Internet Draft Greg Vaudreuil
Expires in six months Lucent Technologies
Glenn Parsons
Nortel Networks
February 1, 1999
Voice Profile for Internet Mail - version 3
<draft-ema-vpimv3-00.txt >
Status of this Memo
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.
This document is an Internet Draft. 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 Drafts.
Internet Drafts are valid for a maximum of six months and may be
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inappropriate to use Internet Drafts as reference material or to cite
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To learn the current status of any Internet-Draft, please check the
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ftp.isi.edu (US West Coast).
Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
This Internet-Draft is in conformance with Section 10 of RFC2026.
Overview
This document profiles Internet mail for unified messaging. It is a
complement to VPIM Version 2 documented in RFC 2021. A list of
changes from that document are noted in Appendix F. As well, Appendix
A summarizes the protocol profiles of this version of VPIM.
Please send comments on this document to the author, Greg Vaudreuil
<gregv@lucent.com>.
Internet Draft VPIM V3 August 20, 1999
Working Group Summary
This is a working draft within being considered within the electronic
messaging association. It is intended that this document be presented
to the IETF for standardization.
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Table of Contents
1. ABSTRACT ..........................................................4
2. KEY CHANGES IN VERSION 3 ..........................................5
3. SCOPE .............................................................6
3.1 Voice and Unified Messaging System Interactions .................6
3.2 Design Goals ....................................................6
4. PROTOCOL RESTRICTIONS .............................................8
5. VOICE MESSAGE INTERCHANGE FORMAT ..................................9
5.1 Message Addressing Formats ......................................9
5.2 Message Header Fields ..........................................10
5.3 MIME Content Descriptions ......................................18
5.4 Voice Message Content Types ....................................19
5.5 Other MIME Content Types .......................................25
5.6 Return and Notification Messages ...............................27
5.7 Forwarded Messages .............................................28
5.8 Reply Messages .................................................29
5.9 Notification Messages ..........................................30
6. MESSAGE TRANSPORT PROTOCOL .......................................31
6.1 ESMTP Commands .................................................31
6.2 ESMTP Keywords .................................................33
6.3 ESMTP Parameters - MAIL FROM ...................................34
6.4 ESMTP Parameters - RCPT TO .....................................35
6.5 ESMTP - SMTP Downgrading .......................................35
7. CONFORMANCE REQUIREMENTS .........................................35
8. SECURITY CONSIDERATIONS ..........................................35
8.1 General Directive ..............................................35
8.2 Threats and Problems ...........................................36
8.3 Security Techniques ............................................36
9. ACKNOWLEDGMENTS ..................................................39
10. COPYRIGHT NOTICE .................................................40
11. AUTHORS' ADDRESSES ...............................................40
12. APPENDIX A - VPIM REQUIREMENTS SUMMARY ...........................41
13. APPENDIX B - EXAMPLE VOICE MESSAGES ..............................42
14. APPENDIX C - EXAMPLE ERROR VOICE PROCESSING ERROR CODES ..........45
15. APPENDIX D - EXAMPLE VOICE PROCESSING DISPOSITION TYPES ..........46
16. APPENDIX F - CHANGE HISTORY: RFC 2421 (VPIM V2) TO THIS DOCUMENT .47
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1. Abstract
General electronic mail (email) provides a facility for exchanging
messages of seemingly arbitrary content. In common email usage, text
is the primary media with one or more attachments.
A class of special-purpose computers has evolved to provide voice
messaging services. These machines generally interface to a telephone
switch and provide call answering and voice messaging services.
Message exchange between these voice-mail only systems can best be
achieved using VPIM Version 2.
Fax messaging is another special purpose messaging system which
interface to a telephone switch and provide the ability to send and
receive images over the PSTN. When sending these messages over the
Internet rather than the PSTN, the simple mode fax profile defined in
RFC ABCD should be used.
Other electronic messaging systems include paging, and short message
service. It is expected that other messaging systems developed for
specific environments will continue to be developed.
