6.2 Network functions and entities

23.5033GPPPolicy and charging control framework for the 5G System (5GS)Release 18Stage 2TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

6.2.1 Policy Control Function (PCF)

6.2.1.1 General

6.2.1.1.1 Session management related functionality

The PCF provides the following session management related functionality:

– Policy and charging control for a service data flows;

– PDU Session related policy control;

– PDU Session event reporting to the AF.

The PCF provides authorized QoS for a service data flow and other network control regarding service data flow detection, gating, QoS and charging (except credit management) towards the SMF.

The PCF uses the service information received from the AF (e.g. SDP information or other available application information) and/or the subscription information received from the UDR to calculate the proper QoS authorization (QoS class identifier, bitrates). The PCF may also take into account the requested QoS received from the SMF and the analytics information (e.g. analytics related to "Service Experience") received from the NWDAF.

NOTE 1: The PCF provides always the maximum values for the authorized QoS even if the requested QoS is lower than what can be authorized.

The PCF may check that the service information provided by the AF is consistent with both the operator defined policies and the related subscription information as received from the UDR during PDU Session establishment before storing the service information. The PCF may reject the request received from the AF when the service information is not consistent with either the related subscription information or the operator defined policies and may indicate, in the response to the AF, the service information that can be accepted by the PCF (e.g. the acceptable bandwidth). In the absence of other policy control mechanisms outside the scope of PCC, it is recommended that the PCF include this information in the response.

In this Release, the PCF supports only the interaction with a single AF for each AF session.

The Authorization of QoS shall be based on complete service information unless the PCF is required to perform the authorization of QoS based on preliminary service information. The PCF shall after receiving the complete service information, update the affected PCC rules accordingly.

At reception of the service information from the AF if configured through policy and taking into account information defined in TS 26.114 [31], the PCF determines the Maximum Packet Loss Rate for UL and DL based on the service information and sends it to SMF along with the PCC rule.

NOTE 2: Based on local configuration, the PCF sets the Maximum Packet Loss Rate (UL, DL) corresponding to either the most robust codec configuration (e.g. codec, mode, redundancy) or the least robust codec configuration of the negotiated set in each direction.

NOTE 3: Details for setting the Maximum Packet Loss Rate are specified by SA4.

The PCF supports usage monitoring control as described in clause 6.2.1.7.

The PCF supports sponsored data connectivity for a service as described in clause 6.2.1.8.

The PCF uses the information relating to subscriber spending available in the CHF as input for policy decisions related to e.g. QoS control, gating or charging conditions. Details for policy decisions based on spending limits are described in clause 6.1.3.17.

The PCF uses one or more pieces of information defined in the clause 6.2.1.2 as input for the selection of traffic steering policies used to control the steering of the subscriber’s traffic as described in clause 6.1.3.14.

The PCF reports PDU Session events, e.g. Access Type, RAT Type (if applicable), Access Network Information, PLMN identifier where the UE is located, as described in clause 6.1.3.18.

The subscription and reporting of events when the target for reporting is an Internal Group Identifier or any UE accessing a combination of (DNN, S-NSSAI), is described in clause 5.2.5.7 of TS 23.502 [3]. The events that can be reported by the PCF are described in clause 6.1.3.18.

The subscription and reporting of events targeting an individual UE IP address (IPv4 address or IPv6 prefix) and optionally the DN information are described below. The events that can be reported by the PCF are described in clause 6.1.3.18.

The PCF shall ensure that the sum of the packet filters used by all PCC rules which trigger the generation of signalled QoS rules does not exceed the number of supported packet filters for signalled QoS rules indicated by the UE for the PDU Session, if this information is provided by the SMF (as defined in clause 6.2.1.2).

For EPC IWK, when PCF receives from the SMF of the report on UE resumed from suspend state, the PCF may provision PCC Rules to the SMF to trigger an IP-CAN Session modification procedure.

The PCF may provide the IP index as the PDU Session related policy to the SMF for IP address/Prefix allocation at SM Policy Association Establishment. If PCF receives from the SMF an allocated IP address/Prefix for the PDU Session, it shall not include IP Index into the PDU Session related policy.

On receiving the DN Authorization Profile Index provided by the SMF at the establishment or modification of the SM Policy Association for a PDU Session, the PCF takes the DN Authorization Profile Index as input for a policy decision and then obtains the list of PCC Rules (as defined in clause 6.3) and/or PDU Session related policy (as defined in clause 6.4) and provides them to the SMF as part of the Session Management Policy Control Data for enforcement.

On receiving the Session-AMBR provided by the SMF at the establishment or modification of the SM Policy Association for a PDU Session under the conditions defined in clause 5.6.6 of TS 23.501 [2], the PCF provides the Authorized Session-AMBR as part of the PDU Session policy control information defined in clause 6.4.

The PCF provides DNAI(s) in the PCC rule(s) to the SMF, taking into account the AF request and the Local routing indication from the PDU Session policy control subscription information.

When the PCF detects that all PCC rules related to an AF session are removed, or the PCF detects that the SM Policy Association is terminated, the PCF shall request the AF to terminate the AF session. If the SMF indicated that the PCC rules were removed or that the SM Policy Association is terminated due to PS to CS handover, the PCF shall indicate PS to CS handover as cause within the request to terminate the AF session.

NOTE 4: For 5G-SRVCC (i.e. SRVCC from NG-RAN to UTRAN) as specified in TS 23.216 [25]), the SM Policy Association is terminated by the SMF. For SRVCC (i.e. SRVCC from E-UTRAN to GERAN/UTRAN) as specified in TS 23.216 [25], the SMF indicates that PCC rules are removed.

6.2.1.1.2 Non-session management related functionality

The PCF provides the following non-session management related functionality:

– Access and mobility related policy control (as described in clause 6.1.2.1);

– UE policy information control (as described in clause 6.1.2.2);

– Negotiation for future BDT (as described in clause 6.1.2.4);

– Negotiation for planned transfer with QoS requirements (as described in clause 6.1.2.7).

6.2.1.1.3 Network slice related functionality

The PCF provides the following network slice related functionality:

– Limitation of the data rate per network slice (as described in clause 6.1.4).

6.2.1.2 Input for PCC decisions

The PCF shall accept input for PCC decision-making from the SMF, the AMF, the CHF, the NWDAF if present, the UDR and if the AF is involved, from the AF, as well as the PCF may use its own predefined information. These different nodes should provide as much information as possible to the PCF. At the same time, the listed information below describes only examples of the information provided by the respective node and is not intended to be complete. Depending on the particular scenario all the information may not be available or is already provided to the PCF.

The AMF may provide information related to the UE as defined in clause 5.2.5.2 of TS 23.502 [3], for example:

– SUPI;

– PEI of the UE;

– Location of the subscriber;

– Service Area Restrictions;

– RFSP Index;

– RAT Type;

– GPSI;

– Access Type;

– Serving Network identifier (PLMN ID or PLMN ID and NID, see clause 5.34 of TS 23.501 [2]);

– Allowed NSSAI;

– UE time zone;

– Subscribed UE-AMBR;

– Configured NSSAI for the serving PLMN;

– Mapping Of Allowed NSSAI;

– S-NSSAI for the PDU Session;

– Requested DNN.

