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Content for  TS 23.502  Word version:  17.4.0

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4.15.7  Network status reporting |R16|Word‑p. 382

This clause contains the detailed description and the procedures for the network status reporting capability.
An AF may request for being notified about the network status, in a specific geographical area or for a specific UE.
The following methods are supported:
  • The AF requests to be informed, one-time, about the network status. This procedure is referred to as one-time network status request;
  • The AF requests to be informed, continuously, about the network status. This procedure is referred to as continuous network status request;
The procedure as described in clause 6.1.1.2 or clause 6.1.2.2 in TS 23.288 is used by an AF to retrieve Network Status Result (NSR) from the network for a specific geographical area or for a specific UE.
After receiving the request for network status notification from the AF, the NEF retrieves user data congestion analytics information from NWDAF, as defined in TS 23.288.
Based on the user data congestion analytics information the NEF receives from the NWDAF, the NEF derives and reports the network status for the geographical area or for the UE as Network Status Result (NSR) to the AF. When reporting to the AF, the NSR shall not include any 3GPP location information.
When an AF requests one-time Network Status from the NEF, the NEF can optionally provide a time interval at which the AF is allowed to re-issue the same request for network status.
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4.15.8  Event exposure controlled by a DCCF |R17|Word‑p. 382

A DCCF can coordinate the subscriptions and notifications to event exposure in Network Functions. This is further described in TS 23.288.

4.15.9  Time Synchronization exposure |R17|Word‑p. 383

4.15.9.1  GeneralWord‑p. 383

Time synchronization exposure allows an AF to configure time synchronization in 5GS. For (g)PTP operation, the Time synchronization service allows an AF to subscribe to the UE and 5GC capabilities and availability for time synchronization service (as described in clause 4.15.9.2), and to configure the (g)PTP instance in 5GS as described in clause 4.15.9.3. For 5G access stratum based time distribution, the AF can influence the 5G access stratum time distribution as described in clause 4.15.9.4. The time synchronization exposure is provided by NEF that uses the service provided by TSCTSF. The AF that is part of operator's trust domain may invoke the services directly with TSCTSF and TSCTSF responds/notifies directly to the AF, accordingly.
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4.15.9.2  Exposure of UE availability for Time Synchronization serviceWord‑p. 383

The procedure is used by the AF to subscribe to notifications and to explicitly cancel a previous subscription for UE availability for time synchronization service. Cancelling is done by sending Nnef_TimeSynchronization_CapsUnsubscribe request identifying the subscription to cancel with Subscription Correlation ID.
Reproduction of 3GPP TS 23.502, Fig. 4.15.9.2-1: Procedure for exposing 5GS and/or UE availability and capabilities for Time Synchronization services
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Step 1.
Upon PDU Session establishment, the PCF determines if the PDU Session is potentially impacted by time synchronization service (based on local configuration or 5GS Bridge information event from SMF as described in SM Policy Association Establishment procedure in clause 4.16.4). In this case the PCF invokes Npcf_PolicyAuthorization_Notify service operation to the TSCTSF discovered and selected as described in clause 6.3.24 of TS 23.501. The Npcf_PolicyAuthorization_Notify service operation includes the UE address of the PDU Session and DNN/S-NSSAI.
The PCF registers to BSF as described in TS 23.503. TSCTSF invokes a Npcf_PolicyAuthorization_Create request message to the PCF, and stores the DNN, S-NSSAI and SUPI as received from PCF and associates them with the AF-session.
If PMIC/UMIC information from the DS-TT or NW-TT is available at the PCF, the PCF reports it to the TSCTSF invoking Npcf_PolicyAuthorization_Notify.
Step 2.
The AF subscribes to the UE availability for time synchronization service and provides the associated Notification Target Address of the AF by sending Nnef_TimeSynchronization_CapsSubscribe request.
Report Type defines the type of reporting requested (e.g. one-time reporting, periodic reporting or event based reporting).
