IMS 5G AND LTE IMS network -> UE RFC 3261 / 3GPP TS 24.229

IMS SIP 480 Temporarily Unavailable

480 Temporarily Unavailable means the target is currently unreachable or unavailable, but not permanently unknown.

Message Fact Sheet

Protocol	ims	Network	5G and LTE
Spec	RFC 3261 / 3GPP TS 24.229	Spec Section	SIP 480 Temporarily Unavailable failure response
Direction	IMS network -> UE	Message Type	SIP request-failure response

Full message name	IMS SIP 480 Temporarily Unavailable
Protocol	IMS
Technology	5G and LTE
Common deployment	VoNR and VoLTE
Direction	IMS network -> UE
Interface	Gm with onward IMS routing
Signaling bearer / channel	IMS SIP signaling / Final request-failure response
Typical trigger	The target user is known, but currently unavailable for service.
Main purpose	Stops the current attempt while indicating the target may become reachable later.
Main specification	RFC 3261 / 3GPP TS 24.229, SIP 480 Temporarily Unavailable failure response
Release added	See specification history
Procedures where used	IMS Reachability Failure, VoNR Call Setup Failure, VoLTE Call Setup Failure

What is IMS SIP 480 Temporarily Unavailable in simple terms?

480 Temporarily Unavailable means the target is currently unreachable or unavailable, but not permanently unknown.

Stops the current attempt while indicating the target may become reachable later.

Why this message matters

480 means the target is temporarily unavailable, not permanently unknown.

Where this message appears in the call flow

IMS Reachability Failure
VoNR Call Setup Failure
VoLTE Call Setup Failure

Call flow position

Previous message(s): IMS SIP INVITE

Next message(s): Retried attempt or procedure stop

Message direction and transport

Sender and receiver: IMS network -> UE

Interface: Gm with onward IMS routing

Domain: IMS reachability handling

Signaling bearer: IMS SIP signaling

Logical channel: Final request-failure response

Transport / encapsulation: SIP over UDP, TCP, or TLS

Security context: Uses the same protected IMS signaling path as the original request.

Message Structure Overview

480 means the target is currently unavailable, not necessarily invalid.

ASN.1 Message Syntax for IMS SIP 480 Temporarily Unavailable

SIP/2.0 480 Temporarily Unavailable
Via:
From:
To:
Call-ID:
CSeq:
Retry-After:                       OPTIONAL
Content-Length: 0

How to read this message syntax

This is SIP response syntax rather than ASN.1.

IMS SIP 480 Temporarily Unavailable - Example Dump

SIP/2.0 480 Temporarily Unavailable
Via: SIP/2.0/UDP ue.example.net;branch=z9hG4bK-inv1
From: <sip:alice@example.net>;tag=mo1
To: <sip:bob@example.net>;tag=term1
Call-ID: call-001@example.net
CSeq: 1 INVITE
Content-Length: 0

Important Information Elements

IE	Required	Description
`Status-Line`	Yes	Shows the 480 failure code.
`Retry-After`	Optional	Can suggest when a retry might make sense.

Detailed field explanation

`Status-Line`

Shows the 480 failure code.

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.

`Retry-After`

Can suggest when a retry might make sense.

Presence: Optional

Common Issues and Troubleshooting

The target looks valid, but the current attempt fails.

Likely cause: The user or service is temporarily unreachable or not available right now.

What to inspect: Check presence, registration state, paging reachability, and any Retry-After information.

Next step: Decide whether to retry later or investigate why the target is currently unavailable.

FAQ

What does 480 Temporarily Unavailable mean in IMS?

It means the target is known, but not currently available for the requested service.

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.