4.6.2.8 Mobility management for optimised handling of temporarily available network slices

The UE and the network may support optimised handling of temporarily available network slices. The support for S-NSSAI time validity information by the UE and the network, respectively, is optional.

If the UE has indicated that it supports S-NSSAI time validity information, then the AMF may include the S-NSSAI time validity information for one or more S-NSSAIs included in the configured NSSAI in the Registration Accept message or the CONFIGURATION UPDATE COMMAND message. If the AMF determines that the S-NSSAI time validity information for an S-NSSAI in the configured NSSAI is changed, the AMF may provide the UE with a new S-NSSAI time validity information for that S-NSSAI via the CONFIGURATION UPDATE COMMAND message.

If the UE supporting S-NSSAI time validity information, is configured with S-NSSAI time validity information for an S-NSSAI and:

• the S-NSSAI time validity information indicates that the S-NSSAI is available, then the UE may request the S-NSSAI in the requested NSSAI in the REGISTRATION REQUEST message;
• the S-NSSAI time validity information indicates that the S-NSSAI is not available, then:
• the UE shall not include the S-NSSAI in the requested NSSAI in the REGISTRATION REQUEST message;
• the UE shall remove the S-NSSAI from the stored allowed NSSAI (if any) and the stored partially allowed NSSAI (if any) in the non-volatile memory in the ME, as specified in annex C;

iii) the S-NSSAI time validity information indicates that the S-NSSAI will not become available again, then the UE shall remove the S-NSSAI from the stored configured NSSAI in the non-volatile memory in the ME, as specified in annex C; and

• the UE shall delete the entry from the alternative NSSAI (if any) containing the S-NSSAI in the replaced S-NSSAI or the alternative S-NSSAI as specified in clause 4.6.2.2.

NOTE 1: If the S-NSSAI to be removed is the only S-NSSAI in the allowed NSSAI and partially allowed NSSAI, if applicable, the UE can before the time validity expiry initiate the registration procedure for mobility and periodic registration update and include a different S-NSSAI from the configured NSSAI in the Requested NSSAI IE of the REGISTRATION REQUEST message. If the UE does not initiate the registration procedure for mobility and periodic registration update and the time validity for the only S-NSSAI in the allowed NSSAI and partially allowed NSSAI expires, the UE locally enters the state 5GMM-DEREGISTERED.

When the S-NSSAI time validity information of an S-NSSAI indicates that the S-NSSAI is not available, then:

• if the AMF receives a requested NSSAI in the REGISTRATION REQUEST message with the S-NSSAI identifying the network slice, the AMF shall:
• to a UE which has indicated that it supports S-NSSAI time validity information, provide:
• a configured NSSAI including the S-NSSAI together with the S-NSSAI time validity information in the REGISTRATION ACCEPT message if the S-NSSAI will become available again; or
• a configured NSSAI not including the S-NSSAI in the REGISTRATION ACCEPT message if the S-NSSAI will not become available again; or
• to a UE which has not indicated that it supports S-NSSAI time validity information, include the S-NSSAI in the rejected NSSAI for the current registration area;
• if the AMF detects that the S-NSSAI is included in the allowed NSSAI or the partially allowed NSSAI of a UE which has:
• indicated that it supports S-NSSAI time validity information, the AMF shall locally remove the S-NSSAI from the allowed NSSAI (if any), the partially allowed NSSAI (if any) and the entry from the alternative NSSAI (if any) containing the S-NSSAI in the replaced S-NSSAI or the alternative S-NSSAI; or

NOTE 2: If there is no S-NSSAI included in the allowed NSSAI and partially allowed NSSAI after local removal of the S-NSSAI from the allowed NSSAI or the partially allowed NSSAI, the network locally enters the state 5GMM-DEREGISTERED for the UE.

• not indicated that it supports S-NSSAI time validity information, the AMF shall remove the S-NSSAI from the stored allowed NSSAI (if any) and partially allowed NSSAI (if any) and include the S-NSSAI in the rejected NSSAI for the current registration area by sending the CONFIGURATION UPDATE COMMAND message.

NOTE 3: If there is no S-NSSAI included in the allowed NSSAI and partially allowed NSSAI after removal of the S-NSSAI from the allowed NSSAI or the partially allowed NSSAI, then the AMF performs the network-initiated de-registration procedure and sets the 5GMM cause value to #62 "No network slices available" in the DEREGISTRATION REQUEST message".

When the S-NSSAI time validity information of an S-NSSAI indicates that the S-NSSAI becomes available again, the AMF shall update the allowed NSSAI or partially allowed NSSAI including the S-NSSAI to a UE which has not indicated that it supports S-NSSAI time validity information by sending CONFIGURATION UPDATE COMMAND message if the UE is subscribed to the S-NSSAI.

The S-NSSAI time validity information is applicable for the current PLMN or SNPN regardless of the access type.