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NAS5GUE to SMF via AMF / SMF to UE via AMF3GPP TS 24.501
5G NAS - 5GSM Status
5GSM Status is the 5GSM message used by both the UE and the network to report protocol errors or invalid session-management conditions for an active PDU session.
Message Fact Sheet
Protocol
nas
Network
5g
Spec
3GPP TS 24.501
Spec Section
8.3.16
Direction
UE to SMF via AMF / SMF to UE via AMF
Message Type
5GSM error reporting
Full message name
5G NAS - 5GSM Status
Protocol
NAS
Technology
5G
Direction
UE to SMF via AMF / SMF to UE via AMF
Interface
N1
Signaling bearer / channel
NAS signaling / Usually carried inside UL NAS Transport or DL NAS Transport depending on sender
Typical trigger
A 5GSM protocol data error, invalid PTI, unsupported message type, or other session-management inconsistency is detected.
Main purpose
Reports 5GSM error conditions so the receiving side can abort the right procedure, stop the right timer, or take local recovery action.
Main specification
3GPP TS 24.501, 8.3.16
Release added
Release 15
Procedures where used
5GSM status procedure, Procedure error reporting, Protocol conformance troubleshooting, Timer and transaction correlation analysis
Related cause values
#81 invalid PTI value, #97 message type non-existent or not implemented
What is 5GSM Status in simple terms?
5GSM Status is the 5GSM message used by both the UE and the network to report protocol errors or invalid session-management conditions for an active PDU session.
Reports 5GSM error conditions so the receiving side can abort the right procedure, stop the right timer, or take local recovery action.
Why this message matters
5GSM Status is the message used to report a 5G session-management protocol error so the other side can stop the bad procedure.
Where this message appears in the call flow
5GSM status procedure
Call flow position: Asynchronous error-report step that can occur whenever a 5GSM protocol data error is detected.
Typical state: The sender has detected an invalid or unsupported 5GSM condition and wants the peer to stop the related procedure.
Preconditions:
A 5GSM procedure is active or has just been received.
The sender detects a PTI, message-type, or protocol inconsistency.
Next likely message: The peer aborts the affected procedure and stops any related timer
5G PDU Session Modification
Call flow position: Error report used when a modification message cannot be processed cleanly.
Typical state: The sender is warning that the current modification branch cannot continue as received.
Preconditions:
A modification-related message was received.
The sender detected an invalid transaction or unsupported content.
Next likely message: The related modification procedure aborts or the session state is corrected locally
Next message(s): Procedure abort, Timer stop or retry handling, Local state correction
Message direction and transport
Sender and receiver: UE to SMF via AMF / SMF to UE via AMF
Interface: N1
Domain: Core-side session-management error reporting with access-side NAS delivery dependency
Signaling bearer: NAS signaling
Logical channel: Usually carried inside UL NAS Transport or DL NAS Transport depending on sender
Transport / encapsulation: 5GSM NAS message transported end-to-end between UE and SMF through AMF mediation
Security context: Normally used while NAS security is active, so engineers usually expect protected NAS handling.
ASN.1 Message Syntax for 5G NAS - 5GSM Status
This message is not typically analyzed as ASN.1 on the wire. It is usually read as a NAS or protocol field structure instead.
This is a 5GSM NAS message defined by structured information elements in 3GPP TS 24.501 rather than ASN.1 syntax.
5G NAS - 5GSM Status - Example Dump
5GSM Status
Extended Protocol Discriminator: 5G Session Management
PDU Session ID: 10
PTI: 6
Message Type: 5GSM Status
5GSM Cause: Invalid PTI value
How to read this dump
Start with PDU Session ID so you know which session the error report belongs to.
Check PTI because 5GSM Status is usually about a transaction mismatch or protocol problem.
Read the Message type field carefully, because it identifies the exact message that triggered the status report.
The cause value tells you whether the issue is a bad PTI, an unsupported message, or another procedure-specific protocol error.
Important Information Elements
IE
Required
Description
PDU Session ID
Yes
Identifies the active PDU session associated with the error condition.
PTI
Yes
Correlates the status message with the procedure transaction that triggered the error.
Message type
Yes
Identifies the 5GSM message that caused the error report.
5GSM cause
Yes
Explains the error condition being reported to the peer.
Detailed field explanation
PDU Session ID
Identifies the active PDU session associated with the error condition.
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.
PTI
Correlates the status message with the procedure transaction that triggered the error.
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 type
Identifies the 5GSM message that caused the error report.
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.
5GSM cause
Explains the error condition being reported to the peer.
Presence: Required
In practice: When this appears in an accept, it often means the network normalized a requested value rather than failing the session outright. Check it together with the selected session type, not in isolation.
What to check in logs and traces
Confirm which side sent the 5GSM Status message, since it can be sent by either the UE or the SMF.
Verify `PDU Session ID` and `PTI` first so you know which procedure the status report is tied to.
Inspect the `Message type` field and correlate it with the message that was actually received.
Check the `5GSM cause` and map it to the exact error handling branch in the UE or SMF.
Stop or start the related timer according to the procedure that was interrupted.
Correlate the status message with the triggering NAS message and any local stack logs.
Common Issues and Troubleshooting
The UE or network suddenly aborts a session-management procedure.
Likely cause: A 5GSM Status message with cause #81 or #97 was generated because the received message had a bad PTI or unsupported type.
What to inspect: Check the triggering 5GSM message, PTI, and message type in the NAS trace.
Next step: Fix the transaction or message-type mismatch and retry the affected procedure.
The wrong timer keeps running after an error.
Likely cause: The receiving side did not stop the timer associated with the failed procedure.
What to inspect: Check the 5GSM status cause and the exact procedure that was active.
Next step: Verify timer ownership and abort handling for the specific procedure branch.
The message is decoded, but the cause does not seem to explain the behavior.
Likely cause: The visible cause may be only the reported symptom while the real local action is implementation dependent.
What to inspect: Check the sender's local logs and the received message context.
Next step: Correlate the status report with the surrounding NAS sequence before drawing a conclusion.
FAQ
What does 5GSM Status do?
It reports a 5GSM protocol error so the peer can stop the affected procedure and correct its state.
Who sends 5GSM Status?
Both the UE and the SMF can send it.
When is 5GSM Status sent?
It is sent whenever a 5GSM error condition is detected while processing a session-management message.
What are the important IEs in 5GSM Status?
Start with PDU Session ID, PTI, Message type, and the 5GSM cause.
What do causes #81 and #97 mean?
Cause #81 means invalid PTI value, and cause #97 means message type non-existent or not implemented.
What happens after 5GSM Status?
The related procedure should abort or be locally corrected, and the relevant timer should stop on the receiving side.
Is ASN.1 used for 5GSM Status?
No. It is a 5GSM NAS message defined by structured information elements in 3GPP TS 24.501.
Can 5GSM Status be sent in both directions?
Yes. It can be sent by the UE or the network depending on where the error is detected.
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.