Source note · Call transfer semantics REFER and Replaces
A user agent server must reject a request with 400 Bad Request if more than one Replaces header field is present in an INVITE, if a Replaces header field is present in a request other than INVITE, or if a Replaces header field is present alongside another header field with contradictory semantics.
Checked 2026-09-16
- Vendor
- IETF
- Product
- Session Initiation Protocol
- Subsystem
- Replaces
- Deployment
- not restricted
- Region
- not restricted
- Release range
- Standards Track
- Checked
- 2026-09-16
Sources
- RFC 3891 — The Session Initiation Protocol (SIP) "Replaces" Header — IETF / RFC Editor · tier 1 standards and regulators · RFC 3891 section 3, paragraphs 3 and 4
Cite this note
APA
WarmTransfer. (2026, September 16). Call transfer semantics REFER and Replaces: source note xfersem-replaces-400-cases. WarmTransfer. https://warmtransfer.net/knowledge/claims/xfersem-replaces-400-cases
BibTeX
@misc{warmtransfer-claim-xfersem-replaces-400-cases,
title = {Call transfer semantics REFER and Replaces: source note xfersem-replaces-400-cases},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/xfersem-replaces-400-cases},
note = {Source note xfersem-replaces-400-cases, checked 2026-09-16}
}