NOTE 1: The Access Type and RAT Type parameters should allow extension to include new types of accesses.

The UE may provide information such as:

– OSId;

– List of PSIs;

– Indication of UE support for ANDSP.

The SMF may provide information related to the PDU Session as defined in clause 5.2.5.4 of TS 23.502 [3], for example:

– SUPI;

– PEI of the UE;

– IPv4 address of the UE;

– IPv6 network prefix assigned to the UE;

– Default 5QI and default ARP;

– Request type (initial, modification, etc.);

– Type of PDU Session (IPv4, IPv6, IPv4v6, Ethernet, Unstructured);

– Access Type;

– RAT Type;

– GPSI;

– Internal-Group Identifier;

– Location of the subscriber;

– S-NSSAI;

– DNN;

– Serving Network identifier (PLMN ID or PLMN ID and NID, see clause 5.34 of TS 23.501 [2]);

– Application Identifier;

– Allocated application instance identifier;

– Detected service data flow descriptions;

– UE support of reflective QoS (as defined in clause 5.7.5.1 of TS 23.501 [2]);

– Number of supported packet filters for signalled QoS rules for the PDU Session (indicated by the UE as defined in clause 5.7.1.4 of TS 23.501 [2]);

– 3GPP PS Data Off status;

– DN Authorization Profile Index (see clause 5.6.6 of TS 23.501 [2]);

– DN authorized Session AMBR (see clause 5.6.6 of TS 23.501 [2]);

– Satellite backhaul category information;

– Provisioning Server address(es) (see clause 5.30 of TS 23.501 [2]).

The UDR may provide the information for a subscriber connecting to a specific DNN and S-NSSAI, as described in the clause 6.2.1.3.

The UDR may provide policy information related to an ASP as defined in clause 5.2.12.2 of TS 23.502 [3], for example:

– The ASP identifier;

– A transfer policy together with a Background Data Transfer Reference ID, the volume of data to be transferred per UE, the expected amount of UEs;

– An PDTQ policy together with an PDTQ Reference ID, the requested QoS for each of the AF session for each of the UEs involved and the expected amount of UEs.

NOTE 2: The information related with AF influence on traffic routing may be provided by UDR when the UDR serving the NEF is deployed and stores the application request.

The UDR may provide the service specific information as defined in clause 4.15.6.7 of TS 23.502 [3].

The AF, if involved, may provide application session related information as defined in clause 5.2.5.3 of TS 23.502 [3] directly or via NEF, e.g. based on SIP and SDP, for example:

– Subscriber Identifier;

– IP address of the UE;

– Media Type;

– Media Format, e.g. media format sub-field of the media announcement and all other parameter information (a= lines) associated with the media format;

– Bandwidth;

– Sponsored data connectivity information;

– Flow description information, e.g. source and destination IP address and port numbers and the protocol and optionally, ToS (IPv4) or TC (IPv6) value (as described in clause 6.1.3.6);

– AF application identifier, i.e. an identifier that refers to the application the AF session belongs to, containing either an AF identifier, an external application identifier (if the NEF is involved and performs the mapping to the application identifier) or an application identifier (if the AF is configured accordingly);

NOTE 3: Either Flow description or (external) application identifier for application detection control can be provided.

– DNN and possibly S-NSSAI;

– AF Communication Service Identifier (e.g. IMS Communication Service Identifier), UE provided via AF;

– AF Application Event Identifier;

– AF Record Information;

– Flow status (for gating decision);

– Priority indicator, which may be used by the PCF to guarantee service for an application session of a higher relative priority;

NOTE 4: The AF Priority information represents session/application priority and is separate from the MPS 5GS Priority indicator.

– Emergency indicator;

– Application service provider;

– DNAI;

– Information about the N6 traffic routing requirements;

– GPSI;

– Internal-Group Identifier;

– Temporal validity condition;

– Spatial validity condition;

– AF subscription for early and/or late notifications about UP management events;

– AF transaction identifier;

– TSC individual QoS information as described in clause 6.1.3.22;

– QoS information to be monitored;

– Service area coverage;

– Indication that high throughput is desired;

– Reporting frequency;

– User Plane Latency Requirement.

The AF may provide BDT related information as defined in clause 5.2.5.5 of TS 23.502 [3] via NEF, for example:

– Background Data Transfer Reference ID;

– BDT Policy;

– Volume per UE;

– Number of UEs;

– Desired time window;

– Network Area Information.

The CHF, if involved, may provide the following information for a subscriber as defined in clause 5.2.5.17 of TS 23.502 [3], for example:

– Policy counter status for each relevant policy counter.

The NWDAF, if involved, may provide analytics information as described in clause 6.1.1.3.

In addition, the predefined information in the PCF may contain additional rules based on charging policies in the network, whether the subscriber is in its home network or roaming, depending on the QoS Flow attributes.

The 5QIs (see clause 5.7.4 of TS 23.501 [2]) in the PCC rule is derived by the PCF from AF or UDR interaction if available. The input can be SDP information or other available application information, in line with operator policy.

The Allocation and Retention Priority in the PCC Rule is derived by the PCF from AF or UDR interaction if available, in line with operator policy.

6.2.1.3 Policy control subscription information management

The PCF may request subscription information at PDU Session establishment, PDU Session modification and during the UE Policy Association Establishment procedure.

The PCF may receive notifications on changes in the subscription information. Upon reception of a notification, the PCF shall make the policy control decisions necessary to accommodate the change in the subscription and shall update the SMF and/or the AMF if needed.

NOTE 1: How the PCF provisions/retrieves information related with policy control subscription data is defined in TS 23.501 [2].

The policy control subscription profile information provided by the UDR during the UE Policy Association Establishment procedure using Nudr service for Data Set "Policy Data" and Data Subset "UE context policy control data" is described in Table 6.2-1:

Table 6.2-1: UE context policy control subscription information

Information name	Description	Category
Subscriber categories	List of category identifiers associated with the subscriber	Optional
Tracing Requirements	Tracing requirements as defined in TS 32.421 [18]	Optional
PEI	The Permanent Equipment Identifier of the UE.	Optional
OSId	Identifies the operating system supported by UE.	Optional
Indication of UE support for ANDSP	Indicates the UE support for ANDSP.	Optional
S-NSSAI subscription information	Contains the list of subscribed S-NSSAIs, its associated subscribed DNNs. For each DNN, it includes the Allowed PDU Session types, the Allowed SSC modes and the ATSSS information (NOTE).	Optional
NOTE: ATSSS information is defined in TS 23.502 [3] Table 5.2.3.3.1-1 and Indicates whether MA PDU Session establishment is allowed.

NOTE 2: S-NSSAI subscription information can be part of UE context policy control subscription information and Session Management Subscription data/Slice Selection Subscription data. UDR implementation and the provisioning system are responsible for keeping the consistency of this information when both Data Sets are stored in the same UDR. The provisioning system is responsible for keeping the consistency of this information when both Data Sets are stored in different UDRs.

