INTERNET-DRAFT Laile L. Di Silvestro
Expires in 6 months Microsoft Corporation
January 6, 1999
Goals for Voice Profile for Internet Messaging, Version 3
<draft-ema-vpimv3-goals-00.txt>
Status of this memo:
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.
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Internet Draft VPIM V3 Goals July 6, 1999
Table of contents:
1. Introduction
2. Goals for Voice Profile for Internet Messaging Version 3
2.1 Interoperability
2.2 Conformance to existing standards
2.3 Backward compatibility
2.4 Robustness
3. Interoperability goals for Voice Profile for Internet
Messaging Version 3
3.1 Interoperability with desktop client applications
3.2 Interoperability with VPIM version 2 and version 3
voice messaging systems
3.3 Interoperability with VPIM version 3 unified messaging
systems
3.4 Interoperability with traditional email servers
4. Acknowledgements
5. Copyright
6. Author's address
7. References
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Abstract
This document describes the goals of the Voice Profile for Internet
Messaging (VPIM), Version 3 work group and establishes a baseline of
desired functionality against which proposed MIME profiles for
Internet voice messaging can be judged. The goals for VPIM version 3
are limited in scope and do not require any changes from the basic
MIME flow defined by VPIM version 2. The primary goal for this
version is to support interoperability with desktop clients. Other
goals for this version of VPIM include expanded interoperability with
unified messaging systems, backward compatibility, and conformance to
Internet standards. This document does not include goals that were met
fully by VPIM version 2.
Different levels of desirability are indicated throughout the
document.
1. 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 [VPIM1] describes a
messaging profile that standardizes the exchange of voice mail over an
IP messaging network using ESMTP [ESMTP] and MIME [MIME1]. VPIM
Version 2 [VPIM2] provides interoperability between voice messaging
services only. 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 unified messaging
systems and desktop applications. Because the number of desktop boxes
is growing rapidly and will soon approach the number of desktop
telephones, it is especially important to consider the requirements of
desktop email client applications.
This document defines the goals for VPIM version 3 [VPIM3]. This
standard will support the interchange of voice messages between voice
mail systems, unified messaging systems, email servers, and desktop
client applications. It will also expand the offerings of service
providers by facilitating access to voice mail from a web client.
1.1 Terminology used within 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.
{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.
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In addition, the following terms are used:
"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.
2. Goals for Voice Profile for Internet Messaging 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:
2.1 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.
It must also [1}, include new functionality to facilitate access to
voice mail messages from desktop applications.
Specific goals for interoperability are detailed in section 3.0.
2.2 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
document.
- 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 standards 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 environment.
2.3 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 or revise version 2. VPIM version 3 must {1} comprise of
superset of VPIM v2 features. It should {2} also provide define a
minimal set of rules and status codes [CODES] for handling
non-delivery of VPIM v3 messages.
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2.4 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
information.
3. Interoperability goals for Voice Profile for Internet Messaging
Version 3
To "support 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 messaging systems
- VPIM version 3 unified messaging systems
- Traditional email servers
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.
3.1 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 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. It is therefore necessary {1} for VPIM version 3
to support a variety of codecs that meet differing processor and
memory constraints. 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)
- Multiple codecs: VPIM version 3 must {1} allow for range of
codecs from low bit rate/high complexity to high bit rate/low
complexity. Clients need choice in codec based on resources
available (bandwidth and CPU). One codec is not suitable for
all devices.
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- Limited number of codecs: VPIM version 3 should {2} not
specify more than 4 or 5 codecs or implementation may be
delayed.
-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 some codecs 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 implementations.
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 desireable {3} to support
streaming of VPIM version 3 audio to the desktop. VPIM version 3
may {3} explicitely 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
specified.
To support devices that are not capable of playing audio, VPIM 3 should
{2} define an optional informational text body part
describing 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. VPIM version 3 must {1} specify discard rules for cases
in which recipient can't render the attachments.
3.2 Interoperability with VPIM version 2 and version 3 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 the purpose.
