Hello, My locale UAs do not know anything about T.38 protocol and I want to send a fax to some PSTN subscriber via OVH, my french VoIP provider, in an RTP/PCMA session. This session begins normally but, as soon as OVH's gateway recognizes fax tones from remote and/or locale side, an undesirable UPDATE with SDP for a T.38 session is sent to my side. The problem is that, immediately, FreeSwitch says "200 OK" instead of something like "488 Not acceptable here" and this is the beginning of a dialogue of the deaf which only takes end when remote fax-machine hangs up. I have done several things that I found in the WIKI: In my dialplan added these lines: <action application="set" data="sip_ignore_reinvites=true"/> <action application="set" data="fax_enable_t38=false"/> <action application="set" data="fax_enable_t38_request=false"/> In ~/conf/vars.xml: <X-PRE-PROCESS cmd="set" data="refuse_t38=true"/> In ~/conf/sip_profiles/external/sip.ovh.fr.xml: <param name="t38-passthru" value="false"/> But without better result. This is an example of the UPDATE request: UPDATE sip:gw+sip.ovh.fr@92.146.52.82:5080;transport=udp;gw=sip.ovh.fr SIP/2.0 Call-ID: 9686bdc8-e997-1231-27aa-001fc61584f4 Contact: <sip:10.7.1.60:5060> Content-Type: application/sdp Cseq: 29265730 UPDATE From: <sip:0556ZZZZZZ@sip.ovh.fr>;tag=00-08184-01c44a83-0e1305300 Max-Forwards: 30 Record-Route: <sip:91.121.129.20:5060;lr> To: \"0033972XXXXXX\" <sip:0033972XXXXXX@sip.ovh.fr>;tag=75761tHD7541g Via: SIP/2.0/UDP 91.121.129.20:5060;branch=z9hG4bK-DIVG-481b17bf-03a84e77 User-Agent: Cirpack/v4.56 (gw_sip) Content-Length: 299 v=0 o=cp10 138814832168 138814832170 IN IP4 10.7.1.132 s=SIP Call c=IN IP4 91.121.128.144 t=0 0 m=image 35996 udptl t38 a=sendrecv a=T38FaxVersion:0 a=T38MaxBitRate:9600 a=T38FaxRateManagement:TransferredTCF a=T38FaxMaxBuffer:1000 a=T38FaxMaxDatagram:200 a=T38FaxUdpEC:t38UDPRedundancy And that is the OK answer: SIP/2.0 200 OK Via: SIP/2.0/UDP 91.121.129.20:5060;branch=z9hG4bK-DIVG-481b17bf-03a84e77 Record-Route: <sip:91.121.129.20:5060;lr> From: <sip:0556ZZZZZZ@sip.ovh.fr>;tag=00-08184-01c44a83-0e1305300 To: \"0033972XXXXXX\" <sip:0033972XXXXXX@sip.ovh.fr>;tag=75761tHD7541g Call-ID: 9686bdc8-e997-1231-27aa-001fc61584f4 Cseq: 29265730 UPDATE Contact: <sip:gw+sip.ovh.fr@92.146.52.82:5080>;transport=udp;gw=sip.ovh.fr User-Agent: FreeSWITCH-mod_sofia/1.5.8b+git~20131213T181356Z~87751f9eaf~64bit Accept: application/sdp Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY Supported: timer, precondition, path, replaces Content-Type: application/sdp Content-Disposition: session Content-Length: 201 v=0 o=FreeSWITCH 1388128642 1388128643 IN IP4 92.146.52.82 s=FreeSWITCH CH c=IN IP4 92.146.52.82 t=0 0 m=audio 19678 RTP/AVP 8 101 13 a=rtpmap:101 telephone-event/8000 a=fmtp:101 0-16 a=ptime:20 Any help much appreciated, thanks in advance...