The policy control subscription profile information provided by the UDR at PDU Session establishment, using Nudr service for Data Set "Policy Data" and Data Subset "PDU Session policy control data" is described in Table 6.2-2.

Table 6.2-2: PDU Session policy control subscription information

Information name	Description	Category
Allowed services	List of subscriber’s allowed service identifiers	Optional
Subscriber categories	List of category identifiers associated with the subscriber	Optional
Subscribed GBR	Maximum aggregate bitrate that can be provided across all GBR QoS Flows for the DNN and S-NSSAI.	Optional
ADC support	Indicates whether application detection and control can be enabled for a subscriber	Optional
Subscriber spending limits control	Indicates whether the PCF must enforce policies based on subscriber spending limits	Optional
IP index information	Information that identifies the IP Address allocation method during PDU Session establishment	Optional
Background Data Transfer Reference ID(s)	Reference ID(s) for Background Data Transfer Policies that apply to the UE.	Optional
Local routing indication	Indication on whether AF influence on traffic routing is allowed or not allowed	Optional
Subscribed UE-Slice-MBR	Subscribed UE-Slice-MBR value per S-NSSAI	Conditional (NOTE 2)
Charging related information	This part defines the charging related information in the policy control subscription profile
Default charging method	Default charging method for the PDU Session (online / offline)	Optional
CHF address	The address of the Charging Function and optionally the associated CHF instance ID and CHF set ID (see clause 6.3.1.0 of TS 23.501 [2])	Optional
Usage monitoring related information	This part includes a list of usage monitoring profiles associated with the subscriber. Each usage monitoring profile is logically associated with a particular operator offer, and includes the following elements
Monitoring key	An identifier to a usage monitoring control instance that includes one or more PCC rules	Conditional (NOTE 1)
Usage monitoring level	Indicates the scope of the usage monitoring instance (PDU Session level or per Service)	Optional
Start date	Start date and time when the usage monitoring profile applies	Optional
End date	End date and time when the usage monitoring profile applies	Optional
Volume limit	Maximum allowed traffic volume	Optional
Time limit	Maximum allowed resource time usage	Optional
Reset period	Time period to reset the remaining allowed consumed usage for periodic usage monitoring control (postpaid subscriptions)	Optional
MPS subscription data	This part defines the MPS subscription information in the policy control subscription profile
MPS priority	Indicates subscription to MPS priority service; priority applies to all traffic on the PDU Session	Conditional (NOTE 1)
IMS signalling priority	Indicates subscription to IMS signalling priority service; priority only applies to IMS signalling traffic	Conditional (NOTE 1)
MPS priority level	Relative priority level for multimedia priority services	Conditional (NOTE 1)
MCS priority	Indicates subscription to MCS priority service; priority applies to all traffic on the PDU Session	Conditional (NOTE 1)
MCS priority level	Relative priority level for MCS services	Conditional (NOTE 1)
NOTE 1: The information is mandatory if the specific part is included in the subscription information (e.g. the monitoring key is mandatory if the usage monitoring information part is included). NOTE 2: The information is used in PCF as described in clause 6.2.1.9 when the monitoring of the UE-Slice-MBR for an S-NSSAI is performed at the PCF. There may be a UE-Slice-MBR value for each S-NSSAI, if applicable.

NOTE 3: Subscribed UE-Slice-MBR can be part of the Access and Mobility Subscription data as described in clause 5.2.3.3.1 of TS 23.502 [3] and can be part of the PDU Session policy control subscription information as described in Table 6.2-2. UDR implementation and the provisioning system are responsible for keeping the consistency of this information when both Data Sets are stored in the same UDR. The provisioning system is responsible for keeping the consistency of this information when both Data Sets are stored in different UDRs.

Table 6.2-3: Remaining allowed usage subscription information

Information name	Description	Category
Remaining allowed usage related information	This part includes a list of Remaining allowed usage associated with the subscriber.
Monitoring key	An identifier to a usage monitoring control included one or more PCC rules	Conditional (NOTE 1)
Usage monitoring level	Iindicates the scope of the usage monitoring (PDU Session level or service level)	Optional
Volume usage	Remaining allowed traffic volume	Optional
Time usage	Remaining allowed resource time usage	Optional
NOTE 1: The information is mandatory if the specific part is included in the subscription information (e.g. the monitoring key is mandatory if the usage monitoring information part is included).

The Allowed services may comprise any number of service identifiers allowed for the subscriber in the PDU Session. The PCF maps those service identifiers into PCC rules according to local configuration and operator policies.

The Subscriber category may comprise any number of identifiers associated with the subscriber (e.g. gold, silver, etc.). Each identifier associates operator defined policies to the subscriber that belong to that category.

The Usage monitoring related information may comprise any number of usage monitoring control instances associated with the subscriber. In each usage monitoring control instance is mandatory to include the Monitoring key. The Reset period only applies to usage monitoring control instances that periodically reset the allowed usage (e.g. daily, monthly, etc.). If the Reset period is not specified, the usage monitoring control instance ends when the allowed data is consumed or when the End date is reached. The usage monitoring related information is used by the PCF instead of the respective information for the subscriber category.

The policy subscription profile may be extended with operator-specific information. Operator-specific extensions may be added both to any specific part of the policy control subscription information (e.g. to the subscriber category part), or as a new optional information block.

Handling of operator specific policy data by the PCF is out of scope of this specification in this release.

The latest list of PSIs and its content delivered to the UE provided by the UDR during the UE Policy Association Establishment procedure using Nudr service for Data Set "Policy Data" and Data Subset "Policy Set Entry" is described in Table 6.2-4.

Table 6.2-4: Policy Set Entry

Information name	Description	Category
Policy Set Entry	List of PSIs and content for each PSI. Content may be Access Network Discovery & Selection Policy Information or UE Route Selection Policy information or both.	Optional

The network slice specific policy control information is per S-NSSAI information stored by the UDR and updated by the PCF during PDU Session Establishment or Modification procedure using Nudr service for Data Set "Policy Data" and Data Subset "Network Slice Specific Control Data" is described in Table 6.2-5:

Table 6.2-5: Network slice specific policy control information

Information name	Description	Category
Maximum Slice Data Rate for UL (per S-NSSAI)	The maximum uplink data rate for the specific network slice	Optional (NOTE 2)
Maximum Slice Data Rate for DL (per S-NSSAI)	The maximum downlink data rate for the specific network slice	Optional (NOTE 2)
Remaining Maximum Slice Data Rate for UL (per S-NSSAI)	The remaining maximum uplink data rate for the specific network slice (NOTE 1).	Optional (NOTE 3)
Remaining Maximum Slice Data Rate for DL (per S-NSSAI)	The remaining maximum downlink data rate limited for a specific network slice (NOTE 1).	Optional (NOTE 3)
NOTE 1: The initial value is set to the Maximum Slice Data Rate for UL/DL value. NOTE 2: The information is only used for limitation of data rate per network slice with assistance of the NWDAF. NOTE 3: The information is only used for limitation of data rate per network slice with PCF based monitoring.

