Source note · Fax and T.38 in cloud calling
RFC 6913 defines the sip.fax media feature tag with values t38 and passthrough so SIP user agents can advertise fax capability in REGISTER and callers can request it with Accept-Contact in INVITE.
Checked 2026-09-24
- 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 4 Usage; Section 7 IANA Considerations
Cite this note
APA
WarmTransfer. (2026, September 24). Fax and T.38 in cloud calling: source note fax-t38-rfc6913-sip-fax-tag. WarmTransfer. https://warmtransfer.net/knowledge/claims/fax-t38-rfc6913-sip-fax-tag
BibTeX
@misc{warmtransfer-claim-fax-t38-rfc6913-sip-fax-tag,
title = {Fax and T.38 in cloud calling: source note fax-t38-rfc6913-sip-fax-tag},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/fax-t38-rfc6913-sip-fax-tag},
note = {Source note fax-t38-rfc6913-sip-fax-tag, checked 2026-09-24}
}