According to your call flow, it appears Broadsoft server acts in a proprietary way that doesn't fit the usual switchover to T.38. Here my opinions:
Problem 1 The parameters you mention (and maybe you expect) are all optional but T38FaxRateManagement, which is the only mandatory parameter. Btw, from my (unfortunately very long) experience in troubleshooting fax problems in VoIP networks, I would strongly suggest you to relax your implementation for interoperating to the real world. Broadsoft's behavior (just m line with no parameters) is actually a common behavior, and even when the parameters are present nobody care about (included the agent that sends the parameter!!). Problem 2 Broadsoft server makes the media inactive, so you cannot do anything else that stopping media. This is definitively a "funny" behavior from Broadsoft. I fear that a custom implementation take place, I'm arguing from the "custom" attribute " a=bsoft: 1 image udptl t38 ", that looks similar to a capability declaration (RFC3407). I think that you should ask Broadsoft about, because you're doing right. About references, the only one is the ITU T.38 Annex D (see latest T.38/2007 specs) Andrea ------------------------------ Message: 2 Date: Wed, 04 Feb 2009 08:54:22 +0900 From: junpark <[email protected]> Subject: [Sip-implementors] T38 FAX flows problem? To: [email protected] Message-ID: <02a701c9865a$bcddf050$8a8ff...@magma> Content-Type: text/plain; charset=us-ascii Dear SIP implementors, Recently I met some problems in SIP T.38 FAX flows when my device was working with a commercial network. Please take a look at the whole SIP flows first, I will explain later. Device VOIP-Network ------- INVITE (audio) --------> <--------- 200 OK ---------------- ----------- ACK ----------------> ========= audio session ======= FAX tone detected and change to FAX session <------- INVITE (t38) ----------- (problem 1) -------- 200 OK -----------------> <---------- ACK ----------------- ========= t38 fax session ======= <---------fax signaling ---------> ------- FCD Frm num: x --------> fax data transmission ------- FCD Frm num: x --------> ------- FCD Frm num: x --------> ----------- RCP -------------------> ----------- RCP -------------------> ----------- RCP -------------------> at this moment, re-INVITE had come from VOIP-Network <------- INVITE (t38 a=inactive) --- (problem 2) -------- 200 OK ----------------------> <---------- ACK ---------------------- I have 2 problems. #1) when my device got the re-INVITE request to change T38 fax session, the SDP body is as follows; v=0 o=BroadWorks 147321730 2 IN IP4 10.7.0.74 s=- c=IN IP4 10.7.0.74 t=0 0 m=image 41432 udptl t38 a=bsoft: 1 image udptl t38 There's no T38 related parameters but "m=image 41432 udptl t38". There's no version information or baud rate. I really don't understand if this kind of SDP body is O.K for T.38 specification. #2) When t38 fax protocol was doing its job, suddenly my device received re-INVITE request with a=inactive. Here's SDP body for this case. v=0 o=BroadWorks 147321730 3 IN IP4 10.7.0.74 s=- c=IN IP4 0.0.0.0 t=0 0 m=image 41432 udptl t38 a=bsoft: 1 image udptl t38 a=inactive I've never heard of this kind of SIP flows. Do you have any idea why the VoIP-Network device did send such an re-INVITE request? At this moment, the FAX session was blocked - i.e. no more fax data transmission was allowed since a=inactive was come. And it turned out to be FAX transmission failure. These two problems bugs me. I couldn't