For a non-INVITE client transaction, Timer E starts at T1 and doubles on each firing while in Trying, capping at T2; after a provisional response it retransmits every T2.
Checked 2026-10-02
- Vendor
- not restricted
- Product
- not restricted
- Subsystem
- SIP non-INVITE transaction
- Deployment
- any
- Region
- not restricted
- Release range
- RFC 4321 describing RFC 3261, 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 1.2
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-rfc4321-timer-e-cap-t2. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-408-timeout-troubleshooting-rfc4321-timer-e-cap-t2
BibTeX
@misc{warmtransfer-claim-sip-408-timeout-troubleshooting-rfc4321-timer-e-cap-t2,
title = {Troubleshooting SIP 408 Request Timeout and calls that get no response: source note sip-408-timeout-troubleshooting-rfc4321-timer-e-cap-t2},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-408-timeout-troubleshooting-rfc4321-timer-e-cap-t2},
note = {Source note sip-408-timeout-troubleshooting-rfc4321-timer-e-cap-t2, checked 2026-10-02}
}