| Protocol | e1ap | Network | 5g |
|---|---|---|---|
| Spec | 3GPP TS 37.483 | Spec Section | Bearer Context Modification failure outcome and related IE definitions (Release 18 baseline) |
| Direction | gNB-CU-UP -> gNB-CU-CP unsuccessfulOutcome | Message Type | UE-associated bearer-context modification rejection |
| Full message name | 5G E1AP - Bearer Context Modification Failure |
|---|---|
| Protocol | E1AP |
| Technology | 5G |
| Direction | gNB-CU-UP -> gNB-CU-CP unsuccessfulOutcome |
| Interface | E1 between gNB-CU-CP and gNB-CU-UP |
| Signaling bearer / channel | UE-associated E1AP signaling / SCTP carried E1AP unsuccessfulOutcome |
| Typical trigger | The CU-UP cannot apply the requested bearer-context modification because the delta is unacceptable, resources are not available, or the current bearer state cannot support the change as requested. |
| Main purpose | Reports that the CU-UP could not apply the requested bearer-context delta and tells the CU-CP why the modification path failed. |
| Main specification | 3GPP TS 37.483, Bearer Context Modification failure outcome and related IE definitions (Release 18 baseline) |
| Release added | Release 17 |
| Procedures where used | Bearer Context Modification, User-plane update failure handling |
Bearer Context Modification Failure is the E1AP unsuccessful outcome the gNB-CU-UP returns when it cannot accept the requested bearer-context changes for an existing UE.
Reports that the CU-UP could not apply the requested bearer-context delta and tells the CU-CP why the modification path failed.
Bearer Context Modification Failure is the CU-UP telling the CU-CP that the requested bearer change could not be applied.
Call flow position: The CU-UP cannot keep the modification procedure on the success path and returns the failure outcome.
Typical state: The requested bearer delta was not accepted in its current form.
Preconditions:
Next likely message: Retry with a corrected delta, alternate handling, or release
Call flow position: The failure reflects that the requested bearer-state delta cannot be applied as requested.
Typical state: The existing bearer context remains subject to the previously valid state until the CU-CP takes a new action.
Preconditions:
Next likely message: Another modification request or teardown decision
Previous message(s): Bearer Context Modification Request
Next message(s): Reworked Bearer Context Modification Request, Bearer Context Release Command
Security context: Bearer Context Modification Failure does not change security context. It reports that the CU-UP could not accept the requested bearer delta.
BearerContextModificationFailure ::= SEQUENCE {
protocolIEs ProtocolIE-Container { {BearerContextModificationFailure-IEs} },
...
}
BearerContextModificationFailure-IEs E1AP-PROTOCOL-IES ::= {
{ gNB-CU-CP UE E1AP ID, mandatory } |
{ gNB-CU-UP UE E1AP ID, mandatory } |
{ Cause, mandatory } |
{ Criticality Diagnostics, optional },
...
}
Modification failure is compact on purpose. Cause is the most important field operationally.
E1AP-PDU
unsuccessfulOutcome
procedureCode: id-bearerContextModification
criticality: reject
value: BearerContextModificationFailure
protocolIEs:
- id: id-gNB-CU-CP-UE-E1AP-ID
value: 0x00004192
- id: id-gNB-CU-UP-UE-E1AP-ID
value: 0x00000087
- id: id-Cause
value:
protocol: semantic-error
| IE | Required | Description |
|---|---|---|
gNB-CU-CP UE E1AP ID | Yes | Mandatory CU-CP side UE identifier used to correlate the failure with the original modification request. |
gNB-CU-UP UE E1AP ID | Yes | Mandatory CU-UP side UE identifier for the bearer context whose modification failed. |
Cause | Yes | Mandatory reason explaining why the CU-UP rejected the requested bearer delta. |
Criticality Diagnostics | Optional | Optional protocol diagnostics that may help the CU-CP understand the rejected modification path. |
gNB-CU-CP UE E1AP IDMandatory CU-CP side UE identifier used to correlate the failure with the original modification request.
Presence: Required
In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.
gNB-CU-UP UE E1AP IDMandatory CU-UP side UE identifier for the bearer context whose modification failed.
Presence: Required
In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.
CauseMandatory reason explaining why the CU-UP rejected the requested bearer delta.
Presence: Required
In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.
Criticality DiagnosticsOptional protocol diagnostics that may help the CU-CP understand the rejected modification path.
Presence: Optional
In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.
Likely cause: The CU-UP rejected the requested bearer delta.
What to inspect: Read Bearer Context Modification Failure and compare Cause with the original modification request.
Next step: Correct the requested delta or choose another control-plane action before retrying.
Response means the CU-UP accepted the requested delta. Failure means the CU-UP rejected it and reports why.
It is the E1AP unsuccessful outcome the CU-UP sends when it cannot accept the requested bearer-context modification.
The most important fields are the two UE identifiers and Cause.
Decode this message with the 3GPP Decoder, inspect the related message database, or open the matching call flow to see where this signaling step fits in the full procedure.