> I should clarify that we support the dtmf tones plus flash but no other tones at this time.

Seems you have not to support other tones, because they are declared as deprecated in RFC4733 (See also a companion RFC4734). Flash is deprecated either, however supporting flash ensures backward compatibility. Anyway it's used only by a few gateways.

RFC 2833 caused me a lot of headaches in the past, there were 13 drafts over 2833, if I'm not mistaken, before they finally published 4733.
It indeed contains some clarifications, while it's mostly backward compatible with 2833.
The most ridiculous part in out of band implementation is robustness against network conditions and interference of in-band and out-of-band tones (SIP -> PSTN) , surely not counting robustness against broken implementations (from Asterisk 1.2 times).

Anyway, section "2.5.2.2. Playout of Tone Events in RFC4733" deserves careful reading.

Regards,
Arsen.

Date: Thu, 23 Apr 2009 11:48:39 -0400
From: Michael Jerris <mike@jerris.com>
Subject: Re: [Freeswitch-users] Is RFC 4733 supported ?
To: freeswitch-users@lists.freeswitch.org
Message-ID: <909FF661-266E-47D1-A881-52D54C99ACCB@jerris.com>
Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes

I should clarify that we support the dtmf tones plus flash but no
other tones at this time.

Mike

On Apr 23, 2009, at 11:17 AM, Steve Underwood wrote:

> Michael Jerris wrote:
>> rfc 4733 attempts (and fails miserably) to clarify rfc2833. It
>> doesn't "really" change anything of any real substnace. Our handling
>> of these packets tries very hard to be strict in what we send and
>> loose in what we accept and we tend to interoperate pretty well with
>> most endpoints. That being said, there are some very broken
>> endpoints
>> out there (such as sonus) that require special hacks, some are
>> automatic, some require settings. All that being said, we should be
>> very compliant with both 2833 and 4733, although you will generally
>> see references in settings refer to 2833.
> RFC4733 largely tries to clarify RFC2833 for the DTMF features.
> However,
> for most other signal it is very incompatible with RFC2833.