find out any kind of RFC or draft related to this problem. If anyone has an idea for these, please let me know. My best regards, Jun P.S: I attached whole SIP messages UDP SIP Packet(984bytes) Sent ---> 10.7.0.73/5060 INVITE sip:[email protected] SIP/2.0 Via: SIP/2.0/UDP 10.251.242.195:5070;branch=z9hG4bKhsig0000000265AAXzcJzGDMYXEQAAAAAAAA From: <sip:[email protected]>;tag=9718bb9b-Nde0-7239063 To: <sip:[email protected]> Call-ID: [email protected] CSeq: 1 INVITE Contact: <sip:[email protected]:5070> P-Preferred-Identity: <sip:[email protected]> Max-Forwards: 70 Allow: INVITE,ACK,BYE,CANCEL,NOTIFY,REFER,OPTIONS,SUBSCRIBE,PRACK,UPDATE,INFO,MESSA GE Supported: 100rel, replaces User-Agent: Samsung-iBG-SIPUA/2.4.0.3 Content-Type: application/sdp Content-Length: 337 v=0 o=89137108 1 1 IN IP4 10.251.242.195 s=- c=IN IP4 10.251.242.195 t=0 0 m=audio 16438 RTP/AVP 8 18 4 4 2 0 a=rtpmap:8 PCMA/8000 a=rtpmap:18 G729/8000 a=fmtp:18 annexb=no a=rtpmap:4 G723/8000 a=fmtp:4 bitrate=6.3;annexa=no a=rtpmap:4 G723/8000 a=fmtp:4 bitrate=5.3;annexa=no a=rtpmap:2 G726-32/8000 a=rtpmap:0 PCMU/8000 Trace Message received from <----- 10.7.0.73/5060 SIP/2.0 100 Trying Via: SIP/2.0/UDP 10.251.242.195:5070;branch=z9hG4bKhsig0000000265AAXzcJzGDMYXEQAAAAAAAA From: <sip:[email protected]>;tag=9718bb9b-Nde0-7239063 To: <sip:[email protected]> Call-ID: [email protected] CSeq: 1 INVITE Trace Message received from <----- 10.7.0.73/5060 SIP/2.0 183 Session Progress Via: SIP/2.0/UDP 10.251.242.195:5070;branch=z9hG4bKhsig0000000265AAXzcJzGDMYXEQAAAAAAAA From: <sip:[email protected]>;tag=9718bb9b-Nde0-7239063 To: <sip:[email protected]>;tag=1281932696-1233246625680 Call-ID: [email protected] CSeq: 1 INVITE Allow: ACK,BYE,CANCEL,INFO,INVITE,OPTIONS,PRACK,REFER,NOTIFY Supported: Contact: <sip:[email protected]:5060;transport=udp> Session: Media Remote-Party-ID: <sip:[email protected];user=phone>;screen=yes;party=called;privacy=off;id-t ype=subscriber Content-Type: application/sdp Content-Length: 145 v=0 o=BroadWorks 143123727 1 IN IP4 10.7.0.74 s=- c=IN IP4 10.7.0.74 t=0 0 m=audio 42212 RTP/AVP 8 a=ptime:10 a=bsoft: 1 image udptl t38 Trace Message received from <----- 10.7.0.73/5060 SIP/2.0 200 OK Via: SIP/2.0/UDP 10.251.242.195:5070;branch=z9hG4bKhsig0000000265AAXzcJzGDMYXEQAAAAAAAA From: <sip:[email protected]>;tag=9718bb9b-Nde0-7239063 To: <sip:[email protected]>;tag=1281932696-1233246625680 Call-ID: [email protected] CSeq: 1 INVITE Allow: ACK,BYE,CANCEL,INFO,INVITE,OPTIONS,PRACK,REFER,UPDATE,NOTIFY Supported: Accept: multipart/mixed,application/media_control+xml,application/sdp Contact: <sip:[email protected]:5060;transport=udp> Remote-Party-ID: <sip:[email protected];user=phone>;screen=yes;party=called;privacy=off;id-t ype=subscriber Content-Type: application/sdp Content-Length: 145 v=0 o=BroadWorks 143123727 1 IN IP4 10.7.0.74 s=- c=IN IP4 10.7.0.74 t=0 0 m=audio 42212 RTP/AVP 8 a=ptime:10 a=bsoft: 1 image udptl t38 Trace Message sent to -----> 10.7.0.73/5060 ACK sip:[email protected]:5060 SIP/2.0 Via: SIP/2.0/UDP 10.251.242.195:5070;branch=z9hG4bK0000000265AAiLgJzPDM8XEgAAAAAAAA From: <sip:[email protected]>;tag=9718bb9b-Nde0-7239063 To: <sip:[email protected]>;tag=1281932696-1233246625680 Call-ID: [email protected] CSeq: 1 ACK Max-Forwards: 70 User-Agent: Samsung-iBG-SIPUA/2.4.0.3 Content-Length: 0 UDP SIP Packet(755bytes) Received <--- 10.7.0.73/5060 INVITE sip:[email protected]:5070 SIP/2.0 Via: SIP/2.0/UDP 10.7.0.73:5060;branch=z9hG4bKg8ejpd10do70mgs145g0sbh87t0d3.1 