Method for accessing serving network and communications apparatus

1. A method for accessing a serving network, comprising:

receiving, by a session management function network element through a wireless network, a session establishment request message from a terminal, wherein the session establishment request message requests the session management function network element to establish a session for the terminal to access an Internet Protocol television (IPTV) network;

obtaining, by the session management function network element from a data management network element, authentication information of the terminal in the serving network, wherein the authentication information is for the terminal to access the serving network, and wherein the serving network is the IPTV network;

receiving, by the session management function network element, an initial access message from the terminal; and

sending, by the session management function network element through a user plane function network element, an access message to the serving network, wherein the access message comprises the authentication information.

2. The method according to claim 1 , further comprising:

obtaining, by the session management function network element, identification information of the serving network based on the session establishment request message;

determining, by the session management function network element based on the identification information of the serving network, a policy control function network element for providing a policy for the serving network;

notifying, by the session management function network element, the policy control network element that the terminal is to obtain a service from the serving network; and

receiving, by the session management function network element, the policy of the serving network from the policy control function network element.

3. The method according to claim 2 , wherein the identification information of the serving network is a data network name (DNN) of the serving network.

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

obtaining, by the session management function network element, identification information of the terminal;

establishing, by the session management function network element, a mapping relationship between the identification information of the terminal and session information of the terminal based on the identification information of the terminal and the session information of the terminal; and

sending, by the session management function network element, the mapping relationship to the user plane function network element.

5. The method according to claim 4 , further comprising:

obtaining, by the session management function network element, the identification information of the terminal from the data function management network element; or

obtaining, by the session management function network element, the identification information of the terminal from the initial access message.

6. The method according to claim 1 , further comprising:

receiving, by the session management function network element, a feedback message of the access message from the serving network, wherein the feedback message comprises identification information of the terminal;

determining, by the session management function network element, session information of the terminal based on the identification information of the terminal and a mapping relationship between the identification information of the terminal and the session information of the terminal; and

sending, by the session management function network element, the feedback message to the user plane function network element, wherein the feedback message comprises the session information of the terminal.

7. The method according to claim 1 , wherein obtaining the authentication information of the terminal comprises obtaining, by the session management function network element from subscription information of the terminal that is stored in the data management network element, the authentication information of the terminal.

8. The method according to claim 1 , further comprising adding, by the session management function network element, the authentication information of the terminal to the initial access message to obtain the access message.

9. The method according to claim 1 , wherein the authentication information of the terminal comprises a line identification (ID) of the terminal.

10. The method according to claim 1 , wherein the data management network element is a unified data management (UDM) network element.

11. The method according to claim 1 , wherein the initial access message and the access message are one of dynamic host configuration protocol (DHCP) discover messages, DHCP request messages, or DHCP solicit messages.

12. The method according to claim 1 , wherein the terminal is a residential gateway.

13. A session management function network apparatus, comprising:

a memory configured to store instructions; and

at least one processor coupled to the memory and configured to execute the instructions to cause the session management function network apparatus to:

receive, through a wireless network, a session establishment request message from a terminal, wherein the session establishment request message requests the session management function network apparatus to establish a session for the terminal to access an Internet Protocol television (IPTV) network;

obtain, from a data management network element, authentication information of the terminal in a serving network, wherein the authentication information is for the terminal to access the serving network, and wherein the serving network is the IPTV network;

receive an initial access message from the terminal; and

send, through a user plane function network element, an access message to the serving network, wherein the access message comprises the authentication information.

14. The session management function network apparatus according to claim 13 , wherein the session management function network apparatus obtains the authentication information of the terminal by obtaining, from subscription information of the terminal that is stored in the data management network element, the authentication information of the terminal.

15. The session management function network apparatus according to claim 13 , wherein the session management function network apparatus further adds the authentication information of the terminal to the initial access message to obtain the access message.

16. The session management function network apparatus according to claim 13 , wherein the authentication information comprises a line identification (ID) of the terminal.

17. The session management function network apparatus according to claim 13 , wherein the initial access message and the access message are Dynamic Host Configuration Protocol (DHCP) discover messages or DHCP request messages.

18. The session management function network apparatus according to claim 13 , wherein the initial access message and the access message are dynamic host configuration protocol (DHCP) solicit messages.

19. The session management function network apparatus according to claim 13 , wherein the terminal is a residential gateway.

20. A non-transitory computer-readable storage medium storing a program to be executed by at least one processor to cause a session management function network apparatus comprising the at least one processor to implement a method comprising:

receiving, through a wireless network, a session establishment request message from a terminal, wherein the session establishment request message requests the session management function network apparatus to establish a session for the terminal to accessing an Internet Protocol television (IPTV) network;

obtaining, from a data management network element, authentication information of the terminal in a serving network, wherein the authentication information is for the terminal to access the serving network, and wherein the serving network is the IPTV network;

receiving an initial access message from the terminal; and

sending, through a user plane function network element, an access message to the serving network, wherein the access message comprises the authentication information.

21. A method for accessing a serving network, comprising:

receiving, by a session management function network element through a wireless network, a session establishment request message from a terminal, wherein the session establishment request message requests the session management function network element to establish a session for the terminal to access an Internet Protocol television (IPTV) network;

sending, by a data management network element, authentication information of the terminal in the serving network;

obtaining, by the session management function network element from the data management network element, authentication information, wherein the authentication information is for the terminal to access the serving network, and wherein the serving network is the IPTV network;

receiving, by the session management function network element, an initial access message from the terminal; and

sending, by the session management function network element through a user plane function network element, an access message to the serving network, wherein the access message comprises the authentication information.