rfc2846.txt

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Network Working Group                                       C. Allocchio
Request for Comments: 2846                                    GARR-Italy
Category: Standards Track                                      June 2000


           GSTN Address Element Extensions in E-mail Services

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 (2000).  All Rights Reserved.

Abstract

   There are numerous applications where there is a need for interaction
   between the GSTN addressing and Internet addressing.  This memo
   defines a full syntax for one specific case, where there is a need to
   represent GSTN addresses within Internet e-mail addresses. This full
   syntax is a superset of a minimal syntax which has been defined in
   [1].

1. Introduction

   The possible elements composing a "Global Switched Telephone Network
   (GSTN) address in e-mail" (also known as the Public Switched
   Telephone Network - PSTN) can vary from a minimum number up to a
   really large and complex collection. As noted the minimal format and
   general address syntax have been defined in [1], along with the
   mechanism needed to define additional address elements. This memo
   uses this extension mechanism to complete the syntax for representing
   GSTN addresses within e-mail addresses and contains the IANA
   registrations for all newly defined elements.

   In particular, the following additional address elements shall be
   defined:

   -  the detailed definition of GSTN number formats, in order to cover
      various alternative standard GSTN numbering schemes, (i.e. gstn-
      phone, sub-addr-spec and post-dial)





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   -  the message originator and/or recipient specification (pstn-
      recipient)

   GSTN addresses in e-mail MAY contain additional elements defined and
   registered in other specifications (see for example "T33S" element in
   [2]), but they MUST use definitions contained in this memo for those
   elements specified here.

   In particular, "service-selector" names and "qualif-type1" elements
   MUST be registered with IANA, and published within the "ASSIGNED
   NUMBERS" document. This provides a standard mechanism for extending
   the element sets and should avoid unnecessary duplication. IANA
   Registration form templates for the purpouse of registering new
   elements are provided in Appendix B. In addition the IANA
   consideration section of this document defines the procedures
   required to proceed with new registrations.

   A collection of forms for already defined "service-selector" and
   "qualif-type1" elements is listed in appendix C and appendix D
   respectively.

   In particular, efforts have been made to maintain compatibility with
   elements defined in existing e-mail gateway services and standard
   specifications. For example, to the extent possible, compatibility
   has been maintained with the MIXER [3] gateways specifications.

1.1 Relationship with Internet addressing other than e-mail

   Even if in this memo we focus on e-mail addresses, a number of
   elements defined in this specification can also be used for other
   specifications dealing with embedding GSTN addresses into other
   addresses: for example there is some work in progress about URLs
   specification which adopts similar definitions, with slight changes
   in the global syntax due to specific URL format.

1.2 Terminology and Syntax conventions

   In this document the formal definitions are described using ABNF
   syntax, as defined into [4]. 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 [5].





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2. GSTN extended number and pstn-mbox extended format

   In reference [1], section 2, the minimal definition of pstn-mbox
   includes the global-phone element, and further details are defined in
   [1] section 2.1.

   However other non global-phone numbering schemes are also possible.
   Thus, the minimal set syntax defined in [1] shall be extended to
   enable support for local-phone elements. Therefore, the gstn-phone
   format is defined as follows:

      gstn-phone = ( global-phone / local-phone )

   The complexity of the GSTN system includes also the optional use of
   subaddresses and post dialling sequences. As a consequence, there is
   a need to extend the definition of pstn-mbox per [1] to include
   support for both the minimal set definition and an extended syntax.

   The expanded definition of pstn-mbox is as follows:

      pstn-mbox = service-selector "=" global-phone

      pstn-mbox =/ service-selector "=" gstn-phone
                   [ sub-addr-spec ] [post-sep post-dial]

   NOTE: see section 4 in the event multiple "sub-addr-spec" elements
   per pstn-mbox need to be specified.

2.1 The local-phone syntax

   The local-phone element is intended to represent the set of possible
   cases where the global-phone numbering schema does not apply. Given
   the different and complex conventions currently being used in the
   GSTN system, the local-phone definition supports a large number of
   elements.

   The detailed syntax for local-phone elements follows:

      local-phone = [ exit-code ] [ dial-number ]

      exit-code = phone-string
                  ; this will include elements such as the digit to
                  ; access outside line, the long distance carrier
                  ; access code, the access password to the service,
                  ; etc...






