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+Network Working Group C. Allocchio
+Request for Comments: 3192 GARR-Italy
+Obsoletes: 2304 October 2001
+Updates: 2846
+Category: Standards Track
+
+
+ Minimal FAX address format in Internet Mail
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2001). All Rights Reserved.
+
+Abstract
+
+ This memo describes a simple method of encoding Global Switched
+ Telephone Network (GSTN) addresses of facsimile devices in the
+ local-part of Internet email addresses.
+
+1. Introduction
+
+ 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
+ (domain).
+
+ 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
+ infrastructure.
+
+ 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.
+
+
+
+Allocchio Standards Track [Page 1]
+
+RFC 3192 Minimal FAX address format in Internet Mail October 2001
+
+
+ These IANA forms used to register the standard elements defined here
+ are given in the "IANA Considerations" chapter (section 7 of this
+ document).
+
+ 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 capitalized words
+
+ "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
+ "SHOULD NOT", "RECOMMENDED", "MAY", "OPTIONAL"
+
+ 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
+ service;
+
+ mta-I-fax:
+ the Internet domain name which identifies uniquely an I-fax
+ device over the Internet (see also mta-I-pstn in [13]);
+
+ fax-email:
+ 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"
+
+
+
+Allocchio Standards Track [Page 2]
+
+RFC 3192 Minimal FAX address format in Internet Mail October 2001
+
+
+ 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
+
+ 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
+
+ Notes:
+
+ 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:
+
+
+
+
+
+Allocchio Standards Track [Page 3]
+
+RFC 3192 Minimal FAX address format in Internet Mail October 2001
+
+
+ FAX=+3940226338
+
+ FAX=+12027653000/T33S=1387
+
+ FAX=+33-1-88335215
+
+ Note:
+
+ the examples shown are just for illustration purposes.
+
+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 purposes 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 standards <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
+
+
+
+Allocchio Standards Track [Page 4]
+
+RFC 3192 Minimal FAX address format in Internet Mail October 2001
+
+
+ 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 is
+ REQUIRED.
+
+ 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:
+
+ FAX=+3940226338@faxworld.org
+
+ FAX=+12027653000/T33S=1387@faxworld.org
+
+ /FAX=+33-1-88335215/@faxworld.org
+
+ Note:
+
+ the examples shown are just for illustration purposes.
+
+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
+ compromised.
+
+
+
+Allocchio Standards Track [Page 5]
+
+RFC 3192 Minimal FAX address format in Internet Mail October 2001
+
+
+ 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"
+
+ To: IANA@iana.org
+ Subject: Registration of updated values for the GSTN address
+ service-selector specifier "FAX"
+
+ service-selector name:
+
+ FAX
+
+ 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 RFC 3192 and RFC 3191.
+
+ Security Considerations:
+
+ See the Security Consideration section of RFC 3192.
+
+ Person & email address to contact for further information:
+
+ Claudio Allocchio
+ INFN-GARR
+ c/o Sincrotrone Trieste
+ SS 14 Km 163.5 Basovizza
+ I 34012 Trieste
+ Italy
+
+
+
+
+
+Allocchio Standards Track [Page 6]
+
+RFC 3192 Minimal FAX address format in Internet Mail October 2001
+
+
+ RFC2822: Claudio.Allocchio@garr.it
+ 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
+
+ To: IANA@iana.org
+ Subject: Registration of updated values for the GSTN address
+ qualif-type1 element "T33S"
+
+ qualif-type1 "keyword" name:
+
+ T33S
+
+ 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 RFC 3192.
+
+ 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 RFC 3192.
+
+ Person & email address to contact for further information:
+
+ Claudio Allocchio
+ INFN-GARR
+ c/o Sincrotrone Trieste
+ SS 14 Km 163.5 Basovizza
+ I 34012 Trieste
+ Italy
+
+
+
+
+
+
+
+Allocchio Standards Track [Page 7]
+
+RFC 3192 Minimal FAX address format in Internet Mail October 2001
+
+
+ RFC2822: Claudio.Allocchio@garr.it
+ X.400: C=it;A=garr;P=garr;S=Allocchio;G=Claudio;
+ Phone: +39 040 3758523
+ Fax: +39 040 3758565
+
+8. Changes since RFC 2304 specification
+
+ Although there are no major or technical changes from RFC 2304
+ 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 ITU E.164 (1991)
+ with ITU E.164 (1997).
+
+
+
+
+
+
+
+
+
+
+
+Allocchio Standards Track [Page 8]
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+RFC 3192 Minimal FAX address format in Internet Mail October 2001
+
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+9. Author's Address
+
+ Claudio Allocchio
+ INFN-GARR
+ c/o Sincrotrone Trieste
+ SS 14 Km 163.5 Basovizza
+ I 34012 Trieste
+ Italy
+
+ RFC2822: Claudio.Allocchio@garr.it
+ X.400: C=it;A=garr;P=garr;S=Allocchio;G=Claudio;
+ Phone: +39 040 3758523
+ Fax: +39 040 3758565
+
+10. References
+
+ [1] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821,
+ August 1982.
+
+ [2] Crocker, D., "Standard for the Format of ARPA Internet Text
+ Messages", STD 11, RFC 822, August 1982.
+
+ [3] Braden, R., "Requirements for Internet hosts - application and
+ support", STD 3, 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", BCP 14, 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
+ 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 - The International Public Telecommunication Numbering
+ Plan E.164/I.331 (May 1997).
+
+
+
+Allocchio Standards Track [Page 9]
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+RFC 3192 Minimal FAX address format in Internet Mail October 2001
+
+
+ [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 3191, October 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.
+
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+Allocchio Standards Track [Page 10]
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+RFC 3192 Minimal FAX address format in Internet Mail October 2001
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+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2001). 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
+ 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.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
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