Write Replace Warning Response is the NGAP warning message sent by the NG-RAN node to the AMF to report the result of a Write Replace Warning Request for public warning broadcast delivery.
Message Fact Sheet
Protocol
ngap
Network
5g
Spec
3GPP TS 38.413
Spec Section
Clause 9.2.8.2 and Warning Message Transmission Messages
NG-RAN has processed a Write Replace Warning Request and reports the warning handling result to AMF.
Main purpose
Confirms the result of a warning broadcast request, reports accepted broadcast handling, may identify cells or areas where broadcast failed, helps AMF track public warning delivery status, and completes the Write Replace Warning request/response pair.
Main specification
3GPP TS 38.413, Clause 9.2.8.2 and Warning Message Transmission Messages
What is Write Replace Warning Response in simple terms?
Write Replace Warning Response is the NGAP warning message sent by the NG-RAN node to the AMF to report the result of a Write Replace Warning Request for public warning broadcast delivery.
Confirms the result of a warning broadcast request, reports accepted broadcast handling, may identify cells or areas where broadcast failed, helps AMF track public warning delivery status, and completes the Write Replace Warning request/response pair.
Why this message matters
Write Replace Warning Response is the gNB's answer to AMF's warning broadcast request. Match Message Identifier and Serial Number, then check completed areas and failed cells.
Where this message appears in the call flow
Write Replace Warning
NG-RAN responds to the AMF request and reports warning handling status.
Call flow position: NG-RAN sends this response after processing an AMF Write Replace Warning Request.
Typical state: AMF learns whether warning handling was accepted and inspects any completed-area or failed-cell information.
Preconditions:
A matching Write Replace Warning Request was sent by AMF.
Message Identifier and Serial Number match the original warning instance.
NG-RAN processed warning area, repetition, and content parameters.
Next likely message: AMF warning broadcast status tracking
Warning broadcast result reporting
Completed area and failed cell information must be decoded separately.
Call flow position: The response can report completed broadcast area and cells where warning broadcast failed.
Typical state: AMF differentiates successful, partial, and failed broadcast handling.
Preconditions:
Broadcast Completed Area List is decoded if present.
Failed Cell List is decoded if present.
Next likely message: Monitoring for PWS Failure Indication if later failures occur
Warning message distinction
The response is immediate request handling; PWS indications report later failure or restart state.
Call flow position: The response is different from PWS Failure Indication and PWS Restart Indication.
Typical state: Trace analysis treats this as the immediate response to a specific request, not later failure or restart reporting.
Preconditions:
Procedure name, trigger, and warning identifiers are checked.
Next likely message: Correct warning-procedure interpretation
Transport / encapsulation: NGAP over SCTP/IP between NG-RAN and AMF
Security context: The message reports warning broadcast handling status and may include completed-area, failed-cell, diagnostics, or RAN node context for public warning delivery.
Message Structure Overview
Write Replace Warning Response is an NG-RAN-to-AMF response message for public warning broadcast handling.
Message Identifier and Serial Number correlate the response to the warning instance from the request.
Broadcast Completed Area List can report where broadcast completed.
Failed Cell List can report cells where broadcast failed.
Criticality Diagnostics and Global RAN Node ID provide troubleshooting context when present.
ASN.1 for 5G NGAP - Write Replace Warning Response
WriteReplaceWarningResponse ::= SEQUENCE {
protocolIEs ProtocolIE-Container { {WriteReplaceWarningResponse-IEs} },
...
}
WriteReplaceWarningResponse-IEs NGAP-PROTOCOL-IES ::= {
{ ID id-MessageIdentifier CRITICALITY reject TYPE MessageIdentifier PRESENCE mandatory } |
{ ID id-SerialNumber CRITICALITY reject TYPE SerialNumber PRESENCE mandatory } |
{ ID id-BroadcastCompletedAreaList CRITICALITY ignore TYPE BroadcastCompletedAreaList PRESENCE optional } |
{ ID id-CriticalityDiagnostics CRITICALITY ignore TYPE CriticalityDiagnostics PRESENCE optional } |
{ ID id-WarningAreaList CRITICALITY ignore TYPE WarningAreaList PRESENCE optional } |
{ ID id-FailedCellList CRITICALITY ignore TYPE FailedCellList PRESENCE optional } |
{ ID id-GlobalRANNodeID CRITICALITY ignore TYPE GlobalRANNodeID PRESENCE optional },
...
}
How to read this ASN.1
Decode Message Identifier and Serial Number first, then inspect completed-area, failed-cell, diagnostics, and RAN node context. A response does not automatically mean every targeted cell succeeded.
5G NGAP - Write Replace Warning Response - Example Dump
Treat this as a teaching example based on the expected message structure, not as a captured network trace.
Message Identifier and Serial Number must match the Write Replace Warning Request.