6.2.1.4 V-PCF

The V-PCF is a functional element that encompasses policy control decision functionalities in the VPLMN.

For session management related policy control, the V-PCF only includes functionality for local breakout roaming scenario based on roaming agreements.

For UE policy control, the V-PCF receives the UE policy from the H-PCF and forwards it to the UE via the AMF. The V-PCF can send additional UE policy information (i.e. ANDSP policies) to the UE which is different from the one from H-PCF.

For Access and mobility related policy control, the V-PCF generates the values for RFSP Index, UE-AMBR, UE-Slice-MBR, Service Area Restriction and SMF selection management.

6.2.1.5 H-PCF

The H-PCF is a functional element that encompasses policy control decision functionalities in the HPLMN.

For session management related policy control, the H-PCF only includes functionality for home routed roaming scenario and provides the same functionality as the PCF in the non-roaming case.

For UE policy control, H-PCF generates the UE policy based on subscription data and transfers the UE policy to the UE via the AMF, or via the V-PCF in the roaming case.

6.2.1.6 Application specific policy information management

The application specific information used for policy control includes:

– Negotiation of BDT information stored in the UDR as Data Set "Policy Data" and Data Subset "Background Data Transfer data": It contains an ASP identifier, Non-IP information or IP 3-tuple to identify the Application server, a transfer policy together with the Background Data Transfer Reference ID, the volume of data to be transferred per UE, the expected amount of UEs and optionally, the subscription to notifications when the BDT policy needs to renegotiated;

– Sponsored data connectivity profile information stored in the UDR as Data Set "Policy Data" and Data Subset "Sponsored data connectivity profile data": It contains a list of ASP identifiers and their applications per sponsor identity;

– Application Function request information for multiple UEs (per group of UEs or all UEs) stored in the UDR as Data Set "Application Data" and Data Subset "AF request information for multiple UEs";

– PDTQ information stored in the UDR as Data Set "Policy Data" and Data Subset "PQDT data": It contains an ASP identifier, a PDTQ policy including the PDTQ Reference ID, the requested QoS for each of the AF session for each of the UEs involved, the expected amount of UEs, the network area information provided by the AF (mapped by NEF) and the subscription to notifications when the PDTQ policy needs to renegotiated.

The application specific policy information may be requested/updated by the PCF per AF request.

The management of Application Function request information for multiple UEs is defined in clause 6.3.7.2 of TS 23.501 [2], the management of policies for the negotiation of BDT is defined in clause 6.1.2.4 of this specification and the provision and usage of sponsored data connectivity profile is defined in clause 6.2.1.1 of this specification.

6.2.1.7 Usage monitoring

The PCF supports usage monitoring control for a PDU Session or per Monitoring Key. Usage is defined as either volume or time of user plane traffic.

The PCF may receive usage monitoring related information per DNN and S-NSSAI combination and UE from the UDR, i.e. the overall amount of allowed resources (based either on traffic volume and/or traffic time) that are to be monitored for the PDU Sessions of a user, together with the corresponding remaining allowed usage related information. In addition, usage monitoring related information for Monitoring key(s) per DNN and S-NSSAI combination and UE may also be received from the UDR, together with the corresponding remaining allowed usage related information. For the purpose of usage monitoring per access type, the PCF receives an individual Monitoring key per access type from UDR. Details about the usage monitoring related information and the remaining allowed usage related information provided by the UDR are described in clause 6.2.1.3.

For the purpose of usage monitoring control the PCF shall request the Usage report trigger and provide the necessary usage threshold(s), either volume threshold, time threshold, or both volume threshold and time threshold, upon which the SMF shall report to the PCF. The PCF shall decide if and when to activate usage monitoring to the SMF.

The PCF may provide a Monitoring time to the SMF for the Monitoring keys(s) and optionally specify a subsequent threshold value for the usage after the Monitoring time.

If the SMF reports usage before the Monitoring time is reached, the Monitoring time is not retained by the SMF. Therefore, the PCF may again provide a Monitoring time and optionally the subsequent threshold value for the usage after the Monitoring time in the response.

It shall be possible for the PCF to request a usage report from the SMF.

NOTE 1: The PCF ensures that the number of requests/following policy decisions provided to the SMF do not cause excessive signalling load by e.g. assigning the same time for the report only for a preconfigured number of PDU Sessions.

Once the PCF receives a usage report from the SMF the PCF shall deduct the value of the usage report from the remaining allowed usage for that DNN and S-NSSAI combination and UE (if usage per PDU Session is reported). If usage is reported from the SMF, the PCF shall deduct the value of the usage report from the remaining allowed usage for individual Monitoring key(s) for that DNN and S-NSSAI combination and UE (if usage for one or several Monitoring keys is reported).

NOTE 2: The PCF maintains usage thresholds for each Monitoring key and PDU Session that is active for a certain DNN and S-NSSAI combination and UE. Updating the remaining allowed usage after the SMF reporting, minimizes the risk of exceeding the usage allowance.

If the remaining allowed usage reaches a value of zero (or below zero), the PCF may apply other policy decisions and interact with the SMF accordingly.

If the SMF reports usage for a certain Monitoring key and if monitoring shall continue for that Monitoring key then the PCF shall provide new threshold value(s) in the response to the SMF respectively. If Monitoring time and subsequent threshold value are used then the PCF provides them to the SMF as well.

The PCF may provide a new volume threshold and/or a new time threshold to the SMF, the new threshold values overrides the existing threshold values in the SMF.

If monitoring shall no longer continue for that Monitoring key, then the PCF shall not provide a new threshold in the response to the SMF.

If the last PDU Session of a user for a DNN and S-NSSAI combination is terminated, the PCF shall store the remaining allowed usage, i.e. the information about the remaining overall amount of resources, in the UDR.

If the End date of the usage monitoring related information (see clause 6.2.1.3 for details) is reached, the PCF shall reset the remaining allowed usage to the value(s) indicated in the usage monitoring related information and shall then interact with the SMF to undo any previously applied policy decisions related to remaining allowed usage of zero (or below zero).

6.2.1.8 Sponsored data connectivity

The PCF may authorise an application service provider to request specific PCC decisions (e.g. authorisation to request sponsored IP flows, authorisation to request QoS resources) based on sponsored data connectivity profile from the UDR. For sponsored data connectivity, the PCF may receive a usage threshold from the AF. If the AF specifies a usage threshold, the PCF shall use the Sponsor Identity to construct a Monitoring key for monitoring the volume, time, or both volume and time of user plane traffic, and invoke usage monitoring on the SMF. The PCF shall notify the AF when the SMF reports that a usage threshold for the Monitoring key is reached provided that the AF requests to be notified for this event, as described in clause 6.1.3.18. If the usage threshold is reached, the AF may terminate the AF session or provide a new usage threshold to the PCF. Alternatively, the AF may allow the session to continue without specifying a usage threshold. If the AF decides to allow the session to continue without specifying a usage threshold, then monitoring in the SMF shall be discontinued for that monitoring key by the PCF, unless there are other reasons for continuing the monitoring.

