Hi Kevin:

   If the the called is an PBX(connected to the called MG's analog line),and caller&called used G.723 to communication. Then caller may need to dail external phone number. The called PBX may can not detect the digit signal even though the digit signal is transmitted within the voice stream, because the signal is distorted when coded into G.723. But the called PBX still has the chance to detect the digit because sometimes the signal is not so distorted.
   So there are risks in transmite digit within the media stream.
   The responsibility of digit transmition falls on the MGC (forget RFC2833,suppose both MGs don't support RFC2833). The MGC may use packet 'dd' to request MG to detect digits and used packet 'tonegen' to request the called MG to play digit signal to the called PBX.
   From my view,  Once the MGC decide to collect numbers from MG, the MG SHOULD automatically erase the digit signal from the sending media stream to avoid repeated digits(one from media stream, another from signal).
   
   

Message: 2
Date: Thu, 1 Dec 2005 04:23:01 -0500
From: "Kevin Boyle" <kboyle <at> nortel.com>
Subject: RE: [Megaco] A question about DTMF erasion
To: <shicao <at> harbournetworks.com>, <megaco <at> ietf.org>
Message-ID: <34B3EAA5B3066A42914D28C5ECF5FEA40573F813 <at> zrtphxm2>

I have thought about this some, and my thoughts are that the MG would
NOT remove the digits from the stream.  Think about what happens when
the keypad is pressed while in an active call: The digit tones are
carried all the way to the far end, even if there is something in the
middle detecting the digits.  Therefore, I believe that the MG would not
alter the media stream.  It would be incumbent upon the MGC to ensure
that the digit collection is done at an appropriate place in the
network, and to discard a repeated digit that is caused by dual
collection.

Kevin


________________________________

                From: shicao <at> harbournetworks.com
[mailto:shicao <at> harbournetworks.com]
                Sent: Monday, November 28, 2005 11:50 PM
                To: megaco <at> ietf.org; Boyle, Kevin [NCRTP:3Z40:EXCH]
                Subject: RE: [Megaco] A question about DTMF erasion
               
               

                Hi Kevin:
                   I think You may have misunderstood my question. May be I have
not clearified the
                situation.
               
                   What I mean is : One MG has been requested to collect digits,
and The MG detects
                a digit from the user's sending media stream. Then MG report the
digit to MGC by
                signaling or hold the digit . But what confused me is whether
the MG should
                automatically erase the DTMF signal from the sending media
stream or Not.
                   
                   If the MG do not erase the DTMF signal from the sending media
stream, The called
                may receive repeated numbers: One from signaling, the other
comes from The caller's
                Media stream.
                   
                   I wonder if there are some rules defining how to handle this
kind of situation.
                 
                   Looking forward to your reply!
                       
                   BEST REGARD!
               
                   ShiCao
                Message: 3
                Date: Sat, 26 Nov 2005 12:21:52 -0500
                From: "Kevin Boyle" <kboyle <at> nortel.com>
                Subject: RE: [Megaco] A question about DTMF erasion
                To: <shicao <at> harbournetworks.com>, <megaco <at> ietf.org>
                Message-ID: <34B3EAA5B3066A42914D28C5ECF5FEA4055D11DB <at> zrtphxm2>
               
                Once a digit is reported to the MGC, I cannot think of a case
where the
                MG should transmit that digit again.  There are explicit
statements in
                the digit collection rules about when to hold digits and when to
discard
                them.
               
                Kevin
               
               
                ________________________________
               
                                From: megaco-bounces <at> ietf.org
[mailto:megaco-bounces <at> ietf.org]
                On Behalf Of shicao <at> harbournetworks.com
                                Sent: Thursday, November 24, 2005 7:16 AM
                                To: megaco <at> ietf.org
                                Subject: [Megaco] A question about DTMF erasion
                               
                               
               
                                Hi:
                               
                                  These days we encoute with such a problem: the
caller recevied
                repeated numbers due to the missunderstanding of DTMF erasion.
                                 
                                  If Softswitch has requested MG to collect
numbers , should MG
                automatically enable DTMF erasion?
                                   
                                  Is any packets defining enbable/disable MG's
DTMF erasion?
                                 

_______________________________________________
Megaco mailing list
Megaco <at> ietf.org
https://www1.ietf.org/mailman/listinfo/megaco