Interworking Dtmf Methods; Fax Negotiation And Transcoding - AudioCodes Mediant 800B User Manual

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Text (m=text)
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Fax (m=image)
Therefore, the device can provide transcoding of various attributes in the SDP offer/answer
(e.g., codec, port, and packetization time) per media type. If the device is unable to perform
transcoding (for example, does not support the codec), it relays the SBC dialog
transparently.

28.4.10 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):
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SBCRFC2833Behavior - affects the RFC 2833 SDP offer\answer negotiation:
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[0] (default): the device does not 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 does not include RFC 2833).
•
[2]: the device removes RFC 2833 from the incoming offer.
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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 this 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
allocation.
28.5

Fax Negotiation and Transcoding

The device can allow fax transmissions to traverse transparently without transcoding or it
can handle the fax as follows:
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Allow interoperability between different fax machines, supporting fax transcoding if
required.
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Restrict usage of specific fax coders to save bandwidth, enhance performance, or
comply with supported coders. These coders include G.711 (A-Law or Mu-Law), VBD
(G.711 A-Law or G.711 Mu-Law), and T38.
Fax configuration is done in the IP Profile and Coder Group Settings tables. The IP Profile
table determines the supported fax coders and the negotiation method used between the
incoming and outgoing fax legs, using the following fax-related parameters:
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IPProfile_SBCFaxBehavior: defines the offer negotiation method - pass fax
transparently, negotiate fax according to fax settings in IP Profile, or enforce remote
UA to first establish a voice channel before fax negotiation.
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IPProfile_SBCFaxCodersGroupID: defines the supported fax coders (from the Coders
Group Settings table).
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IPProfile_SBCFaxOfferMode: determines the fax coders sent in the outgoing SDP
offer.
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IPProfile_SBCFaxAnswerMode: determines the fax coders sent in the outgoing SDP
answer.
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IPProfile_SBCRemoteRenegotiateOnFaxDetection: You can also configure the device
User's Manual
Mediant 800B Gateway and E-SBC
500 Document #: LTRT-10286