If the H-PCF detects that the UE is in a home-routed roaming scenario when sponsored data connectivity is requested by an AF, it may allow the sponsored data connectivity in the service authorization request, reject the service authorization request, or initiate the AF session termination based on home operator policy.

NOTE: Sponsored data connectivity is not supported in the roaming with local breakout scenario in this Release.

If the AF revokes the service information and the AF has notified previously a usage threshold to the PCF, the PCF shall report the usage up to the time of the revocation of service authorization.

If the PDU Session terminates and the AF has specified a usage threshold then the PCF shall notify the AF of the accumulated usage (i.e. either volume, or time, or both volume and time) of user plane traffic since the last usage report.

6.2.1.9 Monitoring the data rate per Network Slice for a UE

A PCF may support monitoring of data rate per S-NSSAI for a UE. The monitoring is performed by aggregating the Session-AMBR values and the MBR values allocated to each PCC Rule (belonging to a GBR service data flow) in all PDU Sessions established for a UE in that S-NSSAI. To enable this monitoring, the SMF selects the same PCF instance for all PDU Sessions of the UE to the S-NSSAI that is subject to this monitoring, this is achieved as described in clause 6.3.7.1 of TS 23.501 [2], for example by using local operator policies in the SMF, SUPI ranges or explicit indication from the AMF to select the PCF selected for the UE.

If the monitored data rate per S-NSSAI for a UE reaches a certain percentage of the UE-Slice-MBR value for that S-NSSAI (detected via operator defined thresholds), the PCF may apply a policy decision to strengthen the traffic restrictions for individual PDU Sessions or PCC rules (e.g. to change Session-AMBR value (if allowed by the HPLMN) or update PCC Rule(s) to change QoS or charging keys(s)) and interact with the SMF accordingly. When the data rate per S-NSSAI for a UE falls below that percentage of the UE-Slice-MBR value, the PCF may relax the traffic restrictions for individual PDU Sessions or PCC rules.

NOTE 1: It is recommended to avoid frequent policy decisions which trigger a signalling with the UE (like change of Session-AMBR or change of MBR in a PCC rule belonging to a GBR service data flow).

NOTE 2: At the same time the UE-Slice-MBR may be enforced in the NG-RAN, as described in clause 5.15.13 of TS 23.501 [2].

6.2.1.10 Monitoring the data rate per Network Slice

6.2.1.10.1 General

The PCF supports monitoring and limitation of the data rate per S-NSSAI.

If the S-NSSAI is subject to network slice data rate limitation the Remaining Maximum Slice Data rate per S-NSSAI is stored in the UDR as Data Set "Policy Data" and Data Subset "Network Slice Specific Policy Control Data" as defined in clause 6.2.1.3.

The PCF interacts with the UDR to update the network slice specific policy control information per S-NSSAI in the UDR, i.e. the Remaining Maximum Slice Data Rate per S-NSSAI, so that the usage of multiple PCFs for the same S-NSSAI is enabled.

6.2.1.10.2 Monitoring the data rate per Network Slice by using QoS parameters

For the purpose of monitoring the data rate per S-NSSAI, the PCF shall perform the following for an SM Policy Association with an S-NSSAI subject to data rate limitation:

– At the establishment of a SM Policy Association, the PCF shall check whether the Remaining Maximum Slice Data Rate is higher than the Authorized Session-AMBR. If so, the PCF shall deduct the value of the Authorized Session-AMBR allocated to the PDU Session from the Remaining Maximum Slice Data Rate for that S-NSSAI in the UDR. If the Remaining Maximum Slice Data Rate is not sufficient, the PCF shall reject the establishment of the SM Policy Association.

– At the time a PCC Rule of a GBR service data flow is installed, modified or activated in the SMF, the PCF requests reporting "Successful resource allocation" with the corresponding Policy Control Request Trigger. When the SMF reports that the resources are successfully allocated, the PCF shall deduct the value of the MBR authorized for the GBR service data flow from the Remaining Maximum Slice Data Rate for that S-NSSAI in the UDR.

– At the time a change of Authorized Session-AMBR occurs or a PCC Rule containing a GBR value is removed or modified, the PCF shall update the Remaining Maximum Slice Data Rate for that S-NSSAI in the UDR accordingly.

– If the Remaining Maximum Slice Data Rate for that S-NSSAI reaches a (operator defined) threshold that indicates that it is closer to zero, the PCF may apply a policy decision to strengthen the traffic restrictions for individual PDU Sessions or PCC rules (see clause 6.1.4.1) and interact with the SMF accordingly. When the Remaining Maximum Slice Data Rate for that S-NSSAI increases again, the PCF may relax the traffic restrictions for individual PDU Sessions or PCC rules.

– At the time the SM Policy Association for an S-NSSAI subject to data rate limitation is terminated, the PCF shall add the value of the Authorized Session-AMBR allocated to the PDU Session to the Remaining Maximum Slice Data Rate for that S-NSSAI in the UDR.

6.2.2 Session Management Function (SMF)

6.2.2.1 General

The SMF is responsible for the enforcement of the policy decisions related to service data flow detection, authorized QoS, charging, gating, traffic usage reporting, packet routing and forwarding and traffic steering. The SMF controls the policy and charging enforcement which includes the binding of service data flows to QoS Flows (as described in clause 6.1.3.2.4) as well as the interaction with the CHF. The SMF interacts with the UPF(s), the RAN and the UE to achieve the appropriate treatment of the user plane traffic.

The SMF control of the UPF(s) is described in TS 23.501 [2] as well as the interaction principles between SMF and RAN and between SMF and UE. The procedures for the interaction between SMF and UPF, SMF and RAN as well as SMF and UE are described in TS 23.502 [3].

The SMF is enforcing the Policy Control as indicated by the PCF in two different ways:

– Gate enforcement. The SMF shall instruct the UPF to allow a service data flow, which is subject to policy control, to pass through the UPF if and only if the corresponding gate is open;

– QoS enforcement:

– 5QI corresponding with 5G QoS Characteristics. The SMF shall be able to convert a 5QI value to 5G QoS Characteristics values.

– PCC rule QoS enforcement. The SMF shall instruct the UPF to enforce the authorized QoS of a service data flow according to the active PCC rule (e.g. to enforce DSCP marking).

– QoS Flow QoS enforcement. The SMF controls the QoS that is provided to a combined set of service data flows. The policy enforcement function ensures that the resources which can be used by an authorized set of service data flows are within the "authorized resources" specified by the PCF. The authorized QoS provides an upper bound on the resources that can be reserved (GFBR) or allocated (MFBR) for the QoS Flow. During QoS Flow QoS enforcement, if packet filters are provided to the UE, the SMF shall provide packet filters with the same content as that in the SDF template filters received from the PCF.

The SMF is enforcing the charging control in the following way:

– For a service data flow (defined by an active PCC rule) that is subject to charging control, the SMF shall allow the service data flow to pass through the UPF if and only if there is a corresponding active PCC rule with and, for online charging, the CHF has authorized credit for the charging key. The SMF may let a service data flow pass through the UPF during the course of the credit re-authorization procedure.

