RFC 4320's rationale is that a 408 to a non-INVITE request always arrives after the requester's own Timer F has already expired, so the requester gains nothing from it.
Checked 2026-10-02
A 408 to non-INVITE will always arrive too late to be useful.
- Vendor
- not restricted
- Product
- not restricted
- Subsystem
- SIP non-INVITE transaction
- Deployment
- any
- Region
- not restricted
- Release range
- RFC 4320, current as of 2026-10-02
- Checked
- 2026-10-02
Sources
- RFC 4320: Actions Addressing Identified Issues with the Session Initiation Protocol's (SIP) Non-INVITE Transaction — RFC Editor / IETF · tier 1 standards and regulators · Section 2.2
Cite this note
APA
WarmTransfer. (2026, October 2). Troubleshooting SIP 408 Request Timeout and calls that get no response: source note sip-408-timeout-troubleshooting-rfc4320-late-408-useless. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-408-timeout-troubleshooting-rfc4320-late-408-useless
BibTeX
@misc{warmtransfer-claim-sip-408-timeout-troubleshooting-rfc4320-late-408-useless,
title = {Troubleshooting SIP 408 Request Timeout and calls that get no response: source note sip-408-timeout-troubleshooting-rfc4320-late-408-useless},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-408-timeout-troubleshooting-rfc4320-late-408-useless},
note = {Source note sip-408-timeout-troubleshooting-rfc4320-late-408-useless, checked 2026-10-02}
}