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full Contents for  TS 23.502  Word version:   16.4.0

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1…   4.2.2.2.2   4.2.2.2.3…   4.2.3…   4.2.3.3   4.2.4…   4.2.6   4.2.7…   4.2.9…   4.3…   4.3.2.2…   4.3.2.2.2   4.3.2.2.3…   4.3.3   4.3.4   4.3.5…   4.3.5.2…   4.3.5.4…   4.3.5.6…   4.3.6…   4.4…   4.5…   4.9…   4.9.1.3…   4.9.2…   4.11…   4.11.1.2.2…   4.11.1.3…   4.11.1.4…   4.11.1.5…   4.11.2   4.11.3…   4.12…   4.12.6…   4.12a   4.12b   4.13…   4.13.4…   4.13.6…   4.14…   4.15…   4.15.4…   4.16…   4.16.4…   4.16.8…   4.17…   4.17.9…   4.18…   4.19…   4.23…   4.23.7…   4.23.9…   4.23.11…   4.24   4.25   4.26…   5…   5.2.3…   5.2.5…   5.2.6…   5.2.7…   5.2.8…   5.2.9…   5.2.12…   A…   E…   F…

 

4.2.4  UE Configuration UpdateWord-p. 65
4.2.4.1  General
UE configuration may be updated by the network at any time using UE Configuration Update procedure. UE configuration includes:
  • Access and Mobility Management related parameters decided and provided by the AMF. This includes the Configured NSSAI and its mapping to the Subscribed S-NSSAIs, the Allowed NSSAI and its mapping to Subscribed S-NSSAIs, the Service Gap time, the list of Rejected NSSAIs if the UE Configuration Update procedure is triggered by the AMF after Network Slice-Specific Authentication and Authorization of S-NSSAIs, the Truncated 5G-S-TMSI Configuration. If the UE and the AMF support RACS, this may also include a PLMN-assigned UE Radio Capability ID or alternatively a PLMN-assigned UE Radio Capability ID deletion indication.
  • UE Policy provided by the PCF.
When AMF wants to change the UE configuration for access and mobility management related parameters the AMF initiates the procedure defined in clause 4.2.4.2. When the PCF wants to change or provide new UE Policies in the UE, the PCF initiates the procedure defined in clause 4.2.4.3.
If the UE Configuration Update procedure requires the UE to initiate a Registration procedure, the AMF indicates this to the UE explicitly.
The procedure in clause 4.2.4.2 may be triggered also when the AAA Server that performed Network Slice-Specific Authentication and Authorization for an S-NSSAI revokes the authorization.
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4.2.4.2  UE Configuration Update procedure for access and mobility management related parameters
This procedure is initiated by the AMF when the AMF wants to update access and mobility management related parameters in the UE configuration.
This procedure is also used to trigger UE to perform, based on network indication, either Mobility Registration Update procedure while the UE is in CM-CONNECTED state to modify NAS parameters that require negotiation (e.g. MICO mode) or Mobility Registration Update procedure after the UE enters CM-IDLE state (e.g. for changes to Allowed NSSAI that require re-registration). If a Registration procedure is needed, the AMF provides an indication to the UE to initiate a Registration procedure.
UE Configuration Update shall be sent over the Access Type (i.e. 3GPP access or non-3GPP access) the UE Configuration Update is applied to, when applicable. If the AMF wants to update NAS parameters in the UE which require UE acknowledgement, then the AMF provides an indication to the UE of whether the UE shall acknowledge the command or not. The AMF should not request acknowledgement of the NITZ command. The AMF shall request acknowledgement for NSSAI information (e.g. Allowed NSSAI), 5G-GUTI, TAI List, and Mobility Restrictions, LADN Information, MICO, Operator-defined access category definitions, PLMN-assigned UE Radio Capability ID and SMS subscription.
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Step 0.
