Re: [hylafax-users] faxing over sip

[A J Stiles <hylafax_resp@xxxxxxxxxxxxxxx>]

On Friday 23 Nov 2007, Lee Howard wrote:
> A J Stiles wrote:
> >A fax is just a collection of zeros and ones.  These are conventionally
> > sent over a circuit-switched analogue connection using a modem.  There's
> > no real reason why the raw zeros and ones that make up a fax image
> > shouldn't be sent over a packet-switched digital connection.  In
> > practice, that doesn't happen; and they end up being transformed into a
> > different stream of zeros and ones, representing the sounds that would
> > have been made by a modem had it been fed the original zeros and ones.
>
> Essentially this is true.  The fax image and all of the fax protocol
> communication is digital (ones and zeros).  Because fax predates the
> internet and because the PSTN was (and still is) more pervasive, this
> digital information was originally modulated (into analogue audio) and
> "reliably" transmitted over the PSTN.  Since then we now very often see
> (and use) digital PSTN circuits, but instead of an analogue audio stream
> a digital representation (usually uLaw, alaw, or slinear) of that audio
> stream is communicated over the circuit.

Is there a protocol where you take the raw zeros and ones that would have been 
sent to the fax machine's modem, bundle them up into packets, send the 
resultant packets over a packet-switched network and recreate the image "at 
leisure"  (i.e., not relying on the carrier frequency or bit rate for timing; 
if necessary, we can buffer it and play it back at a fixed rate)  from the 
reassembled packets at the far end?  Because it seems to me that this would 
be the best way to get fax working properly with packet-switching.  If SIP 
can handle other types of packet beside audio, so much the better.

-- 
AJS
(insert figure one before at sign if replying off-list)


____________________ HylaFAX(tm) Users Mailing List _______________________
  To subscribe/unsubscribe, click http://lists.hylafax.org/cgi-bin/lsg2.cgi
 On UNIX: mail -s unsubscribe hylafax-users-request@xxxxxxxxxxx < /dev/null
  *To learn about commercial HylaFAX(tm) support, mail sales@xxxxxxxxx*