Content for  TS 23.503  Word version:  18.5.0

The AF may subscribe/unsubscribe to notifications of events from the PCF for the PDU Session to which the AF session is bound. The AF can either subscribe/unsubscribe directly at the PCF or indirectly via an NEF or a TSCTSF. The PCF for the UE may subscribe/unsubscribe to notifications of events from the PCF for the PDU Session of a UE. Other NFs may subscribe/unsubscribe to notifications of events from the PCF for a PDU Session or for a UE. The events that can be subscribed by the AF and by other NFs are listed in Table 6.1.3.18-1.

If an AF requests the PCF to report the PLMN identifier where the UE is currently located, then the PCF shall provide the PLMN identifier or the SNPN identifier to the AF if available. Otherwise, the PCF shall provision the corresponding PCC rules, and the Policy Control Request Trigger to report PLMN change to the SMF. The PCF shall, upon receiving the PLMN identifier or the SNPN identifier from the SMF forward this information to the AF, including the PLMN Id and if available the NID. If the H-PCF requests to report the PLMN identifier where the UE is currently located, the V-PCF provisions the PCRT on "PLMN change" to the AMF as described in clause 6.1.2.5 and then forwards the PLMN ID received from the AMF to the H-PCF. If an AF requests the PCF to report on the change of Access Type, the PCF shall provide the corresponding Policy Control Request Trigger to the SMF to enable the report of the Change in Access Type to the PCF. The PCF shall, upon reception of information about the Access Type the user is currently using and upon indication of change of Access Type, notify the AF on changes of the Access Type and forward the information received from the SMF to the AF. The change of the RAT Type shall also be reported to the AF, even if the Access Type is unchanged. For MA PDU Session the Access Type information may include two Access Type information that the user is currently using. If an AF requests the PCF to report on the signalling path status, for the AF session, the PCF shall, upon indication of removal of PCC Rules identifying signalling traffic from the SMF report it to the AF. If an AF requests the PCF to report Access Network Charging Correlation Information, the PCF shall provide to the AF the Access Network Charging Correlation Information, which allows to identify the usage reports that include measurements for the Service Data Flow(s), once the Access Network Charging Correlation Information is known at the PCF. If an AF requests the PCF to report Access Network Information (i.e. the User Location Report and/or the UE Timezone Report) at AF session establishment, modification or termination, the PCF shall set the Access Network Information report parameters in the corresponding PCC rule(s) and provision them together with the corresponding Policy Control Request Trigger to the SMF. For those PCC rule(s) based on preliminary service information the PCF may assign the 5QI and ARP of the QoS Flow associated with the default QoS rule to avoid signalling to the UE. The PCF shall, upon receiving an Access Network Information report corresponding to the AF session from the SMF, forward the Access Network Information as requested by the AF (if the SMF only reported the serving PLMN identifier or the SNPN identifier to the PCF, as described in clause 6.1.3.5, the PCF shall forward it to the AF). For AF session termination the communication between the AF and the PCF shall be kept alive until the PCF report is received. If an AF requests the PCF to report the Usage for Sponsored Data Connectivity, the PCF shall provision the corresponding PCC rules, and the Policy Control Request Trigger to the SMF. If the usage threshold provided by the AF has been reached or the AF session is terminated, the PCF forwards such information to the AF. If an AF or TSCTSF requests the PCF to report the Service Data Flow deactivation, the PCF shall report the release of resources corresponding to the AF session. The PCF shall, upon being notified of the removal of PCC Rules corresponding to the AF session from the SMF, forward this information to the AF. The PCF shall also forward, if available, the reason why the resources are released, the user location information and the UE Timezone. If an AF or TSCTSF requests the PCF to report the Resource allocation outcome, the PCF shall report the outcome of the resource allocation of the Service Data Flow(s) related to the AF session. The AF or TSCTSF may request to be notified about successful or failed resource allocation. In this case, the PCF shall instruct the SMF to report the successful resource allocation trigger (see clause 6.1.3.5). If the SMF has notified the PCF that the resource allocation of a Service Data Flow is successful and the currently fulfilled QoS matches an Alternative QoS parameter set (as described in clause 6.2.2.1), the PCF shall also provide to the AF the QoS Reference parameter or the Requested Alternative QoS Parameter Set which corresponds to the Alternative QoS parameter set referenced by the SMF. If the SMF has notified the PCF about resource allocation failure together with an Access Type (as described in clause 6.1.3.5), the PCF shall only notify the AF when the PCC rule is removed and without forwarding any Access Type information. If the SMF has notified the PCF about resource allocation failure due to UE temporary unreachable together with a maximum waiting time, if available, (as described in clause 6.1.3.5), the PCF shall notify the AF on resource allocation failure and provide the UE temporary unreachable and the maximum waiting time, if available. If an AF requests the PCF to report when the QoS targets can no longer (or can again) be fulfilled for a particular media flow, the PCF shall set the QNC indication in the corresponding PCC rule(s) that includes a GBR or delay critical GBR 5QI value and provision them together with the corresponding Policy Control