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      Internet Draft                                   Laile Di Silvestro
      Expires in six months                             Ambos Corporation
                                                                Rod Miles
                                                          Nortel Networks
      Document: <draft-ema-vpimv3-goals-01.txt>            March 10, 2000
            Goals for Voice Profile for Internet Mail, Version 3
      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-
      Internet Drafts are valid for a maximum of six months and may be
      updated, replaced, or obsoleted by other documents at any time.  It
      is inappropriate to use Internet Drafts as reference material or to
      cite them other than as a "work in progress".
      The list of current Internet-Drafts can be accessed at
      The list of Internet-Draft Shadow Directories can be accessed at
      This draft is a part of the charter of the IETF VPIM BOF/WG. To
      subscribe to the mailing list, send a message to
      <majordomo@lists.neystadt.org> with the text "subscribe vpim" in the
      body of the message. For more information on the VPIM activity see
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      Table of contents:
        1. Abstract
        2. Conventions Used in this Document
        3. Introduction
        4. Goals for Voice Profile for Internet Mail Version 3
                4.1 Interoperability
                    4.1.1 Interoperability with Desktop Email Applications
                    4.1.2 Interoperability with VPIM v2 and VPIM v3 Voice
                        Mail Systems
                    4.1.3 Interoperability with VPIM v3 Unified Messaging
                    4.1.4 Interoperability with Traditional Email Systems
                4.3 Conformance to Existing Standards
                4.4 Backward Compatibility
                4.5 Robustness
        5. Acknowledgements
        6. Author's addresses
        7. References
        8. Copyright
      1.  Abstract
      This document describes the goals of Voice Profile for Internet Mail
      (VPIM), Version 3 and establishes a baseline of desired
      functionality against which proposed MIME profiles for Internet
      voice messaging can be judged. The primary goal for this version is
      to support interoperability with desktop clients. Other goals for
      this version of VPIM include backward compatibility, expanded
      interoperability with unified messaging systems, and conformance to
      Internet standards. This document does not include goals that were
      met fully by VPIM version 2 [VPIM2].
      Different levels of desirability are indicated throughout the
      2.  Conventions used in this document
      Within this document, different levels of desirability for a MIME
      profile for Internet voice messaging are indicated by different
      priorities, indicated in {braces}:
        {1} There is general agreement that this is a critical
      characteristic of any definition of VPIM version 3.
        {2} Most believe that this is an important characteristic of VPIM
      version 3.
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        {3} There is general belief that this is a useful feature of VPIM
      version 3, but that other factors might override; a definition that
      does not provide this element is acceptable.
      In addition, the following terms have specific meaning in this
        "service"      An operational service offered by a service provider
        "application"  A use of systems to perform a particular function
        "terminal"     The endpoint of a communication application
        "goal"         An objective of the standardization process
      The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
      this document are to be interpreted as described in RFC-2119 [REQ].
      3.  Introduction
      Until recently, voice mail and call answering services were
      implemented as stand-alone proprietary systems. Today, standards
      such as the Voice Profile for Internet Mail (VPIM) enable
      interoperability between such systems over the Internet. VPIM
      version 1 [VPIM1] was experimental and was a first attempt at a
      Voice Profile for Internet Mail, but is now classified as
      Historical. VPIM Version 2 [VPIM2] is an improvement on VPIM version
      1 that was originally intended to provide interoperability between
      voice messaging systems only. It describes a messaging profile that
      standardizes the exchange of voice mail over an IP messaging network
      using ESMTP [ESMTP] and MIME [MIME1]. With the trend toward
      integration of voice mail and email through unified messaging (UM),
      it is now necessary to define a new version of VPIM that supports
      the needs of desktop applications and unified messaging systems
      (including Internet Facsimile [EXFAX]). Because the number of
      desktop boxes is growing rapidly and will soon approach the number
      of desktop telephones, it is essential to consider the requirements
      of desktop email client applications (including, but not limited to,
      MIME-compliant email clients).
      This document defines the goals for VPIM version 3 [VPIM3 and IVM].
      This standard will support the interchange of voice messages between
      voice mail systems, unified messaging systems, email servers, and
      desktop client applications. The desktop client applications is of
      particular and important interest to VPIM version 3. This document
      will also expand the offerings of service providers by facilitating
      access to voice mail from a web client.
