PDU Session Establishment

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

PDU Session Establishment Call Flow
PDU Session Establishment Call Flow Description
Step Description
1. Call creation starts at SMF.
2.

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

PCF may enable Static or Predefined rules. These rules can be also enabled with charging, based on the configuration.

3.

After the charging is detected at SMF, SMF initiates a Charging Data Request Initial exchange with CHF. In this exchange SMF may receive the following information 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. SMF sends the N1N2 Exchange and SM Context Update Exchange to AMF.
5. SMF initiates N4 session establishment request exchange with UPF. In the same request, SMF relays the information related to charging in the Create URRs.