AudioCodes Mediant 3000, User Manual

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Version 6.6 419 Mediant 3000
User's Manual 28. SBC Overview
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:

Allow interoperability between different fax machines, supporting fax transcoding if
required.

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:

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.

SBCFaxCodersGroupID: defines the supported fax coders (from the Coders Group
Settings table).

SBCFaxOfferMode: determines the fax coders sent in the outgoing SDP offer.

SBCFaxAnswerMode: determines the fax coders sent in the outgoing SDP answer.
Note: The voice-related coder configuration (Allowed and Extended coders) is
independent of the fax-related coder configuration, with the exception of the
G.711 coder. If the G.711 coder is restricted by the Allowed Coders Group
table, it is not used for fax processing even if it is listed in the Coders Group
Settings table for faxes. However, support for G.711 coders for voice is not
dependent upon which fax coders are listed in the Coders Group Settings
table.
28.6 Limiting SBC Call Duration
You can define a maximum allowed duration (in minutes) for SBC calls. If an established
call reaches this user-defined limit, the device terminates the call. This feature ensures
calls are properly terminated, allowing available resources for new calls. This feature is
configured using the MaxCallDuration parameter.
28.7 SIP Authentication Server for SBC Users
The device can function as an authentication server for SIP SBC message requests, based
on HTTP authentication DIGEST with MD5. Alternatively, such requests can be
authenticated by an external, third-party server.
When functioning as an authentication server (set by the IP Group table parameter,
AuthenticationMode), the device authenticates users belonging to a User-type IP Group.
When the device receives an INVITE or REGISTER request from a client (e.g., SIP phone)
for SIP message authorization, the device processes the authorization as follows:
1. The device verifies the type of incoming SIP method (e.g., INVITE) that must be
challenged for authorization. This is configured using the IP Group table parameter,
MethodList.
2. If the message is received without an Authorization header, the device "challenges"
the client by sending a 401 or 407 SIP response. The client then resends the request