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      4.  Goals for Voice Profile for Internet Mail version 3
      VPIM must define the MIME profile and discard rules which will be
      used for the interchange of voice mail messages over the Internet,
      and must {1} meet the following goals.
      4.1  Interoperability
      Enhanced interoperability is the primary goal of VPIM version 3. The
      profile must {1} enable interoperability between voice mail systems,
      unified messaging systems, Internet email servers, and desktop
      client applications. Such interoperability will require {1} support
      for the new media-agnostic systems, which combine multiple media
      types into a single message, as well as support for legacy voice
      mail and email systems. It will require {1} features to accommodate
      varying capabilities of the voice mail, unified messaging and email
      systems. Furthermore, VPIM version 3 must {1} be compatible with
      Internet Fax (extended mode) proposed standards and VPIM messages
      that are fax messages for both sending and receiving.
      To have "interoperability" means that a VPIM version 3 compliant
      sender attempting to send to a recipient will not fail because of
      incompatibility. It is essential {1} that VPIM version 3 support
      interoperability between most of the systems listed below, and
      desirable {3} to support all of them:
        - Desktop email client applications
        - VPIM version 2 and version 3 voice Mail systems
        - VPIM version 3 unified messaging systems
        - Traditional email servers
      VPIM version 3 must also {1} include new functionality to facilitate
      access to voice mail messages from desktop applications.
      Overall interoperability requires interoperability for all of the
      VPIM elements: critical body parts must {1} be preserved, essential
      information must be provided in a form that is accessible by the
      users {1}, status codes must {1} be understood, and operations that
      are standard for each system should {2} be supported.
      4.1.1  Interoperability with Desktop Email Applications
      Desktop email applications are typically text based. The ability to
      listen to, reply to, forward, and generate voice mail messages from
      a traditional desktop environment is a relatively new development.
      To accommodate current use and future developments in this area,
      VPIM version 3 must {1} provide features to support access to voice
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      mail messages from the desktop and other email-reading devices. It
      would also be desirable {3} for it to support web access to voice
      mail from the desktop.
      VPIM version 3 should not {2} require desktop email applications to
      possess a large amount of processing power, and a base level
      implementation must {1} interoperate, even if it does not offer
      complex processing. There was a strong desire {2} to select a
      mandatory codec. The mandatory codec would be one that is already
      widely available on desktops. There was a strong consensus on MSGSM
      [MSGSM] being the mandatory codec for the interoperability that
      would therefore be provided. For VPIM version 2 interoperability,
      {3} there should also be support for the VPIM v2 mandatory codec
      [ADPCM and G726].
      Any codecs included in the VPIM version 3 specification should {2}
      meet the following criteria:
             - Availability on desktops: Codecs should {2} be available on
                        most platforms Windows, UNIX, Mac)
             - Source code availability
             - Decoding complexity: All codecs must {1} be low complexity
                        to decode
             - Encoding complexity: Some of the codecs must {1} be low
                        complexity to encode.
             - Bit rate: VPIM version 3 must {1} specify a codec with low
                        bit rate for devices (i.e., wireless) that do not
                        have much space/bandwidth.
             - Voice Over IP support: VPIM version 3 should {2} specify at
                       least one codec that supports Voice over IP
      Most desktop email applications and web clients are not capable of
      playing raw audio. To support "out-of-the box" playing of voice mail
      content, VPIM v3 must {1} support wav encapsulation of audio. To
      enable future support of other formats, VPIM version 3 should {2}
      provide identification of the codec used without requiring
      interpretation of an audio format. VPIM v3 may {3} allow audio
      encodings and formats that are not identified in the VPIM version 3
      specification to support environments in which the sender is aware
      of the optimal encoding and format for the recipient.
      Performance and bandwidth issues make it desirable {3} to support
      streaming of VPIM version 3 audio to the desktop. VPIM version 3 may
      {3} explicitly support formats other than raw audio and wav to
      facilitate streaming.
      Because most email readers are text/html based and because many
      devices are not capable of recording audio content, VPIM v3 must {1}
      allow inclusion of text body parts in a voice message. VPIM version
      3 should {2} not explicitly prohibit other media types, as long as
      critical content is identified and minimal discard rules are
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      To support devices that are not capable of playing audio, VPIM 3
      should {2} define an optional way to describe the content of the
      message and indicating how the audio content can be accessed.
