5G E1AP - Bearer Context Setup Failure

Message Fact Sheet

Protocol	e1ap	Network	5g
Spec	3GPP TS 37.483	Spec Section	Bearer Context Setup failure outcome and related IE definitions (Release 18 baseline)
Direction	gNB-CU-UP -> gNB-CU-CP unsuccessfulOutcome	Message Type	UE-associated bearer-context setup rejection

Full message name	5G E1AP - Bearer Context Setup 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 create the requested bearer context because the bearer payload is unacceptable, resources are unavailable, or the control-plane request cannot be applied as sent.
Main purpose	Reports that the CU-UP could not establish the requested bearer context and tells the CU-CP why the setup path failed.
Main specification	3GPP TS 37.483, Bearer Context Setup failure outcome and related IE definitions (Release 18 baseline)
Release added	Release 17
Procedures where used	Bearer Context Setup, Initial user-plane bring-up failure, PDU session user-plane setup rejection

What is Bearer Context Setup Failure in simple terms?

Bearer Context Setup Failure is the E1AP unsuccessful outcome the gNB-CU-UP returns when it cannot accept the requested bearer-context creation for a UE.

Reports that the CU-UP could not establish the requested bearer context and tells the CU-CP why the setup path failed.

Why this message matters

Bearer Context Setup Failure is the CU-UP telling the CU-CP that bearer creation could not be completed.

Where this message appears in the call flow

Bearer setup rejected at CU-UP

5G E1AP flow showing the gNB-CU-UP returning Bearer Context Setup Failure after rejecting bearer-context creation — Rejection branch: the CU-UP cannot accept bearer creation and returns the failure outcome instead of a setup response.

Call flow position: The CU-UP cannot keep the bearer setup procedure on the success path and returns the failure outcome.

Typical state: The requested bearer context was not created in a usable way at the CU-UP.

Preconditions:

The CU-UP evaluated Bearer Context Setup Request.
A failure cause can be assigned to the rejected setup branch.

Next likely message: Later retry, alternate control-plane action, or bearer cleanup

Resource or payload mismatch

5G E1AP flow showing Bearer Context Setup Failure being used to troubleshoot the rejected bearer-setup path — Troubleshooting branch: the failure outcome is read through Cause first, then correlated with the original setup payload.

Call flow position: The failure reflects that the requested bearer payload could not be accepted at the CU-UP.

Typical state: The CU-CP must treat the request as failed and inspect the cause and diagnostics before retrying.

Preconditions:

The setup payload was not acceptable in its current form or could not be supported by available CU-UP state.

Next likely message: Reworked Bearer Context Setup Request or another control-plane fallback

Call flow position

Previous message(s): Bearer Context Setup Request

Next message(s): Re-attempted Bearer Context Setup Request, Bearer Context Release Command

Message direction and transport

Sender and receiver: gNB-CU-UP -> gNB-CU-CP unsuccessfulOutcome

Interface: E1 between gNB-CU-CP and gNB-CU-UP

Domain: CU-CP / CU-UP bearer setup failure reporting

Signaling bearer: UE-associated E1AP signaling

Logical channel: SCTP carried E1AP unsuccessfulOutcome

Transport / encapsulation: E1AP over SCTP/IP between gNB-CU-CP and gNB-CU-UP

Security context: Bearer Context Setup Failure does not alter security context. It reports that the requested CU-UP bearer branch could not be created.

Message Structure Overview

Bearer Context Setup Failure is the unsuccessful outcome of the bearer setup procedure.
The mandatory operational core is the CU-CP UE identifier plus Cause.
In troubleshooting, Cause is the first field to read because it explains why the CU-UP rejected the request.

ASN.1 for 5G E1AP - Bearer Context Setup Failure

BearerContextSetupFailure ::= SEQUENCE {
  protocolIEs ProtocolIE-Container { {BearerContextSetupFailure-IEs} },
  ...
}

BearerContextSetupFailure-IEs E1AP-PROTOCOL-IES ::= {
  { gNB-CU-CP UE E1AP ID, mandatory } |
  { Cause, mandatory } |
  { Criticality Diagnostics, optional },
  ...
}

How to read this ASN.1

Failure is intentionally compact. The real engineering value is the reason it returns, not structural depth.

5G E1AP - Bearer Context Setup Failure - Example Dump

E1AP-PDU
  unsuccessfulOutcome
    procedureCode: id-bearerContextSetup
    criticality: reject
    value: BearerContextSetupFailure
      protocolIEs:
        - id: id-gNB-CU-CP-UE-E1AP-ID
          value: 0x00004192
        - id: id-Cause
          value:
            radioNetwork: resources-not-available
        - id: id-CriticalityDiagnostics
          value:
            procedure-code: id-bearerContextSetup

How to read this dump

Read Cause first because it tells you why the CU-UP rejected bearer setup.
Match the failure to the original setup request using the CU-CP UE identifier.
If diagnostics are present, use them to narrow the rejected branch further.

Important Information Elements

IE	Required	Description
`gNB-CU-CP UE E1AP ID`	Yes	Mandatory CU-CP side UE identifier used to correlate the failure with the original setup request.
`Cause`	Yes	Mandatory reason explaining why the CU-UP rejected bearer-context creation.
`Criticality Diagnostics`	Optional	Optional protocol diagnostics that can help the CU-CP understand how the CU-UP handled the rejected request.

Detailed field explanation

`gNB-CU-CP UE E1AP ID`

Mandatory CU-CP side UE identifier used to correlate the failure with the original setup 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.

`Cause`

Mandatory reason explaining why the CU-UP rejected bearer-context creation.

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 Diagnostics`

Optional protocol diagnostics that can help the CU-CP understand how the CU-UP handled the rejected request.

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.

What to check in logs and traces

Confirm this is Bearer Context Setup Failure and not a later modification failure.
Correlate the failure with the original setup request and its requested bearer payload.
Inspect Cause before attempting any retry logic.

Common Issues and Troubleshooting

The control plane requests bearer creation but the CU-UP never enters the success path.

Likely cause: The CU-UP rejected the bearer setup request because the payload or resources were not acceptable.

What to inspect: Read Bearer Context Setup Failure and compare Cause with the original setup request.

Next step: Correct the request or take an alternate control-plane path before retrying.

LTE / 5G / Variant Comparison

Compared with Bearer Context Setup Response

Response means the CU-UP accepted bearer creation. Failure means the CU-UP rejected it and reports why.

FAQ

What is Bearer Context Setup Failure in 5G E1AP?

It is the E1AP unsuccessful outcome the CU-UP sends when it cannot accept the requested bearer-context setup.

What is mandatory in Bearer Context Setup Failure?

The key mandatory fields are the CU-CP UE E1AP ID and Cause.

Related message pages

Related Procedures

Related Tools

Use This Reference in Practice

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.