Charging Server Reconciliation

The SMF falls back to the first available offline CHF server when the NF selected by NF discovery is unreachable. The CHF Reconciliation feature involves deleting the existing subscribers that are associated to a set of offline NFs, and the subscribers that are in offline fallback mode.

Note

The CHF reconciliation is applicable only when CHF endpoint is selected by NRF through NF discovery service.

The CHF server reconciliation works when one of the following two conditions is met:

  1. If the NRF detects that an offline CHF server is active.

  2. If the RAR is received from the CHF server on an offline converted session.

For the second condition, the session gets deleted directly. With the NF discovery, this feature involves the following steps:

  1. SMF subscribes for the notification of NF instance IDs from NRF through NF_LIB component of Rest-EP.

  2. If the NF discovery query determines that all the NFs are down, the NF_LIB component treats these set of NFs as offline. If any one of the NFs is available again, the NRF triggers notification for the same to the SMF.

  3. The SMF performs NF discovery after revalidation timer. If the NRF detects any new NF, the SMF receives the corresponding notification from the NRF.

  4. When the SMF identifies that an NF is online with all the required NF discovery query parameters, then the SMF initiates the CHF server reconciliation.

The following labels are introduced as part of this feature:

  • disc_pdurel_chf_reconciliation: This label is defined under SMF_DISCONNECT_STATS to show the reason of disconnection.

  • chf_reconl_pdu_sess_rel: This label is defined under smf_service_stats metric to show the number of times the PDU session release procedure is initiated.