Subject: [SIP] DTMF

From: Henning Schulzrinne <[email-masked]>
Date: Thu, 10 Aug 2000 15:46:56 -0400

Besides the philosophical arguments, can somebody please succinctly and
technically characterize why RTP transport of digits does not work or is
not sufficient, given that

- sending a 'tones' RTP packet incurs no more (and plausibly less)
overhead at sender or receiver than a SIP packet

- sending keyboard input as envisioned here has nothing to do with
session setup or control or signaling

- RTP with redundancy is at least as reliable as SIP transport

- REFER and 3pcc can be used to redirect RTP streams wherever they are
needed, either separate from or jointly with the audio stream

- a number of implementations already support the RFC 2833 mechanism -
why should they support another mechanism?

As Colin points out and has been raised on the list before in a
different context, if we're into text communications (full keyboard
set), the RTP text payload type may also be appropriate. 

Thank you.
-- 
Henning Schulzrinne   http://www.cs.columbia.edu/~hgs

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