PDU Session Establishment

The following figure illustrates the call flow of PDU session establishment.

StepDescription
1.Call Setup
2.

SMF performs a Policy Create exchange with PCF. In this exchange, the SMF might receive Charging Data that is associated to a PCC Rule. This indicates that charging is enabled for the session in progress.

It is possible that PCF has enabled Static/Predefined rules. These rules can be also enabled with charging, based on the configuration.

3.

Once charging is detected at SMF, it initiates a Charging Data Request Initial exchange with CHF. In this exchange SMF may receive the following from CHF:

  • CC triggers at session or RG level

  • Session level Time or Volume limits

  • Time or Volume limits at RG level

  • Quota at RG level

4.N1N2 Exchange and SM Context Update Exchange
5.SMF initiates N4 session establishment request exchange with UPF, and in the same request it relays information that is related to charging in the Create URRs.