Session processing method and apparatus

1 . A session processing method comprising:

receiving, by a first session management network element and from a policy control network element, access point information of an application of a first session, wherein the access point information comprises an indication of application relocation possibility indicating that application relocation for the application is not possible, and wherein the first session is for transmitting a first data flow of the application;

determining, by the first session management network element in response to the indication of application relocation possibility indicating that application relocation for the application is not possible, that the first session management network element also serves a second session for transmitting the first data flow;

sending, by the first session management network element and to an access and mobility management function network element, a notification message comprising a first identifier of the first session, a session modification command, and a cause value, wherein the cause value indicates to establish the second session for a same data network as the first session;

receiving, by the first session management network element and from the access and mobility management function network element, a request message requesting establishment of the second session in the data network and comprising the first identifier and a second identifier of the second session; and

allocating, by the first session management network element, a first user plane network element to the second session for transmitting the first data flow.

2 . The session processing method of claim 1 , wherein a mode type of the first session is a session and service continuity (SSC) mode 3.

3 . The session processing method of claim 1 , further comprising releasing, by the first session management network element, the first session a predetermined time after establishing the second session.

4 . The session processing method of claim 1 , further comprising allocating, by the first session management network element, a second user plane network element to the second session for transmitting a second data flow corresponding to a second application that supports a data network access identifier (DNAI) change.

5 . The session processing method of claim 1 , further comprising sending, by the first session management network element and to a second session management network element, policy information that is for the second session management network element to allocate a second user plane network element to the second session for transmitting a third data flow when the application supports a data network access identifier (DNAI) change.

6 . A first session management network element 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 first session management network element to:

receive, from a policy control network element, access point information of an application of a first session, wherein the access point information comprises an indication of application relocation possibility indicating that application relocation for the application is not possible, and wherein the first session is for transmitting a first data flow of the application;

determine, in response to the indication of application relocation possibility indicating that application relocation for the application is not possible, that the first session management network element also serves a second session for transmitting the first data flow;

send, to an access and mobility management function network element, a notification message comprising a first identifier of the first session, a session modification command, and a cause value, wherein the cause value indicates to establish the second session for a same data network as the first session;

receive, from the access and mobility management function network element, a request message requesting establishment of the second session in the data network and comprising the first identifier and a second identifier of the second session; and

allocate a first user plane network element for transmitting the first data flow.

7 . The first session management network element of claim 6 , wherein a mode type of the first session is a session and service continuity (SSC) mode 3.

8 . The first session management network element of claim 6 , wherein the at least one processor is further configured to execute the instructions to cause the first session management network element to release the first session a predetermined time after establishing the second session.

9 . The first session management network element of claim 6 , wherein the at least one processor is further configured to execute the instructions to cause the first session management network element to allocate a second user plane network element to the second session for transmitting a second data flow corresponding to a second application that supports a data network access identifier (DNAI) change.

10 . The first session management network element of claim 6 , wherein the at least one processor is further configured to execute the instructions to cause the first session management network element to send, to a second session management network element, policy information that is for the second session management network element to allocate a second user plane network element to the second session for transmitting a third data flow when the application supports a data network access identifier (DNAI) change.

11 . A communication system comprising:

a user plane network element; and

a session management network element configured to:

receive, from a policy control network element, access point information of an application of a first session, wherein the access point information comprises an indication of application relocation possibility indicating that application relocation for the application is not possible, and wherein the first session is for transmitting a data flow of the application;

determine, in response to the indication of application relocation possibility indicating that application relocation for the application is not possible, that the session management network element also serves a second session for transmitting the data flow;

send, to an access and mobility management function network element, a notification message comprising a first identifier of the first session, a session modification command, and a cause value, wherein the cause value indicates to establish the second session for a same data network as the first session;

receive, from the access and mobility management function network element, a request message requesting establishment of the second session in the data network and comprising the first identifier and a second identifier of the second session; and

allocate the user plane network element to the second session,

wherein the user plane network element is configured to transmit, in the second session, the data flow.

12 . The communication system of claim 11 , further comprising the access and mobility management function network element, wherein the access and mobility management function network element is configured to send the request message to the session management network element.

13 . A method comprising:

receiving, by a session management network element and from a policy control network element, access point information of an application of a first session, wherein the access point information comprises an indication of application relocation possibility indicating that application relocation for the application is not possible, and wherein the first session is for transmitting a first data flow of the application;

determining, by the session management network element in response to the indication of application relocation possibility indicating that application relocation for the application is not possible, that the session management network element also serves a second session for transmitting the first data flow;

sending, by the session management network element and to an access and mobility management function network element, a notification message comprising a first identifier of the first session, a session modification command, and a cause value, wherein the cause value indicates to establish the second session for a same data network as the first session;

receiving, by the session management network element and from the access and mobility management function network element, a request message requesting establishment of the second session in the data network and comprising the first identifier and a second identifier of the second session;

allocating, by the session management network element, a first user plane network element to the second session; and

transmitting, by the first user plane network element, the first data flow.

14 . The method of claim 13 , further comprising allocating, by the session management network element, a second user plane network element to the second session.

15 . The method of claim 14 , further comprising transmitting, by the second user plane network element, a second data flow corresponding to a second application that supports a data network access identifier (DNAI) change in the second session.

16 . The method of claim 13 , wherein a mode type of the first session is a session and service continuity (SSC) mode 3.

17 . The method of claim 13 , further comprising receiving, by the access and mobility management function network element, the notification message.

18 . The method of claim 13 , further comprising sending, by the access and mobility management function network element and to the session management network element, the request message.

19 . A non-transitory computer-readable storage medium configured to store instructions that, when executed by at least one processor, cause a communications apparatus to:

receive, from a policy control network element, access point information of an application of a first session, wherein the access point information comprises an indication of application relocation possibility indicating that application relocation for the application is not possible, and wherein the first session is for transmitting a data flow of the application;

determine, in response to the indication of application relocation possibility indicating that application relocation for the application is not possible, that a session management network element also serves a second session for transmitting the data flow;

send, to an access and mobility management function network element, a notification message comprising a first identifier of the first session, a session modification command, and a cause value, wherein the cause value indicates to establish the second session for a same data network as the first session;

receive, from the access and mobility management function network element, a request message requesting establishment of the second session in the data network and comprising the first identifier and a second identifier of the second session; and

allocate a user plane network element to the second session for transmitting the data flow.

20 . The non-transitory computer-readable storage medium of claim 19 , wherein a mode type of the first session is a session and service continuity (SSC) mode 3.

21 . The non-transitory computer-readable storage medium of claim 19 , wherein the instructions, when executed by the at least one processor, further cause the communications apparatus to release the first session a predetermined time after establishing the second session.

22 . The non-transitory computer-readable storage medium of claim 19 , wherein the instructions, when executed by the at least one processor, further cause the communications apparatus to allocate a second user plane network element to the second session for transmitting a second data flow corresponding to a second application that supports a data network access identifier (DNAI) change.