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rfc:rfc3939

Network Working Group G. Parsons Request for Comments: 3939 J. Maruszak Category: Standards Track Nortel Networks

                                                         December 2004
        Calling Line Identification for Voice Mail Messages

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 (2004).

Abstract

 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.

Parsons & Maruszak Standards Track [Page 1] RFC 3939 Calling Line Identification December 2004

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
 2.  Conventions Used in this Document. . . . . . . . . . . . . . .  3
 3.  Calling Line Identification Field. . . . . . . . . . . . . . .  3
     3.1.  Internal Call. . . . . . . . . . . . . . . . . . . . . .  4
     3.2.  External Call. . . . . . . . . . . . . . . . . . . . . .  4
     3.3.  Numbering Plan . . . . . . . . . . . . . . . . . . . . .  4
     3.4.  Date Header. . . . . . . . . . . . . . . . . . . . . . .  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 . . . . . . . . . . . . . . . . . . . . .  6
 7.  Security Considerations. . . . . . . . . . . . . . . . . . . .  7
 8.  IANA Considerations. . . . . . . . . . . . . . . . . . . . . .  7
 9.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     9.1.  Normative References . . . . . . . . . . . . . . . . . .  8
     9.2.  Informative References . . . . . . . . . . . . . . . . .  8
 10. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . .  9
 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
 Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 11

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 there is no RFC 2822 address 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:;

Parsons & Maruszak Standards Track [Page 2] RFC 3939 Calling Line Identification December 2004

 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 the calling party's information to be displayed 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 available
 information to an analog (non-ISDN) phone (e.g., per [T1.401] in
 North America).
 [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").

2. Conventions Used in this Document

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in BCP 14, [RFC2119].

3. Calling Line Identification Field

 The Calling Line Identification header ("Caller-ID") holds 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, likely to be the 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.

Parsons & Maruszak Standards Track [Page 3] RFC 3939 Calling Line Identification December 2004

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 of up to 15 digits.
 For a call within North America, it is also suggested that 15 digits
 per [T1.625] be supported.  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 limitations of
 various systems will cause this to happen.
 Implementors of this specification should be aware that some phone
 systems are known to truncate international numbers, even though this
 behavior is undesirable.
 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.

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 (i.e., 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 plans.

Parsons & Maruszak Standards Track [Page 4] RFC 3939 Calling Line Identification December 2004

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 will 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
 include:
    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
       [ASCII]
    4) Character Sets for the International Teletex Service [T.61]
 Of these, the IRA and T.61 character sets contain 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].
 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 choose to further limit this to 15 characters for delivery to
 customer equipment, e.g., [T1.401] and [GR-1188-CORE].

Parsons & Maruszak Standards Track [Page 5] RFC 3939 Calling Line Identification December 2004

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

6. Other Considerations

6.1. Compatibility with Other Internet Phone Numbers

 The intent of these headers are to record telephone number that is
 sent by the analog phone system with an incoming call without
 alteration or interpretation.  If sufficient semantic is known or can
 be inferred, this may be included in the NumberingPlan field.  This
 may allow it to be later translated into an addressable phone number.
 Addressable or dialable phone numbers (which this document does not
 define) are defined in other documents, such as GSTN address
 [RFC3191] or telephone URL [RFC2806].

Parsons & Maruszak Standards Track [Page 6] RFC 3939 Calling Line Identification December 2004

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, the recipient is left with incorrect
 information to reply to the message, 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 Name.

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.
 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 appears 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.

Parsons & Maruszak Standards Track [Page 7] RFC 3939 Calling Line Identification December 2004

    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, G. and G. Parsons, "Voice Profile for
                Internet Mail - version 2 (VPIMv2)", RFC 3801, June
                2004.
 [RFC2047]      Moore, K., "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,
                April 2001.
 [RFC2234]      Crocker, D. and P. Overell, "Augmented BNF for Syntax
                Specifications: ABNF", RFC 2234, November 1997.
 [RFC2119]      Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14, RFC 2119, March 1997.

9.2. Informative References

 [RFC2076]      Palme, J., "Common Internet Message Headers", RFC
                2076, February 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 Character Sets for the
                International Teletex Service"

Parsons & Maruszak Standards Track [Page 8] RFC 3939 Calling Line Identification December 2004

 [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 T1.641-1995
 [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
 [RFC3191]      Allocchio, C., "Minimal GSTN address format in
                Internet Mail", RFC 3191, October 2001.
 [RFC2806]      Vaha-Sipila, A., "URLs for Telephone Calls", RFC 2806,
                April 2000.

10. Acknowledgments

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

Parsons & Maruszak Standards Track [Page 9] RFC 3939 Calling Line Identification December 2004

Authors' 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

Parsons & Maruszak Standards Track [Page 10] RFC 3939 Calling Line Identification December 2004

Full Copyright Statement

 Copyright (C) The Internet Society (2004).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM 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 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

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Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Parsons & Maruszak Standards Track [Page 11]

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