NAS 5G AMF to UE 3GPP TS 24.501

5G NAS - Service Accept

Service Accept is the NAS message confirming that the network accepted the UE's service request and that active service can continue.

Message Fact Sheet

Protocol	nas	Network	5g
Spec	3GPP TS 24.501	Spec Section	8.2.17
Direction	AMF to UE	Message Type	5GMM signaling

Full message name	5G NAS - Service Accept
Protocol	NAS
Technology	5G
Direction	AMF to UE
Interface	N1
Signaling bearer / channel	NAS signaling / Dedicated NAS message, commonly via DL Information Transfer
Typical trigger	Sent after the AMF accepts a Service Request.
Main purpose	Confirms successful service continuation after Service Request.
Main specification	3GPP TS 24.501, 8.2.17
Release added	Release 15
Procedures where used	Service Request

What is Service Accept in simple terms?

Service Accept is the NAS message confirming that the network accepted the UE's service request and that active service can continue.

Confirms successful service continuation after Service Request.

Why this message matters

Service Accept means the network approved the UE's request to continue active service.

Where this message appears in the call flow

Service Request

Call flow position: Positive network response after Service Request.

Typical state: UE remains registered and returns to active service use.

Preconditions:

The AMF accepted the Service Request.

Next likely message: Normal data or signaling activity

Call flow position

Previous message(s): Service Request

Next message(s): Normal user-plane or signaling activity

Message direction and transport

Sender and receiver: AMF to UE

Interface: N1

Domain: Core-side mobility management signaling

Signaling bearer: NAS signaling

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

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

Security context: Normally protected because it follows a protected Service Request path.

Message Structure Overview

Service Accept is a short success message.
Its practical meaning is that the service-resumption step succeeded and the UE can continue normal activity.

ASN.1 Message Syntax for 5G NAS - Service Accept

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

Service Accept is a NAS 24.501 message.

5G NAS - Service Accept - Example Dump

Service Accept
  Extended Protocol Discriminator: 5G Mobility Management
  Security Header Type: Integrity protected and ciphered
  Message Type: Service Accept

How to read this dump

The main check is that it appears after Service Request and before normal service resumes.

Important Information Elements

IE	Required	Description
`PDU session status / optional context`	Optional	Optional context that can help explain session state following service restoration.

Detailed field explanation

`PDU session status / optional context`

Optional context that can help explain session state following service restoration.

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 Service Accept follows Service Request.
Correlate the accept with actual restored traffic or signaling.
If service still fails, look beyond this message into session or radio handling.

Common Issues and Troubleshooting

Service Accept is present but traffic still does not flow.

Likely cause: The service request path succeeded, but the later problem may be in session, user-plane, or radio-layer handling.

What to inspect: Check PDU session state, user-plane setup, and radio bearer behavior.

Next step: Move from 5GMM analysis into PDU session and RAN troubleshooting.

FAQ

What does Service Accept mean in 5G?

It means the network accepted the UE's service request and active service can continue.

Related message pages

Related Procedures

5G RRC Resume

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.