Final Unit Indication Support for N40 Interface

The SMF supports N40 Final Unit Indication (FUI) in the Charging Data Initial or Update Response from CHF as per 3GPP TS 32.291, section 6.1.6.2.1.12.

On receiving FUA, the SMF installs a new FAR and associates its FAR-ID in the URR, in the FAR ID Quota Action IE. If a FAR with the same parameters exists, the SMF uses its FAR-ID in the Create or Update URR. The UPF initiates appropriate actions set in FAR after quota exhaustion.

SMF supports FUI in CCA-I or CCA-U message from OCS. On receiving FUA, SMF installs a new FAR and associates its FAR-ID in the URR. If an FAR with the same parameters exists, SMF uses its FAR-ID in create or update URR. UPF initiates appropriate action as set in FAR after the quota exhaustion.

By default, the terminate configuration isn’t activated to terminate the session and SMF only reports the final Used Service Unit to OCS without requesting further quota. UPF drops the further traffic after the quota exhaustion until OCS allocates the new quota through reauthorization.

Note

Reauthorization is supported for Gy.

FUI at MSCC Level—If FUI is received at the MSCC level and FUI CLI is configured to terminate the session, then SMF terminates the session if either the quota is exhausted or no quota is available.

FUI at Command Level—If FUI is received at the command level, then SMF terminates the session after quota is exhausted irrespective of FUI CLI configuration or no quota is available and FUI is received.

Currently, the SMF only supports Terminate and Redirect FU actions in the case of N40.

FUI in the Charging Data Initial or Update Response from CHF
  • At any instance, CHF/OCS provides granted unit (Quota) to the SMF along with FUI.

  • When the SMF receives the granted unit with FUI, the SMF creates FAR toward N4 and associates it to the corresponding URR which carries the quota information.

  • After UPF receives the FAR associated with the URR, the corresponding FAR action is implemented when the quota exhausts.