Fax over VoIP

Fax over VoIP is not reliable and does not work most of the time.

It is possible to get nearly 100% rate in rare circumstances but is very very low chance to get this.

Wide explanation lies in technology mismatch between FAX and VoIP as explained in Steves' Underwood article here.

Steve Underwood developed SpanDSP package which helped to implement FAX support into Asterisk, Freeswitch and other open-source VoIP platforms.

T38 protocol supposed to work reliable over VoIP, but the problems with this protocol are following:

1. Different hardware vendors do not follow standards and T38 implementation on various hardware is mostly broken.
2. Asterisk does not support T38 very well.

Update 2009.12.08

Digium anounced that old fax application/implementation is crap: http://lists.digium.com/pipermail/asterisk-dev/2009-December/041067.html

We will wait till their proposed new application will be fully tested and incorporated into Asterisk with good results.

After that we will implement it in to the MOR.

---

See also:

• Send Receive Fax over T38
• Fax is not received