Traditional faxing represents a significant chunk of a company’s communication expenses. An estimated 40% of calls between the United States and Europe at any given time are fax calls; that figure moves toward 50% between the United States and Asia. Faxing over standard phone lines thus results in a large quantity of expensive international calls.

Faxing over the Internet can eliminate those hefty long-distance charges. When you send a fax over IP, the fax data is transmitted as packets through the public Internet or company Intranet instead of the PSTN (Public Switched Telephone Network). If the fax transmission ever has to go through the PSTN (i.e. if the destination fax is a traditional fax machine), it’s only for the local portion of the call. Companies can send faxes throughout their own private IP network for free.

There are two methods for faxing over the internet: Fax over IP (FoIP) and Fax over VoIP. FoIP represents the only way to reliably send a fax through the IP network, although there are plenty of tech-savvy individuals who can successfully fax over VoIP. Both methods are covered below.

Fax over VoIP

You might expect to be able to send faxes over your VoIP line, just as you can over a traditional phone line. However, it’s not that simple. VoIP lines are not really designed for modem use. For starters, they typically utilize low bitrate codecs to maximize the number of voice calls. These low bitrate codecs cannot transmit modem signals properly (i.e. an 8 kbps G.729 codec cannot convey a 9.6 kbps fax modem signal correctly). Secondly, there’s the issue of packet loss. Losing packets isn’t that significant in voice calls, since you can still understand what the other person is saying. However, data dropout is a different matter. A few lost packets can lead to an error message or dropped call when faxing.

Of course, faxing over VoIP can be done, and both Vonage and AT&T CallVantage offer fax services with VoIP. Here are a few recommended steps:

• You should set up the call using a 64 kbps codec. If you’re using Vonage, the dedicated fax line will use this rate. And with AT&T CallVantage, the second line uses this rate by default as well.
• If you can’t get access to a 64 kbps channel, set the BAUD rate on your fax machine to 9600 bps or lower.
• Set your resolution to standard
• Turn off ECM

Information Source

http://www.voipfrustration.com has information on how to change the settings on over 600 fax machines, and also includes a link to the fax manuals.

Fax over IP

Another faxing option is FoIP (or Fax over IP); this function is similar to Voice over IP, but is optimized for fax transmission. In this model, a fax is sent over the Internet to a fax server nearest the destination fax. Then the fax is transferred to a phone line and sent like a normal fax. Because the fax has traveled over the Internet for most of its transmission path, total transmission costs are much less than those associated with conventional faxing. The ITU has developed two standards for FoIP: T.37 and T.38. T.37 refers to a “store and forward” faxing, where the fax is delivered as an e-mail attachment and then delivered to the destination fax over the PSTN phone line. While this method lowers transmission costs, it cannot provide real-time verification that your fax has been properly received. If you’re used to walking up to a fax machine, sending the fax, and getting your confirmation printout, T.37 is not for you.

ITU’s T.38 standard provides real-time fax delivery over IP and works like traditional faxing. T.38 fax gateways are equipped to handle any delay, jitter, or packet loss in the packet network to minimize their effect on the fax transmission. The standard also reduces the bandwidth needed to send image data.

Information Source

http://www.allaboutfoip.com AllAboutFoIP.com has information about "foIP" (fax over IP) servers and services, post implementation technical support and VoIP compability questions.


See also:

• Digital Adapters
• IP Phones
• Service Providers
• Wireless

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