[asterisk-users] RFC4733 (2833) payload during early audio 183?

Joshua C. Colp jcolp at sangoma.com
Fri Apr 17 08:39:43 CDT 2020

On Fri, Apr 17, 2020 at 5:40 AM BenoƮt Panizzon <benoit.panizzon at imp.ch>

> Hi Gang
> Not a specific Asterisk Question.
> But I wonder, if the called party replies with 183 + SDP indicating
> support for telephony-event.
> Should the caller be able to send DTFM Tones?
> Swiss Railways uses an IVR that kicks in before the call is answered.
> So far I have found no SIP Phone which would allow sending RFC4733
> during the early audio phase (so I cannot test if Asterisk
> would forward them) rendering the IVR unuseable. But the RFC itself
> suggests that there is no restriction on which SDP (183 or 200) the
> telephony-event is announced.

I can't think of anything I've read that says you can't, and from an
Asterisk perspective I don't think we prevent such such an action.

Joshua C. Colp
Asterisk Technical Lead
Sangoma Technologies
Check us out at www.sangoma.com and www.asterisk.org
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