Figure 4.2: Overview of the GPRS Logical Architecture
the SGSN, to record a user's access to PLMN resources, mobility management activities, SMS and LCS usage;
the GGSN, to record a user's access to external networks.
The GSNs send the CDRs to the CGF in near real-time. The responsibility of the CGF is to provide non-volatile CDR storage and the Bp interface towards the Billing Domain. Further details on the CGF can be found in TS 32.240  and TS 32.297 .
Next Modified Section
220.127.116.11Flow Based Bearer Charging
PDP context charging allows the GGSN to collect charging information related to data volumes sent to and received by the UE/MS, categorised by the QoS applied to the PDP context. FBC is supported by the GGSN by the integrated PCEF. When the PCEF is present, the normal PDP context charging is enhanced by the capability to categorise the PDP context data traffic by specific service data flows. I.e., while there is only one uplink an one downlink data volume count per PDP context in PDP context charging, FBC may provide several service data flow counts per defined service data flow. The default service data flow is the wildcard, i.e. all traffic for all IP addresses, all TCP ports, etc.; when no other, specific service data flows are configured, the behaviour of FBC is identical to the normal PDP context charging on the GGSN. When further service data flows are specified, traffic is categorised, and counted, according to the service data flow specification, and the wildcard service data flow applies to all traffic that does not match any of the specific service data flows. Details of this functionality are specified in TS 23.203  and TS 32.240 .
According to TS23.203 , FBC shall support different charging models per service data flow. These charging models may be based on volume and/or time and on number of events matching a specific service data flow template. In general the charging of a service data flow shall be linked to the PDP Context under which the service data flow has been activated. In this scenario the PCEF shall request the reservation of units (number of events) prior to service delivery.
The following chargeable events are defined for FBC:
Start of PDP context. Upon encountering this event, a CCR initial, indicating the start of the PDP context, is sent towards the OCS, and the data volume and/or elapsed time is captured per PDP Context.
Start of service data flow. A CCR update is generated for the PDP context, indicating the start of a new service data flow, and new counts for this service data flow are started. The type of counters shall depend on the charging model configured for the service data flow. When event based charging applies, the first occurrence of an event matching a service data flow template shall be considered as the start of a service.
Termination of service data flow. The service data flow counters are closed, and a CCR update is generated towards the OCS, indicating the end of the service data flow and the final counts for this service data flow. For information on how the termination of service data flows is detected, refer to TS 23.203 . Additionally when event based charging applies, service termination shall also occur when the event service units granted by the OCS are exhausted.
End of PDP context. Upon encountering this event, a CCR termination, indicating the end of the PDP context, is sent towards the OCS together with the final counts for the PDP context and all service data flows.
Expiry of an operator configured time limit per PDP context. This event triggers the emission of a CCR update, indicating the elapsed time and the accrued data volume for the PDP context since the last report.
Expiry of an operator configured time limit per service data flow. The service data flow counters are closed and a CCR update is sent to the OCS, indicating the accrued counts since the last report for that service data flow. A new service data flow container is opened if the service data flow is still active.