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Versions: 00 01 02 03 04 05 06 07 08 09 RFC 3939

VPIM Working Group                                        Glenn Parsons
Internet Draft                                          Janusz Maruszak
Document: <draft-ema-vpim-clid-09.txt>                  Nortel Networks
Category: Standards Track                                      May 2004

          Calling Line Identification for Voice Mail Messages

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
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   The list of current Internet-Drafts can be accessed at
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   This document describes a method for identifying the originating
   calling party in the headers of a stored voice mail message.  Two
   new header fields are defined for this purpose: Caller_ID and
   Called_Name.  Caller_id is used to store sufficient information for
   the recipient to callback, or reply to, the sender of the message.
   Caller-name provides the name of the person sending the message.

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Table of Contents

 1. Introduction ....................................................3
 2. Conventions used in this document ...............................3
 3. Calling Line Identification Field ...............................4
 3.1 Internal Call ..................................................4
 3.2 External Call ..................................................4
 3.3 Numbering Plan .................................................5
 4. Caller Name Field ...............................................5
 5. Formal Syntax ...................................................6
 5.1 Calling Line Identification Syntax .............................6
 5.2 Caller Name Syntax .............................................6
 5.3 Examples .......................................................6
 6. Other Considerations ............................................7
 7. Security Considerations .........................................7
 8.   IANA Considerations ...........................................7
 9. References ......................................................8
 9.1 Normative References ...........................................8
 9.2 Informative References .........................................8
 10. Acknowledgments ................................................9
 11. Author's Addresses .............................................9
 11. Full Copyright Statement .......................................10

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1. Introduction

   There is currently a need for a mechanism to identify the
   originating party of a voice mail message, outside of the "FROM"
   header information.  The telephone number and name of the caller are
   typically available from the telephone network, but there is no
   obvious header field to store this in an Internet Mail message.

   This information is intended for use when the VPIM message format is
   used for storing "Call Answer" voice messages in an Internet Mail
   message store, i.e. the calling party leaves a voice message for the
   recipient, who was unable to answer the call. The implication is
   that no RFC 2822 address is known for the originator.

   [VPIMV2R2] suggests the originating number be included as an
   Internet address, using the first method shown below. There are
   several other ways to store this information, but they all involve
   some manipulation of the "From" field.  For example:

      1. From: "416 555 1234" <non-mail-user@host>
      2. From: "John Doe" <4165551234@host>
      3. From:  unknown:;

   Since any of these is a forced translation, it would be useful to
   store the calling party's name and number as presented by the
   telephone system to the called party without manipulation.  This
   would allow display of the calling party's information to the
   recipient (similar to it appearing on the telephone) and also allow
   future determination of an Internet address for the originator (if
   one exists).  Note that there is no requirement to store meta-data
   (e.g., type of number, presentation restricted) as this information
   is not presented to the called party and is generally not available
   to voice mail systems.  The intent is to store the information
   available to an analog (non-ISDN) phone (e.g., per [T1.401] in North

   [RFC2076] currently lists "phone" as an Internet message header
   which would hold the originating party's telephone number, but it is
   listed as "non-standard", i.e. usage of this header is not generally
   recommended. It also has no defined format, making the information
   unparsable. There is no similar entry for the originator's name.

   It is proposed that two new message header fields be included to
   hold this information, namely the Calling Line Identification
   ("Caller-ID"), and Caller Name ("Caller-Name").

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2. Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   this document are to be interpreted as described in RFC-2119.

3. Calling Line Identification Field

   The Calling Line Identification header ("Caller-ID") is to hold
   sufficient information for the recipient's voice mail system to
   call back, or reply to, the sender of the message.  The number that
   is contained in this header is supplied by the telephone system.
   The exact format of the data received depends on the type of call,
   that is -- internal or external call.

   Note that for both options, the number field MUST contain only
   the digits of the number and MUST be representable using the
   American Standard Code for Information Interchange [ASCII] character
   set; it does not include any separating character (e.g. "-").

   It is expected that default, and likely most common case, will not
   have any numbering plan semantic associated with the number.
   However, in the case that it is known, an optional "NumberingPlan"
   parameter MAY be used to indicate the semantic.

3.1 Internal Call

   For an internal call (e.g. between two extensions within the same
   company), it is sufficient to relay only the extension of the
   calling party, based on the company dialing plan.

   However, the support of longer numbers may be supported by the
   enterprise phone system.

3.2 External Call

   For an international call, the calling party's number must be the
   full international number as described in [E.164], i.e. Country Code
   (CC), National Destination Code (NDC) and Subscriber Number (SN).
   Other information, such as prefixes or symbols (e.g. "+"), MUST NOT
   be included.  [E.164] allows for numbers for up to 15 digits.

   For a call within North America, it is also suggested to support 15
   digits per [T1.625].  However, some service providers may only
   support 10 digits as described in [T1.401] and [GR-31-CORE].  Though
   it is desirable that an international number not be truncated to 10
   digits if it contains more, it is recognized that this will happen
   due to limitations of various systems.

