Network Working C. Allocchio Group GARR-Italy INTERNET-DRAFT March 2001 Obsoletes: RFC2304 Expires: September 2001 Updates: RFC2846 File: draft-ietf-fax-faxaddr-v2-03.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 http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. 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. Also References given in [1] and [2] should eventually be updated with the numbers assigned to the documents obsoleting RFC821 and RFC822. Abstract 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 (domain). 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 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. This 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 capitalised 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" 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 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 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 field defined by this document. Refer to section 4.1 in case multiple per per 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: FAX=+3940226338 FAX=+12027653000/T33S=1387 FAX=+33-1-88335215 Note: 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 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 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 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" To: IANA@isi.edu 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 RFC2304bis and RFC2303bis Security Considerations: See the Security Consideration section of RFC2304bis. 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 RFC822: 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@isi.edu 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 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 INFN-GARR c/o Sincrotrone Trieste SS 14 Km 163.5 Basovizza I 34012 Trieste Italy RFC822: 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. Author's Address Claudio Allocchio INFN-GARR c/o Sincrotrone Trieste SS 14 Km 163.5 Basovizza I 34012 Trieste Italy RFC822: Claudio.Allocchio@garr.it X.400: C=it;A=garr;P=garr;S=Allocchio;G=Claudio; Phone: +39 040 3758523 Fax: +39 040 3758565 9. References [1] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821, August 1982. --> DRUMS? [2] Crocker, D., " Standard for the format of ARPA Internet text messages", STD 11, RFC 822, August 1982. --> DRUMS? [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 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) [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. 10. 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 English. 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