PCC rules can be activated, deactivated, and modified at any time during the PDU session lifetime.

The following attributes can be modified by the PCF in a dynamic PCC rule active in the SMF:

• Charging Key

• Service Identifier

• Measurement Method

Activities on PCC rules and QoS flows are not chargeable events. However, change of charging rule in PCC rules lead to chargeable events such as:

• Start of service data flow

• Termination of service data flow, for the last service data flow for the original PCC rule

The charging key (that is, rating group) is used to request online charging quota.

The charging identifier corelates charging information between the SMF and CHF during the duration of a PDU session. The SMF generates and assigns a charging identifier when a PDU session is established. The charging identifier is unique for that PDU session and is used in all messages that are exchanged in that PDU session.

The SMF collects the following charging information for converged online and offline charging:

• Usage of access and core network resources: Describes the amount of data that is delivered to and forwarded from the UE.

• Usage duration: Time interval from PDU Session Establishment to PDU Session Release.

• User: UE information used by the user for a PDU session.

• Data network: Data network address as determined by the DNN.

• Start time: PDU session start time.

• User location: HPLMN and VPLMN reporting area.

For service-data flows (flow-based charging), the SMF collects the following information:

• PDU session description.

• Data that are transmitted in uplink and downlink directions based on the rating-group information, or a combination of rating-group and service ID during volume-based charging.

• Duration of service data flow based on the rating group, or a combination of rating-group and service ID during event-based charging.

• Events and timestamps based on rating-group or based on a combination of the rating-group and service ID during event-based charging.

The SMF collects charging information for service data flows per UPF, within a PDU session, based on the rating-group or based on a combination of rating-group and service ID.

The SMF supports converged session-based charging (SCUR) as specified in 3GPP TS 32.290, section 5.3.2.3.

The SMF establishes charging session with the CHF with the Charging Data Request and Response (Initial) exchange. During the life of the PDU session, usage is reported with Charging Data Request/Response (Update) exchange. After the session is released, Charging Data Request/Response (Termination) messages are exchanged.

Charging is enabled for a session based on the input that is received from the PCF.

For offline charging, the SMF sends Charging Data Request Initial toward the Charging Function (CHF) based on the presence of charging descriptors and refChgData field set in the smPolicyDecision message from the PCF in SmPolicyControlCreate response.

On determining if charging is required during initial session establishment or post-session establishment, charging is enabled for the PDU session. Once charging is enabled, SMF sends the Charging Data Request (Initial) Message toward the CHF.

The SMF determines Volume/Time threshold value either locally or from Charging Data Response. These values are used to update Volume/Time threshold IE in URR and to set the reporting trigger accordingly. The measurement method that is used in URR is derived from charging data.

For online charging, the SMF receives the Volume/Time Threshold and Quota values from the CHF. These values are received in the Charging Data Response (Initial) or using a Charging Data Request (Update) during a PDU Session Establishment. The SMF relays these Volume/Time Threshold and quota values to the UPF in the corresponding URR.

Note	The threshold values from CHF always override the locally configured values.

The following table maps the IEs that are shared with the UPF during Create or Update URR during online or offline charging scenarios:

The following table lists the reporting triggers and their derived source:

The CHF selection, that is, CHF address determination by the SMF is performed during PDU Session Establishment. This selection is based on the following in order of priority:

1. PCF provides one or more CHF addresses as part of the PCC rule.

2. UDM-provided charging characteristics.

3. NRF-based discovery.

4. SMF locally provisioned charging characteristics.

Note	The local configuration is currently used to get CHF IP/port.

URR Generation Toward N4

The SMF receives charging-data and usage-monitoring-data from the PCF. Based on this information, the SMF derives URR toward N4. In case the SMF is configured with volume/time limit at the session level, the SMF creates session-level URR.

Configuration of static or predefined rules is similar to the procedures on SMF and UPF. The layout of configuration is as follows:

1. Rulebase: A one-to-many rulebase is configurable. For a single PDU session, you can activate a single rulebase any time. PCF can activate the rulebase at SMF by sending the rulebase name in the PCC rule.

2. Ruledef: Each rulebase can have one-to-many ruledef configurations. A ruledef can either be of static or predefined type. Each ruledef is assigned to a charging action.

