Mailinglist Archive: opensuse (878 mails)

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Re: [opensuse] Signing PDFs
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On 2015-08-06 13:46, Anton Aylward wrote:

I have a VoIP service. I don't know if it will work with FAX. I
haven't had a fax machine. ever.

Some time ago I looked at asterisk and faxing, but only in theory, I
had no chance to try it. Googling I just found a document:

http://www.voip-info.org/wiki/view/Asterisk+fax

«Across the Internet even a G.711 codec fax transmission is
unpredictable. An excellent discussion of why faxing and modems don't
work well over VoIP can be found here. However, people often get
perfectly good results on lightly loaded LANs. It still isn't perfect,
as a burst of data on the LAN can still upset things, but some people
get results they can live with.»

That "here" is :

http://www.soft-switch.org/foip.html

Faxing over IP networks


«FAXing over VoIP networks doesn't work. You can sometimes arrange
things so a fairly high percentage of FAXes get through OK. You can
occassionally create setups that work 100% of the time. These are rare
and unrepeatable setups. You need to use a proper FAX over IP
protocol, such as T.38, to achieve consistent reliable FAXing across
IP networks.»

...

«Sending FAXes over VoIP networks usually fails. It is human nature to
look for simple reasons for that, and simple cures. In reality, there
are a number of reasons, and no certain universal cures. VoIP networks
are designed to do a good job with speech. Carrying any sound other
than a single voice speaking is not generally a system requirement. It
shouldn't be too surprising if it works rather poorly.»


The documents discuss how to do it, but setting up an asterisk server
(plus hardware) is not trivial. You rather need access to a gateway
service.


Have a look in the second doc to the paragraphs after «FAX over IP
(FoIP) specifications»

«T.37 defines a procedure for receiving a FAX at a gateway; making an
e-mail message, containing the FAX as an attachment; sending it to a
remote gateway; and dialing out and delivering it from the remote
gateway to the destination machine. It might optionally be delivered
as an e-mail with a FAX attachment directly to the recipient's e-mail
box. Also, FAXes might be sent directly to the store and forward
system from a sender's e-mail box, for delivery to a dialed FAX number.»

«T.38 is the real-time FAX over IP protocol. This means it is designed
to work like traditional FAXing. You call another FAX machine, and
send the FAX as you wait. Either FAX machine could be a traditional
FAX machine connected to the PSTN, an ATA box, or similar; it could be
a FAX machine with an RJ-45 connector plugged straight into an IP
network; it could be a computer pretending to be a FAX machine.»

But that assumes you have the hardware. Maybe it could be possible to
design a software only implementation :-? I don't know. I think not.


I think it must be about a decade since I last sent a fax.

I had to routinely send a fax a month for my mother medicines, till
she died. After that I haven't tried, but I still have the hardware
and software. However, now I have fibre telephone, some kind of VoIP,
I don't know if it would work. My guess is "no".

- --
Cheers / Saludos,

Carlos E. R.

(from 13.1 x86_64 "Bottle" (Minas Tirith))
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