4.6.3.6 Session management for partial network slice

If the S-NSSAI is included in the partially allowed NSSAI and:

• if the current TAI is in the list of TAs for which the S-NSSAI is allowed, the UE may initiate the UE-requested PDU session establishment procedure for the S-NSSAI; or
• if the current TAI is not in the list of TAs for which the S-NSSAI is allowed, the UE shall not initiate the UE-requested PDU session establishment procedure for the S-NSSAI.

If an existing PDU session is established for the S-NSSAI included in the partially allowed NSSAI and the current TAI is in the list of TAs for which this S-NSSAI is allowed:

• the UE:
• may initiate the service request procedure to re-establish the user plane resources for the established PDU session; or
• may initiate for the established PDU session either the UE-initiated NAS transport procedure to send CIoT user data to the SMF (see clause 5.4.5.2.1 case h) or the service request procedure to send CIoT user data to the SMF (see clause 5.6.1.1 case d); and
• the SMF may initiate the network-initiated NAS transport procedure to send CIoT user data to the UE for the established PDU session (see clause 5.4.5.3.1 case l).

If an existing PDU session is established for the S-NSSAI included in the partially allowed NSSAI and the current TAI is not in the list of TAs for which this S-NSSAI is allowed:

• the UE:
• shall maintain the 5GSM contexts for the established PDU session;
• shall not initiate for the established PDU session, the UE-initiated NAS transport procedure to send CIoT user data to the SMF (see clause 5.4.5.2.1 case h) nor the service request procedure to send CIoT user data to the SMF (see clause 5.6.1.1 case d);
• shall not attempt to request the establishment of user plane resources for the established PDU session associated with this S-NSSAI; and
• shall not initiate any UE-requested 5GSM procedure for the established PDU session except:
• the UE-requested PDU session release procedure; or
• the UE-requested PDU session modification procedure to indicate a change of the 3GPP PS data off UE status as specified in 3GPP TS 24.008 [13]; and
• the SMF:
• shall maintain the 5GSM contexts for the established PDU session;
• shall not initiate the network-initiated NAS transport procedure to send CIoT user data to the UE for the established PDU session (see clause 5.4.5.3.1 case l); and
• may initiate the network-requested PDU session release procedure for the established PDU session.

If the SMF cannot determine that the UE is located in a TA within the list of TAs associated with the S-NSSAI of an existing PDU session established for this S-NSSAI, the SMF may according to operator's policy:

• attempt to establish the user plane resources for the PDU session; or
• initiate the network-initiated NAS transport procedure to send CIoT user data to the UE (see clause 5.4.5.3.1 case l).

If the SMF determines that:

• the UE is located in a TA within the list of TAs associated with the S-NSSAI of an existing always-on PDU session;
• the UE is in 5GMM-CONNECTED mode; and
• the user plane resources for the always-on PDU session are not established,

the SMF shall attempt to establish the user plane resources for the always-on PDU session associated with the S-NSSAI included in the partially allowed NSSAI.

NOTE: The session management for partial network slice is not applicable to the PDU session established for onboarding services in SNPN.