This profile defines a new version of the VPIM specification for the
interchange of voice messages between a voice messaging system as
defined in [VPIM] and a unified messaging system. In this sense, a
unified messaging system is capable of sending and receiving each of
several different message types. Typical unified messaging systems
today consolidate fax messages, voice messages, and email messages
into a single system and permit the forwarding a received message of
one type as an attachment to a message of another type.
Further, this profile will define the interactions between a media
agnostic (multi-media) messaging system with unified messaging and
voice messaging systems. A media agnostic system may combine several
media into a single message. Such a message may not have primary a
media but rely upon several components together to convey the
essential information.
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2. Key changes in Version 3
Several new capabilities are added to VPIM to form the Version 3
specification.
1) Three new voice encodings are profiled. While version 2 choose
G726 ADPCM as a compromise, experience has shown a need for a wider
variety of encodings. These encodings range from the larger but
less computationally intensive Mu-Law to the high compression
G.723.1 encoding used by Voice over IP telephony. All VPIM Version
3 systems must be capable of receiving audio encoded in any of
these formats. Sending systems may choose to send audio in any of
the encodings.
2) Support of the Microsoft WAV encapsulation has been added to
provide an option to systems which need to send in a format useful
for installed-base desktop email systems. All VPIM Version 3
systems must be capable of receiving audio encoded raw or in a WAV
wrapper. Sending systems may choose to use send raw audio data or
encapsulate it in the WAV file format.
3) Support the attachment of messages of any type to messages of
any other type. This is the common result of forwarding a message
with cover comments from a terminal type with a primary media other
than that of the original message.
4) Support the inclusion of other non-primary media in a voice
message. In particular, permit the inclusion of textual
information as well as the attachment of arbitrary files in the
voice message type.
5) Create clear discard rules such that messages with message,
media, or attachments not recognized by the sender can be delivered
if the primary media of the message can be deposited in the
recipients mailbox. Messages where the primary media cannot be
preserved must be returned to the sender with an informative
notification message.
6) Define a special case of text such that messages received by a
non-VPIM terminal will display by default advisory text describing
the nature of the messages and providing instructions on how to
download a suitable helper application.
7) When it is known that the receiving system supports the same
voice encoding as the sending system (by per-user, or per-system
configuration), provide an option to send the audio data in the
common audio format, even if not otherwise permitted.
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3. Scope
MIME is the Internet multipurpose, multimedia messaging standard.
This document explicitly recognizes its capabilities and provides a
mechanism for the exchange of various messaging technologies,
primarily voice and facsimile.
This document specifies a restricted profile of the Internet
multimedia messaging protocols for use between voice processing server
platforms and unified messaging platforms. This profile is intended to
specify the minimum common set of features to allow interworking
between compliant systems.
3.1 Voice and Unified Messaging System Interactions
The following are typical interactions between voice messaging and
unified messaging systems that must be addressed by this
specification.
1) Text messages are not normally received and often cannot be easily
displayed or viewed on voice mail machines. They can sometimes be
processed via text-to-speech or text-to-fax features.
2) Unified messaging systems accept addresses in several formats
relative to the type of message. In particular, Internet
addressing uses the domain name system while fax and voice
messaging use the telephone numbering system. Addressing must be
adapted or re-formatted such that a messages from one domain
preserves the ability to reply to all recipients.
3) Voice messaging systems are not capable of rendering all message
types and are not capable of rendering all media types. A
combination of capabilities exchange and clear downgrade rules are
necessary to provide a seamless interaction between more capable
and less capable systems.
4) Error reports must be machine-parseable so that helpful responses
can be presented to users in a manner appropriate to the terminal
where they receive the message at.
3.2 Design Goals
It is a goal of this profile to make as few restrictions and additions
to the existing Internet mail protocols as possible while satisfying
the requirements for interoperability between voice mail system,
unified messaging systems, and general Internet email. It is also a
goal to make the necessary extensions as backward compatible with VPIM
Version 2 as possible. Where this is not possible, it may be
desirable to clarify or revise Version 2 to make it so.
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This profile is intended to be robust enough to be used in an
environment, such as the global Internet with installed-base gateways
which do not understand MIME, though typical use is expected to be
within corporate intranets. Full functionality, such as reliable
error messages and binary transport, will require careful selection of
gateways (e.g., via MX records) to be used as VPIM forwarding agents.
