FAX Problem

[rwalland]

Hi,

We had FAX problems with Quadros or ITSP ever since. I can not say where exactly is the problem so I'll try to solve it here.

Users complain that they can recevie and send faxes only to specific numbers and can't receive and send to another numbers. It is really anoying. I've managed to catch a complete procedure of the FAX session and submited the whole issue to Epygi support. They found out that on this specific case the remote party is always answering with codec G723 which Quadro doesn't support and the remote party gets a "Line disturbance" message on the FAX machine. From the ITSP I've got the answer that the problem could be that the end number was never forwared to the destination due to the country code, because that spcific call was to another country.

I find the Epygi support explanation logical as I've seen to logs my self. What can be done about the G723 issue?

Does anybody have any other ideas?

Thanks,

Robert

[KSComs]

Force own codecs on the extension....

That might solve the situation and force the other end to increase the codec to G711....

Kev

[rwalland]

Hi,

Just wondering... Will be there any support for the G.723 codec from Epygi in the future?
Becuse I see a real issue when we do not manage to fix the fax problem. As I hear there are any or really a small amount of problems with Cisco and other equipment, but also it depends a lot form ITSP configuration of their network.

Regards,

[davrays]

I am not sure what G.723 codec is doing with FAX... Quadro had G.723 codec implemented, but we removed that, as it was not widely used (actually was not used at all), and costed us (and coustomers) monay for the license. You can still buy G.723 license separately for some of the Epygi products.

But... I cannot understand how G723 is connected with FAX. Can you please write the ticket ID here, so we can look?

[rwalland]

Hi David,

The ticket ID is 7076.

Regards,

[davrays]

Robert, I looked into that ticket and the logs... The only thing I can tell - the SIP server you are using has absolutely illogical behaviour (after 2 seconds of the successful call establishment with G.729, it tries to change the codec to G.723, which is absolutely senseless - note that G.723 has nothing to do with FAX, so it has no need to chnage the codec to G.723).

Quadro rejects the attempt to chnage codec, and the call it closed.

Now, there are two ways of fixing this:

1. Buy and install G.723 license on the Quadro (btw, first you need to contact Epygi sales and find out if that license can be sold for your device). This is definitely not the preferred way, because even if you install that codec, there is no guarantee this SIP server will not present new surprises.

2. Go to that SIP server's configuration, and fix that. I have strong feeling that this server is something experimental, and it really works as something not mature (beta-product). They should be able to fix the stupid behaviour of their server (as soon as their device detects it should receive FAX, it should change the codec to PCMU/PCMA or T38, but not to G.723).

3. Change the ITSP to something more mature and tested.

Best regards,
David

[rwalland]

Hi David,

I've opened a new ticket ID 7387.

Please check,...

Thanks and regards,

Robert

[davrays]

Ok, I looked there. In this case the situation is completely different (I suppose your ITSP has fixed something).

In this case there is no serios problem in SIP conversations. I suspect the problem could be in the bug in VBD handling, which we found in Q4x-5.1.18 and Q2x-5.1.19 releases. The problem could be that Quadro is not switching OFF the voice activity detection (VAD) on the call, and sending the RTP "silence packets", which is not allowed during FAX transmission (but is completely normal during normal voice call).

Our TSS guys will give you 5.1.20 test image for Q2x, which have this issue fixed. If my assumption is right, this image will solve this new problem.

Best regards,
David