Failure Handling for SEPP and hSMF/vSMF

The SMF supports failure handling (FH) for hSMF or vSMF and SEPP. The client SMF detects the originator of the failure response based on the 3GPP header message received in the HTTP response. The originator can be either peer SMF or SEPP.

Depending on the NF instance value in the header message, it selects either the SEPP FH profile or the N16 FH profile.

The N16 FH profile works similar to the existing N32 SEPP FH profile. But the N16 FH profile uses an AdditionalHsmfUri attribute instead of the Endpoint (EP) configuration available for other NFs.

Important

AdditionalHsmfUri attribute is used only in the create session procedure.

When there is an error response from SMF, it includes the server header in the following format:

SMF-nf-instance-id

Example: 
SMF-54804518-4191-46b3-955c-ac631f953ed8
 SEPP-35644518-9291-46b3-934c-ac5678f953ed

If the header has the SEPP NF instance value, the client SMF that receives the failure applies the SEPP failure handling configuration.

Note

If the header has two SEPP server names, it deems the failure response as originated from the peer SMF.

Following is the sequence of failure handling steps taken during the PDU session creation procedure:

  1. The vSMF selects the first SEPP based on the locally configured SEPP EPs and appends the “3gg-target-api-root” header with the hSMF URI.

  2. If the first SEPP EP fails, vSMF selects the SEPP FHT and retries the procedure with another EP.

  3. In the absence of SEPP FHT or exhaustion of retry count, the SMF terminates the session.

  4. When the peer SMF fails, vSMF uses N16 FHT and selects the next EP from the AdditionalHsmfUri EPs.

  5. If all the URIs defined in the AdditionalHsmfUri IE fail or the retry count exhaust, the vSMF terminates the procedure..

SEPP and SMF Failure Actions

During the PDU session lifecycle, the SMF checks for the hSMF and SEPP with the NF instance value. Depending on the HTTP status code configured in the FH profile, the SMF takes one of the following actions.

Supported Actions in SEPP and SMF FHT

N16 Procedure

SEPP FHT Actions

SMF FHT Actions

Create

terminate

retry-and-terminate

terminate

retry-and-terminate

Release

terminate

retry-and-terminate

terminate

HsmfPduSessionNotify

terminate

retry-and-terminate

terminate

Note

The SMF overwrites any other configured FH action with the default terminate action.