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      dial-number = phone-string
                  ; this is in many cases composed of different elements
                  ; such as the local phone number, the area code
                  ; (if needed), the international country code
                  ; (if needed), etc...

   Note:
      the "+" character is reserved for use in global-phone addresses
      per [7] and MUST NOT be used as the starting character in a
      local-phone string.

      phone-string = 1*( DTMF / pause / tonewait / written-sep )

      DTMF = ( DIGIT / "#" / "*" / "A" / "B" / "C" / "D" )
                     ; special DTMF codes like "*", "#", "A", "B",
                     ; "C", "D" are defined in [6]
                     ; Important Note: these elements only apply for
                     ; alphabetic strings used in DTMF operations.
                     ; They are NOT applicable for the alphabetic
                     ; characters that are mapped to digits on phone
                     ; keypads in some countries.

      pause = "p"

      tonewait = "w"

   The written-sep element is defined in [1], section 2.1.

   Note:
      "pause" and "tonewait" character interpretation in local-phone
      numbers depends on the specific MTA implementation. Thus its exact
      meaning is not defined here. Both "pause" and "tonewait" are case
      insensitive.

   Important Note:
      A local-phone specification is a sequence which should be used
      only by the destination  MTA specified by mta-I-pstn (see [1],
      section 3). Per [12], other MTAs should transfer the message
      without modifying the LHS.

2.2 The sub-addr-spec element

   In GSTN service there are cases where a sub-addr-spec is required to
   specify the final destination. In particular there are ISDN
   subaddresses [7], which apply for various  services, whereas other
   subaddress types may be service specific (see the fax service T.33
   subaddress [8], [2]).




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   Within actual telephone operations there may be cases where different
   types of subaddresses are used as part of a single complete address.
   Therefore, the sub-addr-spec syntax definition which follows defines
   the subaddress element for the context of ISDN use; the T.33
   subaddress element is defined in [2], section 2.

   The definition of sub-addr-spec is:

      sub-addr-spec = [ isdn-sep isub-addr ]

   In detail:

      isdn-sep = "/ISUB="
                 ; note that "/ISUB=" is case INSENSITIVE

      isub-addr = 1*( DIGIT )

      isub-addr =/ 1*( DIGIT / written-sep )

   The IANA registration form for sub-addr-spec is given in appendix D.2

2.3 The post-sep and post-dial elements

   In some cases, after the connection with the destination GSTN device
   has been established, a further dialling sequence is required to
   access further services. A typical example is an automated menu-
   driven service using DTMF sequences. These cases may be handled using
   "post-sep" and "post-dial" elements as defined below:

      post-sep =  "/POSTD="
                  ; note that "/POSTD=" is case INSENSITIVE

      post-dial = phone-string

   The IANA registration form for post-sep and post-dial are given in
   appendix D.3

3. The pstn-recipient

   There are some application where it is valuable to supplement the
   pstn-mbox element with additional details. Common examples include
   the use of originator and/or recipient names and physical addresses,
   particularly in the context of onramp and/or offramp gateways.

   The optional pstn-recipient element provides support for such
   details.





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   As an example, when an offramp fax gateway is involved, the
   pstn-recipient element could be used to specify the intended
   recipient on a fax cover page, and the fax cover page headers could
   be qualified using the originator pstn-recipient information.

   In the interest of a compact syntax, the pstn-recipient element may
   be used to support both originator and recipient addresses. For all
   cases within the ABNF definitions to follow, the elements labelled
   with "recipient" may also be used for originator information.

   The pstn-recipient is a sequence of qualif-type1 elements as defined
   below:

      pstn-recipient = [ recipient-name ]
                       [ 1*( recipient-qualifier ) ]

   As a consequence, the extended definition of pstn-address becomes:

      pstn-address = pstn-mbox  [ qualif-type1 ]

      pstn-address =/ pstn-mbox [ pstn-recipient ] [ qualif-type1 ]


   The definition for  qualif-type1 elements is contained in [1] section
   2.

