Relay Authentication Response is the NAS message the UE or relay participant sends back after Relay Authentication Request to return the relay-specific authentication result information.
Message Fact Sheet
Protocol
nas
Network
5g
Spec
3GPP TS 24.501
Spec Section
8.2.38
Direction
UE to network
Message Type
5GMM signaling
Full message name
5G NAS - Relay Authentication Response
Protocol
NAS
Technology
5G
Direction
UE to network
Interface
N1
Signaling bearer / channel
NAS signaling / Dedicated NAS message, transported over the existing NAS path
Typical trigger
Sent after the UE or relay participant successfully processes Relay Authentication Request and produces the required relay-authentication response.
Main purpose
Returns the relay authentication response parameters so the relay security procedure can continue or conclude.
What is Relay Authentication Response in simple terms?
Relay Authentication Response is the NAS message the UE or relay participant sends back after Relay Authentication Request to return the relay-specific authentication result information.
Returns the relay authentication response parameters so the relay security procedure can continue or conclude.
Why this message matters
Relay Authentication Response is the relay participant answering the network's relay authentication challenge.
Where this message appears in the call flow
Relay Authentication Procedure
Call flow position: UE response step after Relay Authentication Request.
Typical state: The relay-capable context exists and the relay participant is returning authentication response data.
Preconditions:
Relay Authentication Request was received.
The UE or relay participant could process the relay authentication challenge.
Next likely message: Relay-specific continuation or procedure outcome handling
ProSe Relay Security Handling
Call flow position: Authentication response step in the relay-specific security exchange.
Typical state: The relay authentication branch is returning challenge-response data to the network.
Next message(s): Relay-specific procedure continuation, Relay procedure success or failure handling
Message direction and transport
Sender and receiver: UE to network
Interface: N1
Domain: Core-side mobility management signaling with relay-specific security context
Signaling bearer: NAS signaling
Logical channel: Dedicated NAS message, transported over the existing NAS path
Transport / encapsulation: NAS 5GS message carried end-to-end between the UE-side relay participant and the network NAS entity
Security context: This message belongs to the relay-authentication branch, so it should be interpreted together with the earlier Relay Authentication Request, relay transaction identity, and any later relay-procedure outcome.
Message Structure Overview
Relay Authentication Response is a specialized NAS relay-security response message rather than a mainstream authentication response used in ordinary registration.
In trace analysis, engineers usually inspect the relay transaction identity first and then the relay authentication response parameters that drive the network's next decision.
ASN.1 Message Syntax for 5G NAS - Relay Authentication Response
This message is not typically analyzed as ASN.1 on the wire. It is usually read as a NAS or protocol field structure instead.
Relay Authentication Response follows NAS 24.501 IE structure and is not an ASN.1 message.
5G NAS - Relay Authentication Response - Example Dump
The message is best read as a relay-security response whose value comes from the relay transaction identity and authentication response parameters.
The next useful check is what relay-specific procedure step or outcome follows this response.
Important Information Elements
IE
Required
Description
ProSe relay transaction identity
Yes
Identifies the relay-authentication transaction so the response can be matched with the earlier request.
Relay authentication response parameters
Yes
Carries the relay-specific response data produced after processing the authentication challenge.
Detailed field explanation
ProSe relay transaction identity
Identifies the relay-authentication transaction so the response can be matched with the earlier request.
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.
Relay authentication response parameters
Carries the relay-specific response data produced after processing the authentication challenge.
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
Confirm the message directly follows Relay Authentication Request.
Inspect the ProSe relay transaction identity and match it to the request.
Check the relay authentication response parameters.
Look for the next relay-specific procedure outcome or continuation.
Common Issues and Troubleshooting
Relay Authentication Response is sent but the relay procedure still fails.
Likely cause: The challenge-response exchange may have completed, but the network did not accept the returned relay authentication data.
What to inspect: Check the relay transaction identity, the response parameters, and the next relay-specific network decision.
Next step: Correlate the response with the earlier Relay Authentication Request and compare against a known-good relay trace.
Relay Authentication Request is visible but no Relay Authentication Response follows.
Likely cause: The UE or relay participant may not have processed the challenge correctly or the uplink relay-authentication response was not delivered.
What to inspect: Check UE-side processing, lower-layer delivery, and relay transaction correlation.
Next step: Treat the issue as a relay-authentication branch failure rather than a general NAS connectivity problem.
FAQ
What does Relay Authentication Response do in 5G?
It returns the relay-specific authentication response information after Relay Authentication Request.
Is Relay Authentication Response the same as normal Authentication Response?
No. The normal Authentication Response belongs to mainstream 5GMM authentication, while Relay Authentication Response belongs to the specialized relay-security branch.
What should engineers inspect first?
Start with the relay transaction identity and the relay authentication response parameters.
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.