Nothing in this document precludes use of general purpose MIME email
packages to read and compose VPIM messages. While no special
configuration is required to receive VPIM compliant messages, some may
be required to originate compliant structures.
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4. Protocol Restrictions
<To be added>
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 [REQ].
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5. Voice Message Interchange Format
The voice message interchange format is a profile of the Internet Mail
Protocol Suite. Any Internet Mail message containing the format
defined in this section is referred to as a VPIM Version 3 Message in
this document. As a result, this document assumes an understanding of
the Internet Mail specifications. Specifically, VPIM references
components from the message format standard for Internet messages
[RFC822], the Multipurpose Internet Message Extensions [MIME], the
X.400 gateway specification [X.400], delivery status and message
disposition notifications [REPORT][DSN][DRPT][STATUS][MDN], and the
electronic business card [MIMEDIR][VCARD].
5.1 Message Addressing Formats
[RFC822] addresses are based on the domain name system. This naming
system has two components: the local part, used for username or
mailbox identification; and the host part, used for global machine
identification.
5.1.1 Server-to-Server VPIM Addresses
VPIM Version 3 places no restrictions on the "from:" of the Internet
address. VPIM Version 3 (and v2) systems must be capable of receiving
an arbitrary email address and generating a reply to that address. No
inferences about the structure of the local part (left hand side)
should be necessary.
Recipients email addresses must be created in a form compatible with
the recipients system and consistent with the address entry
capabilities of a telephone user interface.
5.1.2 Special Addresses
Special addresses are provided for compatibility with the conventions
of Internet mail. These addresses do not use numeric local addresses,
both to conform to current Internet practice and to avoid conflict
with existing numeric addressing plans. Two special addresses are
RESERVED for use as follows:
postmaster@domain
By convention, a special mailbox named "postmaster" MUST exist on all
systems. This address is used for diagnostics and should be checked
regularly by the system manager. This mailbox is particularly likely
to receive text messages, which is not normal on a voice processing
platform. The specific handling of these messages is an individual
implementation choice.
non-mail-user@domain
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If a reply to a message is not possible, such as a telephone answering
message or a fax message, then the special address "non-mail-user"
must be used as the originator's address. Any text name such as
"Telephone Answering", or the telephone number if it is available, is
permitted. This special address is used as a token to indicate an
unreachable originator. For compatibility with the installed base of
mail user agents, implementations that generate this special address
MUST send a negative delivery status notification (DSN) for reply
messages sent to the undeliverable address. The status code for such
NDN's is 5.1.1 "Mailbox does not exist".
Examples:
From: Telephone Answering <non-mail-user@mycompany.com>
From: 9727332722 <non-mail-user@mycompany.com>
5.1.3 Distribution Lists
There are many ways to handle distribution list (DL) expansions and
none are 'standard'. Simple alias is a behavior closest to what most
voice mail systems do today and what is to be used with VPIM messages.
That is:
Reply to the originator - (Address in the RFC822 "Reply-to:" or
"From":" field)
Errors to the submitter - (Address in the "MAIL FROM:" field of the
ESMTP exchange and the Return-Path:
RFC 822 field)
Some proprietary voice messaging protocols include only the recipient
of the particular copy in the envelope and include no "header fields"
except date and per-message features. Most voice messaging systems do
not provide for "Header Information" in their messaging queues and
only include delivery information. As a result, recipient information
MAY be in either the To or CC header fields. If all recipients cannot
be presented (e.g. unknown DL expansion) then the recipient header
fields MUST be omitted to indicate that an accurate list of recipients
(e.g. for use with a reply-all capability) is not known.
Note: Discuss use of the group notation of [RFC822] as a placeholder
for unknown recipients.
5.2 Message Header Fields
Internet messages contain a header information block. This header
block contains information required to identify the sender, the list
of recipients, the message send time, and other information intended
for user presentation. Except for specialized gateway and mailing
list cases, header fields do not indicate delivery options for the
transport of messages.
