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: http://www.soft-switch.org/foip.html 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.