From: <sip:[email protected]>;tag=1281932696-1233246625680 To: <sip:[email protected]>;tag=9718bb9b-Nde0-7239063 Call-ID: [email protected] CSeq: 295505626 INVITE Contact: <sip:[email protected]:5060;transport=udp> Allow: ACK,BYE,CANCEL,INFO,INVITE,OPTIONS,PRACK,REFER,UPDATE,NOTIFY Supported: Accept: multipart/mixed,application/media_control+xml,application/sdp Max-Forwards: 9 Content-Type: application/sdp Content-Length: 133 v=0 o=BroadWorks 143123727 2 IN IP4 10.7.0.74 s=- c=IN IP4 10.7.0.74 t=0 0 m=image 42212 udptl t38 a=bsoft: 1 image udptl t38 Trace Message sent to -----> 10.7.0.73/5060 SIP/2.0 200 OK Via: SIP/2.0/UDP 10.7.0.73:5060;branch=z9hG4bKg8ejpd10do70mgs145g0sbh87t0d3.1 From: <sip:[email protected]>;tag=1281932696-1233246625680 To: <sip:[email protected]>;tag=9718bb9b-Nde0-7239063 Call-ID: [email protected] CSeq: 295505626 INVITE Contact: <sip:[email protected]:5070> Content-Type: application/sdp Content-Length: 218 v=0 o=89137108 1 2 IN IP4 10.251.242.195 s=- c=IN IP4 10.251.242.195 t=0 0 m=image 16438 udptl t38 a=T38FaxVersion:0 a=T38MaxBitRate:14400 a=T38FaxRateManagement:transferredTCF a=T38FaxUdpEC:t38UDPRedundancy Trace Message received from <----- 10.7.0.73/5060 ACK sip:[email protected]:5070 SIP/2.0 Via: SIP/2.0/UDP 10.7.0.73:5060;branch=z9hG4bKg8ejpd10do70mgs145g0sch87t0d3.1 From: <sip:[email protected]>;tag=1281932696-1233246625680 To: <sip:[email protected]>;tag=9718bb9b-Nde0-7239063 Call-ID: [email protected] CSeq: 295505626 ACK Contact: <sip:[email protected]:5060;transport=udp> Max-Forwards: 9 Content-Length: 0 UDP SIP Packet(765bytes) Received <--- 10.7.0.73/5060 INVITE sip:[email protected]:5070 SIP/2.0 Via: SIP/2.0/UDP 10.7.0.73:5060;branch=z9hG4bKg8ejpd10do70mgs145g0sbh87tgd3.1 From: <sip:[email protected]>;tag=1281932696-1233246625680 To: <sip:[email protected]>;tag=9718bb9b-Nde0-7239063 Call-ID: [email protected] CSeq: 295505627 INVITE Contact: <sip:[email protected]:5060;transport=udp> Allow: ACK,BYE,CANCEL,INFO,INVITE,OPTIONS,PRACK,REFER,UPDATE,NOTIFY Supported: Accept: multipart/mixed,application/media_control+xml,application/sdp Max-Forwards: 9 Content-Type: application/sdp Content-Length: 143 v=0 o=BroadWorks 143123727 3 IN IP4 10.7.0.74 s=- c=IN IP4 0.0.0.0 t=0 0 m=image 42212 udptl t38 a=bsoft: 1 image udptl t38 a=inactive Trace Message sent to -----> 10.7.0.73/5060 SIP/2.0 200 OK Via: SIP/2.0/UDP 10.7.0.73:5060;branch=z9hG4bKg8ejpd10do70mgs145g0sbh87tgd3.1 From: <sip:[email protected]>;tag=1281932696-1233246625680 To: <sip:[email protected]>;tag=9718bb9b-Nde0-7239063 Call-ID: [email protected] CSeq: 295505627 INVITE Contact: <sip:[email protected]:5070> Content-Type: application/sdp Content-Length: 230 v=0 o=89137108 1 3 IN IP4 10.251.242.195 s=- c=IN IP4 10.251.242.195 t=0 0 m=image 16438 udptl t38 a=T38FaxVersion:0 a=T38MaxBitRate:14400 a=T38FaxRateManagement:transferredTCF a=T38FaxUdpEC:t38UDPRedundancy a=recvonly ACK sip:[email protected]:5070 SIP/2.0 Via: SIP/2.0/UDP 10.7.0.73:5060;branch=z9hG4bKg8ejpd10do70mgs145g0sch87tgd3.1 From: <sip:[email protected]>;tag=1281932696-1233246625680 To: <sip:[email protected]>;tag=9718bb9b-Nde0-7239063 Call-ID: [email protected] CSeq: 295505627 ACK Contact: <sip:[email protected]:5060;transport=udp> Max-Forwards: 9 Content-Length: 0 ___________________________________________ Hyoungjoon Park (Jun Park) PMP#504269 Senior Engineer Ubigate Lab Telecommunication Network Business Samsung Electronics Co., LTD. 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