The request may include DNN and slicing information (S-NSSAI) and shall include an AF-Service-Identifier. If the DNN and S-NSSAI are omitted in the request, the NEF uses the AF-Service-Identifier to determine the target DNN and slicing information (S-NSSAI).
The Event Filter may include a list of UE identities (GPSIs) or Groups of UEs identified by an External Group Identifier that further define the subset of the target UEs. If the request does not include UE identities nor External Group Identifier, the request is targeted to any UE with a PDU Session using the DNN and S-NSSAI. The NEF uses the UDM service to map the GPSIs to SUPIs and to map the External Group Identifier to Internal Group Identifier.
Additionally, the Event Filter may include one or more of the requested PTP instance type, requested transport protocol for PTP, or requested PTP Profile as described in Table 5.2.6.25.6-1.
When the NEF processes the AF request the AF-Service-Identifier may be used to authorize the AF request.
Depending on the AF-Service-Identifier and/or DNN/S-NSSAI, the NEF may reject the request if the list of UE identities or External Group Identifier is not included in the request.
To unsubscribe to the UE availability for time synchronization for a list of UE(s), the AF invokes Nnef_TimeSynchronization_CapsUnsubscribe service operation and provides the Subscription Correlation ID.
Step 3.
(In the case of Ntsctsf_TimeSynchronization_CapsSubscribe): The NEF discovers the TSCTSF as described in clause 6.3.24 of TS 23.501. The NEF invokes the Ntsctsf_TimeSynchronization_CapsSubscribe request service operation to the selected TSCTSF.
(In the case of Ntsctsf_TimeSynchronization_CapsUnsubscribe): The NEF uses the Subscription Correlation ID to determine the TSCTSF and interacts with the TSCTSF by triggering a Ntsctsf_TimeSynchronization_CapsUnsubscribe request message.
The AF that is part of operator's trust domain may invoke the services directly with TSCTSF as described in clause 6.3.24 of TS 23.501.
Step 4.
(in the case of Ntsctsf_TimeSynchronization_CapsSubscribe): The TSCTSF uses the parameters received in step 3 (i.e. DNN, S-NSSAI and the list of SUPIs if present) to find matching AF-session(s). For any such AF-session, the TSCTSF interacts with the PCF by triggering a Npcf_PolicyAuthorization_Update request message.
(in the case of Ntsctsf_TimeSynchronization_CapsUnsubscribe): The TSCTSF uses the Subscription Correlation ID to determine the AF sessions and interacts with the PCF(s) by triggering a Npcf_PolicyAuthorization_Delete request message. Steps 8-13 are skipped.
Step 5.
TSCTSF acknowledges the execution of Ntsctsf_TimeSynchronization_CapsSubscribe to the requester that initiated the request. The acknowledgement contains a Subscription Correlation ID that the requester can use to cancel or modify the subscription.
Step 6.
NEF acknowledges the execution of Nnef_TimeSynchronization_CapsSubscribe to the requester that initiated the request. The acknowledgement contains a Subscription Correlation ID that the AF can use to cancel or modify the subscription.
Step 7.
As part of Npcf_PolicyAuthorization_Create/Update request, the TSCTSF uses the procedures as described in clause K.2.1 of TS 23.501 to determine the (g)PTP capabilities from the DS-TT. If the TSCTSF has not determined the (g)PTP capabilities from the NW-TT, the TSCTSF determines the capabilities using the procedures as described in clause K.2.1 of TS 23.501.
The TSCTSF composes the time synchronization capabilities for the DS-TT/UE(s) connected to the NW-TT based on the capability information received from the DS-TT(s) and NW-TT. If the Ntsctsf_TimeSynchronization_CapsSubscribe request include an Event Filter with one or more of the requested PTP instance type, requested transport protocol for PTP, or requested PTP Profile, the TSCTSF considers only the DS-TT(s) and NW-TT(s) with these capabilities as part of the time synchronization capability set that is reported to the NEF (or AF).
