Executive Summary Excerpts

from HC Standards Update Vol. 1

Facsimile Routing Standards and Practice

Facsimile routing has emerged in numerous surveys of business customers as being one of the main areas where the implementation of Group 3 fax on computers needs improvement. In 1996, the International Telecommunications Union has responded to this need by approving a new standard, the ITU-T T.33 recommendation on Facsimile Routing Utilizing the Subaddress. This standard is quite similar to an interim standard IS-141 on fax routing which was approved in 1994 for use in the United States.

The development of standards based fax routing is a major milestone for the fax industry. Standards based fax routing will enable fax messages to be delivered directly to recipients on Local Area Networks and fax mailbox systems. It will also be a key technology for customers that want to better integrate fax with other messaging technologies such as electronic mail and the Internet. This report addresses what these developments will mean for fax vendors and fax customers.

Technical Overview

The subaddress is an extension to the familiar telephone number that was devised in the 1980’s in preparation for a new era of extended analog and digital telephone networks. Support for a subaddress signal for local routing purposes was added to the Group 3 fax protocol in 1993 and refined in 1994. Since the subaddress is transmitted from the fax sending device to the receiver using the integrity mechanisms of the fax protocol, this transfer of routing information is highly reliable.

The T.33 recommendation was developed to standardize how components of telephone addresses may be transferred using the subaddress. Per T.33, a fax address consists of a telephone number plus an optional subaddress, separated by the # character. As a result, a full fax address can be entered from telephone or fax keypads in the form:

<telephone number>#<subaddress>

The telephone number is dialed and the subaddress portion (after the # delimiter) is transferred using the fax protocol. The most typical application of the subaddress will be to transfer a single "fax extension" (such as 1234), but T.33 provides rules on how to submit multiple extensions, secondary telephone numbers or combinations of these components. This address information can be decoded by a receiving fax device per the rules of T.33 and then used to enable routing of the fax message to the final recipient.

Applications Overview

The subaddress can be used to support many different applications which involve the routing of facsimile messages and the integration of fax with other messaging systems and the Internet.

Fax Routing on a Local Area Network - From a sending fax device, a fax message can be sent with a subaddress to a LAN-Fax server. The LAN-fax server can extract a list of one or more fax extensions from the incoming subaddress and then do a lookup in a table or directory service to find the network or e-mail addresses of the recipients. The fax message can then be transferred directly to the recipient. For example, John’s fax extension may be "1234" and his e-mail address equal to "John@abc.com". The subaddress provides a way to a fax user to send messages using a numeric fax address and then have them routed directly to John at his desktop e-mail address. ...

Routing to Secondary Phone Numbers and Extensions - ...

Universal Mailbox and E-mail/Internet Integration - ...

The correspondence between a fax address and an e-mail (or network) address as enabled by the subaddress is one of the key building blocks which will enable fax to be integrated with the other forms of messaging used in an organization.


The net result is that fax messages accompanied by a subaddress can be delivered on a Local Area Network, Wide Area Network or even via the Internet. .....

Summary of Vendor Plans

Human Communications conducted a survey among vendors in five segments of the fax industry on their plans for implementing the subaddress and the T.33 recommendation. Key results were:


Fax Industry Vendors - ....

In the very near future, the "well connected fax device" will need to be able to communicate both with fax machines and with users connected to the Local Area Networks and Wide Area Networks of an enterprise.

Fax Decision Makers in the Enterprise - The administrators and users in medium and large organizations are the ones who can gain the most benefit by implementing standards based fax routing technology. .....

Small Office and Home Office Users - Our recommendations to fax users in small offices or home offices (SOHO) are similar to those for larger organizations, but the scale of operation is smaller. Initially, we recommend that SOHO users plan to upgrade their fax machines, MFPs or computer fax products to include support for outbound use of the subaddress and T.33. ....

Future Directions

There is now additional standards work in progress will further extend the existing Subaddress capabilities and enable new applications. ......

##### End of Executive Summary #####

The text above is extracted from the Executive Summary of the first volume of Human Communications Standards Update on Fax Routing and Practice. Sections marked with "..." include further details in the report itself.

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