 1 , wherein when the first state is activated, and the second state is deactivated, and after the receiving the second acknowledgment message that is of the second message and that is from the core network device, the communication method further comprises:

determining that the state of the MBS session is deactivated.

7 . A method, comprising:

sending, by a first access network device, a first message, the first message indicating whether a first state of a multicast broadcast service (MBS) session is activated or deactivated;

receiving, by a second access network device, the first message;

sending, by the second access network device, a first acknowledgment message corresponding to the first message; and

receiving, by the first access network device, the first acknowledgment message corresponding to the first message;

wherein after the receiving, by the second access network device, the first message, the method further comprises:

sending, by the second access network device, a second message, the second message requests establishing a user plane tunnel corresponding to the MBS session;

receiving, by a core network device, the second message;

sending, by the core network device, a second acknowledgment message corresponding to the second message, wherein the second acknowledgment message indicates whether a second state of the MBS session is activated or deactivated, the second state is a state of the MBS session after a terminal device is handed over; and

receiving, by the second access network device, the second acknowledgment message.

8 . The method according to claim 7 , wherein:

the first message comprises first state information, and the first state information indicates whether the first state is activated or deactivated; or

the first message indicates whether the first state is activated or deactivated based on whether first state information is or is not comprised within the first message.

9 . The method according to claim 7 , wherein the first message is a handover request message, and the first acknowledgment message is a handover request acknowledgment message.

10 . The method according to claim 7 , wherein the first state is a state of the MBS session before the terminal device is handed over, the second state is a state of the MBS session after the terminal device is handed over, and the MBS is an MBS that the terminal device is interested in or is receiving.

11 . The method according to claim 7 , wherein after the receiving the first message by the second access network device, the method further comprises:

determining, by the second access network device, that a state of the MBS session is the second state.

12 . The method according to claim 7 , wherein when the first state is activated, and the second state is deactivated, and after the receiving the second acknowledgment message by the second access network device, the method further comprises:

determining, by the second access network device, that the state of the MBS session is deactivated.

13 . The method according to claim 7 , before the sending, by the first access network device, the first message, the method further comprises:

receiving, by the first access network device, information from a core network device, the information indicating the first state of the MBS session, wherein:

the information is information comprised in an MBS session modification message;

the information is information comprised in a packet data unit (PDU) session modification message, or the information is information comprised in a PDU session establishment message, wherein the PDU session is associated with the MBS session; or

the information is information in an information field in a packet header of a data packet of the MBS service.

14 . The method according to claim 7 , before the sending, by the core network device, the second acknowledgement message, the method further comprises:

determining, by the core network device, the second state of the MBS session.

15 . An apparatus, comprising a processor configured to execute instructions to cause the apparatus to:

receive a first message from a first access network device, the first message indicating whether a first state of a multicast broadcast service (MBS) session is activated or deactivated;

send a first acknowledgment message corresponding to the first message to the first access network device;

wherein after the receiving the first message from the first access network device, the apparatus is further caused to:

send a second message to a core network device, the second message requests establishing a user plane tunnel corresponding to the MBS session; and

receive a second acknowledgment message corresponding to the second message from the core network device, wherein the second acknowledgment message indicates whether a second state of the MBS session is activated or deactivated.

16 . The apparatus according to claim 15 , wherein:

the first message comprises first state information, and the first state information indicates whether the first state is activated or deactivated; or

the first message indicates whether the first state is activated or deactivated based on whether the first state information is or is not comprised within the first message.

17 . The apparatus according to claim 15 , wherein the first message is a handover request message, and the first acknowledgment message is a handover request acknowledgment message.

18 . The apparatus according to claim 15 , wherein the first state is a state of the MBS session before a terminal device is handed over, the second state is a state of the MBS session after the terminal device is handed over, and the MBS is an MBS that the terminal device is interested in or is receiving.

19 . The apparatus according to claim 15 , wherein after the receiving the first message from the first access network device, the apparatus is further caused to:

determine that a state of the MBS session is the second state.

20 . The apparatus according to claim 15 , wherein when the first state is activated, and the second state is deactivated, and after the receiving the second acknowledgment message that is of the second message from the core network device, the apparatus is further caused to:

determine that the state of the MBS session is deactivated.