DTMF - inband vs. RFC2833

[OTA]

Just curious, does anyone know why some providers use inband DTMF while others use RFC2833? It seems the cheaper ones tend to be inband. I'm curious if there's a logistical reason for this. I'd think RFC2833 would be the way to go.

 

[termy_pe]

inband only works under ulaw or alaw g711. Some some people might not want to have to use the bandwith that is needed for g711 and intend of using g729 with is more compress and takes way less bandwith. But guess what. g729 does not work with inband. So that why we use rfc2833, with work with g729. And some provider got g711 working with either inband or rfc2833.


g729 compatible with rfc2833 9k per channel

711 ulaw&alaw compatible with inband or rfc2833. 64k per channel.


Hope that answer help you.

 

[OTA]

I'm aware of the technical differences, but curious as to why certain providers do/do not support RFC2833. As I noted before it seems the cheaper providers generally tend to work best with inband DTMF, while the enterprise/carrier-grade providers always support RFC2833 even if they don't support g729.

It's not like out-of-band signaling is a new concept. Most analog PBXs from the 1980s to present did out-of-band signaling, ISDN did it. T1/E1 do it. Practically everything is out-of-band except for the analog side of POTS and once that hits the CO it also becomes out-of-band.

 

[termy_pe]

What I been seeing. Some people that have real pots connected to their switch use inband. People that are wholesaling lines at g729, uses rfc2823, then translated to another provider at g711. That what I notice, whoever have new equipment uses rfc2833, while people that have older equipment only works in inband, that the situation I had with MCI. They only had inband 711. That was it. They could not do rfc2833 or g729. I left them and find a provider with g729. Cheaper on the bandwith.