[Asterisk-Users] Asterisk and rfc2833

[James Bushey]

Hi All,

Im having some trouble getting Asterisk to send DTMF via rfc2833.  The 
scenario is this:

For purposes of testing software, I have two applications communicating 
with each other via DTMF.  In between the two applications sits an 
Asterisk.  The applications require that DTMF be sent via rfc2833, 
otherwise they will not understand the DTMF.

The first application (app-a) makes an outbound call to the second 
application (app-b) via SIP through the Asterisk instance.  The Asterisk 
then fully sets up the SIP call and bridges the two applications.  The 
problem is that when DTMF being sent via rfc2833 reaches Asterisk, 
asterisk then puts this DTMF in-band and sends it via the RTP stream.  
Sending DTMF through the other three legs of the call are just fine.  
That is, from app-a to asterisk, and in both directions between asterisk 
and app-b, dtmf is sent via rfc2833, its just this one section of the 
call that goes in-band.

Heres a simple diagram for clarification:

appa                                                  asterisk           
                                       app-b
---------rfc2833---------------------->  
---------------rfc2833------------------->
<---------in-band----------------------  
<-------------rfc2833---------------------

Also note that I can, and sometimes do, substitute a GrandStream 
BudgetTone-100 SIP phone in place of app-a, and the problem persists.

When removing the Asterisk instance from the middle of the call, app-a 
is fully able to communicate with app-b via rfc2833.
Any help would be greatly appreciated.  Let me know if you have any 
questions or need some clarifications.

Thanks,
~James

-- 
James Bushey
Software Engineer
Soleo Communications
ph: 585-641-4300 x0050
fax: 585-641-0502