[cisco-voip] CUCM 10.x and RightFax SR140 v10

[Daniel Pagan]

That can be a possibility for Ed, assuming RightFax is playing the CNG. However, I would add that PRACK doesn't automatically grant early media. The only time PRACK helps with establishing early media is in a call flow with an outbound delayed offer INVITE and an inbound 183 provisional that contains an SDP offer. In that scenario, the only way to send an SDP answer to the offer before the 200 OK is through PRACK, but again it requires a specific flow for PRACK to accomplish it. I would also imagine the call would need to progress past the connected stage in order for the fax to be successful. Without being in a connected state, the OGW and TGW involved the fax call wouldn't be able initiate fax protocol switchover, making me think that early media wouldn't resolve the issue in this case. 

Perhaps SuperG3 is involved here, and the terminating fax machine is attempting to switch to SG3. Technically it should timeout and revert back to G3 but I've seen this cause issues. If the issue is with SG3 destinations, one could try suppressing the ANSAM using the sg3-to-g3 command in IOS. Here's how you quickly identify SG3 - it's an audio file from pcap off a SG3 fax machine connected to a VG2XX.

SuperG3 ANSAM:
https://www.dropbox.com/s/20xhtyc1qcrku4r/ANSam%20Phase%20Reversal.mp3?dl=0

That clicking you hear is the phase reversal - standard G3 doesn't contain that "clicking". If you hear this, you can give ANSAM suppression a shot.

Finally, if anyone needs a recording of a full fax transmission to use as sort of a baseline, here you go:

Originating GW - Audio From PCAP:
https://www.dropbox.com/s/am0lpwsfai8nq6y/FaxCapture%20-%20OGW%20-%20DPagan.mp3?dl=0

Terminating GW - Audio From PCAP:
https://www.dropbox.com/s/j9tqahjfaxqf29r/FaxCapture%20-%20TGW%20-%20DPagan.mp3?dl=0

Open both audio files in Audacity to play both the sending and receiving fax machine tones for a single page fax. This was recorded while using modem pass-through and, when played in Audacity, you can track the entire exchange at your own pace (CNG to CED, DIS to DCS, etc). Note that you won't get the same results using any type of fax relay since PCM audio isn't being transmitted, but the flow remains the same.

Hope this helps.

- Dan

-----Original Message-----
From: NateCCIE [mailto:nateccie at gmail.com] 
Sent: Tuesday, August 18, 2015 6:45 PM
To: Daniel Pagan <dpagan at fidelus.com>
Cc: Countryman, Edward <Edward.Countryman at PresenceHealth.org>; cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] CUCM 10.x and RightFax SR140 v10

I wonder if you have prack enabled if it is a SIP trunk so that early media can be cut through before the connect. 

Sent from my iPhone

> On Aug 18, 2015, at 3:52 PM, Daniel Pagan <dpagan at fidelus.com> wrote:
> 
> "there’s no way to inject the CNG tone"
> 
> Sorry - I should be more specific. What I mean to say is that there's no way to inject the tone from a Cisco device, but don't know of the capabilities of the RightFax server. 
> 
> I'm curious to know if you find an option for generating a CNG tone on RightFax.
> 
> Hope this helps.
> 
> - Dan
> 
> 
> 
>> On Aug 18, 2015, at 5:43 PM, Daniel Pagan <dpagan at fidelus.com> wrote:
>> 
>> there’s no way to inject the CNG tone
> 
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