Interworking Miscellaneous Media Handling; Interworking Dtmf Methods; Interworking Rtp Redundancy - AudioCodes Mediant 4000 SBC User Manual


Video, indicated in the SDP as 'm=video'

Text, indicated in the SDP as 'm=text'

Fax, indicated in the SDP as 'm=image'
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Binary Floor Control Protocol (BFCP), indicated in the SDP as 'm=application <port>
UDP/BFCP'
Therefore, the device supports 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 (e.g., does not support the coder), it relays the SBC dialog transparently.
The device transparently forwards Binary Floor Control Protocol (BFCP) signaling over
UDP between IP entities (RFC 4582). BFCP is a signaling protocol used by some third-
party conferencing servers to share content (such as video conferencing, presentations or
documents) between conference participants (SIP clients supporting BFCP). The SDP
offer/answer exchange model is used to establish (negotiate) BFCP streams between
clients. The BFCP stream is identified in the SDP as 'm=application <port> UDP/BFCP' and
a dedicated UDP port is used for the BFCP streams.

21.5.9 Interworking Miscellaneous Media Handling

This section describes various interworking features relating to media handling.

21.5.9.1 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:
•
[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 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
allocation.

21.5.9.2 Interworking RTP Redundancy

The device supports interworking of RTP redundancy (according to RFC 2198) between
SIP entities. Employing IP Profiles, you can configure RTP redundancy handling per SIP
entity:
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Generate RFC 2198 redundant packets (IpProfile_RTPRedundancyDepth parameter).

Determine RTP redundancy support in the RTP redundancy negotiation in SDP
offer/answer (IpProfile_SBCRTPRedundancyBehavior parameter). If not supported,
the device discards RTP redundancy packets (if present) received from or sent to the
User's Manual 470
Mediant 4000 SBC
Document #: LTRT-40203