AMF has evaluated a UE Context Suspend Request from NG-RAN and accepted suspension of the UE-associated context.
Main purpose
Accepts the NG-RAN suspend request, confirms the successful suspend branch, avoids full UE context release, supports later resume handling, and separates successful suspend from UE Context Suspend Failure.
What is UE Context Suspend Response in simple terms?
UE Context Suspend Response is the NGAP successfulOutcome message sent by the AMF to the NG-RAN node when AMF accepts a UE Context Suspend Request.
Accepts the NG-RAN suspend request, confirms the successful suspend branch, avoids full UE context release, supports later resume handling, and separates successful suspend from UE Context Suspend Failure.
Why this message matters
UE Context Suspend Response means AMF accepted the gNB's request to suspend the UE context. It is a success response, not a release complete message.
Where this message appears in the call flow
UE Context Suspend successful outcome
Successful branch: AMF accepts NG-RAN's suspend request and confirms the context is handled as suspended.
Call flow position: AMF sends this successfulOutcome after accepting NG-RAN's UE Context Suspend Request.
Typical state: The UE context is treated as suspended and can be correlated with a later resume branch.
Preconditions:
NG-RAN sent UE Context Suspend Request.
AMF UE NGAP ID and RAN UE NGAP ID identify the same UE-associated context.
AMF determined the context can be suspended.
Next likely message: Later UE Context Resume Request
Suspend/resume continuity
Outcome comparison: Suspend Response means accepted; Suspend Failure means AMF rejected the suspend request.
Call flow position: The response establishes the successful suspend state that later resume procedures depend on.
Typical state: The context is preserved rather than fully released.
Preconditions:
Suspend Response is present for the same UE IDs as the request.
No UE Context Suspend Failure exists for the same suspend attempt.
Next likely message: UE Context Resume Request followed by Resume Response or Resume Failure
Release comparison branch
Continuity branch: a successful suspend response enables later resume handling for the same UE context.
Call flow position: This response confirms suspension, not cleanup. It must not be interpreted as UE Context Release Complete.
Typical state: The UE-associated context remains in suspend handling instead of being fully torn down.
Preconditions:
Trace analysis distinguishes suspend procedure from release procedure.
Next likely message: Resume handling or later release handling depending on network state
Transport / encapsulation: NGAP over SCTP/IP between AMF and NG-RAN
Security context: The message confirms AMF accepted suspend handling for an existing UE-associated NGAP context. It does not release the context and does not create a new security baseline.
Message Structure Overview
UE Context Suspend Response is the AMF-to-NG-RAN successfulOutcome for the UE Context Suspend procedure.
It follows UE Context Suspend Request when AMF accepts suspend handling.
AMF UE NGAP ID and RAN UE NGAP ID are mandatory and provide request/response correlation.
Criticality Diagnostics is optional.
The message confirms suspend acceptance, not full UE context release.
A later UE Context Resume procedure can bring the suspended context back.
ASN.1 for 5G NGAP - UE Context Suspend Response
UEContextSuspendResponse ::= SEQUENCE {
protocolIEs ProtocolIE-Container { {UEContextSuspendResponse-IEs} },
...
}
UEContextSuspendResponse-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-CriticalityDiagnostics CRITICALITY ignore TYPE CriticalityDiagnostics PRESENCE optional },
...
}
How to read this ASN.1
Decode both UE identifiers first and match them to the earlier UE Context Suspend Request. A normal success response is intentionally small; do not expect a Cause IE in the successful outcome.
5G NGAP - UE Context Suspend Response - Example Dump
Treat this as a teaching example based on the expected message structure, not as a captured network trace.
This is the accepted suspend branch. There is no Cause IE in the successful response.
Use the UE identity pair to correlate this response with the original UE Context Suspend Request.
A later Resume Request should be correlated with this accepted suspended context.
Important Information Elements
IE
Required
Description
Message Type
Yes
Identifies the NGAP PDU as UE CONTEXT SUSPEND RESPONSE.
AMF UE NGAP ID
Yes
Mandatory AMF-side UE identifier used to correlate the response with the earlier suspend request.
RAN UE NGAP ID
Yes
Mandatory NG-RAN-side UE identifier used to bind the accepted suspend result to the radio-side UE context.
