About Internet Fax

The hottest trend in fax communications since Group 3 fax is Internet Fax or IP Fax. Group 3 fax has traditionally run over telephone networks and has become hugely successful. It is estimated that over 100 million Group 3 fax machines are installed worldwide and they can all communicate with each other using the Group 3 fax recommendations T.4 and T.30 which were developed by the ITU-T.  In recent years, Fax over IP has become a growing part of fax communications due to growing demand for Fax over IP within enterprises and the acceleration of related trends such as SIP Trunking and IP fax in the cloud. 

Human Communications worked closely with other leading companies in the fax and messaging industries to develop standards-based Facsimile over the Internet and IP fax. James Rafferty of HC was a chair and co-chair of the Internet Fax working group of the Internet Engineering Task Force and worked with his former co-chair Dave Crocker of Brandenburg Consulting to lead the working group in developing the first set of Internet Fax standards. James was also a major contributor to the other major fax standards group, the ITU-T Study Group 8 (now Study Group 16), whose Question 4 efforts on Internet fax were led by Rapporteur Herman Silbiger of Applicom.

In January, 1998, the two standards bodies (the IETF and ITU-T) decided to work together to ensure that a unified set of Internet Fax standards were developed. In March 1998, the IETF published the first set of standards for Internet Fax, which define the service, file formats and addressing methods for the "Simple Mode" of Internet Fax via e-mail as RFCs 2301-2305. In June 1998, the ITU-T approved the T.37 recommendation, which references the IETF RFCs for its definition of the "simple mode", thus producing a unified standard. Both the IETF and the ITU also plan to work on extensions to the simple mode. In addition, the ITU-T completed a recommendation for Real Time Facsimile Over the Internet, known as T.38, which was also approved in June 1998.

In the years since this time, the ITU-T has continued to fine tune the T.38 recommendation and the UDPTL protocol contained within T.38 has become the favored approach for sending Fax over IP, especially when Fax over IP is being used along with Voice over IP communications.   There has also been interworking activities conducted by the SIP Forum which have resulted in updates to the T.38 recommendation.  

A list of Internet Fax Resources is provided below. 

Internet Fax Resources

1.  What are the standards for Internet Fax? 

A.  Real Time Internet Fax

 The most current versions of the ITU-T recommendations (standards) for T.38 are:

In recent years, the ITU-T has made downloads of their recommendations freely available. 

B.  Store and Forward Internet Fax

The original RFCs for IETF Internet fax are available for downloading from the IETF Web Site as RFCs 2301 to 2306.  Of particular interest, please see: 

In addition, the IETF Fax working group continued its work and additional RFCs were produced at a later date, which included: 

In addition, developers who are interested in the Extended mode of Internet Fax (RFC 2532) should also download the related specifications RFC 2530 and RFC 2531.  

There are also several related Content Negotiations RFCs which are RFC 2506, 2533 and 2534.  They specify a media features framework, definitions and syntax which can be used for content negotiations between Internet Fax servers. 

2.  Are there courses available explaining Internet Fax? 

Human Communications developed a two-day Internet Fax Technology Workshop which reviews the content of the real time and store and forward versions of IP fax.  If your company is interested in such a class or would like to purchase a class workbook, please contact us via email (jayAThumancommDOTcom). 

3.  Is there information that provides background on how the IP fax standards were developed? 

Yes, during the time between 1996 and 1999 when most of the development took place, the Human Communications Digest standards newsletter covered developments in the IETF and ITU-T in detail.   If you'd like to purchase hard or soft copies of the newsletters from this period, please contact us via email. 

4.  Is there any active standards work for IP Fax at this time?  

The IETF Internet Fax working group closed in the 2003 time period.  The ietf-fax mailing list is still open for related discussions and can be accessed at the link contained here

The ITU-T Study Group 16 continues to work on facsimile for both IP and circuit-switched fax.  This is the group that has approved the most recent updates to T.38.   Facsimile protocols and maintenance of protocols such as T.38 are studied under Question 15.   

5.  Have there been Internet Fax interworking events?  

The Internet Mail Consortium and the Electronic Messaging Association were among the industry groups which helped sponsor interworking events for T.37 and the IETF RFC for Internet Fax.  The major events were conducted under the name of Fax Connect. 

On December 1-2, 1998 in San Jose, seventeen companies kicked off the standards based Internet fax industry by conducting interworking tests for products and services that support ITU-T T.37, IETF RFC 2305 (the Simple Mode of Internet Fax via E-mail) and RFC 2301 (TIFF profiles for facsimile). In addition, James compiled a matrix to document how many implementaions are supporting the 30 identified features of RFC 2305 and for which features interworking was tested. For IETF standards, one of the requirements in his role as Internet fax chair is to document successful interworking between at least two independent implementions in order to support progression to the IETF "draft standard" level.  To see the results of Fax Connect I, please read the Fax Connect I report.

On May 18-19 1999, the next round of Fax Connect testing took place in San Jose and Tokyo (on May 19,20) at Fax Connect II. This unique engineering event was held simultaneously on 2 continents, as Internet fax interoperability testing based on RFC 2301-2305 and T.37 were taken to the next level. The report can be found at this link.

If you are an Internet fax vendor that wants to test your own product in-house, you may want to download a blank copy of the RFC 2305 Interworking matrix). In addition, we now have added the RFC 2301 matrix for TIFF profiles and the RFC 2303-2304 matrix for Offramp addressing.  

6. Is there an Industry Association for Internet Fax?

There were a few industry associations established in the US and Japan in the early days of IP fax.  As of this writing, the most active industry association for Fax over IP is the SIP Forum, which has a task group for Fax over IP.   HC founder James Rafferty has been active in various SIP Forum activities, including the Fax over IP working group. 

7. I want to be able to receive standards-based Internet faxes in my e-mail.  Can I do that today?

If your e-mail system supports the reception of MIME attachments, you should be able to receive Internet faxes that are compliant with T.37 and RFC 2305. Jump to our Internet Fax resources page for more details and to download a viewer.

8. Are there an open source versions of Internet fax software available?

There are open source versions of T.38 software which are available.  Some examples include:

Asterisk -  Asterisk is an open source IP PBX.   There are several vendors who build fax capabilities for Asterisk.  See the following link for details and limitations.   

Free Switch - Free switch is an open source softswitch which supports numerous applications.  There are a number of companies who have built applications based on Free Switch.  An example of a free and open source implementation of T.38 based on Free Switch is  http://ictfax.org/

9.  Are Internet Fax compatible TIFF viewers available? 

Most fax software has support for multi-page TIFF-F files.  TIFF-F is defined in RFC 2306 as noted above, but the "S" profile of TIFF contained in RFC 2301 or  RFC 3949 for Internet Fax is technically identical to TIFF-F.  The distinguishing aspect of TIFF-F from most .tif files is that TIFF-F has support for multiple pages, whereas many image formats, including certain flavors of TIFF, only support one page for viewing or printing. 

10.  Pictures of HC founder James Rafferty at the meetings where the original T.37 and T.38 Internet Fax standards were approved. 

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