[asterisk-users] PJSIP - dtmf mode is not updated when the far end doesn't support rfc2833

Matthew Jordan mjordan at digium.com
Tue Mar 11 10:43:37 CDT 2014

On Tue, Mar 11, 2014 at 8:23 AM, Yaron Nachum <nachum.yaron at gmail.com> wrote:
> Hello,
> I have installed the latest version 12 that has been released (12.1.0.rc3).
> I have setup default dtmf mode (rfc47..) but when I am calling to a endpoint
> that doesn't support it (no telephony event in the rtpmap) the asterisk
> responds OK in the signalling but DTMF is not working.
> Is it a known issue?

I don't think that's an issue at all.

Your configured your endpoint to support RFC 4733 DTMF. However, the
INVITE request that was received by Asterisk didn't offer support for
DTMF, so Asterisk can't accept it. It has to accept only what is in
the offer.

Your configuration can't force the UA to offer what it wants - you can
only configure Asterisk with what it should support with that UA.

There's really only two possible outcomes here:
(1) Reject the INVITE request with a 488 (you didn't offer me DTMF!)
(2) Accept the INVITE request but not have DTMF over RFC 4733.

What you're seeing is option (2), which I think is better than
rejecting the entire call simply because the thing you are talking to
doesn't support the DTMF mode you configured it to have.

Matthew Jordan
Digium, Inc. | Engineering Manager
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
Check us out at: http://digium.com & http://asterisk.org

More information about the asterisk-users mailing list