Request Trigger to the SMF. At the time, the SMF notifies that GFBR can no longer (or can again) be guaranteed for a QoS Flow to which those PCC Rule(s) are bound, the PCF shall report to the AF the affected media flow and provides the indication that QoS targets can no longer (or can again) be fulfilled. If additional information is received with the notification from SMF (see clause 5.7.2.4 of TS 23.501), the PCF shall also provide to the AF the QoS Reference parameter or the Requested Alternative QoS Parameter Set which corresponds to the Alternative QoS parameter set referenced by the SMF. If the SMF has indicated that the lowest priority Alternative QoS parameter set cannot be fulfilled, the PCF shall indicate to the AF that the lowest priority QoS Reference or the lowest priority set of Requested Alternative QoS Parameters of the Alternative Service Requirements cannot be fulfilled. If the AF subscribes to be notified of the QoS Monitoring reports, the PCF decides about the path for the QoS Monitoring reports and sets the QoS Monitoring Policy Control Request Trigger accordingly, as described in clause 6.1.3.21. The PCF sends the QoS Monitoring reports to AF based on the QoS Monitoring reports that it receives from the SMF, according to AF subscription and PCF selected notification path e.g. PCF does not report to AF if AF will receive the QoS Monitoring reports directly from the UPF. If the AF subscribes to be notified of Packet Delay Variation reports (the variation of UL/DL packet delay between UE and PSA UPF), the PCF triggers the QoS monitoring procedure, derives the 5GS Packet Delay Variation and reports the value to the AF, as described in clause 6.1.3.26. If the AF subscribes to Round-trip delay measurement over two service data flows considering the UL direction of a service data flows and the DL direction of another service data flow, PCF triggers the QoS monitoring procedure to derive the Round-Trip delay measurement for delay measurements on the individual QoS Flows respectively (as described in clause 6.1.3.27.1 and in clause 5.37.4 of TS 23.501. The PCF derives the Round-Trip delay based on the packet delay measurement reports of the QoS flows of each direction and reports the results to the AF. PCF sets QoS Monitoring Policies for each of the individual service data flows and QoS Monitoring Policy Control Request Trigger as described in clause 6.1.3.21. If the AF indicates ECN marking for L4S support by the application, PCF authorizes the request and sets the ECN marking for L4S can no longer (or can again) be performed trigger accordingly. PCF shall further send the notification it receives from the SMF to AF on whether the network can not (or can again) perform ECN marking for L4S, for example, if due to user mobility neither target RAN nor UPF PSA support ECN marking for L4S. If an AF requests the PCF to report on the Out of credit event for the associated service data flow(s), the PCF shall inform the AF (when it gets informed by the SMF) that credit is no longer available for the services data flow(s) related to the AF session together with the applied termination action. If an AF requests the PCF to report on the Reallocation of credit event for the associated service data flow(s), the PCF shall inform the AF (when it gets informed by the SMF) that credit has been reallocated after credit was no longer available and the termination action was applied for the service data flow(s) related to the AF session. The PCF can arm the trigger of 5GS Bridge/Router information available to SMF based on local policy (i.e. without an AF request) or based on subscription request from TSCTSF. The PCF shall, upon reception of the 5GS Bridge/Router information (refer to clauses 6.1.3.23, 6.1.3.23a, 6.1.3.23b) from the SMF, forward this information to the TSN AF or the TSCTSF. When the PCF has received the User plane node Management Information Container or Port Management Information Container and related port number from SMF, the PCF also provides User plane node Management Information Container or Port Management Information Container and related port number to the TSN AF or TSCTSF. When SMF has reported the 5GS Bridge/Router information and no AF session exists, the PCF forward this information to a pre-configured TSN AF, or to a pre-configured TSCTSF or a TSCTSF discovered and selected via NRF. In the case of private IPv4 address being used for IP type PDU Session, the PCF shall additionally report DNN and S-NSSAI of the PDU Session to TSCTSF. If the AF requests the PCF to report on the outcome of the service area coverage change, the PCF reports the outcome of the service area coverage change to the AF and notifies the current service area coverage to the AF. The outcome is the result of the execution of the request of service coverage change at the PCF; the outcome is successful if the request was executed, and includes the current service area coverage that may be the same or different from the service area coverage provided by the AF. The subscription may also be implicit. In this case there may be bulk subscription, either for an Internal-Group-Id or for any UE. In order to prevent massive notifications to the AF, the request for any UE is associated to a specific Application Identifier or DNN, S-NSSAI. For bulk subscription, when the AF request includes an expiration time, the PCF stops reporting to the AF when the expiration time is reached. If the AF requests the (H-)PCF, via V-PCF when roaming, to report on the outcome of the UE Policies delivery due to service specific parameter provisioning procedure, the (H-)PCF reports the outcome of the related UE Policies provisioning procedure for the related traffic descriptor for the UE to the AF, via V-PCF when roaming. The outcome of the UE Policies provisioning procedure includes the success, the failure with an appropriate cause or the interim status report such as the UE is temporarily unreachable or that URSP Rules have not yet been delivered