VPIM Working Group Stuart McRae
Internet Draft Lotus Development
Document: <draft-ietf-vpim-ivm-01.txt> Glenn Parsons
Category: Standards Track Nortel Networks
November 24, 2000
Internet Voice Messaging
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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1. Abstract
This document provides for the carriage of voicemail messages over
Internet mail as part of a unified messaging infrastructure.
The Internet Voice Messaging (IVM) concept described in this
document was originally called VPIM v3. This term has been dropped
to reflect the fact that it is not a successor format to VPIM v2,
but rather an alternative specification for a different application.
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 RFC-2119
[KEYWORDS].
3. Introduction
People naturally communicate using their voices, and this is
preferable to typing for some forms of communication. By permitting
voicemail to be implemented in an interoperable way on top of
Internet Mail, voice messaging and electronic mail need no longer
remain separate, isolated worlds and users will be able to choose
the most appropriate form of communication. This will also enable
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new types of device, without keyboards, to be used to participate in
electronic messaging when mobile, in a hostile environment, or in
spite of disabilities.
There exist unified messaging systems which will transmit voicemail
messages over the Internet using SMTP/MIME, but these systems suffer
from a lack of interoperability because various aspects of such a
message have not hitherto been standardized. In addition, voicemail
systems can now conform to the Voice Profile for Internet Messaging
(VPIM v2 as defined in RFC 2421 [VPIM2]) when forwarding messages to
remote voicemail systems, but VPIM v2 was designed to allow two
voicemail systems to exchange messages, not to allow a voicemail
system to interoperate with a desktop e-mail client, and it is often
not reasonable to expect a VPIM v2 message to be usable by an e-mail
recipient. The result is messages which cannot be processed by the
recipient (e.g., because of the encoding used), or look ugly to the
user.
This document therefore proposes a standard mechanism for
representing a voicemail message within SMTP/MIME, and a standard
encoding for the audio content, which unified messaging systems and
mail clients MUST implement to ensure interoperability. By using a
standard SMTP/MIME representation, and a widely implemented audio
encoding, this will also permit most users of e-mail clients not
specifically implementing the standard to still access the voicemail
message. In addition, this document describes features an e-mail
client SHOULD implement to allow recipient's to display voicemail
message in a more friendly, context sensitive way to the user, and
intelligently provide some of the additional functionality typically
found in voicemail systems (such as responding with a voice message
instead of e-mail). Finally is explained how a client MAY provide a
level of interoperability with VPIM v2.
It is desirable that unified messaging mail clients also be able to
fully interoperate with voicemail servers. This is possible today,
providing the client implements VPIM v2 [VPIMV2] in addition to this
specification, and uses it to construct messages to be sent to a
voicemail server. Separate work may be undertaken in the VPIM
Working Group to provide further interoperability between clients
implementing this specification and voicemail systems implementing
VPIM.
This definition is based on the IVM goals document [GOALS], which is
being revised to reflect subsequent discussions. This document is
partly derived from VPIM v2 [VPIMV2] as well as ongoing discussion
within the VPIM WG on IVM. It references separate work on critical
content [CRITICAL], content hints [HINT]. Addressing issues are
discussed in a related Internet draft [ADDRESS]. Independent work
within the IETF is also addressing VPIM directory issues.
Further information on VPIM v2 and related activities can be found
at http://www.vpim.org.
4. Message Format
All messages MUST conform with the Internet Mail format as it is
being defined by the DRUMS working group [DRUMSIMF].
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The message header SHOULD indicate a content hint of "voice-message"
(see [HINT]).
If the receiving user agent identifies the message as a voice
message (from the content hint), it MAY present it to the user as a
voice message rather than as an electronic mail message with a voice
attachment.
Any content type is permitted in a message, but the top level
content type on origination of a new, forwarded or reply voice
message SHOULD be multipart/mixed. If the recipient is known to be
VPIM v2 compliant then multipart/voice-message MAY be used instead
(in which case all the provisions of [VPIMV2] SHOULD be
implemented).
If the message was created as a voice message, then the appropriate
audio body part SHOULD be indicated as critical content, via a
Content-Criticality parameter of CRITICAL (see [CRITICAL]).