For a service data flow (defined by an active PCC rule) that is subject to both Policy Control and Charging Control, the SMF shall allow the service data flow to pass through the UPF if and only if the right conditions from both policy control and charging control happen. i.e. the corresponding gate is open and in the case of online charging the CHF has authorized credit for its charging key.

For a service data flow (defined by an active PCC rule) that is subject to policy control only and not charging control, the SMF shall allow the service data flow to pass through the UPF if and only if the conditions for policy control are met.

A SMF may be served by one or more PCF nodes. The SMF shall contact the appropriate PCF as described in clause 6.3.7.1 of TS 23.501 [2].

The operator may configure an indicator in UDM which is delivered to the SMF within the Charging Characteristics and used by the SMF to not establish the SM Policy Association during the PDU Session establishment procedure.

NOTE 1: The decision to not establish the SM Policy Association applies for the life time of the PDU Session.

NOTE 2: The indicator in the UDM is operator specific, therefore its value is understood within the HPLMN and can be used in both non-roaming or home routed roaming cases.

The SMF shall, on request from the PCF, modify a PCC rule, using the equivalent SMF behaviour as the removal of the old and the activation of the new (modified) PCC rule. The SMF shall modify a PCC rule as an atomic operation. The SMF shall not modify a predefined PCC rule on request from the PCF.

The SMF should support predefined PCC rules.

The SMF shall gather and report QoS Flow usage information according to clause 6.1.3.3. The SMF may have a pre-configured Default charging method. Upon the initial interaction with the PCF, the SMF shall provide pre-configured Default charging method if available.

At PDU Session establishment the SMF shall initiate the SM Policy Association Establishment procedure. If no PCC rule was activated for the PDU Session, the SMF shall reject the PDU Session establishment.

If there is no PCC rule active for a successfully established PDU Session at any later point in time, e.g. through a PCF initiated SM Policy Association Modification, the SMF shall initiate a PDU Session termination procedure. If the PCF terminates the SM Policy Association, the SMF shall initiate a PDU Session termination procedure.

If there is no PCC rule active for a successfully established QoS Flow at any later point in time, e.g. through a PCF triggered SM Policy Association Modification, the SMF shall initiate a PDU Session Modification procedure an terminate the QoS Flow.

If the PDU Session is modified, e.g. by changing the characteristics for an QoS Flow, the SMF shall first use the Policy Control Request Trigger to determine whether to request the PCC rules for the modified PDU Session from the PCF; afterwards, the SMF shall use the re-authorisation triggers, if available, in order to determine whether to require re-authorisation for the PCC rules that were either unaffected or modified. If the SMF receives an unsolicited update of the PCC rules from the PCF, the PCC rules shall be activated, modified or removed as indicated by the PCF.

The SMF shall inform the PCF about the outcome of a PCC rule operation. If a QoS Flow cannot be established or modified to satisfy the QoS Flow binding, then the SMF shall reject the activation of a PCC rule. If the SMF is requested to notify the PCF about a successful resource allocation (see clause 6.1.3.5) and the currently fulfilled QoS of an established or modified QoS Flow matches an Alternative QoS Profile (as described in clause 5.7.2.4.3 of TS 23.501 [2]), the SMF shall also provide to the PCF the reference to the Alternative QoS parameter set corresponding to the Alternative QoS Profile referenced by the RAN.

The SMF shall inform the PCF about any removal of a PCC rule, that the PCF has activated, that occurs without explicit instruction from the PCF.

When QoS Flow resources are released, i.e. at SM Policy Association termination or SMF-initiated SM Policy Association modification notifying that PCC Rules are removed, the SMF shall also provide, if available, the reason why resources are released, i.e. RAN/NAS Release Cause.

NOTE 3: In the case of a rejection of a PCC rule activation the PCF may e.g. modify the attempted PCC rule, de-activate or modify other PCC rules and retry activation or abort the activation attempt and, if applicable, inform the AF that transmission resources are not available.

The SMF forwards the Maximum Packet Loss Rate for UL and DL, if received from PCF for the PCC rule bound to a 5QI=1 QoS Flow. In the case multiple PCC Rules share one 5QI=1 QoS Flow and the SMF received multiple Maximum Packet Loss Rates, the SMF chooses the lowest value per direction related to these PCC rules.

When the PCF provides updated PCC rules for the PDU Session to the SMF, and the PCC rules were not enforced due to that the UE is in suspend state, e.g. due to SRVCC to GERAN without DTM support as specified in clause 6.2.2.1 in the TS 23.216 [25] or CSFB to UTRAN without PS Handover as specified in clause 6.5 in the TS 23.272 [26], the SMF shall indicate to the PCF that the PCC Rules were not enforced with the reason that the UE is in suspend state. Upon reception of the failure indication, the PCF may subscribe to UE resumed from suspend state event trigger.

NOTE 4: This above description applies in the case of EPC interworking.

6.2.2.2 Service data flow detection

The Service Data Flow detection uses the service data flow template included in a PCC Rule provide by the PCF. The service data flow template defines the data for the service data flow detection as a set of service data flow filters or an application identifier referring to an application detection filter. The SMF maps the service data flow template in the PCC Rule into the detection information in a Packet Detection Rules to the UPF as described in TS 23.501 [2].

The application detection filters provided to the SMF may be extended with the PFDs provided by the NEF (PFDF). How the SMF uses the service data flow detection capabilities in the UPF is described in clause 5.8.2 of TS 23.501 [2].

For IP PDU Session type and Ethernet PDU Session type, the service data flow filters that may apply for traffic on a PDU Session are defined in clause 5.7.6 of TS 23.501 [2]. The following specifics apply:

– Each service data flow template may contain any number of service data flow filters;

– Each service data flow filter is applicable uplink, downlink or both uplink and downlink;

NOTE 1: Service data flow filters that apply in both uplink and downlink should be used whenever possible.

– Each service data flow filter may contain information about whether the explicit signalling of the corresponding traffic mapping information to the UE is required.

NOTE 2: This information enables e.g. the generation/removal of traffic mapping information for the UE as well as the usage of PCC rules with specific service data flow filters on the QoS Flow associated with the default QoS rule without the need to generate traffic mapping information.

6.2.2.3 Measurement

The SMF shall ensure that the UPF supports data volume, duration, combined volume/duration and event based measurement for charging. The Measurement method indicates what measurement type is applicable to the PCC rule.

NOTE 1: Event based charging is only applicable to predefined PCC rules and PCC rules using an application detection filter (i.e. with an application identifier).

The SMF shall ensure that the UPF measurement measures all the user plane traffic, except traffic that PCC causes to be discarded.

The SMF shall ensure that the UPF maintains a measurement per QoS Flow, and Charging Key combination.

If Service identifier level reporting is mandated in a PCC rule, the SMF shall ensure that the UPF maintains a measurement for that Charging Key and Service Identifier combination, for the QoS Flow.