by the H-PCF (see clauses 4.15.6.7 and 5.2.5.7 of TS 23.502). The PCF reports the outcome of the UE Policy provisioning procedure for each of the UEs that were included as Target UEs in the service specific information Data Subset in UDR. When the AF requested the PCF for the UE to report on the outcome of the UE Policies delivery due to service specific parameter provisioning procedure targeting a single UE, the Result of UE Policy Container delivery via EPS event trigger shall be subscribed. A request to report Start of application traffic detection and Stop of application traffic detection triggers the reporting when the PCF receives start of application traffic detection event or stop of application traffic detection event from SMF. The reception of a subscription to this event triggers the setting of the corresponding Policy Control Request Trigger to SMF, if not already subscribed. A request to forward UE reporting Connection Capabilities from an associated URSP rule triggers the reporting when the PCF receives UE reporting of URSP rule enforcement information from the SMF matching specific Connection Capabilities (see clause 6.6.2.4). The request may include SUPI(s), DNN(s) and/or S-NSSAI(s) to which the request applies. The PCF reports the received Connection Capabilities and PDU session information including the SUPI, UE requested DNN, Selected DNN, S-NSSAI, SSC Mode, Request-Type. The reception of a subscription to this event triggers the setting of the corresponding Policy Control Request Trigger to SMF, if not already subscribed. If an AF requests the PCF to report Start of application traffic detection and Stop of application traffic detection via bulk subscription, the AF shall provide the application identifier together with the S-NSSAI and DNN. The PCF provides a PCC rule for the application identifier together with the corresponding Policy Control Request Trigger to the SMF for every PDU Session to this S-NSSAI and DNN. When the PCF receives start of application traffic detection event or stop of application traffic detection event for the PCC rule in a PDU Session, the PCF forwards the event to the AF together with the UE identifier and optionally the IP address of the PDU Session corresponding to this PCC rule. When the AF removes bulk subscription for this application identifier, then the PCF removes the Policy Control Request Trigger from the SMF for every PDU Session to this S-NSSAN and DNN, if it is not used for other purpose. If an AF requests the PCF to report on the change between different types of satellite backhaul or the change between satellite backhaul and non-satellite backhaul (as specified in clause 5.43.4 of TS 23.501), the PCF shall provide the corresponding Policy Control Request Trigger to the SMF to enable the report of satellite backhaul category change (see clause 6.1.3.5) to the PCF. The PCF shall, upon reception of information about the change of Satellite backhaul category, notify the AF on the Satellite backhaul category change event was met and forward the current Satellite backhaul category received from the SMF to the AF. When the satellite backhaul is no longer used, the Satellite backhaul category indicates that a non-satellite backhaul is used. If 5G DDNMF requests the PCF to report on the Change of PDUID, the PCF shall notify whenever a new PDUID is allocated. Further details on how the 5G DDNMF retrieves and subscribes to notifications on Change of PDUID are defined in TS 23.304. A request to report SM Policy Association established or terminated triggers the reporting when the PCF receives the request for notification on the SM Policy Association from SMF. The PCF notifies on the EventID "SM Policy Association established/terminated", includes the PCF binding information of the PCF for the PDU Session of the UE, as described in clause 6.1.1.2.2. If the TSCTSF requests the PCF notifications for reporting of extra UE addresses, the PCF shall provide the extra UE addresses allocated to the PDU Session due to Framed Routes or IPv6 prefix delegation. The report shall include the actual list of IPv4 address masks or a list of IPv6 prefixes as currently allocated. If the AF provides the Capability for BAT adaptation or BAT Window and subscribes to PCF for Notification on BAT offset, the PCF will trigger the subscription to SMF for Notification on BAT offset defined in clause 6.1.3.5. When the Notification on BAT offset trigger is set and the PCF receives a BAT offset and optionally an adjusted periodicity from the SMF, the PCF identifies the affected AF session (based on the PCC rule indicated by the SMF) and forwards the BAT offset and optionally the adjusted periodicity for this AF session to the TSCTSF. A request to report Network Slice Replacement triggers the reporting when the PCF receives the notification on Network Slice Replacement from SMF. The PCF reports that Network Slice Replacement has occurred and the Alternative S-NSSAI if SMF provided. The reception of a subscription to this event triggers the setting of the corresponding Policy Control Request Trigger to SMF, if not already subscribed. A request to report Result of UE Policy Container delivery via EPS triggers the reporting when the PCF for the PDU Session receives the UE Policy Container from the UE during UE Policy Container delivery via EPS, or a delivery failure result for UE Policy Container delivery via EPS with appropriate reason from the SMF. The reception of a subscription to this event triggers the setting of the corresponding Policy Control Request Trigger to SMF, if not already subscribed. If an AF requests the PCF to report on the UE reachability status change, the PCF shall provide the corresponding Policy Control Request Trigger to the SMF to enable the report of the UE reachability status change to the PCF, if not already subscribed. The PCF shall, upon indication of change of reachability status, notify the AF and forward the information received from the SMF to the AF.

