Network Working C. Allocchio Group GARR-Italy INTERNET-DRAFT April 1999 Obsoletes: RFC2303 Expires: October 1999 Updates: RFC-fulladdr  File: draft-ietf-fax-minaddr-v2-00.txt Minimal GSTN 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. Abstract This memo describes a simple method of encoding GSTN addresses in the local-part of Internet email addresses, along with an extension mechanism to allow encoding of additional standard attributes needed for email gateways to GSTN-based services. 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 GSTN services gateway appeared, a number of different methods to specify a GSTN 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 access GSTN services from his/her e-mail interface, to allow some kind of "GSTN 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 to encode GSTN addresses into e-mail addresses and the standard extension mechanism to allow definition of further standard elements. The opposite problem, i.e. to allow a traditional numeric-only GSTN device user to access the e-mail transport service, is not discussed here. This IANA registration templates which MUST be used to register any standard element defined according to this specification are given in the "IANA Considerations" chapter (section 7 of this document). All implementations supporting this GSTN over e-mail service MUST support as a minimum the specification described in this document. The generic complex case of converting the whole GSTN addressing into e-mail is out of scope in this minimal specification: there is some work in progress in the field, where also a number of optional standard extensions are being defined. 1.1 Terminology and Syntax conventions In this document the formal definitions are described using ABNF syntax, as defined into . This memo also uses 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 . In this document the following new terms are also defined: I-pstn device: a device which has an Internet domain name and it is able to communicate either directly or indirectly with the GSTN network; mta-I-pstn: the Internet domain name which identifies uniquely an I-pstn device over the Internet; pstn-email: the complete Internet e-mail address structure which is used to transport a GSTN address over the Internet e-mail service. 2. Minimal GSTN address The minimal specification of a GSTN address within an e-mail address is as follows: pstn-address = pstn-mbox [ qualif-type1 ] pstn-mbox = service-selector "=" global-phone service-selector = 1*( DIGIT / ALPHA / "-" ) ; note that SP (space) is not allowed in ; service-selector. ; service-selector MUST be handled as a case ; INSENSITIVE string by implementations. Other specifications adopting the "pstn-address" definition MUST define and register with IANA a unique case insensitive "service-selector" element to identify the specific messaging service involved. These specifications and registrations MUST also define which minimal "qualif-type1" extensions, if any, MUST be supported for the specified messanging service. Implementations confirming to this minimal requirements specification are allowed to ignore any other non-minimal extensions address element which is present in the "pstn-address". However, conforming implementations MUST preserve all "qualif-type1" address elements they receive. The generic "qualif-type1" element is defined as: qualif-type1 = "/" keyword "=" string keyword = 1*( DIGIT / ALPHA / "-" ) ; note that SP (space) is not allowed in keyword string = PCHAR ; note that printable characters are %x20-7E As such, all "pstn-address" extension elements MUST be defined in the "qualif-type1" form at the time of registration with IANA. 2.1 Minimal "global-phone" definition The purpouse of global-phone element is to represent standard E.164 numeric addresses  within a syntax for electronic mail addressing that is compliant with standard e-mail specifications given in  and . The minimal supported syntax for global-phone element is as follows: global-phone = "+" 1*( DIGIT , written-sep ) written-sep = ( "-" / "." ) The use of other dialling schemes for GSTN numbers (like private numbering plans or local dialling conventions) is also allowed. However, this does not preclude nor remove the mandatory requirement for support to the "global-phone" syntax within minimal GSTN address format. Any other dialling schemes MUST NOT use the leading "+" defined here between the "=" sign and the dialling string. The "+" sign is strictly reserved for the standard "global-phone" syntax. Note: The specification of alternate dialling schemas is out of scope for this minimal specification. This document also permit the use of written-sep elements in order to improve human readibility of GSTN e-mail addreses. The written-sep are elements which can be placed between dial elements such as digits etc. Implementors' note: Use of the written-sep elements is allowed, but not recommended for transmission. 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 The minimal "pstn-address" examples Some examples of minimal pstn-address follows: VOICE=+3940226338 FAX=+12027653000/T33S=6377 SMS=+33-1-88335215 Note: only the use of registered service-selector and qualif-type1 elements is allowed. The examples shown are just for illustration purpouses. 3. The e-mail address of the I-pstn device: mta-I-pstn An "I-pstn device" has got, 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-pstn" mta-I-pstn = domain For "domain" strings used in SMTP transmissions, the string MUST conform to the requirements of that standard's <domain> specifications , . For "domain" strings used in message content headers, the string MUST conform to the requirements of the relevant standards , . Note: both in the SMTP envelope and in the message headers, the standards permit the use of "domain names" or "domain literals" in addresses. 4. The pstn-email The complete structure used to transfer a minimal GSTN address over the Internet e-mail transport system is called "pstn-email". This object is a an e-mail address which conforms to  and  "addr-spec" syntax, with structure refinements which allows the GSTN number to be identified. pstn-email = ["/"] pstn-address ["/"] "@" mta-I-pstn 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. Implementors are reminded that it is essential that "pstn-address" element MUST strictly follow the "quoting rules" spcified in the relevant standards , . 