Additional important body parts (such as the original audio message
if a voicemail is being forwarded) SHOULD also indicated via a
Content-Criticality of CRITICAL. Contents which are not essential to
communicating the meaning of the message (e.g. an associated vCard
for the originator) MAY be indicated via a Content-Criticality of
IGNORE.
The top level content type on origination of a delivery notification
message MUST be multipart/report. This will allow automatic
processing of the delivery notification - for example, so that text-
to-speech processing can render a non-delivery notification in the
appropriate language for the recipient.
5. Transport
The message MUST be transmitted in accordance with the Simple Mail
Transport Protocol as it is being defined by the DRUMS working group
[DRUMSMTP].
Delivery Status Notifications SHOULD be requested [DSN] if delivery
of the message is important to the originator.
6. Addressing
Any valid Internet Mail address may be used for a voice message.
It is desirable to be able to use and onramp/offramp for delivery of
a voicemail message to a user, which will result in specific
addressing requirements, based on service selectors as defined in
[SELECTOR]. Further discussion of addressing requirements for voice
messages can be found in the VPIM Addressing draft [ADDRESS].
It is desirable to permit the use of a directory service to map
between the E.164 phone number of the recipient and an SMTP mailbox
address. How this might be achieved is currently under study in the
VPIM and ENUM working groups [VPIMENUM],[SCHEMA].
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If a message is created and stored as a result of call answering,
the caller's name and number MAY be stored in the message headers in
its original format per [CLID].
7. Notifications
Delivery Status Notifications MUST be supported. All non-delivery
of messages MUST result in a NDN, if requested [DSN]. If the
receiving system is unable to process all of the critical media
types within a voice message (indicated by the content criticality),
then it MUST non-deliver the entire message.
Message Disposition Notifications SHOULD be supported (but according
to MDN rules the user MUST be given the option of deciding whether
MDNs are returned) [MDN].
If the recipient is unable to display all of the indicated critical
content components indicated, then it SHOULD give the user the
option of returning an appropriate MDN (see [CRITICAL]).
8. Voice Contents
Voice messages may be contained at any location within a message and
MUST be contained in an audio/WAV content-type, unless the
originator is aware that the recipient can handle other content.
Specifically, Audio/32KADPCM MAY be used when the recipient is known
to support VPIM v2 [VPIMV2].
The VOICE parameter from VPIM v2 [VPIMV2] SHOULD be used to identify
the any spoken names or spoken subjects (as distinct from voice
message contents).
The originator's spoken name SHOULD be included with messages as
separate audio contents, if known, and indicated by the Content-
Disposition as defined in VPIM v2 [VPIMV2]. If there is a single
recipient for the message, their spoken name MAY also be included
(per VPIM v2). A spoken subject MAY also be provided (per VPIM v2).
An implementation MAY determine the recipient capabilities before
sending a message and choose a codec accordingly (e.g. using some
form of content negotiation). In the absence of such recipient
knowledge, implementations MUST use MS-GSM within the WAV file -
indicated via "audio/wav; codec=31".
Recipients MUST be able to play such a WAV encapsulated MS-GSM
message, and MAY be able to play G.726 (indicated as audio/32kadpcm)
to provide some interoperability with VPIM v2 [VPIMV2].
An implementation MAY be able to play messages encoded with other
codecs (either natively or via transcoding) but MUST be able to
record WAV with MS-GSM.
An implementation MAY support interoperability with VPIM v2
[VPIMV2], in which case it MUST be able to record G.726 (indicated
as audio/32kadpcm).
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These requirements may be summarised as follows:
Codec No VPIM v2 Support With VPIM V2 Support
Record Playback Record Playback
------ ------ -------- ------ --------
WAV/MS-GSM MUST MUST MUST MUST
G.726 MAY MAY MUST MUST
Other MAY MAY MAY MAY
Editor's Note: Based on ongoing discussions in the
VPIM WG, the baseline codec for IVM may be changed to
G.711 mu-law indicated via "audio/basic" or
"audio/wav; codec=7".
9. Fax Contents
Fax contents SHOULD be carried according to RFC 2532 [IFAX].