Distribution list processors are noted for modifying or adding to the
header fields of messages that pass through them. VPIM systems MUST
be able to accept and ignore header fields that are not defined here.
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The following header lines are permitted for use with VPIM voice
messages:
5.2.1 From
The originator's fully-qualified domain address (a mailbox address
followed by the fully-qualified domain name). The user listed in this
field "SHOULD" be presented in the voice message envelope as the
originator of the message.
SEND RULES
Systems compliant with this profile SHOULD provide the text personal
name of the voice message originator in a quoted phrase, if the name
is available. Text names of corporate or positional mailboxes MAY be
provided as a simple string. From [RFC822]
Example:
From: "Joe S. User" <12145551212@mycompany.com>
From: Technical Support <611@serviceprovider.com>
From: Non-mail-user@myserver.mycompany.com
Voice mail machines may not be able to support separate attributes for
the "From:" and "Reply-To:" header fields and the vCard email
attribute, VPIM-conforming systems SHOULD set these values to the same
address. Use of addresses different than those present in the "From:"
header field address may result in unanticipated reply behavior.
RECEPTION RULES
The "From:" address SHOULD be used for replies (see 5.7.1). However,
if the "From:" address contains <non-mail-user@domain>, the user
SHOULD NOT be offered the option to reply, nor should notifications be
sent to this address.
5.2.2 To
The "To:" field contains the recipient's fully-qualified domain
address. There MAY be one or more "To:" fields in any message.
Examples:
To: +12145551213@mycompany.com
To: Undisclosed Recipient:;
SEND RULES
Systems SHOULD provide a list of recipients only if all recipients are
provided.
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Systems such as gateways from protocols which do not indicate the
complete list of recipients SHOULD provide a "To:" line. Because
these systems cannot accurately enumerate all recipients in the "To:"
headers, no recipients should be enumerated. The group notation of
RFC822 MAY be used in this case.
(see 5.1.3).
RECEPTION RULES
Systems compliant to this profile MAY discard the addresses in the
"To:" fields if they are unable to store the information. This would,
of course, make a reply-to-all capability impossible. If present, the
addresses in the "To:" field MAY be used for a reply message to all
recipients.
5.2.3 Cc
The "Cc:" field contains additional recipients' fully-qualified domain
addresses. Many voice mail systems maintain only sufficient envelope
information for message delivery and are not capable of storing or
providing a complete list of recipients.
SEND RULES
Conforming implementations SHOULD send "Cc:" lists if all recipients
that should be disclosed can be disclosed. The list of disclosed
recipients does not include those sent via a blind copy. If not,
systems SHOULD omit the "Cc:" fields or use the group notation from
RFC822 to indicate that the full list of recipients is unknown or
otherwise unavailable.
Example:
Cc: +12145551213@mycompany.com
RECEIVE RULES
Systems compliant to this profile MAY discard the addresses in the
"Cc:" fields of incoming messages as necessary. If a list of "Cc:"
addresses is present, these addresses MAY be used for a reply message
to all recipients.
5.2.4 Date
The "Date:" field contains the date, time, and time zone in which the
message was sent by the originator.
SEND RULES
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The time zone SHOULD be represented in a four-digit time zone offset,
such as -0500 for North American Eastern Standard Time. This MAY be
supplemented by a time zone name in parentheses, e.g., "-0900 (PDT)".
Compliant implementations SHOULD be able to convert [RFC822] date and
time stamps into local time.
If the VPIM sender is relaying a message from a system which does not
provide a time stamp, the time of arrival at the gateway system SHOULD
be used as the date.
Example:
Date: Wed, 28 Jul 96 10:08:49 -0800 (PST)
RECEIVE RULES
The sending system MUST report the time the message was sent. From
[RFC822]
5.2.5 Sender
SEND RULES
The "Sender:" field contains the actual address of the originator if
the message is sent by an agent on behalf of the author indicated in
the "From:" field. This header field MAY be sent by VPIM-conforming
systems. I
RECEPTION RULES
If the address in the "Sender:" field cannot be preserved in the
recipient's message queues or in the next-hop protocol from a gateway,
the field MAY be silently discarded.
