[VoiceOps] Dynamic T1 Faxing over IP

John Osmon josmon at rigozsaurus.com
Fri Dec 17 01:27:08 EST 2010

On Wed, Dec 15, 2010 at 04:53:54PM -0600, Jeff Anderson wrote:
> We are experiencing a fair amount of heart burn attempting to support faxing
> over our Dynamic T1 product. Some customers it works great and others have
> frequent problems.

A little dated, but decent:

As you've seen -- it *can* work.  But the heartache and pain is
unbelievable in the real world when you can't control the entire
conversation (both FAX machines *AND* the network between them).

Part of it lies in the speeds the FAXes try to negotiate over a
G.711 link.  If you can convince people to set their FAXes to 9600,
you'll get better results.

Another issue is that FAXes send image info inside a continuous signal
envelope -- if there is any interruption (lost packets), they drop the
connection.  You don't just lose part of the image, you lose the rest of
the transmission.  

Other issues crop up as well -- but speed and minor interruptions are
the big killers of FAX.

T.38 should help -- by terminating the envelope in the ATA, then
transporting the image info packetized, and rebuilding an envelope at
the other end -- but the myriad of T.38 implementations/versions make it
difficult to trust that it will work.

In my former life, we did as many here suggest -- get a POTS line for
people that *must* have FAX/Modems running.  They'll thank you in the
long run.

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