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Versions: 00 01 02 03 RFC 3191

Network Working                                            C. Allocchio
Group                                                        GARR-Italy
INTERNET-DRAFT                                               March 2001
Obsoletes: RFC2303                              Expires: September 2001
Updates: RFC2846                 File: draft-ietf-fax-minaddr-v2-03.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
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   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
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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 THIS document
   and all references and occurences given as "RFC2304bis" need to
   be replaced by "RFCyyyy", where "yyyy" is the number which will be
   assigned to draft-ietf-fax-faxaddr-v2-03.txt
   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
   (commonly called "telephone numbers") 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 an MTA that handles messages for the domain given
   in the right-hand-side.

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 entirety of GTSN addressing
   into e-mail is out of scope in this minimal specification.

1.1 Terminology and Syntax conventions

   In this document the formal definitions are described using ABNF
   syntax, as defined into [7]. 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 [6].

   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 purpose of global-phone element is to represent standard E.164
   numeric addresses [10] within a syntax for electronic mail addressing
   that is compliant with standard e-mail specifications given in [1]
   and [2].

   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 the 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 permits 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.


2.2 The minimal "pstn-address" examples

   Some examples of minimal pstn-address are:

      VOICE=+3940226338

      FAX=+12027653000/T33S=6377

      SMS=+33-1-88335215

   Note:
      these examples are given as illustrations only; they
      do not necessarily represent valid pstn-addresses.


3. The e-mail address of the I-pstn device: mta-I-pstn

   An "I-pstn 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-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 [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 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 [2] and [3]
   "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. 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 pstn-email) MUST be added.

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:

      VOICE=+3940226338@worldvoice.com

      FAX=+1.202.7653000/T33S=6377@faxserv.org

      /SMS=+33-1-88335215/@telecom.com

Note:
      these examples are given as illustrations only; they
      do not necessarily represent valid pstn-addresses.

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 [13].

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 [5] 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, 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 fulfill the "Specification Required"
   criterium, as defined in RFC 2434, section 2 [16]:

    "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
   [15].


   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 [4]. To avoid any
      duplication (when appropriate), it MUST also use 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@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 FAX address format in Internet Mail",
        RFC 2304bis, xxxxx 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.

   [16] 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.  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
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