IMS SIP 200 OK | IMS Message

Message Fact Sheet

Protocol	ims	Network	5G and LTE
Spec	RFC 3261 / 3GPP TS 24.229	Spec Section	SIP 200 OK success response in IMS procedures
Direction	UE <-> IMS network	Message Type	SIP success response

Full message name	IMS SIP 200 OK
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 SIP success response
Typical trigger	The request was accepted and the transaction completed successfully.
Main purpose	Carries the final success result for the request and, for INVITE, usually the accepted session description.
Main specification	RFC 3261 / 3GPP TS 24.229, SIP 200 OK success response in IMS procedures
Release added	See specification history
Procedures where used	IMS Registration, IMS Session Setup, IMS Call Release, VoNR, VoLTE

What is IMS SIP 200 OK in simple terms?

200 OK confirms that the SIP request completed successfully.

Carries the final success result for the request and, for INVITE, usually the accepted session description.

Why this message matters

200 OK means the request was accepted successfully.

Where this message appears in the call flow

IMS Registration
IMS Session Setup
IMS Call Release
VoNR
VoLTE

Call flow position

Previous message(s): IMS SIP INVITE, IMS SIP REGISTER, IMS SIP BYE

Next message(s): IMS SIP ACK

Message direction and transport

Sender and receiver: UE <-> IMS network

Interface: Gm with onward IMS routing

Domain: IMS transaction completion

Signaling bearer: IMS SIP signaling

Logical channel: Final SIP success response

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

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

Message Structure Overview

200 OK is the final success response, so it answers the main question of whether the request was accepted.
For INVITE, the SDP body is one of the highest-value fields.

ASN.1 Message Syntax for IMS SIP 200 OK

SIP/2.0 200 OK
Via:
From:
To:
Call-ID:
CSeq:
Contact:                           OPTIONAL
Content-Type:                      OPTIONAL
Content-Length:

SDP body                           OPTIONAL

How to read this message syntax

This is SIP response syntax rather than ASN.1.

IMS SIP 200 OK - Example Dump

SIP/2.0 200 OK
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
Contact: <sip:bob@198.51.100.20:5060>
Content-Length: 0

How to read this dump

200 OK is final success, so the main job is to confirm what was accepted.

Important Information Elements

IE	Required	Description
`Status-Line`	Yes	Shows the 200 OK success code.
`Contact`	Optional	Provides the confirmed contact for the successful branch.
`SDP body`	Optional	For INVITE, often carries the accepted session description.

Detailed field explanation

`Status-Line`

Shows the 200 OK success 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.

`Contact`

Provides the confirmed contact for the successful branch.

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.

`SDP body`

For INVITE, often carries the accepted session description.

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.

Common Issues and Troubleshooting

The request looks successful, but service behavior is still wrong.

Likely cause: The transaction succeeded, but the accepted branch, contact, or SDP may not match expectations.

What to inspect: Read the full 200 OK body and headers, not just the response code.

Next step: Compare the accepted result with the original request and any follow-up ACK.

FAQ

What does 200 OK mean in IMS?

It means the SIP request completed successfully and the final accepted result is now visible.

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.