Internet DRAFT - draft-ietf-fax-faxaddr-v2


Network Working                                            C. Allocchio
Group                                                        GARR-Italy
INTERNET-DRAFT                                                June 2001
Obsoletes: RFC2304                               Expires: December 2001
Updates: RFC2846                 File: draft-ietf-fax-faxaddr-v2-04.txt

              Minimal FAX address format in Internet Mail

Status of this Memo

   This document is an Internet Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   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 time.  It is inappropriate to use Internet-Drafts as 
   reference material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at

   The list of Internet-Draft Shadow Directories can be accessed at

Copyright Notice

   Copyright (C) The Internet Society (1999).  All Rights Reserved.

Important Note for the RFC Editor:

   Within this document all references and occurences given as
   "RFC2303bis" need to be replaced by "RFCxxxx", where "xxxx" is
   the number which will be assigned to draft-ietf-fax-minaddr-v2-03.txt
   and all references and occurences given as "RFC2304bis" need to
   be replaced by "RFCyyyy", where "yyyy" is the number which will be
   assigned to THIS documnt.


   This memo describes a simple method of encoding GSTN addresses of
   facsimile devices in the local-part of Internet email addresses.

   As with all Internet mail addresses, the left-hand-side (local- part)
   of an address generated according to this specification, is not to be
   interpreted except by the MTA that is named on the right-hand-side

1. Introduction

   Since the very first e-mail to fax gateway objects appeared, a
   number of different methods to specify a fax address as an e-mail
   address have been used by implementors. Several objectives for this
   methods have been identified, like to enable an e-mail user to send
   and receive faxes from his/her e-mail interface, to allow some kind of 
   "fax over e-mail service" transport (possibly reducing the costs of
   GSTN long distance transmissions) while using the existing e-mail 

   This memo describes the MINIMAL addressing method and standard
   extensions to encode FAX addresses into e-mail addresses, as required
   in reference [13]. The opposite problem, i.e. to allow a traditional
   numeric-only fax device user to access the e-mail transport service,
   is not discussed here.

   This IANA forms used to register the standard elements defined here
   are given in the "IANA Considerations" chapter (section 7 of this

   All implementations supporting FAX over e-mail address format MUST
   support this minimal specification.

1.1 Terminology and Syntax conventions

   In this document the formal definitions are described using ABNF
   syntax, as defined into [7]. We will also use some of the "CORE
   DEFINITIONS" defined in "APPENDIX A - CORE" of that document. The
   exact meaning of the capitalised words


   is defined in reference [6].

   In this document the following new terms are also defined:

     I-fax device:
        an I-pstn device type [13] which is able to communicate either
        directly or indirectly with the traditional FAX over GSTN

        the Internet domain name which identifies uniquely an I-fax
        device over the Internet (see also mta-I-pstn in [13]);

        the complete Internet e-mail address structure which is used to 
        transport a FAX address over the Internet e-mail service (see
        also pstn-email in [13]).

2. Minimal Fax address

   The minimal fax address within e-mail has been defined for consistency
   with reference [13] and it contains two elements: the fax-mbox and
   an optional qualif-type1 element.

   More precisely the GSTN minimal address specification requires the
   use of a unique service-selector for each specific application 
   (section 2 in [13]).

   The "service-selector" defined for the fax service is as follows:

      service-selector = "FAX"

   In the syntax for the fax address a qualif-type1 element has been
   defined for support of T.30/T.33 subaddresses (see section 2 of [13]).
   The use of this element is OPTIONAL, but compliant implementations
   MUST be able to support and correctly interpret it when present.
   Its definition is as follows:

      qualif-type1 = "/" t33-sep "=" sub-addr


      t33-sep = "T33S"

      sub-addr = 1*( DIGIT )

   Thus, the minimal specification of a fax in e-mail address is:

      fax-address = fax-mbox [ "/T33S=" sub-addr ]

      fax-mbox = "FAX=" global-phone

    For the case of a single subaddress, only numbers are allowed in
    <sub-addr> which is consistent with T.30, T.33, and this document.
    While T.30 and T.33 use SPACE to pad its field, padding isn't necessary
    in the <sub-addr> field defined by this document.

    For the case of multiple subaddresses, T.33 specifies the "#"
    character be used to specify multiple subaddreses.  However,
    only digits are permitted in the <sub-addr> field defined by this
    document. Refer to section 4.1 in case multiple <sub-addr> per
    per <fax-mbox> need to be specified.

   The Minimal supported syntax for global-phone (as described in
   section 2.1 of reference [13]) is:

   global-phone = "+" 1*( DIGIT / written-sep )

   written-sep = ( "-" / "." )

   Refer to section 2.1 in [13] for other important considerations about
   the global-phone element.

