[asterisk-users] Issues with in-call DTMF using Broadvox and Level 3

[Bryant Zimmerman]

The issue we are having is that in-call RFC2833 DTMF digits are being 
dropped with Broadvox and Level 3. This is happening with Grandstream GXP 
and Snom phones. We did some testing with the vendors and here is one of 
the responses we got back. Is there any way to force asterisk to modify the 
DTMF so that these phones will work with the carriers at issue. This is a 
big compatibility issue with SONUS.

Hello,

We have reviewed both captures, one of a good call with proper DTMF passing 
and one with DTMF failing to send properly. The issue still remains the 
same. On the good call, the time between the last RTP packet and the first 
DTMF event was less than 2ms. For the bad call, the time was over 200ms.

Also, to clarify, the 100ms requirement is not per RFC but a standard that 
our switch vendor has put in front of us in order to guarantee proper DTMF 
passing. We have had them troubleshoot this in the past, but unfortunately 
it is something they cannot rectify on their end.

The next course of action now is to see what can be done to work around 
this issue. Here are the following options:

1. Get the time between the packets down to ~100ms or lower.
2. Send DTMF via SIP INFO
3. Send DTMF via Inband.

Please advise our NOC how you would like to proceed.

Thank you,

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