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NASLTEUE to MME3GPP TS 24.301
LTE Authentication Failure
Authentication Failure is the EPS NAS message the UE sends when it cannot accept or complete the LTE/EPS authentication challenge normally.
Message Fact Sheet
Protocol
nas
Network
lte
Spec
3GPP TS 24.301
Spec Section
5.4.2, 8.2.5
Direction
UE to MME
Message Type
EMM signaling
Full message name
LTE Authentication Failure
Protocol
NAS
Technology
LTE
Direction
UE to MME
Interface
N1 over LTE access / S1-MME control path
Signaling bearer / channel
NAS signaling / Commonly carried in uplink NAS transport after Authentication Request when the UE cannot continue with a normal Authentication Response
Typical trigger
Sent after Authentication Request when the UE detects that the challenge cannot be accepted or answered normally.
Main purpose
Lets the UE report that the authentication challenge failed, usually because of MAC failure, synchronization failure, or non-EPS authentication rejection handling.
Main specification
3GPP TS 24.301, 5.4.2, 8.2.5
Release added
Release 8
Procedures where used
EPS NAS Authentication Procedure, LTE Attach Procedure, Tracking Area Updating Procedure, LTE Service Request Procedure
What is LTE Authentication Failure in simple terms?
Authentication Failure is the EPS NAS message the UE sends when it cannot accept or complete the LTE/EPS authentication challenge normally.
Lets the UE report that the authentication challenge failed, usually because of MAC failure, synchronization failure, or non-EPS authentication rejection handling.
Why this message matters
Authentication Failure is the UE telling the network that the LTE/EPS authentication challenge could not be completed normally.
Where this message appears in the call flow
Initial LTE attach authentication failure
In the attach path, Authentication Failure is the UE-side negative outcome when the authentication challenge cannot be completed normally.
Call flow position: UE-side negative outcome sent after Authentication Request in the attach procedure.
Typical state: The attach path entered common NAS authentication, but the UE could not continue with a normal authentication response.
Preconditions:
The UE received Authentication Request during attach.
The UE detected a challenge problem such as MAC failure, synch failure, or another unacceptable authentication condition.
Next likely message: A new Authentication Request, Authentication Reject, or procedure stop
Tracking area update authentication failure
In the TAU path, Authentication Failure shows that the UE could not continue the inserted authentication branch normally.
Call flow position: UE-side negative outcome sent when TAU triggered NAS authentication but the UE could not accept the challenge normally.
Typical state: The UE was trying to preserve EPS context through TAU, but the authentication branch failed on the UE side.
Preconditions:
The UE received Authentication Request during tracking area update.
The UE could not continue with Authentication Response.
Next likely message: Authentication continuation, reject handling, or broader mobility recovery
Service restoration authentication failure
In the service-restoration path, Authentication Failure explains why the branch did not continue directly into later service handling.
Call flow position: UE-side negative outcome sent when service restoration triggered NAS authentication but the UE could not accept the challenge normally.
Typical state: The UE tried to restore service, but the inserted common NAS authentication branch failed on the UE side.
Preconditions:
The UE sent Service Request and received Authentication Request.
The UE detected that the challenge could not be answered normally.
Next likely message: Authentication continuation, Authentication Reject, or service recovery stop
Interface: N1 over LTE access / S1-MME control path
Domain: Core-side EPS mobility management and security signaling used when the UE rejects or cannot complete the authentication challenge
Signaling bearer: NAS signaling
Logical channel: Commonly carried in uplink NAS transport after Authentication Request when the UE cannot continue with a normal Authentication Response
Transport / encapsulation: EPS NAS message sent by the UE and delivered to the MME through the eNodeB as part of the NAS authentication procedure
Security context: Authentication Failure belongs to the UE-side negative authentication branch and appears before later secure continuation is allowed.
Message Structure Overview
Authentication Failure is an EPS mobility-management message rather than an ASN.1 LTE RRC structure.
The practical reading path starts with the EMM cause and whether an authentication failure parameter is present.
In real traces, this message is the UE-side sign that the authentication challenge branch failed before a normal response could continue.
ASN.1 Message Syntax for LTE Authentication Failure
Authentication Failure
EMM cause
Authentication failure parameter OPTIONAL
How to read this message syntax
Authentication Failure is a NAS layer-3 message, not an ASN.1 LTE RRC message. Its meaning depends heavily on the EMM cause and whether the UE included failure parameters for resynchronization.
Reports why the UE could not continue the authentication challenge, such as MAC failure, synch failure, or non-EPS authentication unacceptable.
Authentication failure parameter
Optional
May carry AUTS or related resynchronization information when the UE reports synch failure.
Detailed field explanation
EMM cause
Reports why the UE could not continue the authentication challenge, such as MAC failure, synch failure, or non-EPS authentication unacceptable.
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.
Authentication failure parameter
May carry AUTS or related resynchronization information when the UE reports synch failure.
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 which higher-level NAS procedure triggered Authentication Failure.
Correlate it with the exact Authentication Request that came before it.
Check the EMM cause first.
Inspect whether Authentication failure parameter is present.
Follow the trace into a new Authentication Request, Authentication Reject, or later procedure stop.
Common Issues and Troubleshooting
Authentication starts but the UE never sends a normal Authentication Response.
Likely cause: The UE may have sent Authentication Failure because it detected a problem with the challenge.
What to inspect: Check the EMM cause, any failure parameter, and what the network did after the failure.
Next step: Decide first whether the issue is challenge integrity, synchronization, or a broader unacceptable authentication context.
Attach or TAU enters authentication but then loops or restarts.
Likely cause: Authentication Failure may have triggered resynchronization or another authentication retry branch.
What to inspect: Compare Authentication Request, Authentication Failure, any retried Authentication Request, and any later Authentication Reject.
Next step: Treat the trace as an authentication-branch problem before blaming later attach or TAU messages.
Service restoration never reaches later security or service handling.
Likely cause: The UE may have rejected the inserted authentication challenge and sent Authentication Failure.
What to inspect: Check Service Request, Authentication Request, Authentication Failure, and the next network decision together.
Next step: Read the branch as service restoration blocked by common NAS authentication failure.
LTE / 5G / Variant Comparison
Compared with Authentication Response
Authentication Response is the normal UE answer to the challenge. Authentication Failure is the UE reporting that the challenge could not be accepted or completed normally.
Compared with Authentication Reject
Authentication Failure is sent by the UE. Authentication Reject is the network's later negative decision if the branch cannot continue.
Compared with Authentication Request
Authentication Request is the network challenge. Authentication Failure is the UE-side negative outcome to that challenge.
FAQ
What is Authentication Failure in LTE?
It is the EPS NAS message the UE sends when it cannot complete the authentication challenge normally.
What should I inspect first in Authentication Failure?
Start with the EMM cause, then check whether the authentication failure parameter is present.
What usually comes after Authentication Failure?
The network may retry authentication with a new challenge, send Authentication Reject, or stop the current procedure.
Why is Authentication Failure important in troubleshooting?
Because it shows the authentication branch failed on the UE side before a normal Authentication Response could continue.
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.
