RFC 3261 sets the INVITE transaction timeout, Timer B, to 64*T1, which is 32 seconds with the default T1 of 500 ms.
Checked 2026-10-02
- Vendor
- not restricted
- Product
- not restricted
- Subsystem
- SIP INVITE client transaction
- Deployment
- any
- Region
- not restricted
- Release range
- RFC 3261, current as of 2026-10-02
- Checked
- 2026-10-02
Sources
- RFC 3261 — SIP: Session Initiation Protocol — IETF / RFC Editor · tier 1 standards and regulators · Section 17.1.1.2 Formal Description; Table 4 timer summary
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-rfc3261-timer-b-64-t1. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-408-timeout-troubleshooting-rfc3261-timer-b-64-t1
BibTeX
@misc{warmtransfer-claim-sip-408-timeout-troubleshooting-rfc3261-timer-b-64-t1,
title = {Troubleshooting SIP 408 Request Timeout and calls that get no response: source note sip-408-timeout-troubleshooting-rfc3261-timer-b-64-t1},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-408-timeout-troubleshooting-rfc3261-timer-b-64-t1},
note = {Source note sip-408-timeout-troubleshooting-rfc3261-timer-b-64-t1, checked 2026-10-02}
}