4.1 Multiple subaddresses There are some instances in GSTN applications where multiple subaddresses are used. On the other hand in e-mail practice a separate and unique e-mail address is always used for each recipient. In the event a particular GSTN service requires multiple subaddresses (in any form defined by the standard specification for that GSTN service) that are associated with the same "pstn-mbox", then the use of multiple "pstn-email" elements is REQUIRED. Implementors' note: The UA MAY accept multiple subaddress elements for the same global-phone, but it MUST generate multiple "pstn-mbox" elements when submitting the message to the MTA. 4.2 Some examples of minimal "pstn-email" addresses Some examples of minimal pstn-email addresses follows: VOICEemail@example.com FAX=+1.202.7653000/T33Sfirstname.lastname@example.org /SMSemail@example.com Note: only the use of registered service-selector and qualif-type1 elements is allowed. The examples shown are just for illustration purpouses. 5. Conclusions This proposal creates a minimal standard encoding for GSTN addresses within the global e-mail transport system. It also defines the standard extension mechanism to be used to introduce new elements for GSTN addresses. The proposal is consistent with existing e-mail standards. Each specific GSTN service using this proposal MUST define and register with IANA its own "service-selector" specification and MUST define and register the eventual other "qualif-type1" elements needed for its specifical application. An example of such an application is contained in reference . 6. Security Considerations This document specifies a means by which GSTN 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  become more widely deployed, clients SHOULD employ those mechanisms to verify the authenticity and integrity of mail routing records. 7. IANA Considerations As the service-selector and qualif-type1 elements values are extensible ones, they MUST be registered with IANA. To register a service-selector or a qualif-type1 element, the registration form templates given in 7.1 and 7.2 MUST be used. Any new registration MUST fulfil the "Specification Required" criterium, as defined in RFC 2434, section 2 : "Specification Required - Values and their meaning MUST be documented in an RFC or other permanent and readily available reference, in sufficient detail so that interoperability between independent implementations is possible." IANA MUST NOT accept registrations which are not supplemented by a Specification as defined above and which are not fully specified accoding to the template forms given in 7.1 and 7.2. In case of need for further consultation about accepting a new registration, IANA SHOULD refer to the Application Area Director to be directed to the appropriate "expert" individal or IETF Working Group. After succesful registration, IANA should publish the registered new element in the appropriate on-line IANA WEB site, and include it into the updates of the "Assigned Numbers" RFC series. This section (including 7.1 and 7.2) updates the ones contained in . 7.1: IANA Registration form template for new values of GSTN address service-selector To: IANA@isi.edu Subject: Registration of new values for the GSTN address service-selector specifier "foo" service-selector name: foo Description of Use: foo - ("foo" is a fictional new service-selector used in this template as an example, it is to be replaced with the new value being registered. Include a short description of the use of the new value here. This MUST include reference to Standard Track RFCs and eventaully to other Standard Bodies documents for the complete description; the use of the value must be defined completely enough for independent implementation). Security Considerations: (Any additional security considerations that may be introduced by use of the new service-selector parameter should be defined here or in the reference Standards Track RFCs) Person & email address to contact for further information: (fill in contact information) INFORMATION TO THE SUBMITTER: The accepted registrations will be listed in the "Assigned Numbers" series of RFCs. The information in the registration form is freely distributable. 7.2: IANA Registration form template for new values of GSTN address qualif-type1 keyword and value To: IANA@isi.edu Subject: Registration of new values for the GSTN address qualif-type1 element "bar" qualif-type1 "keyword" name: bar qualif-type1 "value" ABNF definition: abnf - ("abnf" MUST define the ABNF form of the qualif-type1 value. The ABNF specification MUST be self-contained, using as basic elements the tokens given in specification . To avoid any duplication (when appropriate), it MUST also use as building non-basic tokens any already registered non-basic token from other qualif-type1 elements, i.e. it MUST use the same non-basic token name and then repeat its identical ABNF definition from basic tokens). Description of Use: bar - ("bar" is a fictional description for a new qualif-type1 element used in this template as an example. It is to be replaced by the real description of qualif-type1 element being registered. Include a short description of the use of the new qualif-type1 here. This MUST include reference to Standards Track RFCs and eventually to other Standard Bodies documents for the complete description; the use of the value MUST be defined completely enough for independent implementation.) Use Restriction: (If the new qualif-type1 elements is meaningful only for a specific set of service-element, you MUST specify here the list of allowed service-element types. If there is no restriction, then specify the keyword "none") Security Considerations: (Any additional security considerations that may be introduced by use of the new service-selector parameter should be defined here or in the reference Standards Track RFCs) Person & email address to contact for further information: (fill in contact information) INFORMATION TO THE SUBMITTER: The accepted registrations will be listed in the "Assigned Numbers" series of RFCs. The information in the registration form is freely distributable. 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@elettra.trieste.it X.400: C=it;A=garr;P=Trieste;O=Elettra; S=Allocchio;G=Claudio; Phone: +39 040 3758523 Fax: +39 040 3758565 9. References  Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821, August 1982. --> DRUMS?  Crocker, D., " Standard for the format of ARPA Internet text messages", STD 11, RFC 822, August 1982. --> DRUMS?  Braden, R., "Requirements for Internet hosts - application and support", 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", 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 FAX address format in Internet Mail", RFC 2304 bis, xxxxx 1999.  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 xxxx, xxxxxxx 1999.  Narten, T., Alvestrand, H., "Guidelines for Writing an IANA Considerations Section in RFCs", RFC 2434, October 1998. 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. 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