The TSCTSF maintains association between the user-plane Node ID, the time synchronization capabilities, the reference to the capabilities (as identified by the Subscription Correlation ID), the Event Filter (if available), the NEF or AF Notification Target Address, and list of the AF sessions with PCFs with this user-plane Node ID. If the Ntsctsf_TimeSynchronization_CapsSubscribe request includes one or more Event Filter(s), the TSCTSF considers only the matching UE identities and the DS-TT(s) and NW-TT(s) with the matching capabilities to be included in the associated AF sessions.
Step 8.
The TSCTSF sends Ntsctsf_TimeSynchronization_CapsNotify (as described in clause 5.2.27.2.8) to the NEF. The message includes the time synchronization capabilities as composed in step 7. The message contains one or more user-plane Node ID(s) and a list of UE identities associated to each user-plane Node ID and time synchronization capabilities for each set of DS-TTs connected to given user-plane Node ID, as described in Table 5.2.6.25.8-1. The user-plane Node ID identifies the NW-TT to where the UE/DS-TT(s) are connected to.
Step 9.
The NEF sends Nnef_TimeSynchronization_CapsNotify with Time Synchronization capability event (as described in Table 5.2.6.25.8-1) to the AF.
Step 10-11.
Upon PDU Session Establishment as defined clause 4.3.2.2.1-1, steps 1, 7, 8 and 9 are repeated for the new PDU Session.
Step 12.
If necessary, e.g. upon PDU Session establishment or release, the TSCTSF may update the time synchronization capabilities for the DS-TT/UE(s) connected to the NW-TT(s). The TSCTSF sends Ntsctsf_TimeSynchronization_CapsNotify with Time Synchronization capability event (as described in Table 5.2.6.25.8-1) containing the updated capabilities to the NEF.
13. The NEF sends Nnef_TimeSynchronization_CapsNotify containing the updated capabilities to the AF.
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4.15.9.3  Time Synchronization activation, modification, and deactivationWord‑p. 385

4.15.9.3.1  GeneralWord‑p. 385
This procedure can be used by the AF to activate, modify or deactivate the (g)PTP instances in 5GS.
The AF may activate the time synchronization service using the Nnef_TimeSynchronization_ConfigCreate service operation. The service operation creates a time synchronization configuration based on the service parameters as indicated in the create request. The AF may update the time synchronization configuration using the Nnef_TimeSynchronization_ConfigUpdate service operation. The AF may deactivate the time synchronization service using the Nnef_TimeSynchronization_ConfigDelete service operation, which deletes the corresponding time synchronization service configuration.
The Nnef_TimeSynchronization_ConfigCreate and Nnef_TimeSynchronization_ConfigUpdate request may contain the parameters as described in Table 4.15.9.3-1.
Time Synchronization Parameter Description
PTP instance type Identifies the requested PTP instance type as described in clause 5.27.1.4 of TS 23.501.
Transport protocol Identifies the requested transport protocol for PTP instance as described in clause 5.27.1.4 of TS 23.501. This is applicable for IEEE Std 1588 [76] Boundary Clock and Transparent Clock operation.
PTP Profile Identifies the PTP profile for the PTP instance as requested by AF.
Grandmaster enabled Indicates whether the AF requests the PTP instance in 5GS to be able to act as a grandmaster for PTP or gPTP (depending on the requested PTP instance type).
This is applicable for IEEE Std 1588 [76] Boundary Clock or IEEE Std 802.1AS [75] operation.
[optional]
Grandmaster priority Indicates a priority used as defaultDS.priority1 when generating Announce message when 5GS acts as (g)PTP GM. Applicable only if the Grandmaster enabled = TRUE. If omitted, the default value as described in the PTP Profile is used.
[optional]
Time Domain (g)PTP domain of the PTP instance as defined in IEEE Std 1588 [76].
Temporal Validity Condition Indicates start-time and stop-time attributes that describe the time period when the time synchronization service for a PTP instance is active.