   Note that the other defined fields available to non-analog systems
   (e.g., subaddress, redirecting number), as well as the meta-data,
   are not intended to be stored in this header.

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3.3 Numbering Plan

   In this baseline case (i.e., analog lines), no numbering plan
   information is known or implied.  However, in the case that a
   numbering plan is known, an optional "NumberingPlan" parameter MAY
   be used to indicate the semantic.  Only three semantics are defined-
   "unknown", "local" and "e164".  "unknown" is the default if no
   numbering plan semantic is known (and the default if the parameter
   is absent).  "local" has meaning only within the domain of the voice
   mail system that stored the message.  That is, for example, the
   voice mail system knows that the number belongs to a local numbering
   plan.  "e164" indicates that the number is as described in [E.164].
   "x-" may be used to indicate enterprise or service specific dialing

3.4 Date Header

   The date and time may be included by the telephone system with the
   calling party's telephone number per [T1.401].  This MAY be used, as
   there is an existing "Date" Internet header to hold this information.
   It is a local implementation decision whether this time or the local
   system time be recorded in the "Date" header.

4. Caller Name Field

   The name of the person sending the message is also important.
   Information about whether the call is internal or external may be
   included if it is available.  This information may not be available
   on international calls.

   Further, the exact format for this field is typically a service
   provider option per [T1.641].  It is possible for the caller's name
   to be sent in one of several character sets depending on the service
   provider signaling transport (e.g., ISDN-UP, SCCP, TCAP).  These
      1) International Reference Alphabet (IRA), formerly know as
         International Alphabet No.5 or IA5 [T.50]
      2) Latin Alphabet No. 1 [8859-1]
      3) American National Standard Code for Information Interchange
      4) Character Sets for the International Teletex Service [T.61]

   Of these, the IRA and T.61 character set contains a number of
   options that help specify national and application oriented
   versions.  If there is no agreement between parties to use these
   options, then the 7-bit character set in which the graphical
   characters of IRA, T.61 and ASCII are coded exactly the same, will
   be assumed.  Further, the 7-bit graphical characters of [8859-1] are
   the same as in [ASCII].

   Note that for delivery to customer equipment in North America, the
   calling name MUST be presented in ASCII per [T1.401].

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   As a result, for the caller name header defined in this document,
   characters are represented with ASCII characters.  However, if a
   name is received that cannot be represented in 7-bit ASCII, it MAY
   be stored using its native character set as defined in [RFC2047].

   In telephone networks, the length of the name field MUST NOT exceed
   50 characters, as defined in [T1.641].  However, service providers
   may chose to limit this further to 15 characters for delivery to
   customer equipment, e.g., [T1.401] and [GR-1188-CORE].

5. Formal Syntax

   Both Calling Line Identification and Caller Name follow the syntax
   specification using the augmented Backus-Naur Form (BNF) as
   described in [RFC2234].  While the semantics of these headers are
   defined in sections 4 and 5, the syntax uses the 'unstructured'
   token defined in [RFC2822]:

      unstructured = *([FWS] utext) [FWS]

5.1 Calling Line Identification Syntax

      "Caller-ID" ":" 1*DIGIT [ "," "NumberingPlan="
      ( "unknown" / "local" / "e164" / ietf-token / x-token ) ] CRLF

        ietf-token := <An extension token defined by a
                       standards-track RFC and registered
                       with IANA.>

        x-token := <The two characters "X-" or "x-" followed, with
                    no intervening white space, by any token>

5.2 Caller Name Syntax

      "Caller-Name" ":" unstructured CRLF

5.3 Examples

       To: +19725551212@vm1.example.com
       Caller-ID: 6137684087
       Caller-Name: Derrick Dunne

       To: 6137637582@example.com
       Caller-ID: 6139416900
       Caller-Name: Jean Chretien

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6. Other Considerations

6.1 Compatibility with other Internet phone numbers

   The intent of these headers are to record without alteration or
   interpretation the telephone number that is sent by the analog
   phone system with an incoming call.  If sufficient semantic is
   known or can be infered, this may be included in the NumberingPlan
   field.  This may allow it to be later be translated into an
   addressable phone number.  Addressabe or dialable phone numbers
   (which this document does not define) are defined in other
   documents, such as GSTN address [RFC 3191] or telephone URL

6.2 Usage

   There are a few scenarios of how this mechanism may fail that must
   be considered.  The first is mentioned in section 3.2 - the
   truncation of an international number to 10 digits.  This could
   result in a misinterpretation of the resulting number.  For
   instance, an international number (e.g., from Ireland) of the form
   "353 91 73 3307" could be truncated to "53 91 73 3307" if received
   in North America, and interpreted as "539 917 3307" - a seemingly
   "North American" style number.  Thus leaving the recipient with the
   incorrect information to reply to the message _ and possibly with an
   annoyed callee at the North American number.