NOTE 2: In addition, the SMF may instruct the UPF to maintain QoS Flow level measurement if required by the operator.

For usage monitoring, the SMF shall ensure that the UPF supports volume and time measurement for a PDU Session and maintains a measurement for each PDU Session for which the PCF has requested the Usage report trigger and provided threshold values on a PDU Session level. The SMF shall ensure that the UPF is able to support volume and time measurements simultaneously for a given PDU Session.

The SMF shall ensure that the UPF supports volume and time measurement per Monitoring key and maintain a measurement for each Monitoring key if the PCF has requested the Usage report trigger and provided threshold values on Monitoring key level. The SMF shall ensure that the UPF is able to support volume and time measurements simultaneously for a given Monitoring Key.

The SMF shall ensure that the UPF supports simultaneous volume and time measurement for usage monitoring on PDU Session level and Monitoring key level for the same PDU Session.

Volume and time measurements for usage monitoring purposes on PDU Session level and on Monitoring key level shall be performed independently of each other. If the PCC rule is associated with an indication of exclusion from session level monitoring, the SMF shall ensure that the UPF does not consider the corresponding service data flow for the volume and time measurement on PDU Session level.

If the Usage report reached Policy Control Request Trigger is set and a volume or a time threshold is reached, the SMF shall report this event to the PCF. The SMF shall continue to perform volume or time measurement after the threshold is reached and before a new threshold is provided by the PCF. At PDU Session termination or if the conditions defined in clause 6.4 for continued monitoring are no longer met, or if the PCF explicitly requests a usage report, the SMF shall inform the PCF about the resources that have been consumed by the user since the last usage report for the affected Monitoring keys, including the resources consumed before and after the Monitoring time was reached, if provided according to clause 6.2.1.1.

If combined volume and time measurements are requested by the PCF, then the reporting shall be done for both together. For example, if the volume threshold is reached, the consumed time shall be reported as well and, in order to continue combined volume and time measurements, the PCF shall provide a new time threshold along with a new volume threshold. The SMF shall continue to instruct the UPF to perform volume and time measurement after the threshold is reached and before a new threshold is provided by the PCF. If new threshold is provided only for time or volume, then the measurements shall continue only for that provided type and the SMF shall ensure that the accumulated usage for the non provided type is discarded by the UPF.

When the PCF requests to report usage, the SMF shall report the accumulated usage to the PCF according to the provided usage threshold, i.e. the SMF reports accumulated volume when the volume threshold was provided by the PCF, accumulated time when the time threshold was provided by the PCF and both accumulated volume and accumulated time when volume threshold and time threshold were provided by the PCF.

If the Usage thresholds for a Monitoring key are not provided to the SMF in the acknowledgement of a PDU Session modification where its usage was reported, then the usage monitoring shall not continue in the SMF for that Monitoring key.

When the Monitoring time occurs, the accumulated volume and/or time usage shall be recorded by the UPF and reported to the SMF, and:

– If the subsequent usage threshold value is provided, the usage threshold shall be reset to this value by the SMF.

– Otherwise, the usage threshold shall be set by the SMF to the remaining value of the threshold previously sent by the PCF (i.e. excluding the accumulated usage).

The first usage report after the Monitoring Time was reached shall indicate the usage up to the Monitoring time and usage after the Monitoring time.

In order to support time based usage monitoring, the PCF may optionally indicate to the SMF, along with other usage monitoring information provided, the Inactivity Detection Time. This value represents the time interval after which the time measurement shall stop for the Monitoring key, if no packets are received belonging to the corresponding Monitoring Key during that time period. Time measurement shall resume on receipt of a further packet belonging to the Monitoring key.

Time measurement for a Monitoring key shall also be stopped when time based usage monitoring is disabled, if this happens before the Inactivity Detection Time is reached.

If an Inactivity Detection Time value of zero is provided, or if no Inactivity Detection Time is present within the usage monitoring information provided by the PCF, the time measurement shall be performed continuously from the point at which it was started until time based usage monitoring is disabled.

The SMF instructs the UPF to provide usage reports to the SMF as described in TS 23.501, clause 5.8.2.6.

6.2.2.4 QoS control

The SMF receives the authorized QoS for a service data flow in the PCC rule. The SMF derives the QoS parameters for a QoS Flow (other than the QoS Flow associated with the default QoS rule) based on the PCC rule information of the PCC rule(s) bound to this QoS Flow:

– The SMF shall set the QoS Flow parameters 5QI and ARP to the values of the corresponding PCC rule parameters.

– For the QoS Flow parameters QNC, Priority Level, Averaging Window and Maximum Data Burst Volume, the SMF shall use the corresponding PCC rule parameters if they are available in the PCC rule.

– For GBR QoS Flows, the SMF should set the GFBR to the sum of the GBRs of all PCC rules that are active and bound to that QoS Flow and the MFBR to the sum of the MBRs of all PCC rules that are active and bound to that GBR QoS Flow. If a set of PCC Rules is subject to resource sharing as specified in clause 6.1.3.13 the SMF should use, for each applicable direction, the highest GBR from the set of PCC Rules sharing resources as input for calculating the GFBR and may use, for each applicable direction, the highest MBR from the set of PCC Rules as input for calculating the MFBR.

– For GBR QoS Flows, the SMF shall set the QoS Flow parameter Maximum Packet Loss Rate for UL and DL if the corresponding PCC rule parameters are available in the PCC rule. In the case multiple PCC Rules are bound to the QoS Flow and the SMF received multiple Maximum Packet Loss Rates, the SMF chooses the lowest value per direction in all these PCC rules.

– If the PCC rule contains a non-standardized 5QI, the SMF shall also provide the corresponding 5G QoS characteristics parameters (as received in the PDU Session related information Explicitly signalled QoS Characteristics) for the QoS Flow.

– If the PCC rule contains Alternative QoS Parameter Sets, the SMF shall provide their attributes as Alternative QoS Profile(s) (see clause 5.7.1.2a of TS 23.501 [2]) in the same prioritized order (in which they occur in the PCC rule) in addition to the QoS parameters for the QoS Flow.

The SMF shall set the QoS parameters of the QoS Flow associated with the default QoS rule to:

– the PCC rule parameters contained in the PCC rule that is bound to this QoS Flow (in the way it is described above) if the PCC rule attribute Bind to QoS Flow associated with the default QoS rule and apply PCC rule parameters is present; or otherwise

– the Authorized default 5QI/ARP received in the PDU Session related information. If the Authorized default 5QI contains a non-standardized 5QI, the SMF shall also provide the corresponding 5G QoS characteristics parameters (as received in the PDU Session related information Explicitly signalled QoS Characteristics) for the QoS Flow associated with the default QoS rule.

The SMF receives the Authorized Session-AMBR in the PDU Session related information. The SMF ensures that the Authorized Session-AMBR for a PDU Session is enforced for bandwidth policing at the UPF(s) as described in clause 5.7.1 of TS 23.501 [2].

