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.
AbstractThis memo describes a simple method of encoding Global Switched Telephone Network (GSTN) addresses of facsimile devices in the local-part of Internet email addresses. 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.
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. 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 . In this document the following new terms are also defined: I-fax device: an I-pstn device type  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 ); 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] 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 ). 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 ). 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 ) is: global-phone = "+" 1*( DIGIT / written-sep ) written-sep = ( "-" / "." ) Refer to section 2.1 in  for other important considerations about the global-phone element.
FAX=+3940226338 FAX=+12027653000/T33S=1387 FAX=+33-1-88335215 Note: the examples shown are just for illustration purposes. 1], . For "domain" strings used in message content headers, the string MUST conform to the requirements of the relevant standards , . Note: the use of "domain names" or "domain literals" is permitted in addresses in both the SMTP envelope and message header fields. 2] and  "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
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  become more widely deployed, clients SHOULD employ those mechanisms to verify the authenticity and integrity of mail routing records. 15]. 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
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
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 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).
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  Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821, August 1982.  Crocker, D., "Standard for the Format of ARPA Internet Text Messages", STD 11, RFC 822, August 1982.  Braden, R., "Requirements for Internet hosts - application and support", STD 3, RFC 1123, October 1989.  Malamud, C. and M. Rose, "Principles of Operation for the TPC.INT Subdomain: Remote Printing -- Technical Procedures", RFC 1528, October 1993.  Eastlake, D. and C. Kaufman, "Domain Name System Security Extensions", RFC 2065, January 1997.  Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.  Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications", RFC 2234, November 1997.  ITU F.401 - Message Handling Services: Naming and Addressing for Public Message Handling Service; recommendation F.401 (August 1992).  ITU F.423 - Message Handling Services: Intercommunication Between the Interpersonal Messaging Service and the Telefax Service; recommendation F.423 (August 1992).  ITU E.164 - The International Public Telecommunication Numbering Plan E.164/I.331 (May 1997).
 ITU T.33 - Facsimile routing utilizing the subaddress; recommendation T.33 (July 1996).  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).  Allocchio, C., "Minimal GSTN address format in Internet Mail", RFC 3191, October 2001.  Kille, S., "MIXER (Mime Internet X.400 Enhanced Relay): Mapping between X.400 and RFC 822/MIME", RFC 2156, January 1998.  Allocchio, C., "GSTN address element extensions in e-mail services", RFC 2846, June 2000.
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