AMF determines the necessity of UE configuration change due to various reasons (e.g. UE mobility change, NW policy, reception of Subscriber Data Update Notification from UDM, change of Network Slice configuration, need to assign PLMN-assigned UE Radio Capabiity ID) or that the UE needs to perform a Registration Procedure. If a UE is in CM-IDLE, the AMF can wait until the UE is in CM-CONNECTED state or triggers Network Triggered Service Request (in clause 4.2.3.3).
NOTE 1:
It is up to the network implementation whether the AMF can wait until the UE is in CM-CONNECTED state or trigger the Network Triggered Service Request.
NOTE 2:
The AMF can check whether Network Slice configuration needs to be updated by using the Nnssf_NSSelection_Get service operation and in such case the AMF compares the stored information with the output from the NSSF to decide whether an update of the UE is required.
The AMF may include Mobility Restriction List in N2 message that delivers UE Configuration Update Command to the UE if the service area restriction for the UE is updated.
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Step 1.
The AMF sends UE Configuration Update Command containing one or more UE parameters (Configuration Update Indication, 5G-GUTI, TAI List, Allowed NSSAI, Mapping Of Allowed NSSAI, Configured NSSAI for the Serving PLMN, Mapping Of Configured NSSAI, rejected S-NSSAIs, NITZ, Mobility Restrictions, LADN Information, MICO, Operator-defined access category definitions, SMS Subscribed Indication, [PLMN-assigned UE Radio Capability ID], [PLMN-assigned UE Radio Capability ID deletion indication]) to UE. Optionally, the AMF may update the rejected S-NSSAIs in the UE Configuration Update command.
The AMF includes one or more of 5G-GUTI, TAI List, Allowed NSSAI, Mapping Of Allowed NSSAI, Configured NSSAI for the Serving PLMN, Mapping Of Configured NSSAI, rejected S-NSSAIs, NITZ (Network Identity and Time Zone), Mobility Restrictions parameters, LADN Information, Operator-defined access category definitions, PLMN-assigned UE Radio Capability ID, or SMS Subscribed Indication if the AMF wants to update these NAS parameters without triggering a UE Registration procedure.
The AMF may include in the UE Configuration Update Command also Configuration Update Indication parameters indicating whether:
  • Network Slicing Subscription Change has occurred;
  • the UE shall acknowledge the command; and
  • whether a Registration procedure is requested.
If the AMF indicates Network Slicing Subscription Change, then the UE shall locally erase all the network slicing configuration for all PLMNs and, if applicable, update the configuration for the current PLMN based on any received information. If the AMF indicates Network Slicing Subscription Change, the UE shall also be requested to acknowledge in step 2.
If the AMF also includes in the UE Configuration Update Command message a new Configured NSSAI for the Serving PLMN, then the AMF should also include a new Allowed NSSAI with, if available, the associated Mapping Of Allowed NSSAI, unless the AMF cannot determine the new Allowed NSSAI after the Subscribed S-NSSAI(s) are updated, in which case the AMF does not include in the UE Configuration Update Command message any Allowed NSSAI.
When the UE and the AMF supports RACS as defined in TS 23.501, clause 5.4.4.1a, and the AMF needs to configure the UE with a UE Radio Capability ID, and the AMF already has the UE radio capabilities other than NB-IoT radio capabilities for the UE and, the AMF may provide the UE with the UE Radio Capability ID for the UE radio capabilities the UCMF returns to the AMF in a Nucmf_assign service operation for this UE.
If the AMF provided the NG-RAN with updated Mobility Restrictions, the NG-RAN shall trigger a handover procedure or the AN release procedure based on conditions defined in step 2c.
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Step 2a.
If the UE Configuration Update Indication requires acknowledgement of the UE Configuration Update Command, then the UE shall send a UE Configuration Update complete message to the AMF. The AMF should request acknowledgement for all UE Configuration Updates, except when only NITZ is provided. If Registration procedure is not required, steps 3a, 3b, 3c and step 4 are skipped. If the Configuration Update Indication is included in the UE Configuration Update Command message, and it requires a Registration procedure, depending on the other NAS parameters included in the UE Configuration Update command, the UE shall execute steps 3a or 3b or 3c+4 as applicable.
