Internet Draft                                                  D. Dunne
Document: draft-ema-vpim-clid-00.txt                     Nortel Networks
Category: Standards Track
Expires in Six Months                                      July 14, 2000

             Calling Line Identification for VPIM Messages


   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

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   This document describes a method for identifying the originating
   party of a VPIM message.

Table of Contents

   1. Introduction
   2. Calling Line Identification Field
   2.1 Internal Call
   2.2 External Call
   3. Caller Name Field
   4. Syntax
   4.1 Calling Line Identification Syntax
   4.2 Caller Name Syntax
   4.3 Example
   5. IANA Registration
   6. Security Considerations
   7. References
   8. Author's Address
   9. Full Copyright Statement

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1. Introduction

   There is currently a need for a mechanism to identify the
   originating party of a VPIM message, outside of the "FROM" header
   information.  The telephone number and name of the caller are
   typically available from the telephone network, but where to store
   these in an Internet message is not obvious.

   This information is intended for use when the VPIM message format is
   used for storing "Call Answer" messages, i.e. the calling party
   leaves a voice message for the recipient, who was unable to answer
   the call.

   The VPIM specification [3] 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: "Unknown" <4165551234@host>
   3. From:

   As a result, it is useful to be able to store the calling party's
   name and number as-is without manipulation.  This would allow future
   generation of the proper Internet address, and also display of this
   information to the recipient.

   RFC2076 "Common Internet Message Headers" [4] 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 in general 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").

2. Calling Line Identification Field

   The Calling Line Identification header ("Caller-ID") is to hold
   sufficient information for the recipient to call back, or reply to,
   the sender of the message.  This leads to two distinct possibilities:
    internal and external calling.

   Note that for both possibilities, this field contains ONLY the
   digits of the number; it does not include any separating character
   (e.g. "-").

2.1 Internal Call

   For an internal call (e.g. between two extensions within the same

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   company), it is sufficient to relay only the extension of the
   calling party, based on the company dialling plan.

2.2 External Call

   For an international call, the CLID must be the full international
   number as described in E.164 [2], i.e. Country Code (CC), National
   Destination Code (NDC) and Subscriber Number (SN). No other
   information, such as prefixes or symbols (e.g. "+"), should be
   included.  This requires provisioning for up to 15 digits.

   For a call within North America, it is sufficient to only include 10
   digits as described in GR-31-CORE Issue 1 [1].  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.

   Also note that the GR-31-Core document also specifies how to include
   the date and time with the originating telephone number. This need
   not be followed, as there is an existing "Date" Internet header
   intended to hold this information.  It is a local implementation
   decision whether this time or the local system time be recorded in
   the "Date" header.

3. Caller Name Field

   The name of the person sending the message is also important.  It is
   to be included whether the call is internal or external.  The name
   should be representable using the American Standard Code for
   Information Interchange (ASCII) character set.

   The length of the name field should also not exceed 15 characters,
   as defined in TR-NWT-001188 [6].  It may contain punctuation or
   white spaces as appropriate.

4. Syntax

   The syntax of both the Calling Line Identification and Caller Name
   according to ABNF [5] is as follows.

4.1 Calling Line Identification Syntax

   "Caller-ID" ":" 1*15DIGIT CRLF

4.2 Caller Name Syntax

   "Caller-Name" ":" 1*15CHAR CRLF

4.3 Example

    Caller-ID: 6137684087

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    Caller-Name: Derrick Dunne
    Date: Mon, 26 Aug 93 10:20:20 -0700 (CDT)
    MIME-Version: 1.0  (Voice 2.0)
    Content-type: Multipart/Voice-Message; Version=2.0;
    Content-Transfer-Encoding: 7bit
    Sensitivity: Private
    Importance: High

5. IANA Registration

   The values corresponding to the "Caller-ID" and "Caller-Name" fields
   are not fixed, and need not be registered.

6. Security Considerations

   There are two scenarios that must be considered.  The first is
   mentioned in section 2.2 - 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 "539 112
   3456" - a seemingly "North American" style number.  Thus leaving the
   recipient with the incorrect information to reply to the message.

   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 dialling plan could be exposed.

7. References

   1. Telcordia Technologies, "Class Feature: Calling Number Delivery
   Generic Requirements", GR-31-CORE Issue 1, June 2000

   2. International Telecommunications Union - Standardization Sector,
   "Recommendation E.164, The International Public Telecommunication
   Numbering Plan", June 1997

   3. Parsons, Vaudreuil, "Voice Profile for Internet Mail - version 2",
    draft-ietf-vpim-vpimv2r2-00.txt, July 2000

   4. Palme, "Common Internet Message Headers", RFC2076, February 1997

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

   6. Telcordia Technologies, "CLASS Feature: Calling Name Delivery
   Generic Requirements", TR-NWT-001188, Issue 1, December 1991

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   7. Resnick (Editor), "Internet Message Format", draft-ietf-drums-msg-
   fmt-08.txt, January 2000

8. Author's Address

   Derrick Dunne
   Nortel Networks
   P.O. Box 3511, Station
   Ottawa, ON  K1Y 4H7

   Phone: +1-613-768-4087
   Fax: +1-613-763-4461


9. Full Copyright Statement

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   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
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   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than

   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

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