Release of a second session of a wireless device by an access and mobility management function

1. A method comprising:

sending, by a source access and mobility management function (AMF) to a target AMF, a first message indicating:

a handover of a wireless device; and

a source session management function (SMF);

receiving, by the source AMF from the target AMF, a second message causing a release of at least one second session of the wireless device;

sending, by the source AMF to the target AMF, a first indication of the completion of the release of the at least one second session;

sending, by the source AMF to the source SMF, a request for the release of the at least one second session; and

receiving, by the source AMF from the source SMF, a second indication of completion of the release of the at least one second session.

2. The method of claim 1 , wherein the first message comprises at least one of:

an identity of the source SMF; or

an address of the source SMF.

3. The method of claim 1 , further comprising:

receiving, from the target AMF, a response message for the first message, the response message indicating a forward relocation response for the wireless device; and

sending, to a source base station and based on the response message, a third message indicating a handover command for the wireless device.

4. The method of claim 1 , wherein the target AMF:

selects, in response to the handover, a target SMF different from the source SMF; and

sends, to the target SMF, a third message indicating creation of at least one first session, the third message comprising at least one session identifier of the at least one first session.

5. The method of claim 4 , wherein the third message further comprises at least one of:

a single network slice selection assistance information;

a network slicing instance identifier;

a data network name; or

a user identity of the wireless device.

6. The method of claim 4 , wherein the first message further:

indicates establishment of the at least one first session; and

comprises at least one of:

the at least one session identifier of the at least one first session;

a first Internet protocol (IP) address of the wireless device; or

a data network name.

7. The method of claim 4 , wherein the target SMF:

selects, a target user plane function (UPF) different from a source UPF; and

sends, to the target UPF, a fourth message requesting establishment of a session context for the at least one first session.

8. The method of claim 7 , wherein the target SMF receives, from the target UPF, a fifth message acknowledging establishment of the session context.

9. The method of claim 4 , wherein the at least one second session is established before the first session.

10. The method of claim 1 , wherein the source SMF:

sends, to a source user plane function and in response to receiving the request for the release of the at least one second session, a user plane session release message requesting release of one or more user plane sessions of the at least one second session; and

receives, from the source UPF, an indication of release of the one or more user plane sessions.

11. A source access and mobility management function (AMF) comprising:

one or more processors;

memory storing instructions that, when executed by the one or more processors, cause the source AMF to:

send, to a target AMF, a first message indicating:

a handover of a wireless device; and

a source session management function (SMF);

receive, from the target AMF, a second message causing a release of at least one second session of the wireless device;

send, to the target AMF, a first indication of the completion of the release of the at least one second session;

send, to the source SMF, a request for the release of the at least one second session; and

receive, from the source SMF, a second indication of completion of the release of the at least one second session.

12. The source AMF of claim 11 , wherein the first message comprises at least one of:

an identity of the source SMF; or

an address of the source SMF.

13. The source AMF of claim 11 , wherein the instructions, when executed by the one or more processors, further cause the source AMF to:

receive, from the target AMF, a response message for the first message, the response message indicating a forward relocation response for the wireless device; and

send, to a source base station and based on the response message, a third message indicating a handover command for the wireless device.

14. The source AMF of claim 11 , wherein the target AMF:

selects, in response to the handover, a target SMF different from the source SMF; and

sends, to the target SMF, a third message indicating creation of at least one first session, the third message comprising at least one session identifier of the at least one first session.

15. The source AMF of claim 14 , wherein the third message further comprises at least one of:

a single network slice selection assistance information;

a network slicing instance identifier;

a data network name; or

a user identity of the wireless device.

16. The source AMF of claim 14 , wherein the first message further:

indicates establishment of the at least one first session; and

comprises at least one of:

the at least one session identifier of the at least one first session;

a first Internet protocol (IP) address of the wireless device; or

a data network name.

17. The source AMF of claim 14 , wherein the target SMF:

selects, a target user plane function (UPF) different from a source UPF; and

sends, to the target UPF, a fourth message requesting establishment of a session context for the at least one first session, wherein the target SMF receives, from the target UPF, a fifth message acknowledging establishment of the session context.

18. The source AMF of claim 17 , wherein the at least one second session is established before the first session.

19. The source AMF of claim 11 , wherein the source SMF:

sends, to a source user plane function and in response to receiving the request for the release of the at least one second session, a user plane session release message requesting release of one or more user plane sessions of the at least one second session; and

receives, from the source UPF, an indication of release of the one or more user plane sessions.

20. A system comprising:

a target access and mobility management function (AMF);

a source session management function (SMF); and

a source AMF comprising:

one or more processors;

memory storing instructions that, when executed by the one or more processors, cause the source AMF to:

send, to the target AMF, a first message indicating:

a handover of a wireless device; and

the source session management function (SMF);

receive, from the target AMF, a second message causing a release of at least one second session of the wireless device;

send, to the target AMF, a first indication of the completion of the release of the at least one second session;

send, to the source SMF, a request for the release of the at least one second session; and

receive, from the source SMF, a second indication of completion of the release of the at least one second session.