Trace Failure Indication is the NGAP trace message sent by the NG-RAN node to the AMF when a requested trace session cannot be started, continued, or handled.
Message Fact Sheet
Protocol
ngap
Network
5g
Spec
3GPP TS 38.413
Spec Section
Trace procedures and Trace Failure Indication message
NG-RAN cannot start, continue, or handle a trace session requested by AMF.
Main purpose
Reports that a trace session failed, identifies the affected UE context, identifies the trace session, provides the failure reason through Cause, and supports trace troubleshooting and network operations.
Main specification
3GPP TS 38.413, Trace procedures and Trace Failure Indication message
Release added
Release 15
Procedures where used
Trace Failure Indication, UE trace activation troubleshooting, Network trace operations, Radio and signalling diagnostics, Management trace
What is Trace Failure Indication in simple terms?
Trace Failure Indication is the NGAP trace message sent by the NG-RAN node to the AMF when a requested trace session cannot be started, continued, or handled.
Reports that a trace session failed, identifies the affected UE context, identifies the trace session, provides the failure reason through Cause, and supports trace troubleshooting and network operations.
Why this message matters
Trace Failure Indication is the gNB telling the AMF that a UE trace could not be started or continued. Trace ID tells which trace failed, and Cause tells why.
Where this message appears in the call flow
Trace Failure Indication
Trace Failure Indication reports that NG-RAN could not start or continue the requested trace.
Call flow position: NG-RAN sends this UE-associated initiatingMessage to report trace activation or trace handling failure.
Typical state: AMF learns that the requested trace session is not active or cannot continue as expected.
Preconditions:
A trace session was requested or expected.
AMF UE NGAP ID and RAN UE NGAP ID identify the affected UE context.
Trace ID identifies the affected trace session.
Cause explains the failure reason.
Next likely message: Operator correction, retry, ignore, or Deactivate Trace depending on policy
Trace ID correlation
Trace ID identifies the failed trace session; Cause explains the failure.
Call flow position: Trace ID links the failure to the trace request or trace session.
Typical state: Trace analysis uses Trace ID and UE identifiers to avoid mixing failures across UE contexts or trace attempts.
Preconditions:
The original Trace Start or trace activation context is visible or known.
Trace ID is decoded correctly.
Next likely message: Correct trace lifecycle interpretation
Missing trace output analysis
Trace Failure Indication is not a clean stop or trace output; it is the failure branch of trace handling.
Call flow position: Trace Failure Indication can explain why expected trace output or Cell Traffic Trace does not appear.
Typical state: AMF/operator treats missing collected data as a trace failure rather than a silent success.
Preconditions:
No expected trace reports are present after Trace Start.
Cause and trace ID are checked before assuming collection path failure.
Next likely message: Trace configuration or collection path troubleshooting
Call flow position
Previous message(s):Trace Start, NG-RAN attempts to activate or continue trace collection
Next message(s): AMF or operator treats trace as failed, Trace configuration may be corrected, retried, ignored, or deactivated based on policy
Transport / encapsulation: NGAP over SCTP/IP between NG-RAN and AMF
Security context: Trace Failure Indication reports trace handling problems for a UE-specific trace session. It should be correlated with the original trace authorization, Trace Start, and operator trace policy.
Message Structure Overview
Trace Failure Indication is an NG-RAN-to-AMF UE-associated initiatingMessage.
AMF UE NGAP ID and RAN UE NGAP ID bind the failure report to the correct UE context.
Trace ID identifies which trace session failed.
Cause is the primary troubleshooting field.
The message can explain why expected trace output such as Cell Traffic Trace is missing.
ASN.1 for 5G NGAP - Trace Failure Indication
TraceFailureIndication ::= SEQUENCE {
protocolIEs ProtocolIE-Container { {TraceFailureIndication-IEs} },
...
}
TraceFailureIndication-IEs NGAP-PROTOCOL-IES ::= {
{ ID id-AMF-UE-NGAP-ID CRITICALITY reject TYPE AMF-UE-NGAP-ID PRESENCE mandatory } |
{ ID id-RAN-UE-NGAP-ID CRITICALITY reject TYPE RAN-UE-NGAP-ID PRESENCE mandatory } |
{ ID id-TraceID CRITICALITY ignore TYPE TraceID PRESENCE mandatory } |
{ ID id-Cause CRITICALITY ignore TYPE Cause PRESENCE mandatory },
...
}
How to read this ASN.1
Decode the UE identity pair, then Trace ID, then Cause. Trace ID ties the failure to the trace session, while Cause explains the practical failure reason.
