The Peeredge Switches fully support RFC 2833 for passing DTMF signaling in RTP packets. SBC/PBX deployments may require the use of Media Termination Points (MTPs) to terminate the RTP media, extract and forward the DTMF signals to the IP endpoints that do not support RFC 2833 (i.e. H.323 gateways). Introducing MTPs into the call will hairpin the media through the MTPs. Depending on the location of the MTPs, relative to the IP endpoint, additional network bandwidth may be consumed.
Recommendations
46Labs recommends using 101 as the payload type for DTMF.