Mission Critical Services are defined in TS 23.501, TS 23.502 and in TS 23.280, utilising the architecture defined for 5GS. Subscription data for MCX services are provided to PCF through the N36/Nudr. To support MCX services, the PCF shall subscribe to changes in the MCX services subscription data for Priority PDU connectivity service. Dynamic invocation for MCX services provided from an AF using the Priority indicator over N5/Npcf takes precedence over the MCX services subscription. For MCX services the session management relate policy control functionality of the Policy and Charging control framework for the 5G system is as defined in clause 6.1.3.11 for Multimedia Priority Service.

As specified in TS 23.501, the Access Traffic Steering, Switching and Splitting (ATSSS) feature is an optional feature that may be supported by the UE and the 5GC network. The ATSSS feature enables a multi-access PDU Connectivity Service, which can exchange PDUs between the UE and a data network by simultaneously using one 3GPP access network and one non-3GPP access network (both connected to 5GC) when both accesses are allowed for the same S-NSSAI. The multi-access PDU Connectivity Service also supports the exchange of PDUs between the UE and a data network by simultaneously using one 3GPP access network in EPC and one non-3GPP access network in 5GC, or one 3GPP access network in 5GC and one non-3GPP access network in EPC, as described in TS 23.501. This enables a scenario where a MA PDU Session can simultaneously be associated with user-plane resources on 3GPP access network connected to 5GC or EPC and non-3GPP access connected to 5GC, or with user-plane resources on 3GPP access network connected to 5GC and non-3GPP access connected to EPC. The PCF is informed of the ATSSS capabilities of a MA PDU Session by the SMF, as defined in clause 5.32.2 of TS 23.501. The ATSSS capabilities are both the Steering Mode and the Steering Functionality. The PCF control of Access Traffic Steering, Switching and Splitting for a detected service data flow (SDF) is enabled by including Multi-Access PDU (MA PDU) Session Control information in the PCC rule. This allows the PCF to control:

• The Steering Mode that is used to steer/switch/split the detected SDF. The available Steering Modes are defined in TS 23.501.
• The Steering Functionality that is used for the detected SDF, e.g. the MPTCP functionality or the ATSSS-LL functionality or the MPQUIC functionality defined in TS 23.501.
• The Steering Mode Indicator authorized for the detected SDF.
• The Threshold values for RTT and Packet Loss Rate authorized for the detected SDF.
• The Charging information depending on what Access Type is used for a detected SDF.
• The Usage Monitoring information depending on what Access Type is used for a detected SDF.
• Transport Mode that is used for the detected SDF. The available Transport Modes are defined in TS 23.501.