3.1 The recipient-name

   The recipient-name specifies the personal name of the originator
   and/or recipient:

      recipient-name = "/ATTN=" pers-name

      pers-name = [ givenname "." ]
                  [ initials "." ]
                  surname

   The following definitions come directly from the MIXER specification
   [3]:

      surname = printablestring

      givenname = 1*( DIGIT /  ALPHA / SP / "'" / "+" /
                    "," / "-" / "/" / ":" / "=" / "?" )

      initials = 1*ALPHA





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   Note:
      the "initials" element can specify the middle initial which is
      common in some countries; however it is also possible to support
      multiple initials, which may be commonly used in other countries.
      This allows the complete set of givennames initials in any
      possible combination. See examples at section 5.2

   It is essential to remember that the "pstn-address" element (in all
   its components and extensions) MUST strictly follow the "quoting
   rules" specified in the relevant e-mail standards [11], [12].

   The IANA registration form for recipient-name is given in appendix
   D.4.

3.2 The extensible recipient-qualifier

   The recipient-name is sometimes not enough to specify completely the
   originator and/or recipient. An additional set of optional elements,
   whose specific definition is in most cases application dependent, is
   thus defined:

      recipient-qualifier = ( qualif-type1 / qualif-type2 )

   The recipient-qualifier is a qualif-type1 element, and contains a
   qualif-type1 element in a recursive definition which allows an
   extensible format. The purpouse of qualif-type2 element is to permit
   additional extensibility for items which go beyond the scope of those
   defined for use with the qualif-type1 element.

   A series of qualif-type2 elements are defined below:

      qualif-type2 = "/" qual2-label "=" string

      qual2-label = "ORG" / "OFNO" / "OFNA" / "STR" / "ADDR"
                    "ADDU" / "ADDL" / "POB" / "ZIP" / "CO"

      string = PCHAR
               ; note that printable characters are %x20-7E

      printablestring = 1*( DIGIT / ALPHA / SP /
                            "'" / "(" / ")" / "+" / "," / "-" /
                            "." / "/" / ":" / "=" / "?" )
                        ; this definition comes from ITU F.401 [9]
                        ; and MIXER [3]







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   Table 1 includes short definition of qual2-label fields:

                        Table 1 - qual2-label

   qual2-label  Description
   -----------------------------------------------------------------
     "ORG"      Organization Name for Physical Delivery (example: ACME
                Inc)

     "OFNO"     Office Number for physical delivery (example: BLD2-44)

     "OFNA"     Office Name for physical delivery (example: Sales)

      "STR"     Street address for physical delivery (example:
                45, Main Street)

     "ADDR"     Unformatted postal address for physical delivery
                (example: HWY 14, Km 94.5 - Loc. Redhill)

     "ADDU"     Unique postal name for physical delivery (example:
                ACMETELEX)

     "ADDL"     Local postal attributes for physical delivery (example:
                Entrance 3, 3rd floor, Suite 296)

      "POB"     Post Office Box for physical delivery

      "ZIP"     Postal ZIP code for physical delivery

       "CO"     Country Name for physical delivery
   -----------------------------------------------------------------

   One or a combination of some of the above elements is usually enough
   to exactly specify the originator and/or recipient of the message.
   The use of a large number of these elements could in fact create a
   very long recipient-qualifier. Thus, only the strictly needed
   elements SHOULD be used. The maximum total length of the pstn-email
   MUST in fact not exceed the limits specified in the relevant e-mail
   standards [11] [12].

   IMPORTANT NOTE: Although the meaning of the above elements is derived
   directly from similar elements available in F.401 specification [9],
   the naming convention used in this document is explicitly different.
   In this way a conflict is avoided with related X.400 addressing
   rules.  Other specification which use the extension mechanism of this
   document to define new qualif-type1 elements which overlap with F.401
   are cautioned to create new labels which are different than those
   used in F.401.



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   The IANA registration form for these elements is given in appendix
   D.5 to D.14.

4. Multiple sub-addr-spec cases

   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 subaddresses
   are present, the use of multiple "pstn-email" elements [1] 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.

5. Examples

   In order to clarify the specification we present here a limited set
   of examples. Many of the examples refer to the fax service, but also
   additional possible services are included. Check also the examples in
   [1] and [2] for additional information. Please note that all the
   examples are for illustration purpouses, only.

5.1 pstn-mbox examples

   A pstn-mbox address in Italy for the fax service, dialled from
   U.S.A., using local-phone, without sub-addr-spec and without
   written-sep:

      FAX=0103940226338

   A pstn-mbox address in Germany for an hypothetical XYZ service, using
   global-phone, with ISDN sub-addr-spec 1234 and written-sep ".":

      XYZ=+49.81.7856345/ISUB=1234