3. Charging Action: Contains QoS and charging information.

The SMF derives charging data for each charging action in the rulebase. Charging action associated to static rules in the rulebase is immediately derived and updated in the PDU context. Charging action that is associated to predefined rules is derived and updated when PCF activates the specific predefined rule at SMF.

The charging action derived URR has the following behavior:

• Online charging is identified by the "cca charging credit " configuration under charging action.

• Offline charging is identified by the "billing action egcdr " configuration under charging action.

• Armed triggers for volume-limit and time-limit are under the gtpp group configuration, under APN. The UPF automatically detects these values and sends the respective usage reports.

• The SMF, unlike the dynamic case, does not send the Create URR immediately for charging data that is derived from the configured rules.

• Using the online charging method, the UPF sends usage report with the "Start" trigger. The SMF uses CHF to derive the quota for the RG and relays the same information to the UPF in the Update URR message.

• You can configure the UPF threshold at a rulebase level. It creates a rulebase-level URR that is linked to all ruledef-level URR within the rulebase.

• If you have configured session-level volume or time value locally or have received them from the CHF, the SMF creates session-level URR and links it to all URR corresponding to offline charging descriptors.

• If PCF receives multiple charging descriptors that are of the same rating group, the SMF creates extra URR and links it to all URR derived from charging descriptors of the same rating group.

The following figure illustrates how local configuration works.

Note	The SMF supports up to 16 charging characteristic profiles. Each CC profile comprises of charging group and charging profile. The charging server group and charging profile are linked to the DNN profile. Currently, the charging profile supports configuration for trigger and thresholds.

The SMF relays the offline resource usage report from the UPF to the CHF if any of the following conditions is met:

• Reporting type is immediate.

• Reporting type is deferred and the maximum number of deferred reporting is crossed.

The usage report includes the charging records with zero value as well. These zero value records (UUC and CDR-U) occupy unnecessary disk space on the CHF. To avoid this issue, the SMF leverages new configuration to control the offline charging records with zero byte data count.

When you configure the offline zero-usage CLI command in the Charging Profile configuration mode, the SMF relays the usage to the CHF without any overload of UUC or CDR-U.

The users can select the UUC or CDRs they want to suppress based on the CLI configuration.

Important

The CDR release is never be suppressed even if the offline zero-usage drop cdr command is configured in the Charging Profile configuration mode.

For details on the configuration, see the Configuring Zero Usage Report Suppression section.

This section shows the following call flows:

The SMF Charging feature has the following limitations on the N4 interface:

• If the session-level URR (CDR-i) is created once, it remains throughout the session. This URR is not deleted in the subsequent session (CDR-u).

• If the session-level URR is not created, then it is not created in the subsequent CDR-u even if session limits are available.

The SMF is compliant with the 3GPP June 2019 specification TS 32.290 version 15.3.0.

For the June release, the messages goes over the version "v2" as indicated in the following URI format:

nchf-convergedcharging/v2/chargingdata 

The CLI command for compliance configuration is: service nchf-convergedcharging . If this CLI command or version is not configured, the default version from 3GPP December 2018 is applied.

With the 3GPP June 2019 compliance, the following information elements (IE) are added:

• Authorized QoS

• Subscribed QoS

• IEs in QoSData

• Serving Network Function ID

Use the following configuration to configure a DNN profile for SMF Charging.

config 
   profile dnn profile_name 
      charging-profile profile_name 
      network-element-profiles { amf | chf | pcf | udm } profile_name 
      end 

NOTES:

• charging-profile : Specifies the Charging Profile configuration.

• network-element-profiles : Specifies the network element profile. Network element profile can be one of the following:

  • amf : Specifies the AMF network element profile.

  • chf : Specifies the CHF network element profile.

  • pcf : Specifies the PCF network element profile.

  • udm : Specifies the UDM network element profile.

• profile_name : Specifies the name of selected network element profile. After you select the network profile, enter a string.

Use the following configuration to configure charging characteristics profile for SMF Charging.

config 
   profile charging-characteristics cc_value 
      charging-profile profile_name 
      end 

NOTES:

• cc_value : Specifies the charging characteristics value, which is an integer from 1 to 16.

