[Asterisk-Users] How does Vonage support fax machines?

[JD Austin]

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: jd at twingeckos.com
http://www.twingeckos.com
phone/fax: 480.288.8195