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NASLTEUE to MME3GPP TS 24.301
LTE ESM Data Transport
ESM Data Transport is the LTE NAS message used to carry small user data through the control plane when control-plane CIoT EPS optimization is in use.
Message Fact Sheet
Protocol
nas
Network
lte
Spec
3GPP TS 24.301
Spec Section
6.6.1, 8.3.25
Direction
UE to MME
Message Type
ESM signaling
Full message name
LTE ESM Data Transport
Protocol
NAS
Technology
LTE
Direction
UE to MME
Interface
N1 over LTE access / S1-MME control path
Signaling bearer / channel
NAS signaling / Commonly carried inside Control Plane Service Request or sent during control-plane CIoT small-data handling.
Typical trigger
Triggered when small data should use control-plane CIoT EPS optimization instead of normal user-plane bearer setup.
Main purpose
Carries small IP, non-IP, or Ethernet data in the NAS layer so the UE can exchange limited user data without first setting up the normal user-plane path.
Main specification
3GPP TS 24.301, 6.6.1, 8.3.25
Release added
Release 13
Procedures where used
Control Plane CIoT EPS Optimization, ESM Data Transport Procedure
ESM Data Transport is the LTE NAS message used to carry small user data through the control plane when control-plane CIoT EPS optimization is in use.
Carries small IP, non-IP, or Ethernet data in the NAS layer so the UE can exchange limited user data without first setting up the normal user-plane path.
Why this message matters
ESM Data Transport is the LTE NAS message used to move small user data through the control plane.
Where this message appears in the call flow
Mobile-originated control-plane data
The UE can carry small data inside ESM Data Transport when the service branch stays on the control plane.
Call flow position: UE-originated small-data transport carried inside the control-plane CIoT service branch.
Typical state: The UE is sending data through NAS rather than through a normal user-plane bearer.
Preconditions:
Control-plane CIoT EPS optimization is in use.
Next likely message: Downlink NAS Transport or later service completion
Control-plane service after paging
After paging, the UE may continue a control-plane service branch and move small data with ESM Data Transport.
Call flow position: UE-originated small-data continuation after a paging-triggered control-plane restore.
Typical state: The UE is already back in contact with the network and is moving user data through the control plane.
Preconditions:
Paging resumed the UE into a control-plane service branch.
Next likely message: Downlink NAS Transport or service completion
Interface: N1 over LTE access / S1-MME control path
Domain: Core-side EPS session management signaling for control-plane user-data transport.
Signaling bearer: NAS signaling
Logical channel: Commonly carried inside Control Plane Service Request or sent during control-plane CIoT small-data handling.
Transport / encapsulation: EPS NAS ESM message that carries small data through the control plane.
Security context: Protected by the active NAS security context because it carries data through NAS signaling.
Message Structure Overview
ESM Data Transport is the ESM payload used for small-data transfer through the control plane.
In traces, the main question is whether the branch is intentionally using control-plane data transport instead of a normal user-plane bearer.
ASN.1 Message Syntax for LTE ESM Data Transport
ESM Data Transport
User data container
Release assistance indication OPTIONAL
How to read this message syntax
Read the message from the control-plane service context first and then inspect the data-carrying branch.
LTE ESM Data Transport - Example Dump
ESM Data Transport
Protocol discriminator: EPS session management
EPS bearer identity: 0
Procedure transaction identity: 11
Message type: ESM Data Transport
User data container: small IP payload
Release assistance indication: release preferred
How to read this dump
This message matters mainly in CIoT traces where user data stays on the control plane.
Important Information Elements
IE
Required
Description
User data container
Yes
Carries the small IP, non-IP, or Ethernet payload being sent through the control plane.
Release assistance indication
Optional
May tell the network that the NAS signaling connection can be released after data delivery.
Detailed field explanation
User data container
Carries the small IP, non-IP, or Ethernet payload being sent through the control plane.
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.
Release assistance indication
May tell the network that the NAS signaling connection can be released after data delivery.
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 that the wider branch is using control-plane CIoT EPS optimization.
Check whether the message was carried inside Control Plane Service Request.
Look for the matching network-side continuation such as Downlink NAS Transport.
Common Issues and Troubleshooting
Small data moves without a normal user-plane bearer.
Likely cause: The trace may be using ESM Data Transport over the control plane.
What to inspect: Check Control Plane Service Request, ESM Data Transport, and any later Downlink NAS Transport.
Next step: Treat the path as intentional control-plane data transfer before blaming missing user-plane setup.
FAQ
What is ESM Data Transport in LTE?
It is the ESM message used to carry small IP, non-IP, or Ethernet data through the control plane.
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.
