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Versions: 00                                                            
Fax Working Group                                               Dan Wing
Internet Draft                                             Cisco Systems
August 7, 1998
Expires January 1999

            Expressing Fax Capabilities in Internet Protocols

Status of this memo

   This document is an Internet-Draft. Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups.  Note that other groups may also distribute
   working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
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   material or to cite them other than as "work in progress."

   To view the entire list of current Internet-Drafts, please check
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   (US West Coast).

Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

1.  Abstract

   This document describes how the DIS Standard Capabilities and
   Non-Standard Capabilities (NSF) of [T.30] can be expressed using the
   format described by the IETF Content Negotiation Working Group

   The format described in this document, and the format described
   in [FEATURE-ALGEBRA] is intended to be usable in many Internet
   protocols and by a variety of methods.  The specific methods
   are not described by this document.

2. Introduction

   To exchange documents between a sender and recipient it is important
   to know the display or print capabilities of the recipient.

   The fax protocol [T.30] has a long-established method of
   exchanging capabilities.  The fax protocol requires a realtime
   connection between the sender and receiver, and is not designed
   to be cached by the sender or to be shared with multiple senders.
   Additionally, the [T.30] capabilities exchange describes many
   data link layer specific information which is not applicable
   to an Internet application layer program.

   On the Internet, it is not expected that document exchange
   devices and software such as MUAs, printers, word processors,
   or PostScript will have knowledge of the fax protocol [T.30],
   except in the case of Internet Fax (IFax) devices themselves
   or MultiFunction Periphials (MFPs).

   Non-fax devices and software which creates, manipulates, or prints
   images are more likely to use capability expressions which are more
   portable across multiple devices than the capability expressions of

   The portion of the T.30 protocol used to indicate the
   capabilities of the recipient is the DIS Standard Capabilities
   (section of [T.30]) and the Non-Standard Capabilities
   (NSF, section of [T.30]) which is used for vendor-
   specific extensions.

   This draft is being discussed on the "ietf-fax" mailing list.  To
   subscribe, send a message to:
   with the line:
   in the body of the message.  Archives are available from

3. Mapping DIS

   The following DIS bits and their function are described in [T.30] and
   mapped using the descriptions in the following sections.  The
   following sections use ABNF [RFC2234] to describe the syntax.

     DIS bit number     T.30 use                          Section
     --------------     --------                          -------
           1            Reserved
           2            Reserved
           3            Reserved
           4            Reserved
           5            Reserved
           6            V.8 capabilities                  3.1
           7            256/64 octets preferred           3.1
           8            Reserved
           9            Polling                           3.2
          10            Receiver fax operation            3.1
         11-14          Data signalling rate              3.1
          15            Paper size                        3.3
          16            2D coding capability              3.1
         17-18          Scan line width                   3.3
         19-20          Page height                       3.3
         21-23          Scan line receive rate            3.1
          24            Extend field                      3.1
          25            Reserved
          26            Uncompressed mode                 3.11
          27            Error correction mode             3.1
          28            Must be 0                         3.1
          29            Reserved
          30            Reserved
          31            T.6 coding                        3.4
          32            Extend field                      3.1
         33-39          Reserved
          40            Extend field                      3.1
          41            Paper size                        3.3
          42            ?                                ?
          43            Paper size (inch/metric)          3.3
          44            Inch resolution preferred         3.5
          45            Metric resolution preferred       3.5
          46            Scan line receive rate            3.1
          47            Selective polling                 3.2
          48            Extend field                      3.1
          49            Subaddress                        3.6
          50            Password                          3.10
          51            Ready to xmit (polling)           3.2
          52            Reserved
         53-55          Binary File Transfer              3.7
          56            Extend field                      3.1
          57            Binary File Transfer              3.7
          58            Reserved
          59            Ready for polling                 3.2
          60            Character mode                   ?
          61            Reserved
          62            Mixed mode (color)                3.8
          63            Reserved
          64            Extend field                      3.1
          65            T.505                            ?
          66            Digital network capable           3.1
          67            Duplex/half-duplex                3.1
          68            JPEG encoding                     3.9
          69            Full color mode                   3.8
          70            Must be 0                         3.1
          71            8 or 12 bits/pel/component        3.8
          72            Extend field                      3.1
          73            Color subsampling                 3.8
          74            Custom illuminant                 3.8
          75            Custom gamut range                3.8
         76-77          N. American letter/legal          3.3
          78            T.85 capability                  ?
          79            T.85 L0 capability               ?
          80            Extend field

3.1.  Not Applicable to Content Negotiation

   This item is not applicable to content negotiation.  For
   example, this item may refer to data rate of the modem,
   if error correction mode is enabled, or the fastest receive
   rate supported.