2.2 Some examples of a minimal "fax-address"

   Some examples of minimal fax-address follows:




      the examples shown are just for illustration purpouses.

3. The e-mail address of the I-fax device: mta-I-fax

   An "I-fax device" has, among its characteristics, a unique 
   Internet domain name which identifies it on the Internet. Within
   Internet mail, this is the Right Hand Side (RHS) part of the
   address, i.e. the part on the right of the "@" sign. For purpouses
   of this document we will call this "mta-I-fax"

      mta-I-fax = domain

   For "domain" strings used in SMTP transmissions, the string MUST
   conform to the requirements of that standard's <domain>
   specifications [1], [3].  For "domain" strings used in message
   content headers, the string MUST conform to the requirements of the
   relevant standards [2], [3].

   Note: the use of "domain names" or "domain literals"
         is permitted in addresses in both the SMTP envelope
         and message header fields.  

4. The fax-email

   The complete structure used to transfer a minimal FAX address over
   the Internet e-mail transport system is called "fax-email". This
   object is a an e-mail address which conforms to [2] and [3]
   "addr-spec" syntax, with structure refinements which allows the
   FAX number to be identified.

   fax-email = ["""] ["/"] fax-address ["/"] ["""] "@" mta-I-fax

   Implementors' note:
     The optional "/" characters can result from translations from 
     other transport gateways (such as some X.400 gateways) which 
     have included the "/" as an optional element. Implementations
     MUST accept the optional slashes but SHOULD NOT generate them.
     Gateways are allowed to strip them off when converting to 
     Internet mail addressing. The relevant standard [2], [3] define
     exactly when the optional "quotes" characters surrounding the
     entire local part (i.e. the part on the left of the "@" character
     into the fax-email) MUST be added.

4.1 Multiple subaddresses

   There are some instances in GSTN applications where multiple
   subaddresses are used: T.33 subaddresses in fax service are one of
   these cases. In e-mail practice a separate and unique e-mail
   address is always used for each recipient; as such, if multiple T.33 
   subaddresses are present, the use of multiple "fax-email" elements 

   Implementors' note:
     The UA MAY accept multiple subaddress elements for the same
     global-phone, but it MUST generate multiple "fax-mbox" elements
     when submitting the message to the MTA.

4.2 Some examples of minimal "fax-email"

   Some examples of minimal fax-email addresses follows:



      the examples shown are just for illustration purpouses.

5. Conclusion

   This proposal creates a minimal standard encoding for FAX addresses
   within the global e-mail transport system. The proposal is consistent
   with existing e-mail standards.

6. Security Considerations

   This document specifies a means by which FAX addresses can be
   encoded into e-mail addresses. Since e-mail routing is determined by
   Domain Name System (DNS) data, a successful attack to DNS could 
   disseminate tampered information, which causes e-mail messages to be
   diverted via some MTA or Gateway where the security of the software
   has been comprimised.

   There are several means by which an attacker might be able to deliver
   incorrect mail routing information to a client. These include: (a)
   compromise of a DNS server, (b) generating a counterfeit response to
   a client's DNS query, (c) returning incorrect "additional
   information" in response to an unrelated query. Clients SHOULD ensure
   that mail routing is based only on authoritative answers. Once DNS
   Security mechanisms [5] become more widely deployed, clients SHOULD
   employ those mechanisms to verify the authenticity and integrity of
   mail routing records.

7. IANA Considerations

   The IANA registration forms for "FAX" service-selector and "T33S"
   qualif-type1 elements are defined here. These forms update the
   previous registration forms defined in [15].

7.1 IANA Registration form for updated value of GSTN 
    address service-selector "FAX"

   Subject: Registration of updated values for the GSTN address 
            service-selector specifier "FAX"
   service-selector name:


   Description of Use:

      FAX - specify that the GSTN address refers either to an 
      Internet Fax device, or an onramp/offramp Fax gateway.

      For a complete description refer to RFC2304bis and RFC2303bis

   Security Considerations:

      See the Security Consideration section of RFC2304bis.

   Person & email address to contact for further information:

      Claudio Allocchio
      c/o Sincrotrone Trieste
      SS 14 Km 163.5 Basovizza
      I 34012 Trieste

      X.400:   C=it;A=garr;P=garr;S=Allocchio;G=Claudio;
      Phone:   +39 040 3758523
      Fax:     +39 040 3758565

7.2 IANA Registration form for updated value of GSTN 
    address qualit-type1 keyword "T33S" and value

   Subject: Registration of updated values for the GSTN address 
            qualif-type1 element "T33S"
   qualif-type1 "keyword" name:


   qualif-type1 "value" ABNF definition:

      sub-addr = 1*( DIGIT )

   Description of Use:

      T33S is used to specify the numeric only optional fax sub-address
      element described in "ITU T.33 - Facsimile routing utilizing the 
      subaddress; recommendation T.33 (July, 1996)". Further detailed
      description is available in RFC2304.

