RFC 4321 observes that most endpoints emit a 408 for a non-INVITE request 64*T1 after receiving it if no earlier final response was sent, and that such a 408 reaches the upstream element too late to be useful.
Checked 2026-10-02
Such a 408 is guaranteed to arrive at the next upstream element too late to be useful.
- Vendor
- not restricted
- Product
- not restricted
- Subsystem
- SIP non-INVITE transaction
- Deployment
- any
- Region
- not restricted
- Release range
- RFC 4321 (2006 observation), current as of 2026-10-02
- Checked
- 2026-10-02
Sources
- RFC 4321: Problems Identified Associated with the Session Initiation Protocol's (SIP) Non-INVITE Transaction — IETF / RFC Editor · tier 1 standards and regulators · Section 1.4
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-rfc4321-endpoints-late-408. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-408-timeout-troubleshooting-rfc4321-endpoints-late-408
BibTeX
@misc{warmtransfer-claim-sip-408-timeout-troubleshooting-rfc4321-endpoints-late-408,
title = {Troubleshooting SIP 408 Request Timeout and calls that get no response: source note sip-408-timeout-troubleshooting-rfc4321-endpoints-late-408},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-408-timeout-troubleshooting-rfc4321-endpoints-late-408},
note = {Source note sip-408-timeout-troubleshooting-rfc4321-endpoints-late-408, checked 2026-10-02}
}