[asterisk-users] Asterisk DTMF RFC2833 issues

Bryant Zimmerman BryantZ at zktech.com
Fri Aug 27 09:17:19 CDT 2010

Hi all

I have posted a question on the asterisk dev board about this issue but I 
want to see if any users have run up against this.

This issue is that when calls are run through Broadvox and Level 3 the 
in-call rfc2833 dtmf is not reliable. This occured for me on asterisk 
version, it appears to have been fixed when I went to but broken again in
I have tested with Grandstream and SNOM phones and both fail 90% of the 
time Unidata phones fail 10% of the time Audiocodes and Grandstream ATA's  
appear to not suffer from the issue on any version of asterisk. 

What happens is when a caller trys to enter DTMF keys durring a call the 
far end routed through these carriers do not detect all of the digits. We 
did captures with broadvox and here is what they have said.  

Per our phone conversation I have attached our signaling capture. The issue 
is that after we receive a RTP packet, the RTP event that follows needs to 
be sent within 100 ms. Anything greater than 100 ms will not be received. 
Thank you,

Network Operations Center

Any one else seen this? Any ideas?

Please note you must be being proxied directly to the carrier so your RTP 
flows direct other wise you will not see the issue.


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