   As only a file describing the data is transmitted between
   the sender and receiver [TIFF], the only information necessary
   is what data will be understood by the recipient, not other
   information which is performed by the actual fax offramp.

3.2.  Polling

   With SMTP polling is acheived with the TURN, ETRN, and
   ATRN commands [ref].

   With HTTP polling is acheived with GET [ref].

   With FTP polling is acheived with RETR.

   Thus, information about a remote machine's ability to have messages
   polled is not useful to use over the Internet.

3.3.  Paper Size

   Paper size is expressed as:

     papersize = "Papersize" "=" token

     token = "na-letter" / "iso-a4" / "iso-b4" / "iso-a3" / "na-legal"

3.4.  Group 4 Facsimile

   ?  What do we want to say about group 4

3.5.  Inch versus Metric resolution

   The algebra of [FEATURE-ALG] handles both metric- and inch-
   based measurements.

3.6.  Subaddressing

   Subaddressing is handled by the addressing format described
   in [RFC2303, RFC2304], and is ignored by the fax offramp
   if the legacy fax doesn't advertise support for subaddresses.

3.7.  Binary File Transfer

   Binary File Transfer is acheived on the Internet using FTP,
   HTTP, and MIME messages in SMTP.

3.8.  Color Transmission

   ?  What do we want to say about color

3.9.  JPEG Encoding

   For Internet Fax we are only supporting TIFF->FAX and FAX->TIFF.

3.10.  Password

   The password, used to authenticate the recipient, is
   equivalent to the password necessary to retreive POP (or
   IMAP) messages from a POP (or IMAP) server.  Similar
   authentication is available with SMTP with [AUTH], and
   with the password with FTP.

   With SMTP, stronger authentication is available with [SMIME] or
   [PGP-MIME] and [SMTP-TLS], and with HTTP with [HTTP-SSL].

   The fax offramp may wish to use the legacy machine's supplied
   password to authenticate the recipient.  This could be done
   by comparing a special field in the recipient's email address
   (if using SMTP), such as "/T30PASSWORD=8924".

3.11.  Compression

   XXX - we need to determine if the offramp will be responsible
   for changing compressions, or if this will be something that
   is expressed as one of the CONNEG features.

4.  Mapping Non-Standard Features (NSF)

   Many fax manufacturers support features that are not part
   of the [T.30] specification.  These features allow better
   compression, higher resolution, or provide other similar value-
   add features.

   Each fax manufacturer which wishes to provide such a feature
   should map the feature to the algebra described in [FEATURE-ALG].
   This allows the feature to be expressed to senders using
   the same mechanism as described in section 3 of this document.

5.  Security Considerations


5.  Acknowledgments


7.  References

   [EIFAX] L. Masinter, D. Wing, "Extended Facsimile Using Internet
   Mail", Internet Draft, Work in Progress, draft-ietf-fax-eifax-XX.txt

   [FAX-REQ] L. Masinter, "Requirements for Internet FAX", Internet
   Draft, Work in Progress, draft-ietf-fax-requirements-XX.txt.

   [FEATURE-ALGEBRA] G. Klyne, "An algebra for describing media feature
   sets", Internet Draft, Work in Progress,

   [FEATURE-REG] K. Holtman, A. Mutz, T. Hardie, "Content Feature Tag
   Registration Procedure", Internet Draft, Work in Progress,

   [MEDIA-FEATURES] L. Masinter, K. Holtman, D. Wing, "Media Features
   for Display, Print, and Fax", Internet Draft, Work in Progress,

   [RFC2303] C. Allocchio, "Minimal PSTN address format in Internet
   Mail", RFC 1303, March 1998.

   [RFC2304] C. Allocchio, "Minimal FAX address format in Internet
   Mail", RFC 2304, March 1998.

   [RFC2305] K. Toyoda, H. Ohno, J. Murai, D. Wing, "A Simple Mode of
   Facsimile Using Internet Mail", RFC 2305, March 1998.

   [RFC2234] D. Crocker, P. Overell, "Augmented BNF for Syntax
   Specifications:  ABNF", RFC 2234, November 1997.

   [T.30] ITU-T (CCITT), "Procedures for Document Facsimile Transmission
   in the General Switched Telephone Network", ITU-T (CCITT),
   Recommendation T.30, July, 1996.

9.  Copyright

   Copyright (C) The Internet Society 1998.  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implmentation may be prepared, copied, published and
   distributed, in whole or in part, without restriction of any kind,
   provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the  purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an

10.  Author's Address

   Dan Wing
   Cisco Systems, Inc.
   101 Cooper Street
   Santa Cruz, CA 95060  USA

   Phone: +1 408 457 5200
   Fax:   +1 408 457 5208
   EMail: dwing@cisco.com