5.2.6 Return-Path
The "Return-path:" field is added by the final delivering SMTP server.
If present, it contains the address from the MAIL FROM parameter of
the ESMTP exchange (see 6.1.2). Any error messages resulting from the
delivery failure MUST be sent to this address. Note that if the
"Return-path:" is null ("<>"), e.g. no path, loop prevention or
confidential, delivery status and message disposition notifications
MUST NOT be sent.
RECEPTION RULES
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The "Return-path:" field contains special purpose trace information
useful in some implementations where final delivery ocures after the
acceptance of the message by SMTP. A system which provides final
delivery and cannot store the return-path is dangerously broken. If
the receiving system is incapable of storing the return path to be
used for subsequent delivery errors, the receiving system must
otherwise ensure that further delivery errors don't happen. Systems
that do not support the return path MUST ensure that at the time the
message is acknowledged, the message is delivered to the recipient's
ultimate mailbox. Non-Delivery notifications should not be sent after
that final delivery.
Systems should go to heroic extremes to protect the return path in a
store-and-forward multiprotocol gateway.
5.2.7 Message-id
The "Message-Id:" field contains a unique per-message identifier. A
unique message-id MUST be generated for each message sent from a VPIM-
compliant implementation.
Example:
Message-Id: <12345678@mycompany.com>
The message Id is not required to be stored on the receiving system.
This identifier MAY be used for tracking, auditing, and returning
receipt notification reports. From [RFC822]
5.2.8 Reply-To
If present, the "Reply-to:" header provides a preferred address to
which reply messages should be sent (see 5.7.1). Typically, voice
mail systems can only support one originator of a message so it is
likely that this field will be ignored by the receiving system.
Further, the exact semantic meaning of this header is subject to
substantial debate and is considered unclear at this time. From
[RFC822]
SEND RULES
A compliant system SHOULD NOT send a Reply-To header.
RECEPTION RULES
If a "reply-to:" field is present, a reply-to sender message MAY be
sent to the address specified (that is, in lieu of the address in the
"From:" field). If only one address of the originator is supported in
the message store or in the next-hop protocol from a multi-protocol
gateway, the address in the "From:" field MUST be used and the "Reply-
To:" field MAY be silently discarded.
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5.2.9 Received
The "Received:" field contains trace information added to the
beginning of a RFC 822 message by MTAs. This is the only field
permitted to be added by an MTA. Information in this header is useful
for debugging when using an US-ASCII message reader or a header-
parsing tool. From [RFC822]
SEND RULES
A VPIM-compliant system MUST add a "Received:" fields when acting as a
gateway.
RECEPTION RULES
A VPIM-compliant system SHOULD NOT remove any "Received:" fields when
relaying messages to other MTAs or gateways. These header fields MAY
be ignored or deleted when the message is received at the final
destination.
5.2.10 MIME Version
The "MIME-Version:" field indicates that the message conforms to
[MIME]. Systems compliant with this specification SHOULD include a
comment with the words "(Voice 3.0)". [VPIM1] defines an earlier
version of this profile and uses the token (Voice 1.0). RFC [VPIM2]
defines an earlier version of this profile and uses the token (Voice
2.0)
Example:
MIME-Version: 1.0 (Voice Version 3)
This identifier is intended for information only and SHOULD NOT be
used to semantically identify the message as being a VPIM message.
Instead, the presence of the content defined in [V-MSG] SHOULD be used
if identification is necessary.
5.2.11 Sensitivity
The "Sensitivity:" field, if present, indicates the requested privacy
level. The case-insensitive values "Personal", "Private", and
"Normal" are specified. If no privacy is requested, this field is
omitted.
SEND RULES
A VPIM-compliant implementations MAY include this header to indicate
the sensitivity of a message. If the message is of "Normal"
sensitivity, this field MAY be omitted. From: [X.400]
RECEPTION RULES
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If a "Sensitivity:" field with a value of "Personal" or "Private" is
present in the message, a compliant system SHOULD prohibit the
recipient from forwarding this message to any other user. A compliant
system, however, SHOULD allow the responder to reply to a sensitive
message, but SHOULD NOT include the original message content. The
sensitivity of the reply message MAY be set by the responder.