[optional]
Time synchronization error budget Indicates the time synchronization budget for the time synchronization service (as described in clause 5.27.1.9 of TS 23.501).
[optional]
For each PTP port in the PTP instance
Either UE identity (for a DS-TT port), or "N6 interface" indication Identifies the UE/DS-TT which the parameters below apply. "N6 interface" indicates that the parameters below apply to the N6 interface.
If the "PTP port" needs to be identified, this field refers to the UE identity (GPSI or SUPI). If the N6 termination needs to be identified, then this field indicates "N6 interface" flag, instead of SUPI or GPSI.
PTP enabled TRUE/FALSE. This is used to set the portDS.portEnable. If omitted, the default value as described in the PTP Profile is used.
[optional]
Log Sync Interval Specifies the mean time interval between successive Sync messages. This is applicable for IEEE Std 1588 [76] Boundary Clock or IEEE Std 802.1AS [75] operation. If omitted, the default value as described in the PTP Profile is used.
[optional]
Use management settable Log Sync Interval TRUE/FALSE. This is applicable if the PTP Profile is I IEEE Std 802.1AS [75].
When set to FALSE, the Log Sync Interval is used to set the initialLogSyncInterval as described in IEEE Std 802.1AS [75]. When set to TRUE, the Log Sync Interval is used to set the mgtSettableLogSyncInterval as described in IEEE Std 802.1AS [75].
If omitted, the default value as described in the IEEE Std 802.1AS [75] is used.
[optional]
Log Announce Interval Specifies the mean time interval between successive Announce messages. This is applicable for IEEE Std 1588 [76] Boundary Clock or IEEE Std 802.1AS [75] operation. If omitted, the default value as described in the PTP Profile is used.
[optional]
Use management settable Log Announce Interval TRUE/FALSE. This is applicable if the PTP Profile is IEEE Std 802.1AS [75].
When set to FALSE, the Log Announce Interval is used to set the initialLogAnnounceInterval as described in IEEE 802.1AS. When set to TRUE, the Log Announce Interval is used to set the mgtSettableLogAnnounceInterval as described in IEEE Std 802.1AS [75].
If omitted, the default value as described in the IEEE Std 802.1AS [75] is used.
[optional]
The AF may use Nnef_TimeSynchronization_CapsSubscribe service operation as described in clause 4.15.9.2 to learn the UE capabilities for time synchronization service. The Nnef_TimeSynchronization_CapsNotify service operation indicates the list of UE identities, User-plane Node ID, and the Subscription Correlation ID. The AF can use the Subscription Correlation ID and the user-plane node ID received in the Nnef_TimeSynchronization_CapsNotify service operation as a target of the Nnef_TimeSynchronization_ConfigCreate request. The NEF uses the Subscription Correlation ID and user-plane node ID to determine the list of UEs and list of AF-sessions to which the Nnef_TimeSynchronization_ConfigCreate service operation is targeted to.
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4.15.9.3.2  Time synchronization service activationWord‑p. 388
Reproduction of 3GPP TS 23.502, Fig. 4.15.9.3.2-1: Time synchronization service activation
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Step 1.
The AF creates a time synchronization service configuration for a PTP instance by invoking Nnef_TimeSynchronization_ConfigCreate service operation. The request includes the parameters as described in Table 4.15.9.3-1. The request contains a Subscription Correlation ID and user-plane node ID as a reference to the target of the UEs and AF-sessions.
The create request creates also a subscription for the changes in the time synchronization service configuration.
Step 2.
The NEF authorizes the request. After successful authorization, the NEF invokes the Ntsctsf_TimeSynchronization_ConfigCreate service operation with the corresponding TSCTSF, with the parameters as received from the AF.
The AF that is part of operator's trust domain may invoke the services directly with TSCTSF.
Step 3.
The TSCTSF responds with the Ntsctsf_TimeSynchronization_ConfigCreate response. The Ntsctsf_TimeSynchronization_ConfigCreate response includes a PTP instance reference.
