UE Context Resume Response is the NGAP successfulOutcome message sent by the AMF to the NG-RAN node when AMF accepts resumption of a previously suspended UE-associated NGAP context.
AMF has received UE Context Resume Request, found a valid suspended context, and accepted restoration of that context.
Main purpose
Confirms successful UE context resume, tells NG-RAN that the suspended context can be reused, supports fast service continuation, avoids a full new UE context setup path, and pairs with UE Context Resume Request.
What is UE Context Resume Response in simple terms?
UE Context Resume Response is the NGAP successfulOutcome message sent by the AMF to the NG-RAN node when AMF accepts resumption of a previously suspended UE-associated NGAP context.
Confirms successful UE context resume, tells NG-RAN that the suspended context can be reused, supports fast service continuation, avoids a full new UE context setup path, and pairs with UE Context Resume Request.
Why this message matters
UE Context Resume Response means AMF accepted the resume request and the previously suspended UE context can be used again.
Where this message appears in the call flow
UE Context Resume successful outcome
Successful branch: AMF accepts the retained context and confirms resume.
Call flow position: AMF sends this successfulOutcome after accepting NG-RAN's UE Context Resume Request.
Typical state: The suspended UE context is restored to active handling.
Preconditions:
UE Context Resume Request was received.
The UE context was previously suspended successfully.
AMF UE NGAP ID and RAN UE NGAP ID identify the suspended context.
Next likely message: Normal NGAP procedures using the restored context
PDU session continuity after resume
Session branch: inspect the optional resume list by PDU Session ID when validating service continuity.
Call flow position: The response may include PDU Session Resource Resume List to identify session resources resumed with the context.
Typical state: PDU sessions continue according to resumed state rather than being recreated from scratch.
Preconditions:
PDU session resources existed in the retained context.
AMF and NG-RAN agree on session state after resume.
Next likely message: PDU session service continuation
Resume versus setup distinction
Session branch: inspect the optional resume list by PDU Session ID when validating service continuity.
Call flow position: The response confirms a retained context restoration path, not an Initial UE Message or new context setup path.
Typical state: Trace analysis should keep resume separate from fresh setup and fallback branches.
Preconditions:
Prior successful suspend branch exists.
No UE Context Resume Failure exists for the same attempt.
Next likely message: Active context continuation or later recovery procedures
Transport / encapsulation: NGAP over SCTP/IP between AMF and NG-RAN
Security context: The message confirms AMF validated and accepted restoration of a suspended UE-associated NGAP context. It does not create a brand-new context path by itself.
Message Structure Overview
UE Context Resume Response is the AMF-to-NG-RAN successfulOutcome for the UE Context Resume procedure.
It follows UE Context Resume Request when AMF accepts the suspended context restoration.
AMF UE NGAP ID and RAN UE NGAP ID correlate the response with the retained UE context.
PDU Session Resource Resume List is optional and identifies resumed session resources when present.
Criticality Diagnostics is optional.
The message confirms resume success, not initial context setup.
ASN.1 for 5G NGAP - UE Context Resume Response
UEContextResumeResponse ::= SEQUENCE {
protocolIEs ProtocolIE-Container { {UEContextResumeResponse-IEs} },
...
}
UEContextResumeResponse-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-PDUSessionResourceResumeList CRITICALITY ignore TYPE PDUSessionResourceResumeList PRESENCE optional } |
{ 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 UE Context Resume Request and prior successful suspend branch. If PDU Session Resource Resume List is present, correlate each session with later service behavior.
5G NGAP - UE Context Resume Response - Example Dump
Treat this as a teaching example based on the expected message structure, not as a captured network trace.
This is the successful resume branch. Resume Failure is the alternative outcome.
PDU Session Resource Resume List is optional; when present, inspect it by PDU Session ID.
Do not treat this response as initial context setup. It restores retained suspended state.
Important Information Elements
IE
Required
Description
Message Type
Yes
Identifies the NGAP PDU as UE CONTEXT RESUME RESPONSE.
AMF UE NGAP ID
Yes
Mandatory AMF-side UE identifier used to correlate the response with the suspended context and earlier resume request.
RAN UE NGAP ID
Yes
Mandatory NG-RAN-side UE identifier used to bind the restored context to the radio-side UE context.
