You can use the NVDetect stuff from Newman Telecom works with some
success (I had it working).
http://www.voip-info.org/tiki-index.php?page=NVFaxDetect
I think echo cancellation can play a factor too.
It isn't perfect though.. I had some page smearing, especially on the
first page but it worked ok.
They probably don't compensate for packet loss.
Their service isn't perfect either:
http://www.complaints.com/directory/2004/december/28/52.htm
JD
Deon wrote:
My boss is insisting we support fax, and I keep telling him that Fax over
IP is very unreliable and not recommended and his immediate come-back is
"Vonage does it." and it's very hard to figure out how.
I don't think Vonage does T.38, the Linksys/Sipura units they're using
doesn't support T.38 to my knowledge.
That means they have to be using G.711Ulaw to send faxes. But how do they
compensate for packet loss/jitter/etc.
In our test lab, the best we could get was 90% success at sending faxes.
It seemes to screw up the longer the transmission, ie page 1 was usually
ok, but page 2 and 3 and 4 was at serious risk. So if I bought a Vonage
adapter, can I send a 30 page fax? My best guess is they have high quality
voice T1's, like from an ILEC, usually more expensive, and when they sell
a "Fax Line" I noticed it's more expensive. Maybe they route all their fax
calls specifically out these high quality T1's that they own, so that they
can do some type of quality control.
My test lab was a private network, a Cisco 3640 connected to a local voice
PRI T1, and converting to SIP. Asterisk would push the calls to the Cisco
3640 and the Linksys PAP2 would register with Asterisk. All local. I then
tried several test faxes throughout the PSTN. Would it be better to plug
the voice T1 straight into Asterisk using one of Digium's cards?
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JD Austin
Twin Geckos Technology Services LLC
email: [EMAIL PROTECTED]
http://www.twingeckos.com
phone/fax: 480.288.8195
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