SIP seems OK but no data transmission

[stef]

I have succesfully registered 2 IP FAX machines (t38 compliant) to a internal ip network.
I tried to send a fax directly (from ip-fax to ip-fax) and it worked.
I installed 3CX Phone System on a server in the same network.
I succesfully registered the IP FAX machines to 3CX.
Now i want to send a fax from IPFAX1 to IPFAX2 via 3CX.

It seems that the SIP stuff is all OK, but no data is send. I've included the server status and ethereal sip comms at the bottom of this post.

Can you please help?

Stef Lauwers

3CX Phone System v2.0.1618.0 - server status
10:52:10.895 StratLink:nHangUp: Call(C:22): got Hang-Up from Ext.633
10:52:10.184 CallLegImpl:nConnCfmd: ConnCfmd: 633@L:2@C:22
10:52:10.174 StratInOut:nConnected: Call from Ext.969 to Ext.633 is established
10:52:10.174 CallLegImpl:nConnected: Connected: 633@L:2@C:22
10:52:10.174 CallLegImpl:nConnected: Connected: 969@L:1@C:22
10:52:09.853 CallConf:nIncoming: Incoming call from Ext.969 to sip:[email protected]

ethereal capture (filter=sip)
No. Time Source Destination Protocol Info
69 23.468893 172.17.18.126 172.17.18.50 SIP/SDP Request: INVITE sip:172.17.18.50;user=phone, with session description
70 23.655310 172.17.18.50 172.17.18.126 SIP Status: 100 Trying
71 23.656162 172.17.18.50 172.17.18.126 SIP/SDP Status: 180 Ringing, with session description
73 23.722714 172.17.18.50 172.17.18.126 SIP/SDP Status: 200 OK, with session description
74 24.074669 172.17.18.126 172.17.18.50 SIP Request: ACK sip:[email protected];user=phone
78 24.231600 172.17.18.50 172.17.18.126 SIP/SDP Status: 200 OK, with session description
79 24.273585 172.17.18.50 172.17.18.126 SIP/SDP Request: INVITE sip:[email protected];user=phone, with session description
81 24.274462 172.17.18.126 172.17.18.50 SIP Request: ACK sip:[email protected];user=phone
84 24.475305 172.17.18.126 172.17.18.50 SIP/SDP Status: 200 OK, with session description
86 24.672693 172.17.18.50 172.17.18.126 SIP Request: ACK sip:[email protected];user=phone
240 29.583829 172.17.18.126 172.17.18.50 SIP Request: BYE sip:[email protected]
241 29.673022 172.17.18.50 172.17.18.126 SIP Status: 200 OK

 

[Anonymous]

http://www.faqs.org/rfcs/rfc3362.html is some more info for ya,

T38 does not ride on top of any voice codec. More often than not it kicks in as a result of a re-invite.

i.e.

1. Device A calls Device B.
2. RTP media session is established using voice codec (g711, g729 etc).
3. Device B detects the FAX pre-amble.
4. Device B issues a re-invite back to Device A with T38 directives in the SDP message.
5. T38 fax media session is establish and voice stream is muted.
6. Device B detects end of fax and issues a re-invite back to A for voice.
7. RTP media session is re-established using voice codec.

In the above scenario if device A did not support T38 it would have returned a 606 after step 4, resulting in the fallback RTP media session (using g711, g729 etc) being used to send the fax payload.

So having said that, i have to check but I am not sure if 3cx supports G711 if it does it should work, but I am not sure if they yet support fax.

Another thing you might look at is the SIP ports, that you do not have a conflict.