AudioCodes Mediant 4000 SBC, User Manual

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CHAPTER 22 SBC Overview
Mediant 4000 SBC | User's Manual
Interworking SIP re-INVITE Messages
The device supports interworking of SIP re- INVITE messages. This enables communication
between endpoints that generate re-INVITE requests and those that do not support the receipt of re-
INVITEs. The device does not forward re-INVITE requests to IP Groups that do not support it.
Instead, it sends a SIP response to the re-INVITE request, which can either be a success or a
failure, depending on whether the device can bridge the media between the endpoints. The device
can also handle re- INVITEs with or without an SDP body, enabling communication between
endpoints that do not support re-INVITE requests without SDP, and those that require SDP. The
device generates an SDP offer and adds it to the incoming re-INVITE request if it does not contain
an SDP and only then forwards it to the destination endpoint. This interworking support is
configured by the IP Profile parameter, 'SBC Remote Reinvite Support'.
Interworking SIP UPDATE Messages
The device supports interworking of the SIP UPDATED message. This enables communication
between UAs that generate UPDATE requests and those that do not support the receipt of
UPDATE requests. The device does not forward UPDATE requests to IP Groups that do not
support it. Instead, it sends a SIP response to the UPDATE request which can either be a success
or a failure, depending on whether the device can bridge the media between the endpoints. The
handling of UPDATE messages is configured by the IP Profile parameter 'SBC Remote Update
Support'.
Interworking SIP re-INVITE to UPDATE
The device enables communication between endpoints (IP Groups) that do not support re-INVITE
requests but support the UPDATE method, and vice versa. The device translates the re-INVITE
request to the UPDATE request, and vice versa. Note that if a re-INVITE request arrives without
SDP, the device generates the SDP and adds it to the outgoing UPDATE request. To enable this
feature, each IP Group needs to be configured with its unique capabilities by associating it with a
relevant IP Profile. For example, an IP Group that supports UPDATE requests but not re-INVITEs
would be configured as follows:
■ SBCRemoteUpdateSupport = 2 (Supported)
■ SBCRemoteReinviteSupport = 0 (Not Supported)
If a re-INVITE request needs to be forwarded to this IP Group, it is translated to an UPDATE
request.
Interworking Delayed Offer
The device supports interworking of INVITE messages with and without SDP between SIP
entities. The device enables sessions between endpoints (IP Groups) that send INVITEs without
SDP (i.e., delayed media) and those that do not support the receipt of INVITEs without SDP. The
device creates an SDP and adds it to INVITEs that arrive without SDP. Delayed offer is also
supported when early media is present.
Employing IP Profiles, you can configure this interworking feature per SIP entity, using the 'SBC
Remote Delayed Offer Support' parameter (see
Configuring IP Profiles ).
● The above mentioned intervention in the SDP offer-answer process may require
transcoding.
● For SIP entities that do not support delayed offer, you must assign extension
coders to its IP Profile (using the 'Extension Coders' parameter).
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