Step 4.
The NEF responds with the Nnef_TimeSynchronization_ConfigCreate response, including a reference to the time synchronization service configuration (PTP instance reference).
Step 5-6.
The TSCTSF uses the Subscription Correlation ID and user-plane node ID in Ntsctsf_TimeSynchronization_ConfigCreate to determine the target UEs and corresponding AF-sessions. The TSCTSF uses the parameters (e.g. requested PTP instance type, transport protocol, and PTP profile) in the Ntsctsf_TimeSynchronization_ConfigCreate request to determine suitable DS-TT(s) and corresponding AF-sessions among all AF-sessions that are associated with the Subscription Correlation ID and user-plane node ID in the request.
The TSCTSF maintains association between list of suitable AF-sessions, corresponding time synchronization configuration, the PTP instance reference in 5GS, PTP instance references in each involved DS-TT and NW-TT, and Subscription Correlation ID and user-plane node ID as given in step 1.
The TSCTSF uses the procedures described in clause K.2.2 of TS 23.501 to configure and initialize the PTP instance in the DS-TT(s) and NW-TT. The TSCTSF constructs a PMIC to each DS-TT/UE to activate the time synchronization service in DS-TT in respect to the service parameters in the request in step 2. The TSCTSF constructs PMIC(s) and UMIC to NW-TT to activate the time synchronization service in NW-TT in respect to the service parameters in the request in step 2.
Upon reception of responses from each DS-TT and NW-TT, the TSCTSF determines the state of the time synchronization configuration.
The TSCTSF constructs a PMIC to each DS-TT/UE to subscribe for the port management information changes in the DS-TT. The TSCTSF constructs PMIC(s) and UMIC to NW-TT to subscribe for the port management and user-plane management information changes in NW-TT. The TSCTSF retrieves the PMIC(s) and UMIC via means of Npfc_PolicyAuthorization service operations.
The create request creates also a subscription for notifications for the changes in the time synchronization service configuration.
If the Ntsctsf_TimeSynchronization_ConfigCreate request contains a temporal validity condition with a start-time and/or the stop-time that is in the future, the TSCTSF maintains the start-time and stop-time for the time synchronization service for the corresponding time synchronization configuration. If the start-time is in the past, the TSCTSF treats the request as if the time synchronization service was activated immediately. When the start-time is reached, the TSCTSF proceeds as described in this step above. When the stop-time is reached for active time synchronization service configuration, the TSCTSF proceeds as Ntsctsf_TimeSynchronization_ConfigDelete was received as described in clause 4.15.9.3.4.
The TSCTSF uses the procedure in clause 4.15.9.4 to manage the 5G access stratum time distribution for the UEs that are part of the impacted PTP instance.
Step 7.
The TSCTSF notifies the NEF (or AF) with the Ntsctsf_TimeSynchronization_ConfigUpdateNotify service operation, containing the PTP instance reference and the current state of the time synchronization service configuration.
Step 8.
The NEF notifies the AF with the Nnef_TimeSynchronization_ConfigUpdateNotify service operation, containing the PTP instance reference and the current state of the time synchronization service configuration.
Step 9.
Upon a change in the PTP instance in the DS-TT or NW-TT, the DS-TT or NW-TT report the change via PMIC or UMIC to the TSCTSF as described in clause K.2.2 of TS 23.501.
Upon PDU Session release indication from a PCF, the TSCTSF removes the corresponding AF-session from the list of AF-sessions associated with the time synchronization configuration. The TSCTSF uses the procedure in clause 4.15.9.4 to remove the 5G access stratum time distribution parameters for the UE that is removed from the impacted PTP instance.
Upon PDU Session Establishment as defined clause 4.3.2.2.1-1, steps 6-9 in Figure 4.15.9.2-1 are repeated for the new PDU Session and the TSCTSF may notify the NEF (or AF) for the Time Synchronization capability event, optionally with the updated time synchronization capabilities, as described in step 12 in Figure 4.15.9.2-1.