Treat this as a teaching example based on the expected message structure, not as a captured network trace.
Trace ID must be matched to the original trace request or trace context.
Cause is the first field to inspect when trace data is missing.
Important Information Elements
IE
Required
Description
Message Type
Yes
Identifies the NGAP PDU as TRACE FAILURE INDICATION.
AMF UE NGAP ID
Yes
Mandatory UE identity at the AMF.
RAN UE NGAP ID
Yes
Mandatory UE identity at the NG-RAN node.
Trace ID
Yes
Mandatory trace session identifier used to correlate the failure with the original Trace Start or trace context.
Cause
Yes
Mandatory reason why trace activation or trace handling failed.
Detailed field explanation
Message Type
Identifies the NGAP PDU as TRACE FAILURE INDICATION.
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.
AMF UE NGAP ID
Mandatory UE identity at the AMF.
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.
RAN UE NGAP ID
Mandatory UE identity at the NG-RAN node.
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.
Trace ID
Mandatory trace session identifier used to correlate the failure with the original Trace Start or trace context.
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 why trace activation or trace handling 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.
What to check in logs and traces
Confirm Trace Failure Indication follows a matching Trace Start or active trace context.
Match AMF UE NGAP ID and RAN UE NGAP ID to the target UE.
Match Trace ID to the original trace request.
Decode Cause before making assumptions about the failure.
Check whether the trace collection entity and transport path were reachable.
Check whether the UE context was still valid when trace was requested.
Confirm no expected Cell Traffic Trace appears after the failure.
Common Issues and Troubleshooting
Trace Failure Indication appears after Trace Start.
Likely cause: NG-RAN could not activate the requested trace configuration.
What to inspect: Decode Cause and compare Trace ID with the original Trace Start.
Next step: Correct unsupported or malformed trace configuration before retrying.
Trace failure is linked to the wrong trace session.
Likely cause: Trace ID correlation may be wrong or multiple trace attempts may overlap.
What to inspect: Compare Trace ID, UE identifiers, and Trace Activation details across attempts.
Next step: Rebuild the trace lifecycle by Trace ID and UE identity pair.
Cause indicates collection or destination problems.
Likely cause: Trace collection entity address may be invalid, unreachable, or not configured.
What to inspect: Check Trace Activation destination and management-plane reachability.
Next step: Fix the collection endpoint or routing before restarting trace.
Failure occurs after UE release or mobility.
Likely cause: UE context may no longer be valid at NG-RAN for the trace request.
What to inspect: Check UE Context Release, handover, resume, or re-establishment messages around the trace attempt.
Next step: Retry trace against the current UE context if policy allows.
No Cell Traffic Trace appears after Trace Start.
Likely cause: Trace activation may have failed and been reported by Trace Failure Indication.
What to inspect: Search for Trace Failure Indication before investigating reporting output.
Next step: Resolve the Cause IE before expecting trace output.
LTE / 5G / Variant Comparison
Compared with Trace Start
Trace Start requests trace activation. Trace Failure Indication reports that activation or handling failed.
Compared with Deactivate Trace
Deactivate Trace intentionally stops an active trace. Trace Failure Indication reports that trace handling failed.
Compared with Cell Traffic Trace
Cell Traffic Trace is trace output or reporting related. Trace Failure Indication explains why expected trace output may be missing.
FAQ
What is Trace Failure Indication in NGAP?
Trace Failure Indication is the NG-RAN-to-AMF message used to report that a requested trace session could not be started, continued, or handled.
Who sends Trace Failure Indication?
The NG-RAN node sends Trace Failure Indication to the AMF.
What message usually triggers Trace Failure Indication?
It usually follows a Trace Start when NG-RAN cannot activate or continue the requested trace.
What does the Trace ID identify?
Trace ID identifies the affected trace session and should be correlated with the original Trace Start or trace context.
What does the Cause IE mean?
Cause explains why the trace session could not be started or continued.
Does Trace Failure Indication stop an active trace?
It reports trace failure. Deactivate Trace is the intentional message used to stop an active trace session.
How is this different from Deactivate Trace?
Deactivate Trace is AMF-initiated cleanup of an active trace. Trace Failure Indication is NG-RAN reporting that trace handling failed.
How do you troubleshoot Trace Failure Indication?
Match UE IDs and Trace ID to the Trace Start, decode Cause first, check trace configuration, collection entity reachability, UE context validity, and whether expected Cell Traffic Trace output is absent.
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.
