5G NAS - Identity Request

Message Fact Sheet

Protocol	nas	Network	5g
Spec	3GPP TS 24.501	Spec Section	8.2.10
Direction	AMF to UE	Message Type	5GMM signaling

Full message name	5G NAS - Identity Request
Protocol	NAS
Technology	5G
Direction	AMF to UE
Interface	N1
Signaling bearer / channel	NAS signaling / Dedicated NAS message, commonly transported via DL Information Transfer
Typical trigger	Sent when the AMF cannot proceed using the identity already available from Registration Request or later mobility context.
Main purpose	Requests the exact UE identity the AMF needs before it can continue authentication, registration, security handling, or policy decisions.
Main specification	3GPP TS 24.501, 8.2.10
Release added	Release 15
Procedures where used	5G Initial Registration, Mobility Registration Update, Service Request
Related timers	T3570

What is Identity Request in simple terms?

Identity Request is the NAS message the network sends when it needs the UE to provide a specific identity such as SUCI, 5G-GUTI-related context, IMEI, IMEISV, or other identity information.

Requests the exact UE identity the AMF needs before it can continue authentication, registration, security handling, or policy decisions.

Why this message matters

Identity Request is the network asking the UE to provide a specific identity before the procedure can continue.

Where this message appears in the call flow

5G Initial Registration

Call flow position: Network query step after Registration Request when the identity available from the UE is not sufficient for the AMF to continue.

Typical state: UE is trying to enter or refresh 5GMM context, but the network needs more identity information first.

Preconditions:

The AMF has received a NAS request but requires a different or more explicit UE identity.

Next likely message: Identity Response

Mobility Registration Update

Call flow position: Identity clarification step when existing temporary context is not enough for the update procedure.

Typical state: UE has some prior context, but the AMF cannot rely on it directly.

Preconditions:

The AMF needs stronger or alternate identity confirmation.

Next likely message: Identity Response or Authentication Request

Call flow position

Previous message(s): Registration Request, Service Request, Mobility management context evaluation

Next message(s): Identity Response, Authentication Request, Registration Reject

Message direction and transport

Sender and receiver: AMF to UE

Interface: N1

Domain: Core-side mobility management signaling with access-side NAS transport dependency

Signaling bearer: NAS signaling

Logical channel: Dedicated NAS message, commonly transported via DL Information Transfer

Transport / encapsulation: NAS 5GS message carried end-to-end between AMF and UE

Security context: Can appear before full NAS security is active, especially in fresh registration flows where the network still needs identity clarification.

Message Structure Overview

Identity Request is a short NAS 5GMM query message whose main operational value is in the requested identity type.
Engineers usually inspect why the AMF could not continue using the identity already present in the earlier NAS exchange.

ASN.1 Message Syntax for 5G NAS - Identity Request

This message is not typically analyzed as ASN.1 on the wire. It is usually read as a NAS or protocol field structure instead.

Identity Request follows NAS 24.501 encoding rather than ASN.1 syntax.

5G NAS - Identity Request - Example Dump

Identity Request
  Extended Protocol Discriminator: 5G Mobility Management
  Security Header Type: Plain NAS
  Message Type: Identity Request
  Identity Type: SUCI

How to read this dump

The key field is the requested identity type because it explains what the AMF still needs from the UE.
The message is most useful when correlated with the preceding Registration Request and the following Identity Response.

Important Information Elements

IE	Required	Description
`Identity type`	Yes	Tells the UE exactly which identity the network wants, such as SUCI, 5G-GUTI-related identity, IMEI, or IMEISV.

Detailed field explanation

`Identity type`

Tells the UE exactly which identity the network wants, such as SUCI, 5G-GUTI-related identity, IMEI, or IMEISV.

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

Check which identity type the network requested.
Confirm whether the earlier NAS message already carried an identity and why it may not have been sufficient.
Correlate the message with the later Identity Response and Authentication Request.
Inspect whether the request is plain or protected NAS and whether that matches the procedure stage.

Common Issues and Troubleshooting

Registration stalls after Registration Request and the UE receives Identity Request.

Likely cause: The AMF could not proceed using the identity available in the earlier NAS exchange.

What to inspect: Check the requested identity type, the prior UE identity form, and whether the UE answers with Identity Response.

Next step: Compare the identity path with a known-good trace and confirm that the UE provides the requested identity format.

Identity Request repeats unexpectedly.

Likely cause: The Identity Response may be missing, malformed, or not accepted by the network.

What to inspect: Check the returned identity contents and the uplink NAS transport path.

Next step: Move analysis to Identity Response and subsequent Authentication Request / Reject handling.

FAQ

What does Identity Request do in 5G?

It asks the UE to provide a specific identity the network needs before registration or another 5GMM procedure can continue.

What identity can the network request?

Common examples include SUCI-related identity, IMEI, IMEISV, or other identity types defined by the NAS procedure.

Does Identity Request always mean failure?

No. It is often a normal intermediate step in registration when the AMF needs more identity information before continuing.

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.