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To support interoperability between VPIM voice messaging systems and
other compliant systems, VPIM version 3 must {1} 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 {1} a mechanism for identifying essential
content and status codes indicating that a message could not be
delivered due to capability differences. It should {2} also include a
minimum set of discard rules.
The requirement for interoperability with VPIM version 2 voice
messaging systems has strong implications for the specification of
standard audio encoding and format. Interoperability must {1} be able
to depend on the receiving system supporting the VPIM version 2
32KADPCM codec [ADPCM and G726] , and must not {1} 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.
3.3 Interoperability with VPIM version 3 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
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.
To provide interoperability with systems that cannot handle a
particular content type, VPIM version 3 must {1} provide a mechanism
for identifying essential body parts and should {2} define media
specific status codes and strings to handle non-delivery of essential
body parts.
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3.4 Interoperability with traditional email servers
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. Acknowledgements
The author gratefully acknowledges the input and feedback provided by
the members of the VPIM version 3 work group including Kevin Chestnut,
Bernard Elliot, Holly Grabowski, Glen Parsons, and Greg Vaudreuil.
The author also appreciates the contributions of Eric Schultz in
reviewing this document.
5. Copyright
Copyright (C) The Internet Society, 1997. 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 English.
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
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS 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."
6. Author's address
Laile L. Di Silvestro
Microsoft Corporation
One Microsoft Way, MS 34/3308
Redmond, WA 98073
lailed@microsoft.com
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7. References
[ADPCM] G. Vaudreuil and G. Parsons, "Toll Quality Voice - 32 kbit/s
ADPCM: MIME Sub-type Registration", Work In Progress,
<draft-ema-vpim-32kadpcm-02.txt>, November 1997.
[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,
01/15/1996.
[DISP] R. Troost and S. Dorner, Communicating Presentation Information
in Internet Messages: The Content-Disposition Header, RFC 2183,
August 1997
[DRPT] Moore, K. "SMTP Service Extensions for Delivery Status
Notifications", RFC 1891, 01/15/1996
[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.
[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).
[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.
[MIME2] N. Freed and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types ", RFC 2046, Innosoft,
First Virtual, Nov 1996.
[MIME3] K. Moore, "Multipurpose Internet Mail Extensions (MIME)
Part Three: Message Header Extensions for Non-ASCII Text ",
RFC 2047, University of Tennessee, Nov 1996.
[MIME4] N. Freed, J. Klensin and J. Postel, "Multipurpose Internet
Mail Extensions (MIME) Part Four: Registration Procedures",
RFC 2048, Innosoft, MCI, ISI, Nov 1996.
[MIME5] N. Freed and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Five: Conformance Criteria and Examples ",
RFC 2049, Innosoft, First Virtual, Nov 1996.
[REPORT] Vaudreuil, G., "The Multipart/Report Content Type for the
Reporting of Mail System Administrative Messages", RFC 1892,
01/15/1996.
[RFC822] Crocker, D., "Standard for the Format of ARPA Internet Text
Messages", STD 11, RFC 822, UDEL, August 1982.
[SMTP] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821,
USC/Information Sciences Institute, August 1982.
[STATUS] Freed, N. "SMTP Service Extension for Returning Enhanced
Error Codes", RFC 2034, 10/30/1996.
[V-MSG] G. Vaudreuil and G. Parsons, "VPIM Voice Message: MIME
Sub-type Registration", RFC 2022, September 1998.
[VCARD] Dawson, Frank, Howes, Tim, "vCard MIME Directory Profile"
RFC????, September 1998.
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[VPIM1] Vaudreuil, Greg, "Voice Profile for Internet Mail", RFC 1911,
Feb 1996.
[VPIM2] Vaudreuil, Greg, Parsons, Glen, "Voice Profile for Internet
Mail, Version 2", RFC 2421, September 1998.
[VPIM3] Vaudreuil, Greg, "Voice Profile for Internet Mail, Version 2",
", Work In Progress, <draft-ema-VPIMv3-00.txt>, December 1998