Interworking DTMF Methods

The device supports interworking between various DTMF methods such as RFC 2833, In-Band DTMF’s, and SIP INFO (Cisco\Nortel\Korea). By default, the device allows the remote user agents to negotiate (in case of RFC 2833) and passes DTMF without intervention. However, if two user agents (UA) support different DTMF methods, the device can interwork these different DTMF methods at each leg.

This DTMF interworking feature is enabled using IP Profiles (ini file parameter IPProfile):

■

SBCRFC2833Behavior - affects the RFC 2833 SDP offer-answer negotiation:

●

[0]: (default) the device doesn't intervene in the RFC 2833 negotiation.

●

[1]: each outgoing offer-answer includes RFC 2833 in the offered SDP (the device adds RFC 2833 only if the incoming offer doesn't include RFC 2833).

●

[2]: the device removes RFC 2833 from the incoming offer.

■

SBCAlternativeDTMFMethod – the device's first priority for DTMF method at each leg is RFC 2833. Therefore, if a specific leg negotiates RFC 2833 successfully, then the chosen DTMF method for this leg is RFC 2833. For legs where RFC 2833 is not negotiated successfully, the device uses the parameter to determine the DTMF method for the leg.

The chosen DTMF method determines (for each leg) which DTMF method is used for sending DTMF’s. If the device interworks between different DTMF methods and one of the methods is In-band\RFC 2833, detection and generation of DTMF methods requires DSP resources.