Step 10.
The TSCTSF updates the state of the time synchronization configuration and may notify the NEF (or AF) with the Ntsctsf_TimeSynchronization_ConfigUpdateNotify service operation, containing the PTP instance reference and the updated state of the time synchronization service configuration.
Step 11.
The NEF notifies the AF with the Nnef_TimeSynchronization_ConfigUpdateNotify service operation, containing the reference to the time synchronization service configuration (PTP instance reference) and the updated state of the time synchronization service configuration.
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4.15.9.3.3  Time synchronization service modificationWord‑p. 390
Reproduction of 3GPP TS 23.502, Fig. 4.15.9.3.3-1: Time synchronization service modification
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Step 1.
To update an existing time synchronization service configuration of the PTP instance, the AF invokes a Nnef_TimeSynchronization_ConfigUpdate service operation providing the corresponding PTP instance reference.
Step 2.
The NEF invokes the Ntsctsf_TimeSynchronization_ConfigUpdate service operation with the corresponding TSCTSF.
The AF that is part of operator's trust domain may invoke the services directly with TSCTSF.
Step 3.
The TSCTSF responds with the Ntsctsf_TimeSynchronization_ConfigUpdate response.
Step 4.
The NEF responds with the Nnef_TimeSynchronization_ConfigUpdate.
Step 5-6.
The TSCTSF uses the PTP instance reference included in the Ntsctsf_TimeSynchronization_ConfigUpdate request to identify the time synchronization service configuration and the corresponding AF sessions.
If the Ntsctsf_TimeSynchronization_ConfigUpdate request includes updated service parameters for the PTP instance, and if the corresponding DS-TT(s) and NW-TT are suitable with the parameters (e.g. requested PTP instance type, transport protocol, and PTP profile), the TSCTSF uses the procedures described in clause K.2.2 of TS 23.501 to update the PTP instance(s) in the DS-TT(s) and NW-TT.
If the Ntsctsf_TimeSynchronization_ConfigUpdate request includes one or more UE identities to be added to the PTP instance, if the corresponding DS-TT(s) are suitable with the parameters (e.g. requested PTP instance type, transport protocol, and PTP profile) in the time synchronization service configuration as identified by the PTP instance reference in the request:
  • the TSCTSF adds the suitable AF-sessions to the list of AF-sessions that are associated with the time synchronization service configuration; and
  • the TSCTSF uses the procedures described in clause K.2.2 of TS 23.501 to initialize and activate the PTP instance(s) in the corresponding DS-TT(s).
  • the TSCTSF uses the procedure in clause 4.15.9.4 to manage the 5G access stratum time distribution for the UEs that are added to the impacted PTP instance.
If the Ntsctsf_TimeSynchronization_ConfigUpdate request includes one or more UE identities to be removed to the PTP instance, the TSCTSF removes the corresponding AF-sessions from the list of AF-sessions associated with the time synchronization configuration. The TSCTSF uses the procedure in clause 4.15.9.4 to remove the 5G access stratum time distribution parameters for the UEs that are removed from the impacted PTP instance.
Step 7.
The TSCTSF notifies the NEF (or AF) with the Ntsctsf_TimeSynchronization_ConfigUpdateNotify service operation, containing the PTP instance reference and the current state of the time synchronization service configuration.
Step 8.
The NEF notifies the AF with the Nnef_TimeSynchronization_ConfigUpdateNotify service operation, containing the PTP instance reference and the current state of the time synchronization service configuration.
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4.15.9.3.4  Time synchronization service deactivationWord‑p. 391
Reproduction of 3GPP TS 23.502, Fig. 4.15.9.3.4-1: Time synchronization service deactivation
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Step 1.
To remove an existing time synchronization service configuration of the PTP instance, the AF invokes a Nnef_TimeSynchronization_ConfigDelete service operation providing the corresponding PTP instance reference.
