DTMF-Relay
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| − | = Dual-tone Multi-frequency Relay = | + | = Dual-tone Multi-frequency Relay = |
| − | Dual-tone Multi-frequency Relay (DTMF) is the mechanism where a VoIP gateway listens for in-call tones, and relay them to the peer according to the negotiated method. | + | Dual-tone Multi-frequency Relay (DTMF) is the mechanism where a VoIP gateway listens for in-call tones, and relay them to the peer according to the negotiated method. |
| − | Relaying DTMF prevents loosing its signal integrity over VoIP compressed codecs. The relayed DTMF is then being regenerated transparently on the peer side. | + | Relaying DTMF prevents loosing its signal integrity over VoIP compressed codecs. The relayed DTMF is then being regenerated transparently on the peer side. |
| + | <br> | ||
| + | There are 3 common ways of relaying DTMF: | ||
| − | + | #[http://www.ietf.org/rfc/rfc2833.txt RFC2833] | |
| − | + | #SIP INFO | |
| − | #RFC2833 | + | |
| − | #SIP INFO | + | |
#In Band | #In Band | ||
| + | <br> | ||
| + | == RFC2833 == | ||
| − | + | The prefered method for relaying is [http://www.ietf.org/rfc/rfc2833.txt RFC2833], where the in-call DTMF are removed from the in-band voice, and are sent to the peer over the RTP stream, as specially marked packet. | |
| − | + | This method also offers a robustness against packet losses by using redundancy scheme. | |
| − | + | RFC2833 is usually being handled by VoIP hardware, and requires no CPU intervention. | |
| − | + | == SIP INFO == | |
| − | + | This method can be used where the peer VoIP doesn't support RFC2833. This method relies on CPU power to relay the DTMF. | |
| − | + | Content-Type: application/dtmf-relay | |
Revision as of 08:08, 17 March 2010
Dual-tone Multi-frequency Relay
Dual-tone Multi-frequency Relay (DTMF) is the mechanism where a VoIP gateway listens for in-call tones, and relay them to the peer according to the negotiated method.
Relaying DTMF prevents loosing its signal integrity over VoIP compressed codecs. The relayed DTMF is then being regenerated transparently on the peer side.
There are 3 common ways of relaying DTMF:
- RFC2833
- SIP INFO
- In Band
RFC2833
The prefered method for relaying is RFC2833, where the in-call DTMF are removed from the in-band voice, and are sent to the peer over the RTP stream, as specially marked packet.
This method also offers a robustness against packet losses by using redundancy scheme.
RFC2833 is usually being handled by VoIP hardware, and requires no CPU intervention.
SIP INFO
This method can be used where the peer VoIP doesn't support RFC2833. This method relies on CPU power to relay the DTMF.
Content-Type: application/dtmf-relay
