Update Bearer Procedure Failure Handling

This section covers the PGW-initiated update bearer procedure failure scenarios.

The following table summarizes cnSGW-C behavior during different stages in call processing for various failure types:

cnSGW-C Behavior for Update Bearer Procedure Failure Scenarios

Scenarios

S5/Sx Signaling

Output

Update Bearer Request advance validation failure

Negative - Update Bearer Response

No change in Bearer/PDN context.

Update Bearer Request with non-existing EBIs

Update Bearer Response with message level cause as REQ_PARTIALLY_ACCEPTED. Bearer level cause for non-existing EBIs as Context Not Found. (Normal handling for existing EBIs)

Update Bearer Response with message level cause as REQ_PARTIALLY_ACCEPTED.

Bearer level cause for non-existing EBIs as CONTEXT_NOT_FOUND.

Normal handling for existing EBIs.

CDL is updated for existing EBIs only.

Update Bearer Request is sent to MME and waiting for the response

Negative - Update Bearer Response

Negative - Update Bearer Response

CDL is not updated.

S11 Update Bearer Response (Message level Cause == CONTEXT_NOT_FOUND) and S5 Update Bearer Req/Rsp had default bearer in the bearer context list

Sx Delete Req/Rsp

Negative - Update Bearer Response

Negative - Update Bearer Response

CDL is not updated.

Statistics/Transactional Logs

PDN Key Release + PDN deallocation

If this is the last PDN, then resource manager is released, all subscriber keys are released and subscriber deallocation is done.

S11 Update Bearer Response (Message level Cause == CONTEXT_NOT_FOUND) and S5 Update Bearer Req/Rsp didn't have default bearer in the bearer context list

Sx Modify Req/Rsp

Negative - Update Bearer Response

CDL is not updated.

S11 Update Bearer Response (Message level Cause == REQ_PARTIALLY_ACCEPTED, Bearer Context Cause == Any failure for dedicated bearer)

Sx Modify Req/Rsp

Update Bearer Response with message level cause as REQ_PARTIALLY_ACCEPTED

Update Bearer Response with message level cause as REQ_PARTIALLY_ACCEPTED

CDL is updated for successful bearers.

S11 Update Bearer Response (Message level Cause == REQ_PARTIALLY_ACCEPTED, Bearer Context Cause == CONTEXT_NOT_FOUND for default bearer)

Sx Delete Req/Rsp

Negative - Update Bearer Response

Negative - Update Bearer Response

CDL is not updated.

PDN Key Release and PDN deallocation

If this is the last PDN, then resource manager is released, all subscriber keys are released and subscriber deallocation is done.

If Sx modify is triggered after Update Bearer Response:

  • Sx Session Modify Request (IPC/Retransmission Timeout/Internal Failure and so on)

  • Sx Session Modify Response (Cause != ACCEPTED except CONTEXT_NOT_FOUND)

Ignore failure and continue

Ignore failure and continue

If Sx Modify is triggered after Update Bearer Response:

  • Sx Session Modify Response (Cause == CONTEXT_NOT_FOUND)

If Sx Delete is triggered after Update Bearer Response:

  • Sx Session Delete Request (IPC/Retransmission Timeout/Internal Failure and so on)

  • Sx Session Delete Response (Cause != ACCEPTED)

  • Resource manager release (Internal Error)

Ignore failure and continue

Ignore failure and continue

1 As part of Update Bearer Procedure handling, SGW-service triggers new transaction for PDN deletion:
  • Sx Failure Cause received as part of Sx Session Modification Response

    • Context Not Found

SGW Behavior (New Transaction):

  • SGW triggers S11 Delete Bearer Request and S5 Delete Session Request to delete that PDN

  • No Sx Signaling

SGW Behavior (Update Bearer Transaction): SGW sends S5 Update Bearer Response with Cause as No Resource Available, as part of Update Bearer Procedure Transaction. Also, SGW doesn’t initiate any signaling towards UP as soon as it receives Sx Session Modification Response with cause as Context Not Found.

2 As part of Update Bearer Procedure handling, SGW-SVC additionally triggers new transaction for PDN deletion:
  • Sx Failure Cause received as part of Sx Session Modification Response

    • Context Not Found

SGW Behavior (New Transaction):

  • SGW triggers S11 Delete Bearer Request and S5 Delete Session Request to delete that PDN

  • No Sx Signaling

SGW Behavior (Update Bearer Transaction): SGW sends S5 Update Bearer Response with Cause as No Resource Available, as part of Update Bearer Procedure Transaction. Also, SGW doesn’t initiate any signaling towards UP as soon as it receives Sx Session Modification Response with cause as Context Not Found.