LTE RRC DL Information Transfer

Message Fact Sheet

Protocol	lte-rrc	Network	lte
Spec	3GPP TS 36.331	Spec Section	5.3.11, 6.2.2
Direction	eNodeB -> UE	Message Type	Dedicated Information Transfer

Full message name	LTE RRC DL Information Transfer
Protocol	LTE-RRC
Technology	LTE
Direction	eNodeB -> UE
Interface	Uu
Signaling bearer / channel	SRB1 / DL-DCCH
Typical trigger	The network has downlink EPS NAS content that must be delivered to the UE through the current LTE RRC connection.
Main purpose	Transfers core-network signaling transparently across LTE RRC so the UE can receive downlink NAS messages such as attach accept, authentication request, TAU accept, service reject, or other EPS NAS content.
Main specification	3GPP TS 36.331, 5.3.11, 6.2.2
Release added	Release 8
Procedures where used	Initial access and attach continuation, Authentication and security-related NAS delivery, Tracking area update continuation, Connected-mode NAS signaling

What is LTE RRC DL Information Transfer in simple terms?

Downlink LTE RRC message used by the eNodeB to carry NAS payloads toward the UE over the LTE access stratum.

Transfers core-network signaling transparently across LTE RRC so the UE can receive downlink NAS messages such as attach accept, authentication request, TAU accept, service reject, or other EPS NAS content.

Why this message matters

DL Information Transfer is the LTE RRC message that carries downlink NAS signaling from the network to the UE.

Where this message appears in the call flow

LTE initial access

Call flow position: Downlink NAS delivery step after the RRC connection and security path are active.

Typical state: UE is in connected mode and the network uses LTE RRC to deliver EPS NAS content.

Preconditions:

RRCConnectionSetupComplete has already been sent.
The dedicated SRB1 path is active.
The network has NAS content to deliver to the UE.

Next likely message: ULInformationTransfer or later dedicated LTE RRC signaling

Connected-mode NAS delivery

Call flow position: Transparent downlink NAS transport step used while the UE remains in connected mode.

Typical state: LTE RRC carries a NAS container without changing the basic role of NAS as the higher-layer control payload.

Preconditions:

SRB1 is active.
The UE remains in connected mode.
An EPS NAS procedure needs downlink signaling.

Next likely message: ULInformationTransfer or later NAS/RRC continuation

Call flow position

Previous message(s): RRCConnectionSetupComplete, SecurityModeComplete, Earlier NAS-side processing in EPC

Next message(s): ULInformationTransfer, Later RRC or NAS procedure continuation

Message direction and transport

Sender and receiver: eNodeB -> UE

Interface: Uu

Domain: Access-side radio control carrying core-network NAS signaling

Signaling bearer: SRB1

Logical channel: DL-DCCH

Transport / encapsulation: RRC over DCCH on SRB1 carrying a dedicated NAS message container

Security context: This message appears after the dedicated signaling path is active and is used to carry NAS content through protected LTE RRC signaling.

Message Structure Overview

DLInformationTransfer is mainly a transport wrapper for a NAS payload.
The useful read starts with the carried NAS content, not with the outer RRC message name alone.
This message is best read together with the related NAS procedure and the later uplink reply path.

ASN.1 for LTE RRC DL Information Transfer

DLInformationTransfer ::= SEQUENCE {
  rrc-TransactionIdentifier RRC-TransactionIdentifier,
  criticalExtensions CHOICE {
    c1 CHOICE {
      dlInformationTransfer-r8 DLInformationTransfer-r8-IEs,
      spare3 NULL,
      spare2 NULL,
      spare1 NULL
    },
    criticalExtensionsFuture SEQUENCE {}
  }
}

DLInformationTransfer-r8-IEs ::= SEQUENCE {
  dedicatedInfoType CHOICE {
    dedicatedInfoNAS DedicatedInfoNAS,
    ...
  },
  nonCriticalExtension DLInformationTransfer-v8a0-IEs OPTIONAL
}

How to read this ASN.1

The outer message is small. The real operational value comes from identifying the NAS container and reading the carried NAS procedure in context.

