CHAPTER15 Media
Mediant 1000 Gateway & E-SBC | User's Manual
● 'V.22 Modem Transport Type' to Disable (V22ModemTransportType = 0).
● 'V.23 Modem Transport Type' to Disable (V23ModemTransportType = 0).
● 'V.32 Modem Transport Type' to Disable (V32ModemTransportType = 0).
● 'V.34 Modem Transport Type' to Disable (V34ModemTransportType = 0).
● '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).
● 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>
Supported: em,100rel,timer,replaces,path,resource-priority,sdp-anat
Allow:
REGISTER,OPTIONS,INVITE,ACK,CANCEL,BYE,NOTIFY,PRACK,REFER,INFO,SU
BSCRIBE,UPDATE
Remote-Party-ID: <sip:318@10.8.211.250>;party=calling;privacy=off;screen=no;screen-
ind=0;npi=1;ton=0
Remote-Party-ID: <sip:2001@10.8.211.250>;party=called;npi=1;ton=0
User-Agent: AudioCodes-Sip-Gateway-/7.20A.252.011
Content-Type: application/sdp
Content-Length: 433
v=0
o=AudioCodesGW 1938931006 1938930708 IN IP4 10.8.6.55
s=Phone-Call
c=IN IP4 10.8.6.55
t=0 0
m=audio 6010 RTP/AVP 18 97
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=rtpmap:97 telephone-event/8000
a=fmtp:97 0-15
a=ptime:20
a=sendrecv
m=image 6012 udptl t38
a=T38FaxVersion:3
a=T38MaxBitRate:33600
a=T38FaxMaxBuffer:1024
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