DTMF Notes
DTMF Relay H.323
H.245 Alphanumeric used with H.323 In this method DTMF signals are carried as H.245 messages (OOB) debug voice rtp session named-event debug h245 asn1
RTP-NTE or RFC2833 In this method DTMF tones are transported in RTP streams based on RFC2833 debug voice rtp session named-event debug h245 asn1
DTMF Relay SIP
RFC 2833 (RTP-NTE)
KPML (RFC 4730) KPML procedures use a SIP SUBSCRIBE message to register for DTMF digits. The digits themselves are delivered in NOTIFY messages containing an XML-encoded body.
SIP Notify (RFC 3265) Unlike KPML, these NOTIFY messages are unsolicited, and there is no prior registration to receive these messages using a SIP SUBSCRIBE message. But like KPML, Unsolicited Notify messages are out-of-band.
SIP Info (RFC 2976) The SIP INFO method is used by a UA to send call signaling information to another UA with which it has an established media session
debug ccsip messages
INFO sip:2143302100@172.17.2.33 SIP/2.0
Via: SIP/2.0/UDP 172.80.2.100:5060
From: ;tag=43
To: ;tag=9753.0207
Call-ID: 984072_15401962@172.80.2.100
CSeq: 25634 INFO
Supported: 100rel
Supported: timer
Content-Length: 26
Content-Type: application/dtmf-relay
Signal= 1
Duration= 160