[asterisk-users] VOIP & PBX replacement suggestions?

[Lee Howard]

On 06/07/2012 06:18 AM, Daniel Seagraves wrote:
> On Jun 6, 2012, at 10:47 PM, Lee Howard wrote:
>
>> >  Unless you're going to move to an internet fax service provider you'll probably not want to attempt to switch your fax line to a VoIP line and still attempt to fax over it.  And even then, depending on how much fax traffic you have moving to an internet fax service provider may not save you any money.
> I thought that was what iaxmodem was for? Part of the plan here was to dodge buying serial cards or modem banks when we started faxing more.

IAXmodem was developed in order to make the modem hardware-agnostic.  In 
other words, iaxmodem functions independently from the hardware, but 
that doesn't mean that you can provide a suitable audio channel to 
IAXmodem without some kind of hardware.

Every once in a great while someone will come onto this mailing list or 
any number of others and announce that they've successfully got 
fax-over-VoIP going for them.  In almost all of those situations that 
I've been permitted to analyse they're simply getting lucky in that ECM 
(error correction) is saving them, the remote senders and receivers 
support a well-implemented ECM, and the jitter isn't too bad where ECM 
couldn't remedy things.  And I fully expect that at some point down the 
road things the VoIP provider will do things differently or the user 
will change some things on their network, and suddenly what used to work 
tolerably well for them will suddenly stop working.  Save yourself this 
headache.

So it doesn't matter what hardware you use: Digium, Sangoma, OpenVOX, 
etc.  But you'll need to use some kind of hardware to interface with 
your PSTN service for fax.

If your VoIP provider supports T.38 and if their T.38 implementation 
works with the T.38 implementation in t38modem or Asterisk 10 then you 
may be able to utilize one of those and avoid continued use of your PSTN 
fax connection.  Understand, however, that almost all fax failures that 
you may have after that change will not likely be able to be resolved on 
your end alone.  Nearly all fax protocol problems will have to be 
resolved by your T.38 provider, and depending on your relationship with 
them and the demand that you may have on high-reliability faxing this 
could be frustrating.

Thanks,

Lee.