Use the following configuration to configure the charging profile parameters for SMF charging.

config 
   profile charging profile_name  
      limit [ rating-group ] { duration duration_value | volume volume_value } 
      max-charging-condition max_cc_value  
      max-deferred-urr max_urr_value  
      method { none | offline | online } 

      quota request [ always | standard ] 
      quota suppress triggers [ qht ] 
      reporting-level { offline | online { [rating-group]  
      | rating-group | service-id } 
      requested-service-unit time seconds volume downlink downlink_value  
      uplink uplink_value total total_value 
      tight-interworking-mode { false | true } 
      triggers session session_level_triggers 
      end 

NOTES:

• limit : Specifies the threshold limit.

• duration : Specifies the duration threshold for charging. The threshold value ranges from 0 through 2147483647.

• volume : Specifies the volume threshold for charging. The threshold value ranges from 0 through 9223372036854775807.

• rating-group : Specifies the volume and duration threshold for a Rating Group.

• max-charging-condition max_cc_value : Specifies the maximum number of changes to the charging condition. max_cc_value must be an integer ranging from 0 through 500. The default value is 20.

• max-deferred-urr max_urr_value : Specifies the maximum number of deferred USU containers. max_urr_value must be an integer ranging from 0 through 200. The default value is 50.

• method : Specifies the charging method. The default charging method is offline.

• quota request [ always | standard ] : Controls the requesting of quota from the CHF for online charging services based on the configuration. If the quota request always is configured, the SMF always requests for quota. If the no quota request or quota request standard CLI command is configured, then the SMF requests the quota for specific trigger types as defined in standard, which is the default behaviour.

• quota suppress triggers [ qht ] : Suppresses the quota from the CHF upon configuring the usage report trigger type "qht".

• reporting-level : Specifies the reporting level configuration to be used for offline and online charging.

  The default value is [rating-group] level.

• requested-service-unit: Configures the value for the requested service units.

  • time seconds : Configures the time quota value in seconds from 1 through 4000000000.

  • downlink downlink_value : Configures the downlink volume in bytes from 1 through 4000000000.

  • uplink uplink_value : Configures the uplink volume in bytes from 1 through 4000000000.

  • total total_value : Configures the total volume in bytes from 1 through 4000000000.

• tight-interworking-mode : Configuration to enable tight interworking mode for online or offline charging methods.

• triggers : Specifies the list of triggers to be configured.

• session session_level_triggers : Specifies the list for Session Level Triggers. The list of Session Level Triggers is as follows:

  • repor3gpp-ps-change

  • ambr-change

  • max-number-of-changes-in-charging-conditions

  • plmn-change

  • qos-change

  • rat-change

  • serv-node-change

  • tarrif-time-change

  • ue-pra-change

  • ue-time-change

  • upf-add

  • upf-rem

  • user-loc-change

The following is a sample configuration for SMF Charging:

config 
   charging-server ch1 
      fqdn abc.com 
      capacity 10 (default : 10) 
      priority 1 (default: 1) 
      ip-address 127.0.0.1 
      port 1234 
      ! 
      ! 
   dnn-profile dnn1 
      charging-server-name [ chserv1 ] 
      charging-profile chProf1 
      ! 
   profile charging ch1 
      limit volume tot 2000 
      limit duration 20 
      limit rating-group volume tot 4000 
      limit rating-group duration 40 
      triggers session [ ambr-change qos-change] 
   max-charging-condition 20 
      max-deferred-urr 100 
      reporting-level service-id 
      requested-service-unit time 20 volume downlink 8000 uplink 2000 total 10000 
      ! 
   profile charging-characteristics 1 
   charging-profile ch1 
   ! 

Use the following configuration to enable the zero usage report suppression feature.

config 
   profile charging ChargingProfile_name 
      offline zero-usage [ drop { cdr | uuc } | measurement { duration | volume } | trigger { external | final | internal } ] 
      end 

NOTES:

• offline zero-usage : The SMF suppresses the offline URR with zero volume and duration. By default, the zero usage drop configuration is disabled on SMF.