Failed Cell List should be decoded separately from Broadcast Completed Area List.
Check later PWS Failure Indication for failures after the immediate response.
Important Information Elements
IE
Required
Description
Message Type
Yes
Identifies the NGAP PDU as WRITE-REPLACE WARNING RESPONSE.
Message Identifier
Yes
Mandatory warning message type or category identifier used to correlate with the request.
Serial Number
Yes
Mandatory warning instance identifier used to correlate with the request.
Broadcast Completed Area List
Optional
Optional area where warning broadcast has been completed.
Criticality Diagnostics
Optional
Optional protocol diagnostics for IE handling or criticality issues.
Warning Area List
Optional
Optional warning area associated with the response.
Failed Cell List
Optional
Optional cells where warning broadcast could not be completed successfully.
Global RAN Node ID
Optional
Optional RAN node identity context for the response.
Detailed field explanation
Message Type
Identifies the NGAP PDU as WRITE-REPLACE WARNING RESPONSE.
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.
Message Identifier
Mandatory warning message type or category identifier used to correlate with the 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.
Serial Number
Mandatory warning instance identifier used to correlate with the 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.
Broadcast Completed Area List
Optional area where warning broadcast has been completed.
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.
Criticality Diagnostics
Optional protocol diagnostics for IE handling or criticality issues.
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.
Warning Area List
Optional warning area associated with the response.
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.
Failed Cell List
Optional cells where warning broadcast could not be completed successfully.
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.
Global RAN Node ID
Optional RAN node identity context for the response.
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 the response follows a matching Write Replace Warning Request.
Match Message Identifier and Serial Number to the request.
Decode Failed Cell List if present.
Check Broadcast Completed Area List if present.
Review Criticality Diagnostics if present.
Check Global RAN Node ID in multi-node traces if present.
Look for later PWS Failure Indication if broadcast problems continue.
Common Issues and Troubleshooting
Response is correlated to the wrong warning.
Likely cause: Message Identifier or Serial Number may not match the original Write Replace Warning Request.
What to inspect: Compare both fields across request and response.
Next step: Rebuild warning-instance correlation before judging broadcast handling.
Response is treated as full success in every cell.
Likely cause: Failed Cell List or completed-area details may be ignored.
What to inspect: Decode Failed Cell List and Broadcast Completed Area List separately.
Next step: Treat the response as request handling status, not proof that every intended cell succeeded.
Cells did not broadcast even though a response exists.
Likely cause: The response may include failed cells, or a later PWS Failure Indication may report post-response failure.
What to inspect: Check Failed Cell List and search for later PWS Failure Indication.
Next step: Troubleshoot failed cells using RAN node and cell-level warning logs.
Response is confused with PWS Failure Indication.
Likely cause: Both can carry failure-related warning context but have different triggers.
What to inspect: Check whether the message directly follows Write Replace Warning Request or appears later as NG-RAN failure reporting.
Next step: Use Response for immediate request result and PWS Failure Indication for later failure conditions.
Multi-node trace is hard to interpret.
Likely cause: Global RAN Node ID may be missing or ignored, or warning responses from multiple nodes may be mixed.
What to inspect: Check Global RAN Node ID and NGAP association context.
Next step: Group responses by RAN node and warning identifiers.
LTE / 5G / Variant Comparison
Compared with Write Replace Warning Request
Request asks NG-RAN to start or replace warning broadcast. Response reports the handling result.
Compared with PWS Failure Indication
Write Replace Warning Response is the immediate response to a request. PWS Failure Indication reports later warning broadcast failure conditions.
Compared with PWS Restart Indication
Write Replace Warning Response reports processing of a specific request. PWS Restart Indication reports warning-related restart information from NG-RAN.
FAQ
What is Write Replace Warning Response in NGAP?
It is the NG-RAN-to-AMF response message used to report the result of a Write Replace Warning Request.
Who sends Write Replace Warning Response?
The NG-RAN node sends Write Replace Warning Response to the AMF.
What message triggers this response?
It is triggered by a preceding Write Replace Warning Request from the AMF.
What do Message Identifier and Serial Number mean?
Message Identifier identifies the warning type or category. Serial Number identifies the warning instance and is used for request/response correlation.
What is Failed Cell List?
Failed Cell List identifies cells where the warning broadcast could not be completed successfully.
Does the response mean the warning was broadcast everywhere?
No. Engineers should check Broadcast Completed Area List and Failed Cell List, and later PWS Failure Indication if broadcast issues continue.
How is this different from PWS Failure Indication?
Write Replace Warning Response is the immediate response to a request. PWS Failure Indication reports later warning broadcast failure conditions.
How do you troubleshoot Write Replace Warning Response?
Match Message Identifier and Serial Number to the request, decode Failed Cell List and completed area fields, inspect diagnostics, and check later PWS Failure Indication when needed.
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.