**** The following requirement from VPIM needs to be evaluated in
light of general Internet email client behaviors ******
If the receiving system does not support privacy and the sensitivity
is one of "Personal" or "Private", a negative delivery status
notification MUST sent to the originator with the appropriate status
code (X.Y.Z) indicating that privacy could not be assured. The message
contents SHOULD be returned to the sender to allow for a voice context
with the notification. A non-delivery notification to a private
message SHOULD NOT be tagged private since it will be sent to the
originator. From: [X.400]
(Is is worth differentiating between private and personal for the
purposes of sending the NDN?)
5.2.12 Importance
Indicates the requested importance to be given by the receiving
system. The case-insensitive values "low", "normal" and "high" are
specified. If no special importance is requested, this header may be
omitted and the value of the absent header assumed to be "normal".
From: [X.400]
SEND RULES
Compliant implementations MAY include this header to indicate the
importance of a message
RECEPTION RULES
If the receiving system does not support importance, the attribute may
be silently dropped. If the attribute is supported, it can be used
for various user interface purposes including the ordering messages
within a mailbox or trigging notification devices such as pagers.
5.2.13 Subject
The subject field is often provided by email systems but is not widely
supported on Voice Mail platforms. From [RFC822]
SEND RULES
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For compatibility with text based mailbox interfaces, a text subject
field SHOULD be generated by a compliant implementation. It is
recommended that voice-messaging systems that do not support any text
user interfaces (e.g. access only by a telephone) insert a generic
subject header of "Voice Message" for the benefit of GUI enabled
recipients.
RECEPTION RULES
It is anticipated that many voice-only systems will be incapable of
storing the subject line. The subject MAY be discarded if present by a
receiving system.
5.2.14 Disposition-Notification-To
This header MAY be present to indicate that the sender is requesting a
receipt notification from the receiving user agent. This message
disposition notification (MDN) is typically sent by the user agent
after the user has listened to the message and consented to an MDN
being sent
Example:
Disposition-notification-to: +12145551213@mycompany.com
SEND RULES
VPIM-compliant implementations MAY include this header to request a
disposition indication such as a listen confirmation.
RECEPTION RULES
The presence of a "Disposition-notification-to:" header in a message
is merely a request for an MDN described in 5.6.3. The recipients'
system is always free to silently ignore such a request so this header
does not burden any system that does not support it. From [MDN].
5.2.15 Disposition-Notification-Options
This header MAY be present to define future extensions parameters for
an MDN requested by the presence of the header in the previous
section.
SEND RULES
No "Disposition-notification-options:" are defined that are useful for
voice messaging. Sending systems MUST NOT request disposition
notification options by sending a disposition-notification-options
header.
RECEPTION RULES
Currently no parameters are defined by this document or by [MDN].
However for forward compatibility with future extensions,, this header
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MUST be processed if present, if MDNs are supported. If it contains a
extension parameter that is required for proper MDN generation (noted
with "=required"), then an MDN MUST NOT be sent if the parameter is
not understood. See [MDN] for complete details.
Example:
Disposition-notification-options:
whizzbang=required,foo
5.3 MIME Content Descriptions
5.3.1 Content-Description:
This field MAY be present to facilitate the text identification of
these body parts in simple email readers. Any values may be used,
though it may be useful to use values similar to those for Content-
Disposition.
