Source note · Call transfer semantics REFER and Replaces
RFC 5589 requires that the Transferor and the Transferee are not removed from a session as part of a transfer transaction, and states that without this requirement some current behaviours such as ringback on transfer failure would be lost.
Checked 2026-09-16
The Transferor and the Transferee must not be removed from a session as part of a transfer transaction.
- Vendor
- IETF
- Product
- Session Initiation Protocol
- Subsystem
- Transfer requirements
- 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 4 Requirements, requirement 2 and the paragraph following it
Cite this note
APA
WarmTransfer. (2026, September 16). Call transfer semantics REFER and Replaces: source note xfersem-transferor-and-transferee-stay-in-the-session. WarmTransfer. https://warmtransfer.net/knowledge/claims/xfersem-transferor-and-transferee-stay-in-the-session
BibTeX
@misc{warmtransfer-claim-xfersem-transferor-and-transferee-stay-in-the-session,
title = {Call transfer semantics REFER and Replaces: source note xfersem-transferor-and-transferee-stay-in-the-session},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/xfersem-transferor-and-transferee-stay-in-the-session},
note = {Source note xfersem-transferor-and-transferee-stay-in-the-session, checked 2026-09-16}
}