The SMF generates QoS rule(s) as described in TS 23.501 [2]. For a PDU Session of unstructured type, only one PCC Rule allowing all packets is to be activated in the SMF and only the QoS Flow associated with the default QoS rule exists as described in clause 5.7.1 of TS 23.501 [2].

6.2.2.5 Application detection

The SMF shall instruct the UPF to detect the Start and Stop of the application traffic for the PCC rules used for application detection (i.e. with application identifier) that the PCF has activated at the SMF.

If the PCF has subscribed to the event and notification is not muted for the specific PCC Rule, the SMF shall also instruct the UPF to report the Start/Stop of application, as described in the TS 23.501 [2].

When receiving the application detection report from UPF, the SMF shall forward the application identifier, the start/stop indication and, when service data flow descriptions were deduced, the application instance identifier(s) and the service data flow description(s), to the PCF.

NOTE: The PCF can make policy decision when receiving the application detection report.

6.2.2.6 Traffic steering

The SMF shall support traffic steering control as defined in clause 6.1.3.14 and in the case of AF influenced Traffic Steering, also as defined in clause 5.6.7 of TS 23.501 [2].

The SMF may be configured with the traffic steering policy IDs related to the mechanism enabling traffic steering to the N6-LAN, DN and/or DNAIs associated with N6 traffic routing requirements.

Upon receiving a PCC rule which contains the traffic steering control information, the SMF shall provide the information to the UPF for the enforcement.

In the case of AF influenced Traffic Steering, the traffic steering control information in the PCC rule may include a set of DNAI(s) and for each DNAI a traffic steering policy identifier and/or N6 traffic routing information dynamically provided by the AF. Based on the received traffic steering policy identifier(s), the UPF may remove or insert VLAN tags on N6 interface for downlink and uplink frames, respectively. The details of the scenario is defined in clause 5.6.10.2 of TS 23.501 [2].

NOTE: The UPF can, for example, perform marking packets in order to indicate a certain type of traffic to the DN side of the N6 reference point which enables those packets to be steered in the DN. As another example the UPF can forward, i.e. offload, traffic identified by the traffic descriptor to a local tunnel.

6.2.2.7 Access Traffic Steering, Switching and Splitting

The SMF may support functionality for traffic steering, switching and splitting within a MA PDU Session, as described in TS 23.501 [2].

Upon receiving a PCC rule which contains the MA PDU Session Control information, the SMF shall instruct the UPF accordingly and shall also create and provide applicable ATSSS rules to the UE (the details for both SMF actions are described in TS 23.501 [2]).

6.2.3 Application Function (AF)

The Application Function (AF) is an element offering applications that require dynamic policy and/or charging control over the user plane behaviour and/or an element requesting non-session based network capability exposure. In this specification, the functionality of the AF is only defined with respect to the interaction with the 5G Core Network.

An AF may contact the PCF via the NEF for network capability exposure as defined in clause 4.3.6. Based on operator deployment, an AF considered to be trusted by the operator can be allowed to interact directly with the PCF. AFs not allowed by the operator to directly interact with the PCF shall use the network capability exposure framework (see clause 7.3 of TS 23.501 [2]) to interact with the PCF via the NEF.

An AF may communicate with multiple PCFs. The mechanism for an AF to select the PCF associated to a PDU Session based on the UE address is described in clause 6.1.1.2.

The AF shall communicate with the PCF to transfer dynamic session information, required for PCF decisions as well as to receive access network specific information and notifications about events related to the PDU Session or the QoS Flow transferring the application traffic. One example of an AF is the P‑CSCF of the IM CN subsystem.

The AF may receive an indication that the service information is not accepted by the PCF together with service information that the PCF would accept. In that case, the AF rejects the service establishment towards the UE. If possible, the AF forwards the service information to the UE that the PCF would accept.

For certain events related to policy control, the AF shall be able to give instructions to the PCF to act on its own, i.e. based on the service information currently available as described in clause 6.1.3.6.

NOTE 1: The QoS authorization based on incomplete service information is required for e.g. IMS session setup scenarios with available resources on originating side and a need for resource reservation on terminating side.

The AF may request the PCF to report events related to the PDU Session or the QoS Flow transferring the application traffic as defined in clause 6.1.3.18. The AF may use the access network specific information and notifications about events in the AF session signalling or to adjust the event reporting related to the PDU Session or the QoS Flow transferring the application traffic.

The AF may contact the PCF to request a time window and related conditions for future BDT. Details of the AF behaviour to support future BDT are defined in clause 6.1.2.4.

To support sponsored data connectivity the AF may provide the PCF with the sponsored data connectivity information, including optionally a usage threshold, as specified in clause 6.2.1.1. The AF may request the PCF to report events related to sponsored data connectivity.

NOTE 2: Annex D describes the scenario for sponsored data connectivity.

The AF may receive a request to terminate an AF session. The PCF may include an indication that the transmission resources are lost due to PS to CS handover.

NOTE 3: The AF action upon reception of the indication that the transmission resources are lost due to PS to CS handover is application specific. The IMS uses the indication to prevent a termination of an ongoing session as specified in TS 24.229 [29] and TS 24.237 [30].

The AF may send guidance to PCF for the determination of proper URSP rules for the UE. Details of the AF guidance are described in clause 6.6 of TS 23.548 [33] and in clause 4.15.6.10 of TS 23.502 [3].

For Time Sensitive Communication and Time synchronization as specified in clause 5.27 of TS 23.501 [2] and in clause 6.1.3.23a, the AF interacts with the TSCTSF (directly or via NEF) and the TSCTSF is interacting with the PCF. Based on operator deployment, an AF considered to be trusted by the operator can be allowed to interact directly with the TSCTSF. AFs not allowed by the operator to directly interact with the TSCTSF shall use the network capability exposure framework (see clause 7.3 of TS 23.501 [2]) to interact with the TSCTSF via the NEF.

6.2.4 Unified Data Repository (UDR)

The Unified Data Repository (UDR) is defined in TS 23.501 [2].

6.2.5 Charging Function (CHF)

The Charging Function is specified in TS 32.240 [8].

6.2.6 Void

6.2.7 Network Exposure Function (NEF)

The Network Exposure Function (NEF) is defined in TS 23.501 [2] and additionally supports the following policy related functionalities:

– Service specific policy and charging control;

– Management of packet flow descriptions;

– Sponsor data connectivity including usage monitoring (as defined in clause 6.2.1.1);

– Negotiations for future BDT.

6.2.8 Access and Mobility Management Function (AMF)

The Access and Mobility Management Function (AMF) is defined in TS 23.501 [2] and additionally supports the following policy related functionalities:

– Enforcement of access and mobility related policies received from the PCF;

– Transfers of UE policy information received from the PCF to the UE via N1 interface;

– Reporting of events to the PCF that the PCF has subscribed to.

6.2.9 Network Data Analytics Function (NWDAF)

The Network Data Analytics Function (NWDAF) is defined in TS 23.288 [24].

6.2.10 Void

6.2.11 Time Sensitive Communication and Time Synchronization Function (TSCTSF)

The Time Sensitive Communication and Time Synchronization Function (TSCTSF) is defined in TS 23.501 [2].