Section: 4.6.2.8 Mobility management for optimised handling of temporarily available network slices
Content: 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: a) 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; b) the S-NSSAI time validity information indicates that the S-NSSAI is not available, then: i) the UE shall not include the S-NSSAI in the requested NSSAI in the Registration Request message; ii) 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; and 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. When the S-NSSAI time validity information of an S-NSSAI indicates that the S-NSSAI is not available, then: a) if the AMF receives a requested NSSAI in the REGISTRATION REQUEST message with the S-NSSAI identifying the network slice, the AMF shall: i) to a UE which has indicated that it supports S-NSSAI time validity information, provide: 1) 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 2) a configured NSSAI not including the S-NSSAI in the Registration Accept message if the S-NSSAI will not become available again; or ii) to a UE which has not indicated that it supports S-NSSAI time validity information, reject the S-NSSAI for the current PLMN or SNPN. If the registration request is accepted, the AMF shall include a configured NSSAI not including the S-NSSAI; b) if the AMF detects that the S-NSSAI is included in the allowed NSSAI or the partially allowed NSSAI of a UE which has: i) indicated that it supports S-NSSAI time validity information, the AMF shall locally remove the S-NSSAI from the allowed NSSAI (if any) and the partially allowed NSSAI (if any); or ii) not indicated that it supports S-NSSAI time validity information, the AMF shall remove the S-NSSAI from the stored configured NSSAI (if any), allowed NSSAI (if any), and partially allowed NSSAI (if any) by sending the CONFIGURATION UPDATE COMMAND 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 configured 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.