Criticality Diagnostics
Optional
Optional protocol diagnostics related to IE handling or criticality behavior. It is not the main operational payload in a normal success response.
Detailed field explanation
Message Type
Identifies the NGAP PDU as UE CONTEXT SUSPEND 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.
AMF UE NGAP ID
Mandatory AMF-side UE identifier used to correlate the response with the earlier suspend 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.
RAN UE NGAP ID
Mandatory NG-RAN-side UE identifier used to bind the accepted suspend result to the radio-side UE 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.
Criticality Diagnostics
Optional protocol diagnostics related to IE handling or criticality behavior. It is not the main operational payload in a normal success 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 UE Context Suspend Request.
Confirm direction is AMF to NG-RAN node.
Match AMF UE NGAP ID and RAN UE NGAP ID with the original suspend request.
Confirm no UE Context Suspend Failure exists for the same attempt.
Check Criticality Diagnostics if present.
Do not expect a Cause IE in the successful response.
Correlate later UE Context Resume messages with the same suspended context.
Common Issues and Troubleshooting
Suspend Response is interpreted as full release completion.
Likely cause: The success outcome is being confused with UE Context Release Complete.
What to inspect: Check the procedureCode, message name, and whether UE Context Release Command/Complete occurred separately.
Next step: Treat this as context preservation for later resume unless release signaling follows.
Analyzer expects a Cause IE in the response.
Likely cause: Suspend Response is being decoded like Suspend Failure.
What to inspect: Compare the message PDU type and outcome branch: successfulOutcome versus unsuccessfulOutcome.
Next step: Use UE ID correlation for success; look for Suspend Failure only when rejection reason is needed.
Resume later fails even though Suspend Response exists.
Likely cause: The later resume attempt may not match the same suspended context or the context may have expired or been released afterward.
What to inspect: Correlate UE IDs and any later release, failure, or context retention events between suspend response and resume request.
Next step: Build the suspend-to-resume timeline before blaming the suspend response.
PDU sessions are assumed to be released after suspend.
Likely cause: Suspend is being treated as release cleanup.
What to inspect: Look for PDU session release signaling and UE Context Release messages; absence of those means suspend alone is not proof of session teardown.
Next step: Analyze PDU session impact through later resume or release procedures.
Wrong UE is linked to the successful suspend response.
Likely cause: UE ID mapping may be mixed during concurrent suspend, release, or resume events.
What to inspect: Match both AMF UE NGAP ID and RAN UE NGAP ID across Suspend Request, Suspend Response, and later Resume Request.
Next step: Resolve identity correlation before interpreting the context state.
LTE / 5G / Variant Comparison
Compared with UE Context Suspend Request
Suspend Request is NG-RAN asking for suspension. Suspend Response is AMF accepting that request.
Compared with UE Context Suspend Failure
Suspend Response is the successful branch. Suspend Failure is the rejected branch and carries failure context.
Compared with UE Context Release Complete
Suspend Response confirms preserved context handling. Release Complete confirms full cleanup.
FAQ
What is UE Context Suspend Response in NGAP?
It is the AMF-to-NG-RAN successfulOutcome sent when AMF accepts a UE Context Suspend Request.
Who sends UE Context Suspend Response?
The AMF sends UE Context Suspend Response to the NG-RAN node.
What message triggers UE Context Suspend Response?
UE Context Suspend Request from NG-RAN triggers the response when AMF accepts the suspend request.
What is the difference between Suspend Response and Suspend Failure?
Suspend Response means AMF accepted the suspend request. Suspend Failure means AMF rejected it.
Does Suspend Response release the UE context?
No. It confirms suspend handling, which preserves context continuity rather than completing release cleanup.
Can the UE context be resumed after Suspend Response?
Yes. A later UE Context Resume Request can resume the suspended context when the resume procedure is triggered.
Does this message contain a Cause IE?
No. Cause belongs to the request or failure branch. The successful response is mainly correlated by AMF UE NGAP ID and RAN UE NGAP ID.
How do you troubleshoot UE Context Suspend Response?
Match both UE NGAP IDs with the Suspend Request, confirm the direction is AMF to NG-RAN, verify no Suspend Failure exists for the same attempt, and correlate later resume messages.
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.