10. Further Work
The above text provides some guidelines as to how to ensure that a
VPIM v2 message arriving on at a compliant mail system might be
rendered useful to the recipient. However, a thorough investigation
of interoperability with VPIM v2 is beyond the scope of this
document.
Other areas which are candidates to be referenced from this document
include: Content Negotiation (inc. RESCAP); the VPIM Directory work;
Spoken Header fields (embedded or references); the inclusion of
additional voice message specific header information in the RFC822
header; and a consideration of interoperability with e-mail clients
not supporting this specification.
11. Security Considerations
It is anticipated that there are no additional security issues
beyond those identified in VPIM v2.
12. References
[ADDRESS] Parsons, G., "VPIM Addressing", <draft-ietf-vpim-address-
00.txt>, November 2000, Work in Progress.
[CLID] Collins, J., "Calling Line Identification for VPIM Messages",
<draft-ema-vpim-clid-01.txt>, November 2000, Work in Progress.
[CRITICAL] Burger, E., Candell, E., "Critical Content of Internet
Mail" <draft-burger-vpim-cc-02.txt>, November 2000, Work in
Progress.
[DSN] Moore, K., "SMTP Service Extension for Delivery Status
Notifications" RFC 1891, January 1996.
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Internet Voice Messaging November 2000
[DRUMSMTP] Klensin, J., "Simple Mail Transfer Protocol", <draft-
ietf-drums-smtpupd-13.txt>, Work in Progress.
[DRUMSIMF] Resnick, P., "Internet Message Format", <draft-ietf-
drums-msg-fmt-09.txt>, Work in Progress.
[HINT] Burger, E., Candell, E., Eliot, C., Klyne, G. "Message
Context Internet Mail" <draft-ietf-vpim-hint-01.txt>, Novemebr 2000,
Work in Progress.
[IFAX] Masinter, L., Wing, D. "Extended Facsimile Using Internet
Mail", RFC 2532, March 1999.
[KEYWORDS] Bradner, S., "Key Words for use in RFCs To Indicate
Requirement Levels", RFC 2119, March 1997.
[GOALS] Candell, E., "Goals for Internet Voice MAil", <draft-ietf-
vpim-ivm-goals-00.txt>, November 2000, Work in Progress.
[MIME] Freed, N., Borenstein, N., "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message Bodies", RFC
2045, November 1996.
[SELECTOR] Allocchio, C., "Minimal PSTN address format in Internet
Mail", RFC 2303, March 1998.
[] Vaudreuil, G. "Voice Message Routing Service",<draft-
ietf-vpim-routing-01.txt> , October 2000, Work in Progress.
[SCHEMA] Brown, A., Vaudreuil, G. "Voice Messaging Directory
Service",<draft-ietf-vpim-vpimdir-01.txt> , July 2000, Work in
Progress.
[VPIMV2] Vaudreuil, G., Parsons, G., "Voice Profile for Internet
Mail - version 2", RFC 2421, September 1998.
[VPIMV2R2] Vaudreuil, G., Parsons, G., "Voice Profile for Internet
Mail - version 2", <draft-ietf-vpim-vpimv2r2-01.txt>, November 2000,
Work in Progress.
[VPIMVM] Vaudreuil, G., and Parsons, G., "VPIM Voice Message: MIME
Sub-type Registration", RFC 2423, September 1998.
[WAVMGSM] Di Silvestro, L., Baribault, G., "Waveform Audio File
Format MIME Sub-type Registration" <draft-ema-vpim-wav-00.txt>. Work
in Progress.
13. Author's Addresses
Stuart J. McRae
Lotus Development
43 Seymour Gardens
Twickenham, United Kingdom
TW1 3AR
Phone: +44 208 891 1896
Fax: +44 1784 499 112
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Internet Voice Messaging November 2000
Email: stuart_mcrae@lotus.com
Glenn W. Parsons
Nortel Networks
P.O. Box 3511, Station C
Ottawa, ON K1Y 4H7
Canada
Phone: +1-613-763-7582
Fax: +1-416-597-7005
Email: gparsons@nortelnetworks.com
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