[Freeswitch-users] FreeSWITCH support for RFC 4733

Lawrence Conroy lconroy at insensate.co.uk
Mon Jun 26 16:07:57 UTC 2017

Hi Michael, Naseer, folks,
 "It'll Work": Absolutely Agreed.
Strictly, RFC2833 was kinda thrown together to capture what people knew or could guess then & to avoid everyone inventing their own incompatible schemes;
Scott Petrack, plus Tom Taylor and his MEGACO crowd pulled together ideas on data that was carried/processed by kit as they had experienced/tested it AT THE TIME.

After that, a number of interop issues (e.g., how long are those events?) occurred and RFC 4733 was intended to resolve those.
Given two ways of interpreting things, some implementors will always invent their own new way :/

Some features had NOT really interworked reliably well (e.g., interpretation of a number of trunk & line events differed,
depending on the gateway sending or receiving it), so those were deprecated. On the other hand, other hacks (or "neat ideas")
had popped up in the mean time in different bits of kit, so there was a slight pressure to add those (generally pushed back).
The doc itself was re-structured to make it a bit easier for mere mortals/implementers to understand.

I'm not aware of any kit that claims 4733 compatibility that won't work with 2833 stacks; if there are, avoid!

So ... apart from the process wonk bit on IANA registries, trying to re-write it in English & avoid ambiguities, it's pretty much the same as 2833.

See Appendix A of <http://www.ietf.org/rfc/rfc4733> for the changes.

all the best

On 26 Jun 2017, at 16:01, Michael Jerris <mike at jerris.com> wrote:
> we have 2833… 4733 is mostly a super set of that.  I have personally never seen a device that supports anything in the superset part, so we’ve never made any efforts to add any of the new tone stuff it can do, but regular dtmf handling interpos properly with almost all things out there.
>> On Jun 26, 2017, at 10:53 AM, Muhammad Naseer Bhatti <nbhatti at gmail.com> wrote:
>> Hi, like the subject says, do we have support for RFC 4733? Can’t seem to find anything references in the code so far. 

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