Source note · Calls that drop after about 30 seconds

Under RFC 6026, a proxy must not forward a response for which it has no matching transaction state machine, so it can no longer statelessly forward stray 2xx responses.

Checked 2026-09-25

The proxy MUST NOT forward the response if there is no matching transaction state machine.

Vendor: IETF
Product: SIP
Subsystem: proxy response processing
Deployment: any
Region: not restricted
Release range: RFC 6026 and later
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 · Change to RFC 3261 section 16.7 (Response Processing)

Cite this note

APA

WarmTransfer. (2026, September 25). Calls that drop after about 30 seconds: source note sip-calls-drop-30-seconds-proxy-no-stray-2xx. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-calls-drop-30-seconds-proxy-no-stray-2xx

BibTeX

@misc{warmtransfer-claim-sip-calls-drop-30-seconds-proxy-no-stray-2xx,
  title  = {Calls that drop after about 30 seconds: source note sip-calls-drop-30-seconds-proxy-no-stray-2xx},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/claims/sip-calls-drop-30-seconds-proxy-no-stray-2xx},
  note   = {Source note sip-calls-drop-30-seconds-proxy-no-stray-2xx, checked 2026-09-25}
}

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