LTE Bearer Resource Allocation Request

Message Fact Sheet

Protocol	nas	Network	lte
Spec	3GPP TS 24.301	Spec Section	6.5.3, 8.3.8
Direction	UE to MME	Message Type	ESM signaling

Full message name	LTE Bearer Resource Allocation 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 PDN connection already exists and the UE needs another dedicated bearer resource.
Typical trigger	Triggered when the UE needs a new dedicated bearer resource for an active PDN connection.
Main purpose	Requests dedicated bearer establishment with traffic-flow and QoS information so the EPC can decide whether to create additional bearer resources.
Main specification	3GPP TS 24.301, 6.5.3, 8.3.8
Release added	Release 8
Procedures where used	Bearer Resource Allocation Procedure
Related timers	T3480

What is LTE Bearer Resource Allocation Request in simple terms?

Bearer Resource Allocation Request is the LTE NAS message the UE sends when it wants the network to allocate a dedicated bearer resource for an active PDN connection.

Requests dedicated bearer establishment with traffic-flow and QoS information so the EPC can decide whether to create additional bearer resources.

Why this message matters

Bearer Resource Allocation Request is the UE asking the network for a new dedicated bearer resource.

Where this message appears in the call flow

Requested dedicated bearer allocation

LTE flow showing Bearer Resource Allocation Request followed by dedicated bearer activation — The UE requests a dedicated bearer resource and the network decides whether to continue with dedicated bearer activation.

Call flow position: UE-originated bearer request sent when an active PDN needs a new dedicated resource.

Typical state: The UE already has a default bearer and is asking for another bearer tied to the same PDN.

Preconditions:

A PDN connection is active.

Next likely message: Activate Dedicated EPS Bearer Context Request or Bearer Resource Allocation Reject

IMS or QoS-sensitive service request

LTE flow showing Bearer Resource Allocation Request for IMS or another QoS-sensitive service — For IMS or another QoS-sensitive path, the UE can ask for a dedicated bearer resource tied to the active PDN connection.

Call flow position: UE-originated bearer request used when a service path such as IMS needs a dedicated bearer.

Typical state: The UE is asking for a more specific bearer treatment than the default bearer can provide.

Preconditions:

The service path requires dedicated bearer resources.

Next likely message: Activate Dedicated EPS Bearer Context Request or Bearer Resource Allocation Reject

Call flow position

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

Next message(s): Activate Dedicated 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 setup.

Signaling bearer: NAS signaling

Logical channel: Sent after a PDN connection already exists and the UE needs another dedicated bearer resource.

Transport / encapsulation: EPS NAS ESM message sent by the UE to request dedicated bearer allocation.

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

Message Structure Overview

Bearer Resource Allocation Request is the UE asking for a new dedicated bearer resource on top of an existing PDN connection.

ASN.1 Message Syntax for LTE Bearer Resource Allocation Request

Bearer Resource Allocation Request
  Linked EPS bearer identity
  Traffic flow aggregate
  Required traffic flow QoS
  Protocol configuration options       OPTIONAL
  Device properties                    OPTIONAL
  NBIFOM container                     OPTIONAL
  Extended protocol configuration options OPTIONAL
  Extended EPS QoS                     OPTIONAL

How to read this message syntax

Read the linked bearer identity, traffic flow aggregate, and requested QoS first.

LTE Bearer Resource Allocation Request - Example Dump

Bearer Resource Allocation Request
  Protocol discriminator: EPS session management
  EPS bearer identity: 0
  Procedure transaction identity: 9
  Message type: Bearer Resource Allocation Request
  Linked EPS bearer identity: 5
  Traffic flow aggregate: IMS signaling
  Required traffic flow QoS: QCI 5

How to read this dump

The traffic flow aggregate and required QoS explain why the UE asked for a dedicated bearer.

Important Information Elements

IE	Required	Description
`Linked EPS bearer identity`	Yes	Identifies the default bearer and PDN connection the new resource should be linked to.
`Traffic flow aggregate`	Yes	Describes the traffic flow the UE wants the dedicated bearer to cover.
`Required traffic flow QoS`	Yes	Describes the QoS the UE is requesting for that dedicated bearer.

Detailed field explanation

`Linked EPS bearer identity`

Identifies the default bearer and PDN connection the new resource should be linked 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 the UE wants the dedicated bearer to cover.

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`

Describes the QoS the UE is requesting for that dedicated bearer.

Presence: Required

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.

What to check in logs and traces

Check which PDN and default bearer the request is linked to.
Inspect the traffic flow aggregate and requested QoS.
Look for later dedicated bearer activation or reject handling.

Common Issues and Troubleshooting

A service path needs a dedicated bearer but only the default bearer remains active.

Likely cause: The UE may have requested a dedicated resource, but the branch did not continue into activation.

What to inspect: Check Bearer Resource Allocation Request and the later activation or reject branch.

Next step: Decide whether the issue is request content, network policy, or later activation handling.

FAQ

What is Bearer Resource Allocation Request in LTE?

It is the UE message that asks the network to allocate a dedicated bearer resource for an active PDN connection.

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.