If the PLMN-assigned UE Radio Capability ID is included in step1, the AMF stores the UE Radio Capability ID in UE context if receiving UE Configuration Update complete message.
If the UE receives PLMN-assigned UE Radio Capability ID deletion indication in step 1, the UE shall delete the PLMN-assigned UE Radio Capability ID(s) for this PLMN. If UE Configuration Update is only for this purpose, the following steps are skipped.
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Step 2b.
[Conditional] The AMF also uses the Nudm_SDM_Info service operation to provide an acknowledgment to UDM that the UE received CAG information as part of the Mobility Restrictions (if the CAG information was updated), or the Network Slicing Subscription Change Indication (if this was indicated in step 1) and acted upon it.
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Step 2c.
[Conditional] If the AMF has reconfigured the 5G-GUTI over 3GPP access, the AMF informs the NG-RAN of the new UE Identity Index Value (derived from the new 5G-GUTI) when the AMF receives the acknowledgement from the UE in step 2a.
[Conditional] If the UE is registered to the same PLMN via both 3GPP and non-3GPP access and if the AMF has reconfigured the 5G-GUTI over non-3GPP access, and the UE is in CM-CONNECTED state over 3GPP access, then the AMF informs the NG-RAN of the new UE Identity Index Value (derived from the new 5G-GUTI) when the AMF receives the acknowledgement from the UE in step 2a.
[Conditional] If the AMF has configured the UE with a PLMN-assigned UE Radio Capability ID, the AMF informs NG-RAN of the UE Radio Capability ID, when it receives the acknowledgement from the UE in step 2a.
[Conditional] If the Mobility Restrictions for the UE were updated and the Mobility Restrictions were not provided in the N2 message that delivers the UE Configuration Update Command, the AMF provides the NG-RAN with updated Mobility Restrictions. Based on received Mobility Restrictions, the NG-RAN shall trigger a handover procedure or the AN release procedure if any of the condition is true:
  • If the UE accesses a CAG cell and the CAG Identifier(s) supported by the CAG cell was removed from the Allowed CAG list; or
  • If the UE accesses a non-CAG cell and the UE is only allowed to access CAG cells.
NOTE 3:
When the UE is accessing the network for emergency service the conditions in clause 5.16.4.3 of TS 23.501 apply.
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Step 2d.
[Conditional] If the UE is configured with a new 5G-GUTI in step 2a via non-3GPP access and the UE is registered to the same PLMN via both 3GPP and non-3GPP access, then the UE passes the new 5G-GUTI to its 3GPP access' lower layers.
If the UE is configured with a new 5G-GUTI in step 2a over the 3GPP access, the UE passes the new 5G-GUTI to its 3GPP access' lower layers.
NOTE 4:
Steps 2c and 2d are needed because the NG-RAN may use the RRC Inactive state and a part of the 5G-GUTI is used to calculate the Paging Frame (see TS 38.304 and TS 36.304). It is assumed that the UE Configuration Update Complete is reliably delivered to the AMF after the 5G-AN has acknowledged its receipt to the UE.
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Step 3a.
[Conditional] If only NAS parameters that can be updated without transition from CM-IDLE are included, e.g. MICO mode, the UE shall initiate a Registration procedure immediately after the acknowledgement to re-negotiate the updated NAS parameter(s) with the network. Steps 3b, 3c and step 4 are skipped.
3b. [Conditional] If a new Allowed NSSAI and/or a new Mapping Of Allowed NSSAI and/or a new Configured NSSAI provided by the AMF to the UE in step 1 does not affect the existing connectivity to Network Slices (i.e. any S-NSSAI(s) the UE is connected to), the AMF needs not release the NAS signalling connection for the UE after receiving the acknowledgement in step 2, and immediate registration is not required. The UE can start immediately using the new Allowed NSSAI and/or the new Mapping Of Allowed NSSAI. The UE cannot connect to an S-NSSAI included in the new Configured NSSAI for the Serving PLMN but not included in the new Allowed NSSAI until the UE performs a Registration procedure and includes a Requested NSSAI based on the new Configured NSSAI, following the requirements described in TS 23.501, clause 5.15.5.2. Steps 3c and 4 are skipped.