Step 2.
The NEF invokes the Ntsctsf_TimeSynchronization_ConfigDelete service operation with the corresponding TSCTSF.
The AF that is part of operator's trust domain may invoke the services directly with TSCTSF.
Step 3.
The TSCTSF responds with the Ntsctsf_TimeSynchronization_ConfigDelete response.
Step 4.
The NEF responds with the Nnef_TimeSynchronization_ConfigDelete response.
Step 5-6.
The TSCTSF uses the PTP instance reference included in the Ntsctsf_TimeSynchronization_ConfigDelete request to identify the time synchronization service configuration and the corresponding AF sessions. The TSCTSF uses the procedures described in clause K.2.2 of TS 23.501 to disable the corresponding PTP instance(s) in the DS-TT(s) and NW-TT. The TSCTSF deletes the time synchronization service configuration for the respective PTP instance.
The TSCTSF uses the procedure in clause 4.15.9.4 to deactivate the 5G access stratum time distribution for the UEs that are part of the impacted PTP instance.
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4.15.9.4  Procedures for management of 5G access stratum time distributionWord‑p. 392

The AF can use the procedure to activate, update or delete the 5G access stratum time distribution for one UE, group of UEs or any UE using the DNN and S-NSSAI.
The AF may query the status of the 5G access stratum time distribution using Nnef_ASTIGet service operation. The Nnef_ASTICreate and Nnef_ASTIUpdate request may contain the parameters as described in Table 4.15.9.4-1.
Parameter Description
5G access stratum time distribution indication (enable, disable) Indicates that the access stratum time distribution via Uu reference point should be activated or deactivated for the associated UE identities.
Time synchronization error budget Indicates the time synchronization error budget for the time synchronization service (as described in clause 5.27.1.9 of TS 23.501).
[optional]
Temporal Validity Condition Indicates start-time and stop-time attributes that describe the time period when the time synchronization service is active.
[optional]
Reproduction of 3GPP TS 23.502, Fig. 4.15.9.4-1: Management of 5G access stratum time information
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Step 1.
AM Policy Association establishment as described in clause 4.16.1.
Step 2.
(When the procedure is triggered by the AF request to influence the 5G access stratum time distribution):
  • To create a new request, the AF provides access stratum time distribution parameters to the NEF using the Nnef_ASTICreate service operation (together with the AF identifier and potentially further inputs as specified in Table 4.15.9.4-1), including a target (one UE identified by SUPI or GPSI, a group of UEs identified by an External Group Identifier. The NEF maps the External Group Identifier to an Internal Group Identifier and any GPSI to a SUPI.
  • To update or remove an existing request, the AF invokes an Nnef_ASTIUpdate or Nnef_ASTIDelete service operation providing the corresponding time synchronization configuration id.
  • To query the status of the access stratum time distribution, the AF invokes Nnef_ASTIGet service operation providing the target (List of UE identities (SUPI or GPSI)).
The AF that is part of operator's trust domain may invoke the services directly with the TSCTSF.
Step 3.
(When the procedure is triggered by the AF request to influence the 5G access stratum time distribution):
  • The NEF authorizes the request. After successful authorization, the NEF invokes the Ntsctsf_ASTICreate/Update/Delete/Get service operation with the TSCTSF discovered and selected as described in clause 6.3.24 of TS 23.501.
(When the procedure is triggered by the AF request to influence the 5G access stratum time distribution):
  • The TSCTSF determines whether the targeted UE is part of a PTP instance in 5GS, if so the TSCTSF rejects the request (steps 4-7 .are skipped).
(When the procedure is triggered by PTP instance activation, modification, or deactivation in the TSCTSF):
  • If time synchronization error budget is provided by the AF, the TSCTSF may use the PTP port state of each DS-TT to determine an Uu time synchronization error budget for corresponding SUPIs that are part of the PTP instance.
