Source note · Fax and T.38 in cloud calling
RFC 6913 motivates the sip.fax tag by noting that fax calls are treated as voice calls until after they are connected which can route them to non-fax endpoints.
Checked 2026-09-24
fax calls are always considered voice calls until after they are connected
- Vendor
- IETF
- Product
- RFC 6913
- Subsystem
- SIP signalling
- Deployment
- standard
- Region
- not restricted
- Release range
- RFC 6913 (March 2013)
- Checked
- 2026-09-24
Sources
- Indicating Fax over IP Capability in the Session Initiation Protocol (SIP) — IETF RFC Editor · tier 1 standards and regulators · Section 3 Motivation
Cite this note
APA
WarmTransfer. (2026, September 24). Fax and T.38 in cloud calling: source note fax-t38-rfc6913-voice-until-connected. WarmTransfer. https://warmtransfer.net/knowledge/claims/fax-t38-rfc6913-voice-until-connected
BibTeX
@misc{warmtransfer-claim-fax-t38-rfc6913-voice-until-connected,
title = {Fax and T.38 in cloud calling: source note fax-t38-rfc6913-voice-until-connected},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/fax-t38-rfc6913-voice-until-connected},
note = {Source note fax-t38-rfc6913-voice-until-connected, checked 2026-09-24}
}