Hi, i have the following scenario when sending a fax: ATA => FS => Provider => destination The ATA tries to send a fax to destination and in the middle of the call there is the re-invite in t38 from the provider. In dialplan i have: <action application="export" data="t38_passthru=true"/> The invite from the provider is: INVITE sip:gw+TRUNKIP@10.10.1.254:5060;transport=udp;gw=TRUNKIP SIP/2.0 Via: SIP/2.0/UDP 10.10.1.1:5060;branch=z9hG4bKno6j3r305os1nm4ph2a1sb0000010.1 Call-ID: badda7ee-3980-1231-8db4-b4b52f5e67f8 From: <sip:4774@10.10.1.1:5060>;tag=dg2aai02-CC-52 To: "5313" <sip:nousername@10.10.1.254:5060>;tag=t6DB42KFXarmN CSeq: 2 INVITE Contact: <sip:4774@10.10.1.1:5060;transport=udp> Max-Forwards: 69 Content-Length: 437 Content-Type: application/sdp v=0 o=HuaweiSoftX3000 38317113 38317116 IN IP4 10.10.1.2 s=Sip Call c=IN IP4 10.10.1.2 t=0 0 m=image 29090 udptl t38 a=T38FaxVersion:0 a=T38MaxBitRate:14400 a=T38FaxRateManagement:transferredTCF a=T38FaxUdpEC:t38UDPRedundancy m=audio 34264 RTP/AVP 8 0 101 a=rtpmap:8 PCMA/8000 a=rtpmap:0 PCMU/8000 a=rtpmap:101 telephone-event/8000 a=ptime:20 a=silenceSupp:off - - - - a=ecan:fb on - a=X-fax a=fmtp:101 0-15 And the invite sent to the ATA is: INVITE sip:5313@192.168.1.97:5060;ref=5313 SIP/2.0 Via: SIP/2.0/UDP 10.10.1.254;rport;branch=z9hG4bK87p0gpcv4p31g Max-Forwards: 70 From: <sip:4774@sipdomain.net>;tag=mKN5ZFeQ19XDr To: "5313" <sip:5313@sipdomain.net>;tag=5de97158a7c051b0o0 Call-ID: 6aa68878-1a412510@192.168.1.97 CSeq: 44056889 INVITE Contact: <sip:4774@10.10.1.254:5060;transport=udp> User-Agent: suvoz Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY, PUBLISH, SUBSCRIBE Supported: precondition, path, replaces Content-Type: application/sdp Content-Disposition: session Content-Length: 291 v=0 o=FreeSWITCH 1368772703 1368772705 IN IP4 10.10.1.254 s=FreeSWITCH c=IN IP4 10.10.1.254 t=0 0 m=image 13196 udptl t38 a=T38FaxVersion:0 a=T38MaxBitRate:14400 a=T38FaxRateManagement:transferredTCF a=T38FaxMaxBuffer:500 a=T38FaxMaxDatagram:500 a=T38FaxUdpEC:t38UDPRedundancy As you can see the audio part is not send to the ata. I understand that is another "call" between the ATA and FS, but should FS send an invite to the ATA containing a audio part as well? I'm not sure that is a bug or Is the normal behavior? should i open a jira for it? Searching for previous issues i found this, but there was no reply ... http://freeswitch-users.2379917.n2.nabble.com/Doubts-about-T38-passthru-td75... Thanks for the help, António