LTE ESM Status | NAS Message

Message Fact Sheet

Protocol	nas	Network	lte
Spec	3GPP TS 24.301	Spec Section	Release 18 message definition for ESM Status
Direction	UE to MME	Message Type	ESM signaling

Full message name	LTE ESM Status
Protocol	NAS
Technology	LTE
Direction	UE to MME
Interface	N1 over LTE access / S1-MME control path
Signaling bearer / channel	NAS signaling / Sent during active ESM signaling when an ESM protocol error is detected.
Typical trigger	Triggered when an ESM message is semantically wrong, malformed, or not compatible with the current ESM state.
Main purpose	Carries an ESM cause value so the peer can understand why the received ESM message could not be processed correctly.
Main specification	3GPP TS 24.301, Release 18 message definition for ESM Status
Release added	Release 8
Procedures where used	ESM protocol error handling
Related cause values	ESM cause

What is LTE ESM Status in simple terms?

ESM Status is the LTE NAS message used to report an ESM protocol error, invalid state, or malformed session-management message.

Carries an ESM cause value so the peer can understand why the received ESM message could not be processed correctly.

Why this message matters

ESM Status is the LTE NAS message used to report a session-management protocol error.

Where this message appears in the call flow

ESM protocol-state mismatch reporting

LTE flow showing ESM Status after an ESM protocol-state mismatch — If the received ESM message does not fit the current ESM state, the peer can answer with ESM Status.

Call flow position: Error-report message sent when the received ESM message does not fit the current ESM state.

Typical state: The branch is active, but the peer sent an ESM message that cannot be handled in the current state.

Preconditions:

An ESM message was received.
The receiving side detected a protocol-state mismatch.

Next likely message: Procedure abort or later corrected signaling

Malformed ESM information reporting

LTE flow showing ESM Status after malformed ESM information — ESM Status can also report that the previous ESM message was malformed or missing mandatory information.

Call flow position: Error-report message sent when mandatory information is missing or invalid in an ESM message.

Typical state: The receiving side rejects the current ESM message as a protocol error.

Preconditions:

An ESM message contained invalid or missing information.

Next likely message: Procedure abort or recovery handling

Call flow position

Previous message(s): PDN Connectivity Request, Activate Default EPS Bearer Context Request, Modify EPS Bearer Context Request

Next message(s): Procedure abort, Protocol recovery handling

Message direction and transport

Sender and receiver: UE to MME

Interface: N1 over LTE access / S1-MME control path

Domain: Core-side EPS session management error reporting.

Signaling bearer: NAS signaling

Logical channel: Sent during active ESM signaling when an ESM protocol error is detected.

Transport / encapsulation: EPS NAS ESM message sent in response to an incompatible or invalid ESM message.

Security context: Usually protected because it reports an error on an already active ESM branch.

Message Structure Overview

ESM Status is the generic ESM-layer error-reporting message.

ASN.1 Message Syntax for LTE ESM Status

ESM Status
  ESM cause

How to read this message syntax

Read ESM Status from the returned ESM cause first and then correlate it with the message that triggered the protocol error.

LTE ESM Status - Example Dump

ESM Status
  Protocol discriminator: EPS session management
  EPS bearer identity: 0
  Procedure transaction identity: 3
  Message type: ESM Status
  ESM cause: message type not compatible with protocol state

How to read this dump

Start with the ESM cause.
Then identify the earlier ESM message that triggered the status response.

Important Information Elements

IE	Required	Description
`ESM cause`	Yes	Explains why the received ESM message could not be processed.

Detailed field explanation

`ESM cause`

Explains why the received ESM message could not be processed.

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.

What to check in logs and traces

Identify the message immediately before ESM Status.
Inspect the ESM cause first.
Decide whether the issue is state mismatch, malformed information, or unsupported message handling.

Common Issues and Troubleshooting

A session-management branch stops without a normal reject or success outcome.

Likely cause: The branch may have ended with ESM Status because one side treated the previous ESM message as invalid.

What to inspect: Check the earlier ESM message and the returned ESM cause.

Next step: Treat the branch as protocol error handling rather than normal PDN or bearer reject logic.

FAQ

What is ESM Status in LTE?

It is the LTE NAS message used to report an ESM protocol error or invalid session-management message handling condition.

Related message pages

Related Procedures

Related Tools

Use This Reference in Practice

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.