Fax Over IP - How Fax Services Are Being Modernized by IP

In all the excitement about traditional PSTN voice systems being replaced by VoIP, Fax seems to not have gotten the attention it deserves. Yet, in many ways converting old fax systems to a new one can save you a lot of money, just like VoIP can save you from unnecessary telephone bills. In this article, we take a look at how new protocols and devices are replacing the old infrastructure.

Old Fax systems use a standard formalized way back in the 1980s called T.30 which has seen worldwide adoption. Most fax machines you have seen use the T.30 protocol and two fax machines using the same protocol have no problems communicating with each other. But what happens when your organization switches to VoIP and gives up its telephone connection. We all know that fax machines have their own telephone number and rely on the PSTN system to operate. Is it possible to migrate the fax machines too?

Unfortunately, VoIP technology is uniquely suited for voice data. Meaning that certain optimizations that VoIP systems use for sound are very unsuitable for data transmission such as that contained in an image. The end result is most unsatisfactory. Therefore, we needed a new protocol to tell the encoders and intermediate points that the data coming through isn't web or voice data, but something else. In 1998, the T.38 protocol was released.

It's important to note that T.38 can't work on its own. We still need a protocol which constructs and sets up the call in the first place. This is typically the SIP protocol these days - a good example of why SIP is popular. It just sticks to doing what it does and lets other protocols handle the rest.

The FoIP system also uses UDP instead of TCP because certain acknowledgment and retransmission procedures required by TCP delay the Fax and may cause it to drop entirely. To compensate for the problems introduced by not using these techniques, the T.38 protocol sends redundant data to allow the receiving system to reconstruct the fax in case it didn't receive any earlier packets.

To use FoIP on your network, you need a fax machine with is T.38 enabled. Of course, this is true only if you actually have a physical piece of paper and need to quickly send it to someone who can't receive a scanned copy of it for whatever reason. Individual users can easily configure their computer systems to fax an image - simulating a T.38 fax machine.

And that's the great thing about IP. So many different ways to do the same thing!

Bhagwad is an expert consultant on Hosted Business IP PBX Services. He also specializes in Mobile VoIP PBX Services.