Source note · Calls that drop after about 30 seconds
With the common T1 of 500 ms, 64*T1 is 32 seconds. A call that is answered and then torn down by the called side about 32 seconds later therefore matches the missing-ACK timeout, not a session-timer expiry.
inferred · Checked 2026-09-25
- Vendor
- IETF
- Product
- SIP
- Subsystem
- troubleshooting
- Deployment
- any
- Region
- not restricted
- Release range
- implementations using T1 = 500 ms
- Status
- inferred
- Checked
- 2026-09-25
Sources
- RFC 6026: Correct Transaction Handling for 2xx Responses to Session Initiation Protocol (SIP) INVITE Requests — IETF / RFC Editor · tier 1 standards and regulators · Table 4 entries for Timer L/M (64*T1), combined with the Asterisk DEFAULT_TIMER_T1 = 500
Cite this note
APA
WarmTransfer. (2026, September 25). Calls that drop after about 30 seconds: source note sip-calls-drop-30-seconds-32s-signature. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-calls-drop-30-seconds-32s-signature
BibTeX
@misc{warmtransfer-claim-sip-calls-drop-30-seconds-32s-signature,
title = {Calls that drop after about 30 seconds: source note sip-calls-drop-30-seconds-32s-signature},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-calls-drop-30-seconds-32s-signature},
note = {Source note sip-calls-drop-30-seconds-32s-signature, checked 2026-09-25}
}