The rest of the information in the PCC Rule apply to the SDF as such and are not dependent on what Access Type is used for a packet. The MA PDU Session Control information in the PCC rules is used by the SMF in order to create applicable N4 rules for the UPF and ATSSS rules for the UE, as described in TS 23.501. The ATSSS rules are sent to UE via NAS when the MA PDU Session is created or updated by the SMF/PCF, as described in TS 23.501 and TS 23.502. When MA PDU Session Control Information is provided to the SMF within a PCC Rule, the (H-)PCF provides both the Service Data Flow templates to identify a Service Data Flow in the UPF and if the Service Data Flow template includes an application identifier, then the corresponding Application descriptors to identify the application traffic in the UE is also included. The (H-) PCF may use the OSid stored in the UDR as DataSet "Policy Data" and Data Subset "UE context policy control data" to determine the OSAppId supported by the OSid. The (H-)PCF may also provide multiple Application descriptors to identify application traffic in the UE, this is determined by the (H-)PCF local policies that indicates e.g. the operating system supported by the UE. If no OSid is available in the UDR, the (H-)PCF may use the PEI to determine the OSid supported by the UE. The Traffic Descriptor in the ATSSS rule is generated by the SMF from the SDF template of the PCC rule. If the SDF template contains SDF filters, the SMF uses the UL SDF filters for the generation of the IP descriptors or Non-IP descriptors, respectively. If the SDF template contains an application identifier, the SMF includes the Application descriptors received from the PCF as part of the MA PDU Session information in the PCC Rule within the Traffic Descriptors in the ATSSS rule. For the Load-Balancing steering mode with fixed split percentages (i.e. without the Autonomous load-balance indicator or UE-assistance indicator), the PCF may provide one or more threshold values together with the split percentages. For the Priority-based steering mode, the PCF may provide one or more threshold values together with the priority of the accesses. For the Redundant steering mode, the PCF may provide one threshold value and/or a primary access. For the Load-Balancing and the Priority-based steering mode, one threshold value for the Round Trip Time (RTT) and/or one threshold value for the Packet Loss Rate (PLR) may be included in a PCC Rule. For the Redundant steering mode, either one threshold value for the Round Trip Time (RTT) or one threshold value for the Packet Loss Rate (PLR) may be included in a PCC Rule based on local configuration or QoS requirements received from AF as specified in clause 4.15.6.6 or clause 4.15.6.6a of TS 23.502. The threshold values are not dependent on what Access Type is used for a packet, i.e. a given threshold value is applicable to both accesses. The threshold values are applied by the UE and UPF as described in TS 23.501. The MA PDU Session Control information in a PCC rule may contain only one of the following Steering Mode Indicators:

• Autonomous load-balance indicator: This indicator may be included only when the Steering Mode is Load-Balancing and indicates whether autonomous load-balance operation is allowed. Further details are specified in clause 5.32.8 of TS 23.501.
• UE-assistance indicator: It indicates that the UE can decide how to distribute the UL traffic based on its internal state (e.g. battery level), and that the UE can request from UPF to apply the same distribution for the DL traffic. Further details are specified in clause 5.32.8 of TS 23.501.

