LTE Bearer Resource Modification Request

Message Fact Sheet

Protocol	nas	Network	lte
Spec	3GPP TS 24.301	Spec Section	6.5.4, 8.3.10
Direction	UE to MME	Message Type	ESM signaling

Full message name	LTE Bearer Resource Modification Request
Protocol	NAS
Technology	LTE
Direction	UE to MME
Interface	N1 over LTE access / S1-MME control path
Signaling bearer / channel	NAS signaling / Sent after a dedicated bearer resource already exists and the UE wants to update it.
Typical trigger	Triggered when the UE needs to change QoS or traffic-flow parameters of an existing dedicated bearer resource.
Main purpose	Requests modification of a bearer resource that already exists so the network can adjust QoS or traffic-flow handling without creating a fresh bearer.
Main specification	3GPP TS 24.301, 6.5.4, 8.3.10
Release added	Release 8
Procedures where used	Bearer Resource Modification Procedure
Related timers	T3480
Related cause values	ESM cause

What is LTE Bearer Resource Modification Request in simple terms?

Bearer Resource Modification Request is the LTE NAS message the UE sends when it wants to change QoS or traffic-flow settings for an existing dedicated bearer resource.

Requests modification of a bearer resource that already exists so the network can adjust QoS or traffic-flow handling without creating a fresh bearer.

Why this message matters

Bearer Resource Modification Request is the UE asking to change a dedicated bearer resource that already exists.

Where this message appears in the call flow

Requested QoS adjustment

LTE flow showing Bearer Resource Modification Request for a QoS change — The UE asks the network to adjust QoS on an existing dedicated bearer resource.

Call flow position: UE-originated bearer-modification request used when an active dedicated bearer needs new QoS.

Typical state: The bearer already exists and the UE wants the network to adjust its definition.

Preconditions:

A dedicated bearer resource is already active.

Next likely message: Modify EPS Bearer Context Request or Bearer Resource Modification Reject

Requested traffic-flow change

LTE flow showing Bearer Resource Modification Request for a traffic-flow change — The UE can ask the network to change traffic-flow handling on a dedicated bearer that already exists.

Call flow position: UE-originated bearer-modification request used when the traffic-flow handling on an active bearer should change.

Typical state: The bearer stays active while the UE asks for a changed live definition.

Preconditions:

The dedicated bearer resource is already active.

Next likely message: Modify EPS Bearer Context Request or Bearer Resource Modification Reject

Call flow position

Previous message(s): Activate Dedicated EPS Bearer Context Accept

Next message(s): Modify EPS Bearer Context Request

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 signaling for UE-requested dedicated-bearer modification.

Signaling bearer: NAS signaling

Logical channel: Sent after a dedicated bearer resource already exists and the UE wants to update it.

Transport / encapsulation: EPS NAS ESM message sent by the UE to modify an existing bearer resource.

Security context: Protected by the active NAS security context because it changes live bearer state.

Message Structure Overview

Bearer Resource Modification Request is the UE asking to change a dedicated bearer resource that already exists.

ASN.1 Message Syntax for LTE Bearer Resource Modification Request

Bearer Resource Modification Request
  Linked EPS bearer identity
  Traffic flow aggregate
  Required traffic flow QoS            OPTIONAL
  ESM cause                            OPTIONAL
  Protocol configuration options       OPTIONAL
  Device properties                    OPTIONAL
  NBIFOM container                     OPTIONAL
  Header compression configuration     OPTIONAL
  Extended protocol configuration options OPTIONAL

How to read this message syntax

Read the linked bearer identity and traffic-flow aggregate first, then inspect what live parameter the UE wants to change.

LTE Bearer Resource Modification Request - Example Dump

Bearer Resource Modification Request
  Protocol discriminator: EPS session management
  EPS bearer identity: 0
  Procedure transaction identity: 10
  Message type: Bearer Resource Modification Request
  Linked EPS bearer identity: 5
  Traffic flow aggregate: IMS voice media
  Required traffic flow QoS: QCI 1

How to read this dump

The request makes sense only if a dedicated bearer resource is already active.

Important Information Elements

IE	Required	Description
`Linked EPS bearer identity`	Yes	Identifies the default bearer and PDN connection the modified resource belongs to.
`Traffic flow aggregate`	Yes	Describes the traffic flow that should use the modified resource definition.
`Required traffic flow QoS`	Optional	Shows the new QoS the UE is requesting for the modified resource.
`ESM cause`	Optional	May explain why the bearer resource should be changed from the UE side.

Detailed field explanation

`Linked EPS bearer identity`

Identifies the default bearer and PDN connection the modified resource belongs to.

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.

`Traffic flow aggregate`

Describes the traffic flow that should use the modified resource definition.

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.

`Required traffic flow QoS`

Shows the new QoS the UE is requesting for the modified resource.

Presence: Optional

In practice: QoS rules are the real service profile of the session. Inspect the QFI mapping, packet filters, and precedence because those values explain how user traffic will actually be classified and forwarded.

`ESM cause`

May explain why the bearer resource should be changed from the UE side.

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 bearer resource already exists.
Inspect the linked bearer identity and requested change.
Look for later Modify EPS Bearer Context Request or reject handling.

Common Issues and Troubleshooting

A dedicated bearer needs different behavior, but the change never happens.

Likely cause: The bearer-modification branch may have stalled or been rejected.

What to inspect: Check Bearer Resource Modification Request and the next ESM branch.

Next step: Treat the issue as a modification problem on an existing bearer, not as a fresh bearer setup failure.

FAQ

What is Bearer Resource Modification Request in LTE?

It is the UE message that asks the network to change an already active bearer resource.

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.