Re: Hylafax without modems - SIP?

On Tuesday 26 Jan 2016, Gary Stainburn wrote:
> I've just had to replace my Hylafax server as the cooling fan in the rack
> case has died and could not be replaced.

Who told you that?  They obviously weren't trying very hard!  A fan ought to 
be pretty easy to replace .....  At the very worst, it might require some 
light metalwork and maybe the addition of a power supply.  Where there's a 
will, there's a way .....
 
> My box runs three fax modems, one for each of the original 3 fax machines
> that got skipped years ago.
> 
> This means that I now have 3 lots of:
> 
> USB to seral converter (new box doesn't have any COM ports.
> 9pin->25-pin serial cable
> Modem
> power supply
> phone line
> analogue port on our Mitel 3300 controller
> 
> I was wondering if there a better way?

You might be better off with a dedicated fax modem card that plugs into a PCI 
or PCI Express slot.  If your Mitel system can do ISDN, then so much the 
better  (you can get 30 separate conversations down one ISDN line).  Or even a 
PCI multi-serial-port card.

> I've done lots of Googling and there is a lot of conflicting - and mostly
> very old - information out there.
> 
> Does anyone have any more up-to-date opinions or advice on doing this?

The information is conflicting because sometimes it works and sometimes it 
doesn't, and experiences vary.

UDP, which is the transport layer upon which SIP rides, doesn't mind dropping 
the odd packet to keep things flowing smoothly  (earning it the nickname 
"Unreliable Datagram Protocol").  That's fine for voice, which has plenty of 
redundancy; but not OK for fax, which has a timing signal embedded into it and 
barfs over dropped packets.

In a pessimistic vision of an ideal world, fax over SIP simply should not 
work; in an optimistic vision of an ideal world, it absolutely should work.  
And the ones who shout the loudest often either have never tried it, or have 
an agenda to push.  In real life, what actually happens is somewhere between 
these two extremes.

And the information is mostly very old because little has changed in the 
meantime .....  The best advice I or anyone can give is still "Try it, if you 
must, but don't be too disappointed if it doesn't work".


> Most of the concerns about reliability were based on IP latency, but my fax
> server and my Mitel controller are both on the same Procurv Gigabit switch
> so hopefully that would be quick enough

Yes, but you don't know what the rest of the Internet beyond your Procurv 
switch is going to do to your packets, if they have to leave the safety of 
your LAN .....


For what it's worth, I've got away with plugging a fax machine into a 
Grandstream HandyTone 286 analogue telephone adaptor plugged into an Asterisk 
server, using its own connection straight to the switch as opposed to the 
little switch built into the SIP phone on his desk.  But it wasn't really used 
for anything mission-critical; just to make a tie-wearer feel important enough 
to have his own fax machine in his office.

-- 
AJS
(Originating address does not accept e-mail.  Insert a figure "one" before the 
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 [email protected] < /dev/null
  *To learn about commercial HylaFAX(tm) support, mail [email protected].*