5.6.5a Supporting LADN per DNN and S-NSSAI

The 5GS may support LADN per DNN and S-NSSAI and the functions specified in clause 5.6.5 are used (with the extension to apply per DNN and S-NSSAI whenever applicable) with the following enhancements:

• The UE indicates the support of LADN per DNN and S-NSSAI in the UE MM Core Network Capability of the Registration Request message.
• The LADN service area can be provisioned for a group (e.g. 5G VN group) or an individual subscriber using UDM/NEF parameter provisioning service triggered by AF request as described in clause 4.15.6 of TS 23.502 [3].
• LADN service area per DNN and S-NSSAI may be configured in the AMF. The LADN service area may also be provided to AMF as part of the subscription data from UDM.
• The LADN Service Area Information provided to the UE is determined by AMF, based on the Registration Area that the AMF assigns to the UE and either the local configured LADN service area or the LADN service area received from UDM. In case there is both a configured LADN service area and a LADN service area received from UDM, the AMF decides based on operator configuration which one takes precedence.
• If the UE indicates support of LADN per DNN and S-NSSAI, the AMF may provide the LADN Service Area Information per LADN DNN and S-NSSAI to the UE.
• When the UE has an ongoing PDU session and there is no LADN service area for the DNN and S-NSSAI of the PDU session, the AMF will release the ongoing PDU session if the AMF determines to configure the LADN service area configured per LADN DNN and S-NSSAI for the associated DNN and S-NSSAI (e.g. due to notification from UDM or local configuration update).
• When the UE has an ongoing PDU session subject to LADN per LADN DNN and S-NSSAI, the AMF will release the ongoing PDU session if the AMF determines the LADN service area for the DNN and S-NSSAI is removed (e.g. due to notification from UDM or local configuration update).

NOTE 1: After the UE receives the LADN Information per LADN DNN and S-NSSAI, it is up to the UE implementation whether to re-establish the PDU session.

• If the UE does not indicate support of LADN per DNN and S-NSSAI and the AMF has a LADN service area for the DNN as well as a LADN service area for the DNN and S-NSSAI, the AMF may determine the LADN Service Area Information per LADN DNN sent to UE using the LADN service area for the DNN as described in clause 5.6.5.
• If the UE does not indicate support of LADN per DNN and S-NSSAI and the AMF has no LADN service area for the DNN but there is a LADN service area for the DNN and S-NSSAI, then the AMF may determine the LADN Service Area Information per LADN DNN sent to UE using this LADN service area for the DNN and S-NSSAI as the LADN service area for that DNN as described in clause 5.6.5 if the UE is not subscribed to the same DNN for multiple S-NSSAI(s) (i.e. the UE is subscribed to the DNN for a single S-NSSAI only).

NOTE 2: In order to serve the UEs that do not support LADN per DNN and S-NSSAIs, the operator can avoid using the same DNN for multiple S-NSSAIs if LADN service area is configured per DNN and S-NSSAI.

• If the UE does not indicate support of LADN per DNN and S-NSSAI and the AMF neither has a LADN service area for the DNN nor has a LADN service area for the DNN and S-NSSAI, the AMF shall not provide any LADN Information to the UE.
• The AMF enforces the LADN Service Area per LADN DNN and S-NSSAI in the same way as is described in clause 5.6.5 with the difference that the LADN service area is defined per DNN and S-NSSAI.
• The UE enforces the LADN Service Area per LADN DNN and S-NSSAI, if received from the AMF, in the same way as is described in clause 5.6.5 with the difference that the LADN service area is defined per DNN and S-NSSAI.
• If the AMF enforces the LADN Service Area per LADN DNN and S-NSSAI for the UE, the AMF indicates to the SMF during PDU Session Establishment that the PDU Session is subject to LADN per LADN DNN and S-NSSAI.
• If indicated by AMF at PDU Session Establishment that PDU Session is subject to LADN per LADN DNN and S-NSSAI, the SMF configures the DNN of PDU Session as LADN DNN. The SMF shall subscribe to "UE mobility event notification" for reporting UE presence in Area of Interest by providing LADN DNN and S-NSSAI to the AMF as described in clauses 5.6.11 and 5.3.4.4. The SMF handles the PDU session in the same way as described in clause 5.6.5.

NOTE 3: If the UE has overlapping areas between LADN service area configured per DNN & S-NSSAI, Partial network slice support area, or any combination of them, then the evaluation of Partial network slice support area take precedence over the evaluation of LADN service area configured per DNN and S-NSSAI.