Example:
Content-Description: Big Telco Voice Message
5.3.2 Content-Disposition:
This field MUST be present to allow the parsable identification of
these body parts. This is especially useful if, as is typical,
more than one Audio/* body occurs within a single level (e.g.
multipart/voice-message). Since a VPIM voice message is intended
to be automatically played upon display of the message, in the
order in which the audio contents occur, the audio contents must
always be of type inline. However, it is still useful to include a
filename value, so this should be present if this information is
available. From [DISP]
In order to distinguish between the various types of audio contents
in a VPIM voice message a new disposition parameter "voice" is
defined with the parameter values below to be used as appropriate
(see Error! Reference source not found.):
Voice-Message - the primary voice message,
Voice-Message-Notification - a spoken delivery notification
or spoken disposition notification,
Originator-Spoken-Name - the spoken name of the originator,
Recipient-Spoken-Name - the spoken name of the recipient if
available to the originator and present if there is ONLY one
recipient,
Spoken-Subject- the spoken subject of the message, typically
spoken by the originator
Note that there SHOULD only be one instance of each of these types
of audio contents per message level. Additional instances of a
given type (i.e., parameter value) may occur within an attached
forwarded voice message.
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Implementations that do not understand the "voice" parameter (or
the Content-Disposition header) can safely ignore it, and will
present the audio bodyparts in order (but will not be able to
distinguish between them).
5.3.3 Content-Duration:
This field MAY be present to allow the specification of the length
of the audio bodypart in seconds. The use of this field on
reception is a local implementation issue. From [DUR]
Example:
Content-Duration: 33
5.3.4 Content-Language:
This field MAY be present to allow the specification of the spoken
language of the audio bodypart. The encoding is defined in [LANG].
The use of this field on reception is a local implementation issue.
Example for UK English:
Content-Language: en-UK
5.4 Voice Message Content Types
MIME, introduced in [MIME1], is a general-purpose message body format
that is extensible to carry a wide range of body parts. It provides
for encoding binary data so that it can be transported over the 7-bit
text-oriented SMTP protocol. This transport encoding (denoted by the
Content-Transfer-Encoding header field) is in addition to the audio
encoding required to generate a binary object.
MIME defines two transport encoding mechanisms to transform binary
data into a 7 bit representation, one designed for text-like data
("Quoted-Printable"), and one for arbitrary binary data ("Base64").
While Base64 is dramatically more efficient for audio data, either
will work. Where binary transport is available, no transport encoding
is needed, and the data can be labeled as "Binary".
An implementation in compliance with this profile SHOULD send audio
and/or facsimile data in binary form when binary message transport is
available. When binary transport is not available, implementations
MUST encode the audio and/or facsimile data as Base64. The detection
and decoding of "Quoted-Printable", "7bit", and "8bit" MUST be
supported in order to meet MIME requirements and to preserve
interoperability with the fullest range of possible devices. However,
if a content is received in a transfer encoding that cannot be
rendered to the user, an appropriate negative delivery status
notification MUST be sent.
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The content types described in this section are identified for use
within the multipart/voice-message; version = Version 3 content. This
content, which is the fundamental part of a VPIM Version 3 message, is
referred to as a VPIM voice message in this document.
Contents in the multipart/voice message which are not primary may be
discarded as necessary to accomplish delivery. A system which needs
to drop content to achieve delivery MUST provide notification to the
recipient indicating that content was dropped is required.
5.4.1 Multipart/Voice-Message
This MIME multipart structure provides a mechanism for packaging a
voice message into one container that is tagged as VPIM Version 3
compliant. The semantic of multipart/Voice-Message (defined in [V-
MSG]) is identical to multipart/mixed and may be interpreted as that
by systems that do not recognize this content-type.
The Multipart/Voice-Message content-type MUST only contain the
profiled media and content types specified in this section (i.e.
audio/*, image/*, message/rfc822 and text/directory). The most common
will be: spoken name, spoken subject, the message itself, attached fax
and directory info. Forwarded messages are created by simply using
the message/rfc822 construct.
Conformant implementations MUST send voice messages with the
multipart/voice-message as the top level (i.e. in the Content-Type
header). Conformant implementations MUST recognize the
Multipart/Voice-Message content (whether it is a top level content or
below a multipart/mixed) and be able to separate the contents (e.g.
spoken name or spoken subject).
5.4.2 Message/RFC822
MIME requires support of the Message/RFC822 message encapsulation body
part. This body part is used within a multipart/voice-message to
forward complete messages (see 5.7) or to reply with original content
(see 5.7.1). From [MIME2]
RECEPTION RULES
May flatten structure if necessary. If flattening, must discard other
vCards of forwarded parts such that only the outermost vCard is
retained.
