Source note · Call transfer semantics REFER and Replaces
Removing a PSTN gateway from the path after a transfer is only possible when both legs of the target call are on the same gateway, and RFC 5589 states that in the consultative case nothing relates the consultation to the original call and in the blind case nothing relates the target dialog to the original dialog, so a proxy has no information with which to coerce them onto one gateway.
Checked 2026-09-16
- Vendor
- IETF
- Product
- Session Initiation Protocol
- Subsystem
- Gateway transfer
- Deployment
- not restricted
- Region
- not restricted
- Release range
- BCP 149
- Checked
- 2026-09-16
Sources
- RFC 5589 — Session Initiation Protocol (SIP) Call Control - Transfer — IETF / RFC Editor · tier 1 standards and regulators · RFC 5589 section 11.1 Coerce Gateway Hairpins to the Same Gateway
Cite this note
APA
WarmTransfer. (2026, September 16). Call transfer semantics REFER and Replaces: source note xfersem-gateway-hairpin-cannot-be-coerced. WarmTransfer. https://warmtransfer.net/knowledge/claims/xfersem-gateway-hairpin-cannot-be-coerced
BibTeX
@misc{warmtransfer-claim-xfersem-gateway-hairpin-cannot-be-coerced,
title = {Call transfer semantics REFER and Replaces: source note xfersem-gateway-hairpin-cannot-be-coerced},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/xfersem-gateway-hairpin-cannot-be-coerced},
note = {Source note xfersem-gateway-hairpin-cannot-be-coerced, checked 2026-09-16}
}