Session management method, device, and system

1. A session management method, comprising:

sending, by a remote anchor session management network element, one or more local data network access identifiers (DNAIs) to an intermediate session management network element;

receiving, by the intermediate session management network element, the one or more local DNAIs from the remote anchor session management network element;

determining, by the intermediate session management network element, a target DNAI based on current location information of a terminal and the one or more local DNAIs; and

selecting, by the intermediate session management network element, a local user plane function network element for the terminal based on the target DNAI.

2. The session management method according to claim 1 , wherein the one or more local DNAIs correspond to a session of the terminal, wherein the one or more local DNAIs are supported by the intermediate session management network element, and wherein the one or more local DNAIs are in a policy and charging control (PCC) rule.

3. The session management method according to claim 1 , further comprising:

obtaining, by the intermediate session management network element from the remote anchor session management network element, information about a session access mode;

determining, by the intermediate session management network element, that the session access mode is a multi-homing mode according to the information about the session access mode;

sending, by the intermediate session management network element, a local Internet Protocol (IP) address of the terminal to the remote anchor session management network element; and

receiving, by the remote anchor session management network element, the local IP address.

4. The session management method according to claim 1 , further comprising:

obtaining, by the intermediate session management network element, application identification information corresponding to the target DNAI; and

generating, by the intermediate session management network element, a target rule based on the application identification information corresponding to the target DNAI, wherein the target rule instructs the local user plane function network element to forward a received data packet.

5. The session management method according to claim 1 , wherein the local user plane function network element is a branching point, wherein the session management method further comprises notifying, by the intermediate session management network element, the local user plane function network element to offload a data packet to a local data network corresponding to the target DNAI, wherein the local user plane function network element is for accessing the local data network, and wherein a source address of the data packet is a local Internet Protocol (IP) address.

6. The session management method according to claim 5 , wherein notifying the local user plane function network element to offload the data packet comprises:

sending, by the intermediate session management network element, a first local routing rule to the local user plane function network element, wherein the first local routing rule is to offload the data packet to the local data network corresponding to the target DNAI; and

receiving, by the local user plane function network element, the first local routing rule.

7. The session management method according to claim 1 , further comprising:

obtaining, by the intermediate session management network element, a remote Internet Protocol (IP) address; and

generating, by the intermediate session management network element, a target rule based on the remote IP address, wherein the target rule is for the local user plane function network element to forward a received data packet.

8. The session management method according to claim 1 , wherein the local user plane function network element is a branching point, wherein the session management method further comprises:

notifying, by the intermediate session management network element, the local user plane function network element to offload a data packet to a remote anchor user plane function network element, wherein a source address of the data packet is a remote Internet Protocol (IP) address; and

receiving, by the intermediate session management network element from the remote anchor session management network element, the remote IP address.

9. The session management method according to claim 8 , wherein notifying the local user plane function network element to offload a data packet comprises:

sending, by the intermediate session management network element, a remote routing rule to the local user plane function network element, wherein the remote routing rule is to offload the data packet to the remote anchor user plane function network element; and

receiving, by the local user plane function network element, the remote routing rule.

10. The session management method according to claim 1 , further comprising:

sending, by the intermediate session management network element, the target DNAI to the remote anchor session management network element, wherein the target DNAI is for determining a policy and charging control (PCC) for the local user plane function network element; and

receiving, by the remote anchor session management network element, the target DNAI.

11. A session management system, comprising:

a remote anchor session management network element configured to send one or more local data network access identifiers (DNAIs); and

an intermediate session management network element configured to:

receive the one or more local DNAIs from the remote anchor session management network element;

determine a target DNAI based on current location information of a terminal and the one or more local DNAIs; and

select a local user plane function network element for the terminal based on the target DNAI.

12. The session management system according to claim 11 , wherein the one or more local DNAIs correspond to a session of the terminal, wherein the one or more local DNAIs are supported by the intermediate session management network element and are comprised in a policy and charging control (PCC) rule.

13. The session management system according to claim 11 , wherein the intermediate session management network element is further configured to:

obtain from the remote anchor session management network element, information about a session access mode;

determine that the session access mode is a multi-homing mode according to the information about the session access mode; and

send a local Internet Protocol (IP) address of the terminal to the remote anchor session management network element.

14. The session management system according to claim 11 , the intermediate session management network element is further configured to:

obtain application identification information corresponding to the target DNAI; and

generate a target rule based on the application identification information corresponding to the target DNAI, wherein the target rule is for the local user plane function network element to forward a received data packet.

15. The session management system according to claim 11 , wherein the local user plane function network element is a branching point, wherein the intermediate session management network element is further configured to notify the local user plane function network element to offload a data packet to a local data network corresponding to the target DNAI, wherein the local user plane function network element is for accessing the local data network, and wherein a source address of the data packet is a local Internet Protocol (IP) address.

16. The session management system according to claim 11 , further comprising the local user plane function network element, wherein the intermediate session management network element is configured to send a first local routing rule to the local user plane function network element, wherein the first local routing rule is to offload a data packet to the local data network corresponding to the target DNAI, and wherein the local user plane function network element is configured to receive the first local routing rule.

17. The session management system according to claim 11 , wherein the intermediate session management network element is further configured to:

obtain a remote Internet Protocol (IP) address; and

generate a target rule based on the remote IP address, wherein the target rule is for the local user plane function network element to forward a received data packet.

18. The session management system according to claim 11 , wherein the local user plane function network element is a branching point, wherein the intermediate session management network element is further configured to notify the local user plane function network element to offload a data packet to a remote anchor user plane function network element, wherein a source address of the data packet is a remote Internet Protocol (IP) address received by the intermediate session management network element from the remote anchor session management network element.

19. The session management system according to claim 11 , wherein the intermediate session management network element is configured to send a remote routing rule to the local user plane function network element, wherein the remote routing rule is to offload a data packet to a remote anchor user plane function network element, and wherein the local user plane function network element is configured to receive the remote routing rule.

20. The session management system according to claim 11 , wherein the intermediate session management network element is further configured to send the target DNAI to the remote anchor session management network element, wherein the target DNAI is for determining a policy and charging control (PCC) for the local user plane function network element, and wherein the remote anchor session management network element is further configured to receive the target DNAI.