   The second scenario is the possibility of sending an internal
   extension to an external recipient when a Call Answer message is
   forwarded.  This poses two problems, the recipient is given the
   wrong phone number, and the company's dialing plan could be exposed.

   The final concern deals with exercising character options that are
   available in coding the Calling Name field. An international system
   may send a message with coding options that are not available on the
   receiving system. Thus giving the recipient an incorrect Caller

 7. Security Considerations

   Note that unlisted and restricted numbers are not a concern as these
   header fields are defined to contain what the called party would see
   (e.g., 'Private Name'), as opposed to the complete details exchanged
   between service providers.

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   However, it must also be noted that this mechanism allows the
   explicit indication of phone numbers in the headers of an email
   message (used to store voice messages).  While the rationale for
   this is reviewed in section 1, the recipient of this message may not
   be aware that this information is contained in the headers unless
   the user's client presents the information.  Its use is intended to
   be informative as it is when it would appear on a telephone screen.

8.   IANA Considerations

   This document defines an IANA-administered registration space for
   Caller-ID numbering plans in section 5.1. Each registry entry
   consists of an identifying token and a short textual description of
   the entry. There are three initial entries in this registry:

     unknown - The number's semantics are unknown.  This value is the
               default in the absence of this parameter.

     local   - The number only has meaning within the domain of the
               sending system identified by the RFC 2822 From field
               of the message.

     e164    - The number's semantics are described in [E.164].

   The only way to add additional entries (ietf-token in section 5.1)
   to this registry is with a standards-track RFC.

9. References

9.1 Normative References

   [VPIMV2R2] Vaudreuil, Greg, Parsons, Glenn, "Voice Profile for
   Internet Mail, version 2", RFC 3801, June 2004.

   [RFC2047] K. Moore, "MIME (Multipurpose Internet Mail Extensions)
   Part Three:  Message Header Extensions for Non-ASCII Text",
   RFC 2047, November 1996

   [RFC2822] Resnick, P., "Internet Message Format", RFC 2822,  June

   [RFC2234] Crocker, D. and Overell, P.(Editors), "Augmented BNF for
   Syntax Specifications: ABNF", RFC 2234, Internet Mail Consortium and
   Demon Internet Ltd., November 1997

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9.2 Informative References

   [RFC2076] Palme, "Common Internet Message Headers", RFC 2076,
        May 1997

   [E.164] ITU-T Recommendation E.164 (1997), "The international public
   telecommunication numbering plan"

   [T.50] ITU-T Recommendation T.50 (1992), "International Reference
   Alphabet (IRA)"

   [T.61] CCITT Recommendation T.61 (1988) (Withdrawn), "Character
   Repertoire and Coded Chaacter Sets for the International Teletex

   [8859-1] ISO/IEC International Standard 8859-1 (1998), Information
   Technology _ 8-bit single-byte coded graphic character sets _
   Part 1: Latin Alphabet No. 1

   [ASCII] American National Standards Institute (ANSI), Coded
   Character Set - 7-Bit American National Standard Code for
   Information Interchange, ANSI X3.4, 1986.

   [T1.401] American National Standards Institute (ANSI),
   Telecommunications _ Network-to-Customer Installation Interfaces _
   Analog Voicegrade Switched Access Lines with Calling Number
   Delivery, Calling Name Delivery, or Visual Message-Waiting Indicator
   Features, ANSI T1.6401.03-1998

   [T1.625] American National Standards Institute (ANSI),
   Telecommunications - Integrated Services Digital Network (ISDN) _
   Calling Line identification Presentation and Restriction
   Supplementary Services, ANSI T1.625-1993

   [T1.641] American National Standards Institute (ANSI),
   Telecommunications - Calling Name Identification Presentation, ANSI

   [GR-1188-CORE] Telcordia Technologies, "CLASS Feature: Calling Name
   Delivery Generic Requirements", GR-1188-CORE, Issue 2, December 2000

   [GR-31-CORE] Telcordia Technologies, "CLASS Feature: Calling Number
   Delivery", GR-31-CORE, Issue 1, June 2000

   [RFC 3191] Minimal GSTN address format in Internet Mail, RFC 3191,
   Oct 2001

   [RFC 2806] URL for Telephone Calls, RFC 2806, April 2000

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10. Acknowledgments

   The previous authors of drafts of this document were Derrick Dunne
   and Jason Collins. The current authors would like to thank Derrick
   and Jason for their contributions.

11. Author's Addresses

   Glenn Parsons
   Nortel Networks
   P.O. Box 3511, Station C
   Ottawa, ON K1Y 4H7
   Phone: +1-613-763-7582
   Email: gparsons@nortelnetworks.com

   Janusz Maruszak
   Phone: +1-416-885-0221
   Email: jjmaruszak@sympatico.ca

12. Full Copyright Statement

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