Prince,

RTP DTMF as per RFC 2833 is still "out of
band"...although it is sometimes referred to as inband
in context to separate signalling path.
So, you have multiple options for out-of-band -RFC
2833, SIP INFO, SIP NOTIFY. Ideally(only) from
interoperability perspective your equipment should be
prepared to receive DTMF based upon any method
(including in-band) and send it only thru' the method
published by the peer end. 
Typically, SIP level lack of support can be detected
only thru' a 5xx error which causes unacceptable delay
for transmitting DTMF on media path, therefore it
might also be a good idea to offer DTMF options as
configurable on your equipment (although this may
reduce on the fly interoperability...may be acceptable
in certain cases)

I have seen IP equipments offer RTP DTMF in SDP by
default but are prepared to receive RTP DTMF by all
means. And, would send RTP DTMF only if peer end
publishes the same in SDP else use SIP INFO method.

hope this helps,
-kapil nayar

--- Prince Arimboor Philip
<[EMAIL PROTECTED]> wrote:

> Hi all,
> 
> what is the recommended way of communicating the
> DTMF digits?
> 
> Also please tell me which is the mechanism used by
> most of the SIP end 
> points to communicate the DTMF digits?
> 
> thanks in advance,
> Prince
> 
> 
> 
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