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

IMS SIP 481 Call or Transaction Does Not Exist

481 Call or Transaction Does Not Exist means the receiving side could not match the request to a valid dialog or transaction.

Message Fact Sheet

Protocol	ims	Network	5G and LTE
Spec	RFC 3261 / 3GPP TS 24.229	Spec Section	SIP 481 Call or Transaction Does Not Exist failure response
Direction	UE <-> IMS network	Message Type	SIP request-failure response

Full message name	IMS SIP 481 Call or Transaction Does Not Exist
Protocol	IMS
Technology	5G and LTE
Common deployment	VoNR and VoLTE
Direction	UE <-> IMS network
Interface	Gm with onward IMS routing
Signaling bearer / channel	IMS SIP signaling / Final request-failure response
Typical trigger	A request refers to a dialog or transaction that the far side no longer recognizes.
Main purpose	Stops in-dialog or transaction-specific signaling that no longer matches active SIP state.
Main specification	RFC 3261 / 3GPP TS 24.229, SIP 481 Call or Transaction Does Not Exist failure response
Release added	See specification history
Procedures where used	IMS Dialog State Failure

What is IMS SIP 481 Call or Transaction Does Not Exist in simple terms?

481 Call or Transaction Does Not Exist means the receiving side could not match the request to a valid dialog or transaction.

Stops in-dialog or transaction-specific signaling that no longer matches active SIP state.

Why this message matters

481 means the receiving side could not match the request to a live dialog or transaction.

Where this message appears in the call flow

IMS Dialog State Failure

Call flow position

Previous message(s): IMS SIP ACK, IMS SIP BYE, IMS SIP UPDATE

Next message(s): Dialog cleanup or retried setup

Message direction and transport

Sender and receiver: UE <-> IMS network

Interface: Gm with onward IMS routing

Domain: IMS dialog and transaction state 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

481 is about state mismatch between the request and the receiver's active SIP context.

ASN.1 Message Syntax for IMS SIP 481 Call or Transaction Does Not Exist

SIP/2.0 481 Call/Transaction Does Not Exist
Via:
From:
To:
Call-ID:
CSeq:
Content-Length: 0

How to read this message syntax

This is SIP response syntax rather than ASN.1.

IMS SIP 481 Call or Transaction Does Not Exist - Example Dump

SIP/2.0 481 Call/Transaction Does Not Exist
Via: SIP/2.0/UDP ue.example.net;branch=z9hG4bK-bye1
From: <sip:alice@example.net>;tag=mo1
To: <sip:bob@example.net>;tag=term1
Call-ID: call-001@example.net
CSeq: 2 BYE
Content-Length: 0

Important Information Elements

IE	Required	Description
`Status-Line`	Yes	Shows the 481 failure code.
`Call-ID`	Yes	Helps identify which dialog or transaction failed to match.

Detailed field explanation

`Status-Line`

Shows the 481 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.

`Call-ID`

Helps identify which dialog or transaction failed to match.

Presence: Required

Common Issues and Troubleshooting

An in-dialog SIP message is rejected even though the session looked valid earlier.

Likely cause: The far side lost or no longer recognizes the dialog or transaction state.

What to inspect: Check Call-ID, tags, route set, and whether the dialog was already released elsewhere.

Next step: Treat it as a state-correlation problem before assuming a media or policy issue.

FAQ

What does 481 Call or Transaction Does Not Exist mean?

It means the far side could not match the request to an active SIP dialog or transaction.

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.