LTE RRC DL Information Transfer - Example Dump

DL-DCCH-Message
  message c1 : dlInformationTransfer : {
    rrc-TransactionIdentifier 3,
    criticalExtensions c1 : dlInformationTransfer-r8 : {
      dedicatedInfoType dedicatedInfoNAS : '274201...'H
    }
  }

How to read this dump

Start by confirming that the payload is dedicatedInfoNAS.
The next useful step is decoding the carried NAS payload and placing it in the active EPS procedure.
Do not stop at the outer RRC decode when the real meaning sits inside the NAS container.

Important Information Elements

IE	Required	Description
`rrc-TransactionIdentifier`	Yes	Transaction identifier for the LTE RRC message exchange.
`dedicatedInfoType`	Yes	Wrapper that identifies the payload type being carried by DLInformationTransfer.
`dedicatedInfoNAS`	Yes	NAS message container delivered transparently to the UE.
`lateNonCriticalExtension / nonCriticalExtension`	Optional	Release-extension branch for later additions.

Detailed field explanation

`rrc-TransactionIdentifier`

Transaction identifier for the LTE RRC message exchange.

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.

`dedicatedInfoType`

Wrapper that identifies the payload type being carried by DLInformationTransfer.

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.

`dedicatedInfoNAS`

NAS message container delivered transparently to the UE.

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.

`lateNonCriticalExtension / nonCriticalExtension`

Release-extension branch for later additions.

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 message appears on SRB1 / DL-DCCH.
Check that the payload is a NAS container.
Decode the carried NAS message and identify the active EPS procedure.
Correlate the message with the earlier RRC connection and security path.
Follow the next uplink NAS or RRC continuation instead of reading the message in isolation.

Common Issues and Troubleshooting

DLInformationTransfer is present but the procedure meaning is unclear.

Likely cause: The outer RRC wrapper was read, but the carried NAS payload was not decoded or correlated with the EPS procedure.

What to inspect: Decode the NAS container and map it to attach, authentication, TAU, service, detach, or other EPS signaling.

Next step: Move from the RRC wrapper into the NAS message reference path.

The UE receives DLInformationTransfer but no expected uplink continuation follows.

Likely cause: The problem may be in the carried NAS procedure, not in the transport wrapper itself.

What to inspect: Check the carried NAS message, the security state, and the expected uplink reply such as ULInformationTransfer.

Next step: Read the message inside the wider NAS request-response sequence.

The message appears during connected mode and looks unrelated to RRC.

Likely cause: DLInformationTransfer is often only the LTE RRC transport path for EPS NAS signaling.

What to inspect: Check the NAS container first before assuming the issue is radio-control specific.

Next step: Treat the message as a bridge between LTE RRC and EPS NAS rather than a standalone control action.

LTE / 5G / Variant Comparison

Compared with ULInformationTransfer

DL Information Transfer carries NAS payloads from the network to the UE. ULInformationTransfer carries NAS payloads from the UE to the network.

Compared with RRCConnectionReconfiguration

RRCConnectionReconfiguration changes radio configuration. DL Information Transfer mainly transports a NAS container over the LTE RRC signaling path.

FAQ

What is DL Information Transfer in LTE?

It is the downlink LTE RRC message used to carry NAS payloads from the network to the UE.

What does DL Information Transfer carry?

It typically carries a dedicated NAS container, so the real procedure meaning comes from the NAS message inside it.

What should I inspect first in DL Information Transfer?

Start by confirming the NAS container and decoding the carried NAS payload.

Why is DL Information Transfer important in troubleshooting?

It marks the point where EPS NAS signaling is delivered through LTE RRC, so problems often sit in the carried NAS procedure rather than in the outer wrapper.

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.