      It is also a desktop requirement {1} to support attachments of any
      media type.
      4.1.2  Interoperability with VPIM v2 and v3 Voice Messaging Systems
      Voice messaging systems are generally implemented as special-purpose
      machines that interface to a telephone switch and provide call
      answering and voice messaging services. VPIM version 2 was designed
      to support interoperability between such systems and remains the
      best messaging profile for this purpose.
      To support interoperability between VPIM voice messaging systems and
      other compliant systems, VPIM version 3 should {3} have a simple
      minimum set of required features that will guarantee
      interoperability, as well as provision for additional functionality
      that may be supported by more capable systems. Support for this
      additional functionality requires {3} a mechanism for identifying
      essential content and status codes indicating that a message could
      not be delivered due to capability differences. It should {3} also
      include a minimum set of discard rules to enable back-down from VPIM
      V3 to V2.
      Interoperability with VPIM version 2 voice messaging systems is
      desirable, but not required. Interoperability should {3} be able to
      depend on the receiving system supporting the VPIM version 2
      32KADPCM codec [ADPCM and G726] , and should not {3} depend on the
      receiving system supporting any additional VPIM version 3 codecs or
      audio formats.
      To ensure interoperability between VPIM version 2 and version 3
      systems, it may {3} be desirable to revise the VPIM version 2
      specification to include new status codes and discard rules.
      4.1.3  Interoperability with VPIM v3 Unified Messaging Systems
      Unified messaging solutions typically leverage common store,
      directory, and transport layers to provide greater interoperability
      and accessibility to a variety of media content. They support
      creation of and access to voicemail, email, and fax messages from a
      single user interface.
      Most unified messaging systems preserve the notion of a primary
      media type with multiple message components that convey essential
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      information. Because unified messaging clients have varying
      capabilities, these components may have a different media type than
      the message. It is also common for unified messaging systems to
      permit forwarding and replying to messages of one type as an
      attachment to a message of another type.
      To accommodate the common functionality of unified messaging
      systems, VPIM version 3 must {1} support the inclusion of body parts
      of a type other than the primary content type. It must {1} also
      support the embedding of VPIM messages as attachments to messages of
      another type (such as multipart/mixed), as well as the embedding of
      messages of another type as attachments to VPIM messages.
      Interoperability with fax and fax messages is a must {1}.
      To provide interoperability with systems that cannot handle a
      particular content type, VPIM version 3 must {1} provide a mechanism
      for identifying essential or primary body parts and may {3} define
      media specific status codes and strings to handle non-delivery of
      these body parts.
      4.1.4  Interoperability with Traditional Email Servers
      Traditional email servers are those that support only textual media
      as inline content. VPIM version 3 must {1} interoperate consistently
      with the current Internet mail environment. If VPIM version 3
      messages arrive in users' mailboxes, it is required {1} that the
      standard interoperate successfully with common user practices for
      mail messages: storing them in databases, retransmission,
      forwarding, creation of mail digests, and replying to messages using
      non-audio equipment.
      4.3  Conformance to Existing Standards
      It is the goal of VPIM version 3 to conform as closely as possible
      to existing standards while meeting the other goals defined in this
      - Restrictions: The profile should {2} impose as few restrictions as
      possible to existing Internet mail standards. In particular, it must
      {1} support all elements of RFC 822 [RFC822] except those that
      prevent the profile from meeting other VPIM version 3 goals.
      - Additions: The profile should {2} make as few additions as
      possible to existing internet mail standards. It should also {2}
      adhere to existing desktop conventions in desktop-related areas such
      as file extensions. If it is necessary to define new MIME types or
      sub-types, the VPIM version 3 work group should {2} propose terms
      that are already standard or in common use in the desktop
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      4.4  Backward compatibility
      It is a goal of this profile to assure backwards compatibility with
      VPIM version 2. Where this is not possible, it may be {2} necessary
      to clarify version 2. VPIM version 2 has already gone through some
      clarifications to aid in interoperability with version 3. VPIM
      version 3 should {2} provide and define a minimal set of rules and
      status codes [CODES] for handling non-delivery of VPIM v3 messages.
