Minimal FAX address format in Internet Mail
draft-ietf-fax-minaddrfax-00

Network Working Group                                      C. Allocchio
INTERNET-DRAFT                                               GARR-Italy
Expires: June 1998                                        December 1997

             Minimal FAX address format in Internet Mail

                 (draft-ietf-fax-minaddrfax-00.txt)

Status of this Memo

This document is an Internet Draft.  Internet Drafts are working
documents of the Internet Engineering Task Force (IETF), its Areas,
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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. Two major objectives for 
   this were

     - enable an e-mail user to send faxes from his/her e-mail
       interface;

     - enable some kind of ''fax over e-mail service'' transport, to
       reduce the costs of fax transmissions, and use the existing
       e-mail infrastructure.

   This memo describes the MINIMAL addressing method and standard
   extensions to encode FAX addresses in 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.

   All implementations supporting this FAX over e-mail address format
   MUST support as a minimum the specification described in this document.
   The generic complex case of converting the whole PSTN addressing in 
   e-mail is out of scope in this minimal specification: there is some 
   work in progress in the field, where also a number of standard optional 
   extensions are being defined.

   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

      "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
      "SHOULD NOT", "RECOMMENDED",  "MAY", "OPTIONAL"

   is defined in reference [6].

2. Minimal Fax address

   The "service-selector" defined in section 2 of reference [13] for
   the fax service is:

      service-selector = "FAX"

   The minimal addressing for the fax service also requires support
   for a "qualif-type1" element (see section 2 of reference [13]).
   This element is an OPTIONAL element of the fax address, but its
   support, when present, is REQUIRED:

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

   where

      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 

   Note:
     See section 4.1 in case multiple sub-addr 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 = ( "-" / "." )

   The use of other dialling schemas for PSTN numbers (like private
   numbering plans or local dialling conventions) is also allowed.
   However, this does not preclude nor remove the minimal compulsory
   requirement to support the "global-phone" syntax as defined above.

   Any non "global-phone" dialling schema MUST NOT use the leading
   "+" between the "=" sign and the dialling string. The "+" sign is
   strictly reserved for the standard "global-phone" syntax.

   Note:
     The specification of these different dialling schemas is out of scope
     for this minimal specification.

   User specification of PSTN e-mail addresses will be facilitated if
   they can insert these separators between dial elements like digits etc.
   For this reason we allow them in the syntax the written-sep element.

   Implementors' note:
     Use of the written-sep elements is allowed, but not recommended. Any
     occurences of written-sep elements in a pstn-mbox MUST be ignored by
     all conformant implementations. User Agents SHOULD remove written-sep
     elements before submitting messages to the Message Transport System.

                              
2.2 Some examples of a minimal "fax-address"

      FAX=+3940226338

      FAX=+12027653000/T33S=1387

      FAX=+33-1-88335215

3. The e-mail address of the I-fax device: mta-I-fax
  
   An "I-fax device" has an e-mail address, or to be more exact, a 
   name which enables a mail system to identify it on the e-mail 
   global system.

   In Internet mail, this is the Right Hand Side (RHS) part of the 
   address, i.e. the part on the right of the "@" sign. 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]
   and their updates. For "domain" strings used in message content headers,
   the string MUST conform to the requirements of the relevant standards [2],
   [3] and their updates.

   Note: in both cases, the standards permit use of "domain names" or "domain
         literals" in addresses. 

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
   an e-mail address which conforms to RFC822 [2] (and its updates)
   "addr-spec" syntax, with some extra structure which allows the FAX 
   number to be identified.

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

   Implementors' note:
     The optional "/" characters can result from other mail transport
     services gateways, where it is also 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.
                          

4.1 Multiple subaddresses

   In case a particular service requires multiple T.33 subaddresses, and
   these subaddresses need to be given on the same "fax-mbox", multiple
   "fax-email" elements will be used.

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

4.2 Some examples of minimal "fax-email"

      FAX=+3940226338@faxworld.org

      FAX=+12027653000/T33S=1387@faxworld.org

      /FAX=+33-1-88335215/@faxworld.org

5. Conclusion

   This proposal creates a minimal standard encoding for FAX addresses
   within the global e-mail transport system. The proposal requires no 
   changes to existing e-mail software.

6. Security Considerations

   This document specifies a means by which FAX addresses can be
   encoded into e-mail addresses. As routing of e-mail messages is
   determined by Domain Name System (DNS) information, a successful 
   attack on this service could force the mail path via some particular
   gateway or message transfer agent where mail security can be
   affected by compromised software.

   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. Copyright

   "Copyright (C) The Internet Society (date). 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 English.

   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
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT
   NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL
   NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR
   FITNESS FOR A PARTICULAR PURPOSE." 

8. Author's Address

   Claudio Allocchio
   Sincrotrone Trieste
   SS 14 Km 163.5 Basovizza
   I 34012 Trieste
   Italy

   RFC822: Claudio.Allocchio@elettra.trieste.it
   X.400:  C=it;A=garr;P=Trieste;O=Elettra;
           S=Allocchio;G=Claudio;
   Phone:  +39 40 3758523
   Fax:    +39 40 3758565

9. References

[1]  RFC821 Simple Mail Transfer Protocol. J. Postel. (August 1982)

[2]  RFC822 Standard for the format of ARPA Internet text messages. D.
     Crocker. (August 1982)

[3]  RFC1123 Requirements for Internet hosts - application and support. R.T.
     Braden. (October 1989)    

[4]  RFC1528 Principles of Operation for the TPC.INT Subdomain: Remote
     Printing -- Technical Procedures. C. Malamud & M. Rose. (October 1993)

[5]  RFC2065 Domain Name System Security Extensions. D. Eastlake, 3rd, C.
     Kaufman. (January 1997)

[6]  RFC2119 Key words for use in RFCs to Indicate Requirement Levels.
     S. Bradner (March 1997)

[7]  RFC2234 Augmented BNF for Syntax Specifications. D. Crocker,
     P. Overell (November 1997).

[8]  ITU F.401 - Message Handling Services: Naming and Addressing for Public
     Message Handling Service; recommendation F.401 (August 1992)

[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 - Numbering plan for the ISDN era; recommendation E.164/I.331 
     (August 1991)

[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] RFCxxxx (DRAFT-IETF-FAX-ADDRMINGEN-xx.TXT) Minimal PSTN address format 
     in Internet Mail. C. Allocchio. (xxxx 199x)

[14] RFCxxxx (DRAFT-KILLE-MIXER-RFC1327BIS-xx.TXT) MIXER (Mime Internet
     X.400 Enhanced Relay): Mapping between X.400 and RFC 822/MIME.
     S.E. Kille. (xxxx 199x)