[Asterisk-Users] FAX, IAX and *....Maybe I'm dreaming...:-)

Jim Flagg flaggj at comcast.net
Fri Dec 12 07:54:28 MST 2003

----- Original Message ----- 
From: "Dan" <dtoma at fx.ro>
To: "Asterisk Users" <asterisk-users at lists.digium.com>
Sent: Friday, December 12, 2003 8:25 AM
Subject: [Asterisk-Users] FAX, IAX and *....Maybe I'm dreaming...:-)

> It would be great if the IAX protocol will be able to tranfer fax data (even
> converted in another format) between Asterisk boxes, using low bandwidth
> codecs like GSM.
> I know that this is possible only with the G.711 now (passing faxes using
> the audio stream), but.... maybe in the future...some native support will
> permit this.

Sounds like you are thinking of something like T.38.  T.38 is a FAX over IP
protocol but my guess is that there would be licensing issues using it with

It probably would not be that hard for someone to come up with a completely 
open FAX over IP protocol.  A FAX over IP protocol would not have to
operate in real time like VOIP.  You could actually use acknowledge signals
and retransmit packets that are dropped so that you get a perfect fax
transmission. This can not be done with VOIP because by the time you
realize you have missed a packet it is too late to re-transmit the packet.
With FAX over IP it just means it takes a little longer to transmit the page.
You could also design the protocol so that you could transmit at whatever
rate you wanted.  Slower links would use less bandwidth but take longer to

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