Difference between revisions of "Fax over VoIP"

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<big>'''Fax over VoIP is not reliable and does not work most of the time.'''</big>
[[File:evil_fax.png|right]]<big>'''Fax over VoIP is not reliable and does not work most of the time.'''</big>


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


Wide explanation lies in technology mismatch between FAX and VoIP as explained in Steves' Underwood article [http://www.soft-switch.org/foip.html here].
The broad explanation lies in a technology mismatch between FAX and VoIP, as explained in Steve Underwood's article [http://www.soft-switch.org/foip.html here].


Steve Underwood developed SpanDSP package which helped to implement FAX support into Asterisk, Freeswitch and other open-source VoIP platforms.
Steve Underwood developed the 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:
The T38 protocol is supposed to work reliably over VoIP, but the problems with this protocol are the following:


# Different hardware vendors do not follow standards and T38 implementation on various hardware is mostly broken.
# Different hardware vendors do not follow standards and T38 implementation on various hardware is mostly broken.
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<br><br>
<br><br>
== Update 2009.12.08 ==
=See also=


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.
<br><br>
----
See also:
* [[Send_Receive_Fax-T38 | Send Receive Fax over T38]]
* [[Send_Receive_Fax-T38 | Send Receive Fax over T38]]
* [[Fax is not received]]
* [[I have a problem with Fax]]
* [[I have a problem with Fax]]

Latest revision as of 19:02, 2 September 2013

Evil fax.png

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

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

The broad explanation lies in a technology mismatch between FAX and VoIP, as explained in Steve Underwood's article here.

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

The T38 protocol is supposed to work reliably over VoIP, but the problems with this protocol are the 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.




See also