PDU Session Resource Resume List
Optional
Optional list of PDU session resources resumed as part of the UE context resume procedure.
Criticality Diagnostics
Optional
Optional protocol diagnostics related to IE handling or criticality behavior.
Detailed field explanation
Message Type
Identifies the NGAP PDU as UE CONTEXT RESUME 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 suspended context and earlier resume 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 restored context 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.
PDU Session Resource Resume List
Optional list of PDU session resources resumed as part of the UE context resume procedure.
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 related to IE handling or criticality behavior.
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 Resume Request.
Confirm direction is AMF to NG-RAN node.
Match AMF UE NGAP ID and RAN UE NGAP ID with the suspended context.
Confirm the context was previously suspended successfully.
Decode PDU Session Resource Resume List if present.
Confirm no UE Context Resume Failure exists for the same attempt.
Verify PDU sessions continue after resume.
Common Issues and Troubleshooting
Resume Response appears without a valid prior suspend.
Likely cause: The trace may be incomplete, or the response is being correlated with the wrong UE context.
What to inspect: Search backward for UE Context Suspend Request and Suspend Response with matching AMF UE NGAP ID and RAN UE NGAP ID.
Next step: Fix the suspend-to-resume timeline before interpreting the response.
PDU sessions are assumed to have all resumed.
Likely cause: The optional PDU Session Resource Resume List may not have been decoded or may not include every expected session.
What to inspect: Decode the resume list and correlate PDU Session IDs with later PDU session and user-plane behavior.
Next step: Troubleshoot continuity by PDU Session ID rather than top-level response alone.
Resume Response is confused with Initial UE setup.
Likely cause: The retained-context path is being analyzed like a new context creation path.
What to inspect: Compare the resume response with Initial UE Message or setup signaling and verify retained UE IDs.
Next step: Keep resume and setup branches separate, especially after fallback.
Service fails shortly after successful resume.
Likely cause: Context restoration succeeded, but radio, location, PDU session, or retained state synchronization may still be inconsistent.
What to inspect: Check PDU Session Resource Resume List, later PDU session messages, and any release or failure that follows.
Next step: Treat the response as successful restoration, then analyze later failures as separate continuity issues.
Wrong UE is linked to resumed state.
Likely cause: AMF UE NGAP ID and RAN UE NGAP ID mapping may be stale across suspend, resume, release, or fresh setup branches.
What to inspect: Rebuild both UE ID timelines across Suspend Request, Suspend Response, Resume Request, and Resume Response.
Next step: Resolve identity correlation before deciding whether resume succeeded for the intended UE.
LTE / 5G / Variant Comparison
Compared with UE Context Resume Request
Resume Request asks AMF to restore suspended context. Resume Response confirms AMF accepted the restoration.
Compared with UE Context Resume Failure
Resume Response is the successful branch. Resume Failure rejects the restore attempt and may require fallback.
Compared with Initial UE setup
Resume Response restores retained suspended context. Initial setup creates a new context path.
FAQ
What is UE Context Resume Response in NGAP?
It is the AMF-to-NG-RAN successfulOutcome sent when AMF accepts resumption of a previously suspended UE-associated NGAP context.
Who sends UE Context Resume Response?
The AMF sends UE Context Resume Response to the NG-RAN node.
What message triggers UE Context Resume Response?
UE Context Resume Request from NG-RAN triggers the response when AMF accepts the restore attempt.
What is the difference between Resume Response and Resume Failure?
Resume Response means AMF accepted and restored the suspended context. Resume Failure means AMF rejected the resume attempt.
Does Resume Response create a new UE context?
No. It restores an existing suspended context. New context creation belongs to the setup path.
Can PDU sessions continue after Resume Response?
Yes. The successful resume branch is intended to preserve continuity, and the optional PDU Session Resource Resume List identifies resumed session resources when present.
What should be checked before expecting Resume Response?
Confirm the UE context was previously suspended successfully and that the Resume Request used the correct AMF UE NGAP ID and RAN UE NGAP ID.
How do you troubleshoot UE Context Resume Response?
Match the UE IDs across suspend and resume, verify no Resume Failure exists for the same attempt, decode the optional PDU session resume list, and check later service continuity.
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.
