Failure Handling

cnSGW-C supports failure handling for creating or deleting IDFT request procedure.

Following are the failure types that can occur during message processing:

  • Advance validation failure on request and response

  • Retransmissions timeout

  • Transaction SLA

  • Failure reported from peer (UP/PGW/MME), depending on the stage of message processing.

The following table depicts the behavior of cnSGW-C during different failure scenarios in call processing.

Failure Scenario

SGW-SVC behavior

Signaling (S11)

  1. Create IDFT Request advance validation failure.

  2. cnSGW doesn’t have a bearer context for any of the EBIs received in Create IDFT.

Sends failure or No signaling over Sx.

Negative Create IDFT response.

Single PDN
  1. Sx Session Modify Request (for example, IPC, Retransmission, Internal Failure) with single PDN

  2. Sx Session Modify Response (Cause!= ACCEPTED) with single PDN

  3. Sx Modification Response validation failure

Sends failure.

Sends Context not found of nonexisting EBI.

Clear the PDN if sxCause = Context Not Found.

Negative Create IDFT response.

DBR and DSR over S11 and S5 when sxCause = Context Not Found.

Multi PDN (Partial Failure)
  1. Partial Existing PDN: Continue with existing PDN

  2. Sx Session Modify Request (for example, IPC, Retransmission Timeout, Internal Failure) for some PDNs

  3. Sx Session Modify Response (Cause!= ACCEPTED) for some PDN

  4. Sx Modification Response validation failure

Send Context Not Found for nonexisting PDNs.

Send failure in Bearer Context for PDNs for which Sx Modification Request fails.

Partially Accepted Create IDFT Response.

DBR and DSR over S11 and S5 for the PDN for which sxCause = Context Not Found.

Multi PDN (Complete Failure):
  1. Partial Existing PDN: Continue with existing PDN.

  2. Sx Session Modify Request (for example, IPC, Retransmission Timeout, Internal Failure)

  3. Sx Session Modify Response (Cause!= ACCEPTED)

  4. Sx Modification Response validation failure

Send Context Not Found for nonexisting PDNs.

Send failure in Bearer Context for PDNs which has Sx Modification Request fails.

Negative Create IDFT Response.

DBR and DSR over S11 and S5 for the PDN for which sxCause = Context Not Found.

Delete IDFT Request Advance validation failure.

Send failure or No signaling over Sx.

Negative Delete IDFT response.

  1. Single and Multi-PDN

  2. Sx Session Modify Request (for example, IPC, Retransmission Timeout, Internal Failure)

  3. Sx Session Modify Response (Cause!= ACCEPTED)

Ignore Failure.

Positive Delete IDFT Response.

DBR and DSR over S11 and S5 for the PDN for which sxCause = Context Not Found.