      4.5  Robustness
      VPIM v3 must {1} be usable in an environment in which there exist
      legacy gateways that do not understand MIME. Core features and
      critical data must {1} not be lost when messages pass through AMIS
      gateways [AMIS-A and AMIS-D]. VPIM version 3 should {2} allow
      interoperability with recipient devices and gateways which have
      limited buffering capabilities and cannot buffer all header
      5.  Acknowledgements
      The authors gratefully acknowledge the input and feedback
      provided by the members of the EMA and IETF VPIM work groups that
      has resulted in this revision including: Kevin Chestnut, Bernard
      Elliot, Holly Grabowski, Graham Klyne, Larry Masinter, Glenn
      Parsons, Eric Schultz, and Greg Vaudreuil.
      6.  Authors' addresses
      Laile L. Di Silvestro
      Ambos Corporation
      Phone: +1-425-557-2805
      Email: laile@mindspring.com
      Rod Miles
      Nortel Networks
      P.O. Box 3511 Station C
      Ottawa, ON  K1Y 4H7
      Phone: +1-613-768-4087
      Fax  : +1-616-763-4461
      Email: rodmi@nortelnetworks.com
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      7.  References
      [ADPCM] G. Vaudreuil and G. Parsons, "Toll Quality Voice - 32 kbit/s
      ADPCM: MIME Sub-type Registration", RFC 2422, September 1998
      [AMIS-A] Audio Messaging Interchange Specifications (AMIS) - Analog
      Protocol Version 1, Issue 2, February 1992.
      [AMIS-D] Audio Messaging Interchange Specifications (AMIS) - Digital
      Protocol Version 1, Issue 3 August 1993.
      [CODES] Vaudreuil, G. "Enhanced Mail System Status Codes", RFC 1893,
      [ESMTP] Klensin, J., Freed, N., Rose, M., Stefferud, E., and D.
      Crocker, "SMTP Service Extensions" RFC 1869, United Nations
      University, Innosoft International, Inc., Dover Beach Consulting,
      Inc., Network Management Associates, Inc., The Branch Office,
      November 1995.
      [EXFAX] Masinter, L., Wing, D., "Extended Facsimile Using Internet
      Mail", RFC 2532, Xerox Corporation, Cisco Systems, March 1999.
      [G726] CCITT Recommendation G.726 (1990), General Aspects of
      Digital Transmission Systems, Terminal Equipment - 40, 32, 24,16
      kbit/s Adaptive Differential Pulse Code Modulation (ADPCM).
      [IVM] McRae, S., "Internet Voice Messaging", Work In Progress,
      <draft-ema-vpim-voicemsg-00.txt>, October 22, 1999.
      [MIME1] N. Freed and N. Borenstein,  "Multipurpose Internet Mail
      Extensions (MIME) Part One: Format of Internet Message Bodies", RFC
      2045, Innosoft, First Virtual, Nov 1996.
      [MSGSM] Di Selvestro, L., Hedberg, E., Baribault, G., "Toll
      Quality Voice - Microsoft GSM MIME Sub-type Registration", Work In
      Progress, <draft-ema-vpim-msgsm-00.txt>, Microsoft Corporation,
      April 1, 1999.
      [PCM] CCITT, Fascicle III.4 - Recommendation G.711,  Geneva, 1972,
      "Pulse Code Modulation (PCM) of Voice Frequencies".
      [REQ] Bradner, S., "Key words for use in RFCs to Indicate
      Requirement Levels", BCP 14, RFC 2119, March 1997.
      [RFC822] Crocker, D., "Standard for the Format of ARPA Internet
      Text Messages", STD 11, RFC 822, UDEL, August 1982.
      [VPIM1] Vaudreuil, Greg, "Voice Profile for Internet Mail", RFC
      1911, Feb 1996.
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      [VPIM2] Vaudreuil, Greg, Parsons, Glen, "Voice Profile for Internet
      Mail, Version 2", RFC 2421, September 1998.
      [VPIM3] Parsons, Glenn, "Voice Profile for Internet Mail - Version 3
      A Simple Approach", Work In Progress, <draft-ema-simplev3-00.txt>,
      Nortel Networks, June 25, 1999.
      8.  Full Copyright Statement
      Copyright (C) The Internet Society (2000). 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
      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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