The AMF may, based on its policy, provide anyway an indication that a Registration procedure is required even though the UE Configuration Update Command in step 1 does not affect the existing connectivity to Network Slices: in such a case only step 3c is skipped.
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Step 3c.
[Conditional] If a new Allowed NSSAI and/or a new Mapping Of Allowed NSSAI and/or a new Configured NSSAI provided by the AMF to the UE in step 1 affects ongoing existing connectivity to Network Slices, then the AMF shall provide an indication that the UE shall initiate a Registration procedure.
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Step 4.
[Conditional] After receiving the acknowledgement in step 2, the AMF shall release the NAS signalling connection for the UE, unless there is one established PDU Sessions associated with regulatory prioritized services. If there is one established PDU Session associated with regulatory prioritized services, the AMF informs SMFs to release the PDU Session(s) associated with non regulatory prioritized services for this UE (see clause 4.3.4).
The AMF shall reject any NAS Message from the UE carrying PDU Session Establishment Request for a non-emergency PDU Session before the required Registration procedure has been successfully completed by the UE.
The UE initiates a Registration procedure (see clauses 4.2.2.2.2 and 4.13.3.1) with registration type Mobility Registration Update after the UE enters CM-IDLE state and shall not include the 5G-S-TMSI or GUAMI in Access Stratum signalling and shall include, subject to the conditions set out in clause 5.15.9 of TS 23.501, a Requested NSSAI in access stratum signalling. If there is an established PDU Session associated with emergency service and the UE has received an indication to perform the Registration procedure, the UE shall initiate the Registration procedure only after the PDU Session associated with emergency service is released.
NOTE 5:
Receiving UE Configuration Update command without an indication requesting to perform re-registration, can still trigger Registration procedure by the UE for other reasons.
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4.2.4.3  UE Configuration Update procedure for transparent UE Policy deliveryWord-p. 69
This procedure is initiated when the PCF wants to update UE access selection and PDU Session selection related policy information (i.e. UE policy) in the UE configuration. In the non-roaming case the V-PCF is not involved and the role of the H-PCF is performed by the PCF. For the roaming scenarios, the V-PCF interacts with the AMF and the H-PCF interacts with the V-PCF.
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Step 0.
PCF decides to update UE policy based on triggering conditions such as an initial registration, registration with 5GS when the UE moves from EPS to 5GS, or need for updating UE policy as follows:
  • For the case of initial registration and registration with 5GS when the UE moves from EPS to 5GS, the PCF compares the list of PSIs included in the UE access selection and PDU session selection related policy information in Npcf_UEPolicyControl_Create request and determines, as described in clause 6.1.2.2.2 of TS 23.503, whether UE access selection and PDU Session selection related policy information have to be updated and be provided to the UE via the AMF using DL NAS TRANSPORT message; and
  • For the network triggered UE policy update case (e.g. the change of UE location, the change of Subscribed S-NSSAIs as described in clause 6.1.2.2.2 of TS 23.503), the PCF checks the latest list of PSIs to decide which UE access selection and/or PDU Session selection related policies have to be sent to the UE.
The PCF checks if the size of the resulting UE access selection and PDU Session selection related policy information exceeds a predefined limit:
  • If the size is under the limit, then UE access selection and PDU Session selection related policy information are included in a single Namf_Communication_N1N2MessageTransfer service operation as described below.
  • If the size exceeds the predefined limit, the PCF splits the UE access selection and PDU Session selection related policy information in smaller, logically independent UE access selection and PDU Session selection related policy information ensuring the size of each is under the predefined limit. Each UE access selection and PDU Session selection related policy information will be then sent in separated Namf_Communication_N1N2MessageTransfer service operations as described below.
NOTE 1:
NAS messages from AMF to UE do not exceed the maximum size limit allowed in NG-RAN (PDCP layer), so the predefined size limit in PCF is related to that limitation.
NOTE 2:
The mechanism used to split the UE access selection and PDU Session selection related policy information is described in TS 29.507.
