Under RFC 4733, the events an endpoint supports are declared in SDP with an fmtp line on the telephone-event payload type, for example a range 0-15 covering the DTMF events.

Checked 2026-09-25

Vendor
IETF
Product
RTP telephone-event payload
Subsystem
dtmf
Deployment
any
Region
not restricted
Release range
RFC 4733
Checked
2026-09-25

Sources

Cite this note

APA

WarmTransfer. (2026, September 25). SIP trunk carrier turn-up and acceptance testing: source note sip-trunk-carrier-turn-up-rfc4733-sdp-fmtp. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-trunk-carrier-turn-up-rfc4733-sdp-fmtp

BibTeX

@misc{warmtransfer-claim-sip-trunk-carrier-turn-up-rfc4733-sdp-fmtp,
  title  = {SIP trunk carrier turn-up and acceptance testing: source note sip-trunk-carrier-turn-up-rfc4733-sdp-fmtp},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/claims/sip-trunk-carrier-turn-up-rfc4733-sdp-fmtp},
  note   = {Source note sip-trunk-carrier-turn-up-rfc4733-sdp-fmtp, checked 2026-09-25}
}

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