   Use Restriction:

      The use of "T33S" is restricted to "FAX" service-selector, is it has
      no meaning outside the fax service.

   Security Considerations:

      See the Security Consideration section of RFC2304bis.

   Person & email address to contact for further information:

      Claudio Allocchio
      c/o Sincrotrone Trieste
      SS 14 Km 163.5 Basovizza
      I 34012 Trieste

      X.400:   C=it;A=garr;P=garr;S=Allocchio;G=Claudio;
      Phone:   +39 040 3758523
      Fax:     +39 040 3758565   

8. Changes since RFC2304 specification

   Although there are no major or technical changes from RFC2304 
   specification, this section briefly describes where updates and 
   clarifications were introduced:

   - considering the case that telephony systems do not conform any
     more to the "single/few" Public Operator paradigm, the old
     definition "PSTN - Public Switched Telephone Network" was changed
     into the more adequate "GSTN - Global Switched Telephone Network"
     one. However, in order to remain consistent with the previous
     specification, the ABNF variables names were not changed.

   - section 7 "IANA Considerations" and the IANA registration forms 
     for the "FAX" "service-selector" and for the "T33S" "qualif-type1" 
     elements were added; 
   - an explicit list of "new terms" with explanations was added to
     section 1.1;

   - the case when multiple T.33 subaddresses are present was 
     described more explicitly in order to clarify how to handle them 
     (section 4.1);

   - in section 3 the language describing "mta-I-fax" was updated to 
     better describe its relationship with an Internet Mail address;

   - in section 4. the quoting rules of the "fax-address" and their
     practical use was made explicit both in the definition of 
     "fax-email" and in the Implementors' note;

   - the Author's Address was updated;

   - the References list was updates to substitute RFC821 with RFC2821,
     RFC822 with RFC2822 and ITU E.164 (1991) with ITU E.164 (1997),

9. Author's Address

   Claudio Allocchio
   c/o Sincrotrone Trieste
   SS 14 Km 163.5 Basovizza
   I 34012 Trieste

   X.400:   C=it;A=garr;P=garr;S=Allocchio;G=Claudio;
   Phone:   +39 040 3758523
   Fax:     +39 040 3758565

10. References

   [1]  Klensin, J., "Simple Mail Transfer Protocol", STD 10, RFC 2821,
        April 2001.

   [2]  Resnick, P., " Internet Message Format", STD 11, RFC 2822,
        April 2001.

   [3]  Braden, R., "Requirements for Internet hosts - application and
        support", RFC 1123, October 1989.

   [4]  Malamud, C. and M. Rose, "Principles of Operation for the
        TPC.INT Subdomain: Remote Printing -- Technical Procedures", RFC
        1528, October 1993.

   [5]  Eastlake, D. and C. Kaufman, "Domain Name System Security
        Extensions", RFC 2065, January 1997.

   [6]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", RFC 2119, March 1997.

   [7]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
        Specifications", RFC 2234, November 1997.

   [8]  ITU F.401 - Message Handling Services: Naming and Addressing for
        Public Message Handling Service; recommendation F.401 (August

   [9]  ITU F.423 - Message Handling Services: Intercommunication
        Between the Interpersonal Messaging Service and the Telefax
        Service; recommendation F.423 (August 1992)

   [10] ITU E.164 - The International Public Telecommunication Numbering
        Plan E.164/I.331 (May 1997)

   [11] ITU T.33 - Facsimile routing utilizing the subaddress;
        recommendation T.33 (July, 1996)

   [12] ETSI I-ETS 300,380 - Universal Personal Telecommunication
        (UPT): Access Devices Dual Tone Multi Frequency (DTMF) sender
        for acoustical coupling to the microphone of a handset telephone
        (March 1995)

   [13] Allocchio, C., "Minimal GSTN address format in Internet Mail",
        RFC 2303bis, xxxx 2001.

   [14] Kille, S., "MIXER (Mime Internet X.400 Enhanced Relay): Mapping
        between X.400 and RFC 822/MIME", RFC 2156, January 1998.

   [15] Allocchio, C. "GSTN address element extensions in e-mail 
        services", RFC 2846, June 2000.

11.  Full Copyright Statement

   Copyright (C) The Internet Society (1999).  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 implementation 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