AudioCodes Mediant 500L MSBR

User's Manual 17. Media
Version 6.8 191 Mediant 500L MSBR
 To allow V.34 fax relay over T.38:

In the Advanced Parameters page (Configuration tab > VoIP menu > SIP Definitions >
Advanced Parameters), set the 'SIP T.38 Version' parameter to Version 3
(SIPT38Version = 3).
 To force V.34 fax machines to use their backward compatibility with T.30 faxes
and operate in the slower T.30 mode:

Set the 'SIP T.38 Version' parameter to Version 0 (SIPT38Version = 0).
17.2.3.3 V.34 Fax Relay for SG3 Fax Machines
Super Group 3 (SG3) is a standard for fax machines that support speeds of up to 33.6
kbps through V.34 half duplex (HD) modulation. The following procedure describes how to
configure V.34 (SG3) fax relay support based on ITU Specification T.38 version 3.
 To enable support for V.34 fax relay (T.38) at SG3 speed:
1. In the IP Profile table (Configuration tab > VoIP menu > Coders and Profiles > IP
Profile Settings), configure an IP Profile with the 'Fax Signaling Method' parameter
(IpProfile_IsFaxUsed) set to T.38 Relay.
2. In the Coders Table (Configuration tab > VoIP menu > Coders and Profiles >
Coders), set the coder used by the device to G.729 (or any other supported codec).
3. On the Fax/Modem/CID Settings page, do the following settings:
a. 'SIP T.38 Version' to Version 3 (SIPT38Version = 3).
b. 'Fax Relay Max Rate' (RelayMaxRate) to 33,600bps (default).
c. 'CNG Detector Mode' (CNGDetectorMode) to Disable (default).
d. 'V.21 Modem Transport Type' to Disable (V21ModemTransportType = 0).
e. 'V.22 Modem Transport Type' to Disable (V22ModemTransportType = 0).
f. 'V.23 Modem Transport Type' to Disable (V23ModemTransportType = 0).
g. 'V.32 Modem Transport Type' to Disable (V32ModemTransportType = 0).
h. 'V.34 Modem Transport Type' to Disable (V34ModemTransportType = 0).
i. 'CED Transfer Mode' to Fax Relay or VBD (CEDTransferMode = 0).
4. Set the ini file parameter, V34FaxTransportType to 1 (i.e., relay).
5. Set the ini file parameter, T38MaxDatagramSize to 560 (default).
Notes:
• The T.38 negotiation should be completed at call start according to V.152
procedure (as shown in the INVITE example below).
• T.38 mid-call Re-INVITEs are supported.
• If the remote party supports only T.38 Version 0, the device "downgrades" the
T.38 Version 3 to T.38 Version 0.
For example, the device sends or receives the following INVITE message, negotiating both
audio and image media:
INVITE sip:2001@10.8.211.250;user=phone SIP/2.0
Via: SIP/2.0/UDP 10.8.6.55;branch=z9hG4bKac1938966220
Max-Forwards: 70
From: <sip:318@10.8.6.55>;tag=1c1938956155
To: <sip:2001@10.8.211.250;user=phone>
Call-ID: 193895529241200022331@10.8.6.55
CSeq: 1 INVITE
Contact: <sip:318@10.8.6.55:5060>