| Protocol | ims | Network | 5G and LTE |
|---|---|---|---|
| Spec | RFC 3261 / 3GPP TS 24.229 | Spec Section | SIP 408 Request Timeout failure response |
| Direction | IMS network -> UE | Message Type | SIP request-failure response |
| Full message name | IMS SIP 408 Request Timeout |
|---|---|
| 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 | A transaction or expected response path timed out before completion. |
| Main purpose | Ends the transaction when the request or expected follow-up did not complete within the allowed time. |
| Main specification | RFC 3261 / 3GPP TS 24.229, SIP 408 Request Timeout failure response |
| Release added | See specification history |
| Procedures where used | IMS Transaction Timeout |
408 Request Timeout means the expected transaction progress did not happen in time.
Ends the transaction when the request or expected follow-up did not complete within the allowed time.
408 means the SIP transaction timed out instead of completing normally.
Previous message(s): IMS SIP INVITE, IMS SIP REGISTER
Next message(s): Retried request if policy allows
Security context: Uses the same protected IMS signaling path as the original request.
SIP/2.0 408 Request Timeout
Via:
From:
To:
Call-ID:
CSeq:
Content-Length: 0
This is SIP response syntax rather than ASN.1.
SIP/2.0 408 Request Timeout
Via: SIP/2.0/UDP ue.example.net;branch=z9hG4bK-inv1
From: <sip:alice@example.net>;tag=mo1
To: <sip:bob@example.net>
Call-ID: call-001@example.net
CSeq: 1 INVITE
Content-Length: 0
| IE | Required | Description |
|---|---|---|
Status-Line | Yes | Shows the 408 timeout code. |
Call-ID | Yes | Correlates the timeout with the failed transaction. |
Status-LineShows the 408 timeout 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-IDCorrelates the timeout with the failed transaction.
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.
Likely cause: The transaction stalled on routing, response handling, or transport timing.
What to inspect: Check the last seen provisional step and any retransmission behavior.
Next step: Decide whether this was a true network delay, missing response, or lost transaction branch.
It means the SIP transaction did not complete within the expected time.
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.