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Step 1.
PCF invokes Namf_Communication_N1N2MessageTransfer service operation provided by the AMF. The message includes SUPI, UE Policy Container.
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Step 2.
If the UE is registered and reachable by AMF in either 3GPP access or non-3GPP access, AMF shall transfers transparently the UE Policy container to the UE via the registered and reachable access.
If the UE is registered in both 3GPP and non-3GPP accesses and reachable on both access and served by the same AMF, the AMF transfers transparently the UE Policy container to the UE via one of the accesses based on the AMF local policy.
If the UE is not reachable by AMF over both 3GPP access and non-3GPP access, the AMF reports to the PCF that the UE Policy container could not be delivered to the UE using Namf_Communication_N1N2TransferFailureNotification as in the step 5 in clause 4.2.3.3.
If AMF decides to transfer transparently the UE Policy container to the UE via 3GPP access, e.g. the UE is registered and reachable by AMF in 3GPP access only, or if the UE is registered and reachable by AMF in both 3GPP and non-3GPP accesses served by the same AMF and the AMF decides to transfer transparently the UE Policy container to the UE via 3GPP access based on local policy, and the UE is in CM-IDLE and reachable by AMF in 3GPP access, the AMF starts the paging procedure by sending a Paging message described in the step 4b of Network Triggered Service Request (in clause 4.2.3.3). Upon reception of paging request, the UE shall initiate the UE Triggered Service Request procedure (clause 4.2.3.2).
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Step 3.
If the UE is in CM-CONNECTED over 3GPP access or non-3GPP access, the AMF transfers transparently the UE Policy container (UE access selection and PDU Session selection related policy information) received from the PCF to the UE. The UE Policy container includes the list of Policy Sections as described in TS 23.503.
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Step 4.
The UE updates the UE policy provided by the PCF and sends the result to the AMF.
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Step 5.
If the AMF received the UE Policy container and the PCF subscribed to be notified of the reception of the UE Policy container then the AMF forwards the response of the UE to the PCF using Namf_Communication_N1MessageNotify.
The PCF maintains the latest list of PSIs delivered to the UE and updates the latest list of PSIs in the UDR by invoking Nudr_DM_Update (SUPI, Policy Data, Policy Set Entry, updated PSI data) service operation.
If the PCF is notified about UE Policy delivery failure the PCF may initiate UE Policy Association Modification procedure to provide a new trigger "Connectivity state changes" in Policy Control Request Trigger of UE Policy Association to AMF as defined in clause 4.16.12.2.
NOTE 3:
For backward compability the PCF may subscribe the "Connectivity state changes (IDLE or CONNECTED)" event in Rel-15 AMF as defined in clause 5.2.2.3.
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4.2.5  Reachability proceduresWord-p. 70
4.2.5.1  General
Elements of this procedure are used for UDM/NF initiated UE Reachability Notification requests, e.g. for "SMS over NAS".
The procedure applies to UEs that are in RRC-Idle, RRC-Inactive and RRC-Connected states.
There are two procedures necessary for any service related entity that would need to be notified by the reachability of the UE:
  • UE Reachability Notification Request procedure; and
  • UE Activity Notification procedure.
4.2.5.2  UE Reachability Notification Request procedure
The UE Reachability Notification Request procedure is illustrated in figure 4.2.5.2-1.
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Step 1.
When a service-related entity requests the UDM to provide an indication regarding UE reachability, the UDM checks whether that service-related entity is authorized to perform this request on this subscriber.
NOTE 1:
This request for UE Reachability Notification is received in UDM using different interfaces/services depending on the service-related entity. For example, an SBI capable service-related entity can use the Nudm_EventExposure_Subscribe service while an SMS-GMSC uses triggers theis procedure as described in TS 23.040.
The UDM may retrieve from the UDR the list of NF IDs for Network Functions authorized by the HPLMN to request notifications on this UE's reachability.
If the entity is not authorized, the UDM may reject the request (e.g. if the requesting entity is recognized as being a valid entity, but not authorized for that subscriber) or discard it silently (e.g. if the requesting entity is not recognized). Appropriate O&M reports are generated.