• drop { cdr | uuc } : The SMF suppresses the CDR or UUC with zero usage. If there are mutiple reports, then the SMF drops only the reports with zero usage. Note that there is no impact on the online reporting.

  If the drop command is not configured, the SMF stops sending UUC for the offline usage report.

• measurement { duration | volume } : The SMF specifies the measurement method of the network usage for suppression. The measurement method is based on volume and duration.

  If the measurement command is not configured, the SMF suppresses the records with both zero volume and zero duration, or the records with zero volume or zero duration depending on the configuration.

• trigger { external | final | internal } : Specifies the list of triggers to be suppressed.

  • external : The SMF suppresses the usage reports that are generated due to external triggers such as QoS Change, RAT change, User Location change, and PLMN Change.

  • final : The SMF suppresses the usage reports that are generated at the end of a context.

  • internal : The SMF suppresses the usage reports that are generated due to internal triggers such as volume limit, time limit, and tariff change.

The SMF provides the different reporting levels for online and offline charging with the following rules:

• Configured rules are derived from the static or predefined charging actions.

• Session-level Usage Reporting Rule (URR) is derived from CHF trigger or local configuration.

• The SMF does not associate session-level URR for online and offline method charging description.

• The SMF does not associate session-level URR to the configured charging-action URRs.

• Rulebase URR is applicable only for the offline configured URR.

• For the configured online or online-offline charging method, if Ignore Service ID configuration exists, the URR list must contain "rg x urr-id y". Else, the SMF drops the charging actions as malformed.

Important

The SMF supports multiple charging methods within the same rating group.

This feature has the following limitations:

• Same rating group is not supported for multiple Charging-action of rulebase and Dynamic Charg-Desc.

• Tight interworking mode is not supported for the service which is at the rating group level.

• One service at the rating group level and another service at service ID level are not supported.

The Different Reporting Level Support for Online and Offline Charging feature complies with the following standards:

• 3GPP TS 32.255

• 3GPP TS 32.290

The following table provides details of the application error codes with the corresponding SMF action.

Note

The error code 403 is not configured in the failure handling template. CHARGING_NOT_APPLICABLE (Disable charging) for static and predefined rules, occurs when a proprietary IE “Charging Disabled” in subscriber params is sent in the N4 modification or establishment request. This request is sent to prevent UPF from generating Start of Traffic for the URRs pending for activation.

The following table provides details of the result code with the corresponding SMF action.

The SMF supports dynamic change in the ACS configuration during the run time. The ACS Profile configuration defines various parameters for the ACS profile.

The following table lists the SMF and UPF behavioral changes during the dynamic update of ACS configuration in different scenarios.

NOTES:

• If the online report includes service id and the ignore-service-id is not configured in credit control profile, the SMF drops the report.

• If the new online URR contains the same RG as an existing URR, then the SMF drops the usage report.

• If the new offline URR contains the same RG+service ID as an existing URR, the SMF drops the usage report.

• In the same usage report, if the next online URRs include the same RG and the next offline URRs include with the same RG + service ID, the SMF drops the usage report.

The Charging Profile supports dynamically updating the configuration based on the values that you pass during the runtime. The refresh operation of the values takes place considering the following scenarios:

• Configuration reflects in the next encounter to access: If the values are updated while an operation is in-progress, the SMF ignores the new values and continues to use the old values. For example, Limits in Charg-Profile and CC triggers.

• Configuration reflects only on a new session: If the configuration is specific to a session and the session has already considered the values, then the SMF does not consider the new values. For example, PduContext (DB entry). This case indicates that any update to the configuration does not impact the sessions that are already created. For instance, Charging Method in Profile or Charg-Profile in Charging Characteristics.

• Configuration reflects instantly: Configurations immediately consider the dynamic values whenever they are updated. If SMF has already used a configuration and it is later updated, then it uses the latest values.

If a session is created using a Charging Profile, which later gets deleted from the Ops Center, the session might attempt to access the configuration structure of the deleted profile. In such cases, the Smf-Service pod maintains a default profile mapped to the sessions whose profiles are missing.

The Charging Profile is responsible for handling the SMF charging parameters.

The following table lists the configuration parameters with the dynamic configuration change and its impact on the existing sessions.