[Asterisk-Users] FAX over IAX

[Ben Klang]

I've personally had nothing but problems getting FAX to work over IAX. 
Some of my problems were resovled by tweaking echo cancellation and
jitterbuffer (I turned them both off essentially).  Keep in mind this is
on a local 100Mbit ethernet switch.  I can only imagine performance
degrades as latency and throughput decrease.

On a suggestion from Mark, I have begun testing with SIP, with some
favorable results.  One thing I noticed while testing with IAX is that
the Asterisk box closest to a DTMF source would mute the DTMF audio and
pass it out-of-band to the destination Asterisk box, where it would be
repeated, only at a fixed lenght.   So a 5 second DTMF tone would reduce
to an approx 1/3 second DTMF to the listening side.  I theorize that
some of the FAX tones were interpreted as DTMF and were thus mangled.  I
have not yet confirmed that theory.

In the end, I have found IAX completely unusable for FAX.  Generally I
would only be able to send or receive about a third of a page before my
machines gave up.  This was tested with both hardware FAX machines (2
brands) and 2 modems connected to desktops running FAX software.

I'll try to post again when I find out if SIP will work for me.  Hope
this helps.

-BAK
On Thu, 2003-04-03 at 11:20, Brian Jones wrote:
> You should be able to packetize your fax calls without any problems.  We have hundreds of fax and modem lines on MGCP IADs that connect to PRI gateways without problem, although I haven't tried with IAX.
> 
> Be sure to use G.711 codec and disable echo cancellation, and if your network is robust with low latency and jitter, you should be fine.
> 
> Brian
> 
> --------------------
> Brian F. Jones
> bjones at kancharla.com
> 256.705.5012
> 888.357.0500 x 5012
> --------------------
> 
> -----Original Message-----
> From: Brian J. Schrock [mailto:brians at columbus.rr.com] 
> Sent: Thursday, April 03, 2003 9:21 AM
> To: asterisk-users at lists.digium.com
> Subject: Re: [Asterisk-Users] FAX over IAX
> 
>  From what I have heard packetizing fax does not work well, does not 
> matter if it is IAX or SIP. I think that was straight from digium tech 
> support.
> 
> On Wednesday, April 2, 2003, at 09:53 AM, John Harragin wrote:
> 
> > Hi,
> >
> > We are looking at consolidating our lines with PRI. This will allow the
> > elimination of many fax lines. Some of them will be replaced with this 
> > type
> > of config ...
> > PRI * IAX * Channel-Bank FAX
> > We will have daggressor suppressor enabled. Is anyone doing this and 
> > should
> > I expect smooth operation?
> >
> > John
> >
> >
> > This e-mail was scanned and found clean by Monroe-Woodbury CSD 
> > Antivirus.
> >
> > _______________________________________________
> > Asterisk-Users mailing list
> > Asterisk-Users at lists.digium.com
> > http://lists.digium.com/mailman/listinfo/asterisk-users
> >
> >
> Brian J. Schrock
> Network Engineer, RHCE, CCNA
> Anistone Technologies
> Phone: 614-798-9106
> FAX: 614-573-7165
> 6926 Avery Rd.
> Dublin, OH 43017
> 
> _______________________________________________
> Asterisk-Users mailing list
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> http://lists.digium.com/mailman/listinfo/asterisk-users
> 
> _______________________________________________
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