1a. The UDM stores locally the identity of the service-related entity and sets the URRP-AMF flag parameter to indicate that such request is received from an authorised NF.
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Step 2.
[Conditional] If the value of URRP-AMF flag parameter changes from "not set" to "set" and an AMF is registered in the UDM for the target UE, the UDM initiates Namf_EventExposure_Subscribe service operation towards the AMF. The UDM may indicate if direct notification to NF shall be used by the AMF. When direct notification to NF is indicated to the AMF, the URRP-AMF is not set in the UDM in step 1a for NF initiated requests.
NOTE 2:
The UDM can trigger UE Reachability Notification Request procedure with two different AMFs for a UE which is connected to 5G Core Network over 3GPP access and non-3GPP access simultaneously. Also, for interworking with EPC, the UDM/HSS can trigger UE Reachability Notification Request procedure with MME as described in TS 23.401.
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Step 3.
The AMF checks that the requesting entity is authorized to perform this request on this subscriber.
If the AMF has an MM Context for that user, the AMF stores the NF ID in the URRP-AMF information, associated with URRP-AMF information flag to indicate the need to report to the UDM or directly to the NF with a UE Activity Notification (see clause 4.2.5.3).
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Step 4.
[Conditional] If the UE state in AMF is in CM-CONNECTED state and the Access Type is 3GPP access, the AMF initiates N2 Notification procedure (see clause 4.8.3) with reporting type set to Single RRC-Connected state notification.
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4.2.5.3  UE Activity Notification procedureWord-p. 71
The UE Activity Notification procedure is illustrated in figure 4.2.5.3-1.
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Step 1a.
For a UE in CM-IDLE, the AMF receives (N1) NAS signalling implying UE reachability, e.g. a Registration Request or Service Request message from the UE, the AMF performs step 2;
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Step 1b.
For a UE in CM-CONNECTED, if the AMF has initiated the N2 Notification procedure in Step 4 of clause 4.2.5.2 and when the AMF receives a (N2) UE Notification (see clause 4.8.3) or a (N2) Path Switch Request (see clause 4.9.1.2) from the NG-RAN, the AMF performs step 2. Otherwise, i.e. UE is in CM-CONNECTED and AMF has not initiated N2 Notification procedure, the AMF performs step 2; or
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Step 1c.
The UE's reachability state changes from reachable to unreachable, then AMF performs step 2.
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Step 2.
If the AMF has an MM context for the UE and the URRP-AMF information flag associated with the subscribing NF is set to report once that the UE is reachable, the AMF initiates the Namf_EventExposure_Notify service operation (SUPI, UE-Reachable) message to the UDM or directly to the NF (if direct notification is previously indicated to AMF in step 2 in clause 4.2.5.2). The AMF clears the corresponding URRP-AMF information for the UE. If the UE was in CM-IDLE and the UE's reachability state changes from reachable to unreachable, the AMF initiates the Namf_EventExposure_Notify service operation (SUPI, UE-UnReachable).
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Step 2a.
When the UDM receives the Namf_EventExposure_Notify service operation (SUPI, UE-Reachable) message or Nudm_UECM_Registration service for a UE that has URRP-AMF information flag set in the UDM, it triggers appropriate notifications to the NFs associated with the URRP-AMF information flag (e.g. SMS-GMSC) that have subscribed to the UDM for this notification. UDM clears the local URRP-AMF information for the UE.
NOTE:
The UE Reachability Notification is sent by the UDM using different interfaces/services depending on the service-related entity. For example, an SBI capable service-related entity can receive the notification using the Nudm_EventExposure_Notify service operation (if previously subscribed) while an SMS-GMSC gets the notification as described in TS 23.040.
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Step 2b.
When the AMF receives Namf_EventExposure_Subscribe_service operation directly from an NF authorised to receive direct notifications, or the UDM indicates that the notification needs to be sent directly to the NF, the AMF initiates the Namf_EventExposure_Notify service operation (SUPI, UE-Reachable) message directly to the NF.
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