Fax outbound interrupted

[tim942]

All,

I have an issue that I am sure I will get some heat about my configuration, I am using Sangoma's Netborder Express (unsupported by 3CX) successfully for the most part. The inbound faxing into 3CX has been working wonderfully and as expected for the last year and a half. In the last week, I picked up a Cisco SPA 112 (again, unsupported by 3CX) and I am trying to make it work, but I am getting about 7 seconds of dead air right after the outbound fax tries to connect. Connecting into the Fax machine from an outside line seems to be completely normal.

I have been going through any documentation I can find for the Cisco, Sangoma, and 3CX I can find, and I can't find where the disconnect is. Via Wireshark, the normal G711u call starts, when the fax tones are detected, a reinvite to the T.38 protocol starts, then the 3CX server waits 7 seconds before reconnecting (but now the whole fax session is fubar'd as the fax machine doesn't acknowledge it as a fax.). I am seeing the normal INVITE, OK, and ACK that I think I should be seeing.

Putting the NBE in debug, I see it is communicating through 3CX normally, but then the logs just stop for 7 seconds before "CONNECTED" (it was already connected without disconnecting). I'm running out of things to check, hostname check was never enabled, and Comcast's Adtran has to be configured, or else how could it connect at all? I might be able to pull a pcap out of the NBE.

Also, I believe that the Cisco's configuration is mostly correct as I can fax to the default 888 perfectly fine and it will receive from an outside number without this hiccup.

Any ideas or suggestions would be appreciated.

Excerpt from the NBE debug:
2017-07-26 16:41:44:028 -0500 [2196:4496] INFO - netborder.sip.message : RECEIVED SIP MESSAGE (REQUEST) via UDP from %PhoneServer%:5060 :
ACK sip:NetborderExpressGateway@%PhoneServer%:5066;transport=udp SIP/2.0
Via: SIP/2.0/UDP %PhoneServer%:5060;rport=5060;branch=z9hG4bK-524287-1---931d265687194166
Max-Forwards: 70
Contact: <sip:90001@%PhoneServer%:5060>
To: <sip:%CalleeNumber%@%PhoneServer%:5066>;tag=ds-440d-98c1e342
From: <sip:%CallerNumber%@%PhoneServer%:5066>;tag=5708c305
Call-ID: mm141sz65DcSyr7tr15q1w..
CSeq: 1 ACK
User-Agent: 3CXPhoneSystem 15.5.1694.0 (1587)
Content-Length: 0



2017-07-26 16:41:44:299 -0500 [2196:7300] INFO - netborder.media.sangoma.endpoint.device : disable echo canceller tone detected
2017-07-26 16:41:44:300 -0500 [2196:7300] INFO - netborder.media.sangoma.endpoint.realtime : stopping VAD.
2017-07-26 16:41:44:300 -0500 [2196:7300] INFO - netborder : stop voice activity detection (VAD).
2017-07-26 16:41:44:300 -0500 [2196:7300] INFO - netborder.media.jitterBuffer.simple : , ept-id=b2(B2 - A101_digital)di1(B2I1)-c23, name=Sangoma -> RTP enabled FAX mode
2017-07-26 16:41:44:555 -0500 [2196:7300] INFO - netborder.media.sangoma.endpoint.device : disable echo canceller tone detected
2017-07-26 16:41:44:556 -0500 [2196:7300] INFO - netborder.media.sangoma.endpoint.realtime : stopping VAD.
2017-07-26 16:41:44:556 -0500 [2196:7300] INFO - netborder : stop voice activity detection (VAD).
2017-07-26 16:41:44:556 -0500 [2196:7300] INFO - netborder.media.jitterBuffer.simple : , ept-id=b2(B2 - A101_digital)di1(B2I1)-c23, name=Sangoma -> RTP enabled FAX mode
2017-07-26 16:41:51:459 -0500 [2196:4976] INFO - netborder.pstn.sangoma.isdn.channel : Channel[b2(B2 - A101_digital)di1(B2I1)-c23]; State[CONNECTED] Disabling fax tone detection
2017-07-26 16:42:03:372 -0500 [2196:7300] INFO - netborder.media.rtp.JRtpEndpoint.device : Sent 1000 packet(s)
2017-07-26 16:42:03:712 -0500 [2196:7300] INFO - netborder.media.rtp.JRtpEndpoint.device : Received 1000 packet(s)

 

[tim942]

I seem to have found a work around for the moment, just turn T.38 support off on the NBE Gateway! Oddly enough my faxes are working perfectly fine on G.711u and I no longer get any cut offs during the fax. I think the 7 second interruption was more in my head, I think it was part of normal fax communication, however there is no more re-invite, no delays, no poor connection messages.

 

[tim942]

I think the baked in fax server in 3CX does not like the G.711u codec from NBE/PRI (I enabled the beta feature since it is available). The fax errors out about twenty seconds in after the "Fax exchange" completes. I will leave fax number pointed at the fax machine for now.

Faxing from the fax machine to the fax extension works fine and you can see it negotiating versions, which it doesn't do for the NBE via G.711u.

Excerpt from 3CXIVR.log
28/07/2017 08:11:21.769 [00000a34] [FAX] Probing voice for 10 seconds
28/07/2017 08:11:24.601 [00000538] [FAX] Set rx type 0
28/07/2017 08:11:24.601 [00000538] [FAX] Set tx type 4
28/07/2017 08:11:24.601 [00000538] [FAX] VOICE mode selected!
28/07/2017 08:11:27.261 [00000538] [FAX] Set rx type 4
28/07/2017 08:11:27.261 [00000538] [FAX] Set tx type 0
28/07/2017 08:11:30.719 [00000664] [FAX] Set rx type 0
28/07/2017 08:11:30.719 [00000664] [FAX] Set tx type 4
28/07/2017 08:11:33.381 [00000538] [FAX] Set rx type 4
28/07/2017 08:11:33.381 [00000538] [FAX] Set tx type 0
28/07/2017 08:11:36.839 [00000664] [FAX] Set rx type 0
28/07/2017 08:11:36.840 [00000664] [FAX] Set tx type 4
28/07/2017 08:11:39.501 [00000538] [FAX] Set rx type 4
28/07/2017 08:11:39.501 [00000538] [FAX] Set tx type 0
28/07/2017 08:11:42.959 [00000664] [FAX] Set rx type 0
28/07/2017 08:11:42.959 [00000664] [FAX] Set tx type 4
28/07/2017 08:11:44.102 [00000538] [FAX] Set rx type 0
28/07/2017 08:11:44.102 [00000538] [FAX] Set tx type 1
28/07/2017 08:11:45.102 [00000538] [FAX] Set rx type 9
28/07/2017 08:11:45.102 [00000538] [FAX] FAX exchange complete
28/07/2017 08:11:45.102 [00000538] [FAX] Set tx type 9
28/07/2017 08:11:45.102 [00000538] [FAX] FAX exchange complete
28/07/2017 08:11:45.672 [00000a34] [FAX] Dropping call : after document timeout elapsed
28/07/2017 08:11:45.673 [00000a34] [FAX] VOICE Error receiving fax_1500939830_no22.tif: Disconnected after permitted retries