  • If time synchronization error budget is provided by the AF, the TSCTSF calculates the Uu time synchronization error budget as described in clause 5.27.1.9 of TS 23.501.
Step 4.
The TSCTSF searches the PCF for the UE using Nbsf_Management_Subscribe with SUPI as an input parameter, indicating that it is searching for the PCF that handles the AM Policy Association of the UE.
Step 5.
The BSF provides to the TSCTSF the identity of the PCF for the UE for the requested SUPI via an Nbsf_Management_Notify operation. If matching entries already existed in the BSF when step 6 is performed, this shall be immediately reported to the TSCTSF.
Step 6.
The TSCTSF sends to the PCF for the UE its request for the AM policy of the UE (identified by SUPI) using Npcf_AMPolicyAuthorization request, containing the 5G access stratum time distribution indication (enable, disable) and optionally the calculated Uu time synchronization error budget.
Step 7.
If the PCF receives multiple time synchronization error budgets for a given UE, then the PCF picks the most stringent budget. The PCF takes a policy decision and then the PCF may initiate an AM Policy Association Modification procedure for the UE as described in clause 4.16.2.2 to provide AMF the 5G access stratum time distribution parameters. As part of this, the AMF shall, if supported, send the 5G access stratum time distribution indication (enable, disable) and the Uu time synchronization error budget, when they are available, to an NG-RAN node using NGAP procedures (e.g., UE Context Setup/Modification) specified in TS 38.413. The NG-RAN node shall, if supported, store the information in the UE Context. Based on this information, the NG-RAN node provides the 5GS access stratum time to the UE according to the Uu time synchronization error budget as provided by the TSCTSF (if supported by UE and NG-RAN).
Step 8.
The PCF of the UE replies to the TSCTSF with the result of Npcf_AMPolicyAuthorization operation.
Step 9.
The TSCTSF responds the AF with the Ntsctsf_ASTICreate/Update/Delete/Get service operation response.
Step 10.
The NEF informs the AF about the result of the Nnef_ASTICreate/Update/Delete/Get service operation performed in step 2.
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4.15.10  AF specific UE ID retrieval |R17|Word‑p. 394

This clause contains the detailed description and the procedures for the AF specific UE ID retrieval. The AF specific UE Identifier is represented by the External Identifier as defined in TS 23.003.
Reproduction of 3GPP TS 23.502, Fig. 4.15.10-1: AF specific UE ID retrieval
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Step 1.
AF requests to retrieve UE ID via the Nnef_UEId_Get service operation. The request message shall include UE address (IP address or MAC address) and AF Identifier, it may include, MTC Provider Information, Application Port ID, IP domain. The MTC Provider Information identifies the MTC Service Provider and/or MTC Application. If available the AF may also provide the corresponding DNN and/or S-NSSAI.
Step 2.
The NEF authorizes the AF request. If the authorisation is not granted, the NEF replies to the AF with a Result value indicating authorisation failure; otherwise the NEF proceeds with the following steps. The NEF determines corresponding DNN and/or S-NSSAI information: this may have been provided by the AF or is determined by the NEF based on the requesting AF Identifier, MTC Provider Information.
Step 3-4.
The NEF may use the Nbsf_Management_Discovery service operation with UE address and IP domain and /or DNN and/or S-NSSAI. to retrieve the session binding information of the UE. If no SUPI is received in the session binding information from the BSF, the NEF replies to the AF with a Result value indicating that the UE ID is not available.
Step 5.
The NEF interacts with UDM to retrieve the AF specific UE Identifier via the Nudm_SDM_Get service operation. The request message includes SUPI and at least one of Application Port ID, MTC Provider Information or AF Identifier.
Step 6.
The UDM responds to the NEF with an AF specific UE Identifier represented as an External Identifier for the UE which is uniquely associated with the Application Port ID, MTC provider Information and/or AF Identifier.
Step 7.
The NEF further responds to the AF with the information (including the AF specific UE Identifier represented as an External Identifier) received from the UDM.
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