The PCF may also provide URSP rules to the UE for instructing the UE to establish a MA PDU Session, as described in clause 6.6.2. The PCF control of PDU Session level Usage Monitoring depending on what access type is used to carry the traffic is enabled by providing Usage Monitoring control related information per access in the PDU Session related policy control information (as described in clause 6.4). The Transport Mode may be included in a PCC rule that is used for the detected SDF only when the Steering functionality is the MPQUIC functionality. If the MA PDU Session is capable of supporting one of the following:

• MPTCP and ATSSS-LL with any Steering Mode (i.e. any Steering Mode allowed for ATSSS-LL) in the downlink and MPTCP and ATSSS-LL with Active-Standby in the uplink;
• MPQUIC and ATSSS-LL with any Steering Mode (i.e. any Steering Mode allowed for ATSSS-LL) in the downlink and MPQUIC and ATSSS-LL with Active-Standby in the uplink;
• MPTCP, MPQUIC and ATSSS-LL with any Steering Mode (i.e. any Steering Mode allowed for ATSSS-LL) in the downlink and MPTCP, MPQUIC and ATSSS-LL with Active-Standby in the uplink,

then the PCF shall provide a PCC Rule for "match all" traffic. This PCC Rule contains a "match all" SDF template, the lowest precedence, the Steering Functionality set to "ATSSS-LL" and the Steering Mode set to "Active-Standby" for the uplink direction, and the Steering Functionality set to "ATSSS-LL" and the Steering Mode set to any supported steering mode (i.e. any Steering Mode allowed for ATSSS-LL) for the downlink direction. If the MA PDU Session is capable of supporting one of the following:

• MPTCP with any Steering Mode in the downlink, ATSSS-LL with any steering mode except Smallest Delay steering mode and Redundant steering mode in the downlink, and MPTCP and ATSSS-LL with Active-Standby in the uplink;
• MPQUIC with any Steering Mode in the downlink, ATSSS-LL with any steering mode except Smallest Delay steering mode and Redundant steering mode in the downlink, and MPQUIC and ATSSS-LL with Active-Standby in the uplink;
• Both MPTCP and MPQUIC with any Steering Mode in the downlink, ATSSS-LL with any steering mode except Smallest Delay steering mode and Redundant steering mode in the downlink, and MPTCP, MPQUIC and ATSSS-LL with Active-Standby in the uplink,

then the PCF shall provide a PCC Rule for "match all" traffic. This PCC Rule contains a "match all" SDF template, the lowest precedence, the Steering Functionality set to "ATSSS-LL" and the Steering Mode set to "Active-Standby" for the uplink direction, and the Steering Functionality set to "ATSSS-LL" and the Steering Mode set to any supported steering mode except Smallest Delay steering mode and Redundant steering mode for the downlink direction. If the MA PDU Session is capable of supporting one of the following:

• MPTCP and ATSSS-LL with Active-Standby in the uplink and downlink;
• MPQUIC and ATSSS-LL with Active-Standby in the uplink and downlink;
• MPTCP, MPQUIC and ATSSS-LL with Active-Standby in the uplink and downlink,

then the PCF shall provide a PCC Rule for "match all" traffic. This PCC Rule contains a "match all" SDF template, the lowest precedence, the Steering Functionality set to "ATSSS-LL" and the Steering Mode set to "Active-Standby" for the uplink direction and the downlink direction. If the MA PDU Session is capable of supporting one of the following:

• MPTCP and ATSSS-LL with any Steering Mode (i.e. any Steering Mode allowed for ATSSS-LL) in the uplink and downlink;
• MPQUIC and ATSSS-LL with any Steering Mode (i.e. any Steering Mode allowed for ATSSS-LL) in the uplink and downlink;
• MPTCP, MPQUIC and ATSSS-LL with any Steering Mode (i.e. any Steering Mode allowed for ATSSS-LL) in the uplink and downlink,

then the PCF shall provide a PCC Rule for "match all" traffic. This PCC Rule may contain a "match all" SDF template, the lowest precedence, the Steering Functionality set to "ATSSS-LL" and the Steering Mode set to any supported steering mode for the uplink direction and for the downlink direction (i.e. any Steering Mode allowed for ATSSS-LL). The Steering functionality "ATSSS-LL" shall not be provided together with Steering Mode "Redundant". These PCC Rules are used by the SMF to generate an ATSSS rule for the UE and an N4 rule for the UPF to route the "match all" traffic of the MA PDU Session in the uplink and downlink direction respectively. When the Redundant steering mode is used and resources are not available in one access, the SMF will notify the PCF about the resource allocation failure and indicate the respective Access Type (as described in clause 6.1.3.5). The PCF can then determine by implementation specific means how to proceed with such a GBR SDF for which redundant traffic transmission is no longer possible.