6.2.6 Local area data network (LADN)

The UE can receive the local area data network (LADN) information consisting of LADN DNNs and LADN service area information (a set of tracking areas that belong to the current registration area) during the registration procedure or the generic UE configuration update procedure (see clause 5.5.1 and clause 5.4.4).

If the UE supports LADN per DNN and S-NSSAI, the UE can additionally receive the extended local area data network (LADN) information consisting of LADN DNNs, S-NSSAIs and LADN service area information (a set of tracking areas configured per DNN and S-NSSAI that belong to the current registration area) during the registration procedure or the generic UE configuration update procedure (see clause 5.5.1 and clause 5.4.4).

If the UE is not operating in SNPN access operation mode, the UE considers the received LADN information or the extended LADN information to be valid only in the TAIs of the registered PLMN that are in the LADN service area information, and in the TAIs of the equivalent PLMNs if the LADN service area information includes TAIs for the equivalent PLMNs. When the AMF provides the UE with LADN service area information containing TAIs for the equivalent PLMNs, the AMF shall include these TAIs of the equivalent PLMNs in the UE's registration area.

If the UE is operating in SNPN access operation mode, the UE considers the received LADN information or the extended LADN information to be valid only in the TAIs of the registered SNPN that are in the LADN service area information.

The LADN DNN(s) received by the UE is also considered as LADN DNN(s) in the equivalent PLMNs.

The UE shall consider itself to be located inside the LADN service area based on the LADN service area information. If the UE does not have an LADN service area information for the LADN DNN, the UE shall consider itself to be located outside the LADN service area.

When the UE is located in the LADN service area and the UE is in substate 5GMM-REGISTERED.NORMAL-SERVICE, the UE may initiate:

• the UE-requested PDU session establishment procedure with an LADN DNN to establish a PDU session for LADN;
• the UE-requested PDU session establishment procedure with an LADN DNN and an S-NSSAI associated with the LADN to establish a PDU session for LADN if the extended LADN information is available at the UE;
• the UE-requested PDU session modification procedure to modify the PDU session for LADN;
• the service request procedure to re-establish the user-plane resources for the PDU session for LADN; or
• the service request procedure or the UE-initiated NAS transport procedure to send CIoT user data via the control plane for a PDU session for LADN.

NOTE 1: If the service area list for the service area restrictions is available in the UE, and at least one of the LADN information or the extended LADN information are available in the UE, the service area list is evaluated before the LADN information and extended LADN information.

NOTE 1A: If the partially allowed NSSAI, the partially rejected NSSAI, or both are available in the UE, and at least one of the LADN information or the extended LADN information are available in the UE, the UE evaluates the partially allowed NSSAI and the partially rejected NSSAI before the LADN information and extended LADN information.

When the UE is located outside the LADN service area, the UE is allowed:

• to initiate the UE-requested PDU session release procedure to release a PDU session for LADN; or
• to initiate the UE-requested PDU session modification procedure to indicate a change of 3GPP PS data off UE status.

The AMF shall determine the UE presence in LADN service area as out of the LADN service area in the following cases:

• if the DNN used for the LADN is included in the LADN information and the UE is located outside the LADN service area indicated in the LADN information;
• if the DNN and the S-NSSAI used for the LADN are included in the extended LADN information and the UE is located outside the LADN service area indicated in the extended LADN information;
• if the DNN used for the LADN is included in the extended LADN information and there is no S-NSSAI provided by the UE to establish a PDU session for LADN; or
• if the DNN used for the LADN is included in the extended LADN information and the S-NSSAI provided by the UE to establish a PDU session for LADN is not associated with that LADN.

If the UE has moved out of the LADN service area:

• the SMF shall:
• release the PDU session for LADN; or
• release the user-plane resources for the PDU session for LADN and maintain the PDU session for LADN;

according to operator's policy; and

• the SMF shall not initiate the transfer of CIoT user data via the control plane to the UE for the PDU session for LADN.

In case a2) and b):

• if the UE has returned to the LADN service area within a specific period of time according to operator's policy, and the network has downlink user data pending, the network re-establishes the user-plane resources for the PDU session for LADN;
• if the UE has returned to the LADN service area within a specific period of time according to operator's policy, and the network has downlink CIoT user data pending, the SMF shall initiate the CIoT user data via the control plane transfer to the UE; and
• if the UE has not returned to the LADN service area after a specific period of time according to operator's policy, the SMF may release the PDU session for LADN.

When the UE moves to 5GMM-DEREGISTERED state, the UE shall delete the stored LADN information, if any, and the stored extended LADN information, if any.

NOTE 2: In this release, LADNs apply only to 3GPP access.

Upon inter-system change from N1 mode to S1 mode in EMM-IDLE mode, the UE shall not transfer a PDU session for LADN to EPS.

If:

• the UE supports LADN per DNN and S-NSSAI;
• the UE has a PDU session established using the DNN and S-NSSAI which are not associated with any LADN service area indicated in the extended LADN information;
• an LADN service area is configured in the extended LADN information which is associated with the DNN and S-NSSAI of the PDU session; and
• the AMF determines the UE presence in LADN service area as out of the LADN service area configured in the extended LADN information;

the AMF requests the SMF to release this PDU session as specified in 3GPP TS 23.502 [9].

If:

• the UE supports LADN per DNN and S-NSSAI;
• the UE has a PDU session for LADN established; and
• the AMF determines that the LADN service area associated with the DNN and S-NSSAI of the PDU session for LADN is removed from the extended LADN information;

the AMF requests the SMF to release this PDU session as specified in 3GPP TS 23.502 [9].