5.4.3 Text/Directory
This section needs to be adjusted to meet the needs of the
helper-application based clients. The vCard must contain all
informaiton necessary to construct a valid reply-to-sender
message. This should be possible by tighning the rules a bit.
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This content allows for the inclusion of a Versit vCard [VCARD]
electronic business card within a VPIM message. The format is
suitable as an interchange format between applications or systems, and
is defined independent of the method used to transport it. It
provides a useful mechanism to transport information about the
originator that can be used by the receiving VPIM system or other
local applications
Each vCard MUST be contained within a Text/Directory content type
[MIMEDIR] within a VPIM message. [MIMEDIR] requires that the
character set MUST be defined as a parameter value (typically us-ascii
for VPIM) and that the profile SHOULD be defined (the value MUST be
vCard within VPIM messages).
Each VPIM message SHOULD be created with a Text/Directory (vCard
profile) content type that MUST contain the preferred email address,
telephone number, and text name of the message originator as well as
the vCard version. The vCard SHOULD contain the spoken name and role
of the originator, as well as the revision date. Any other vCard
attribute MAY also be present. The intent is that the vCard be used
as the source of information to contact the originator (e.g., reply,
call). The vCard profile [VCARD] MUST specify at least the following
attributes:
TEL - Public switched telephone number in international (E.164)
format (various types, typically VOICE)
EMAIL - email address (various types, typically INTERNET; the
type VPIM is optionally used to denote an address that
supports VPIM messages. This address will be used for
reply-to-sender functionality when the RFC822 header
fields are not acessable to the voice mail helper
application.
Version - Indicates the version of the vCard profile. Version 3.0
[VCARD] MUST be used.
The following attributes SHOULD be specified:
N - Family Name, Given Name, Additional Names, Honorific
Prefixes, and Suffixes. Because it is expected that
recipients using a telephone user interface will use the
information in the vCard to identify the originator, and
the GUI will see the information presented in the FROM
line, all present components in the text name of the FROM
header field MUST match the values provided by the Vcard.
SOUND - spoken name sound data (various types, typically 32KADPCM)
REV - Revision of vCard in ISO 8601 date format
The following attributes MAY be specified:
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The vCard MAY use other attributes as defined in [VCARD] or extensions
attributes not yet defined (e.g. recipient media capabilities).
If present, the spoken name attribute must be included inline in the
vCard. This is a change from VPIM V2 to facilitate easier processing
by desktop clients that launch vCard viewers via helper application
launched with only the contents of a single mime body part.
Each multipart/voice-message content MUST only contain one vCard --
more than one is an error condition. A VPIM message may contain
forwarded messages. VCards that are part of the forwarded messages
are permitted. However, these vCards MUST be associated with the
originator(s) of the forwarded message(s) and the originator of the
forwarding message. As a result, all forwarded vCards will be
contained in message/rfc822 contents -- only the vCard of forwarding
originator will be at the top-level.
Example:
Content-Type: text/directory; charset=us-ascii; profile=vCard
Content-Transfer-Encoding: 7bit
BEGIN:VCARD
N:Parsons;Glenn
ORG:Northern Telecom
TEL;TYPE=VOICE;MSG;WORK:+1-613-763-7582
EMAIL;TYPE=INTERNET;glenn.parsons@nortel.ca
EMAIL;TYPE=INTERNET;VPIM:6137637582@vm.nortel.ca
SOUND;TYPE=32KADPCM;ENCODING=B;
Base-64 encoded spoken name data
REV:19960831T103310Z
Version: 3.0
END:VCARD
5.4.4 Required Audio Formats
SEND RULES
VPIM Version 3 implementations MAY send audio in any of the profiled
voice encodings. Implementations MAY send the audio in either native
MIME packaging or encapsulated within the Microsoft WAV packaging.
RECEIVE RULES
VPIM Version 3 implementations MUST be capable of receiving each of
the below profiled voice encodings. Implementations MUST accept audio
in either the native MIME packaging or encapsulated within the
Microsoft WAV packaging.
If an implementation can only store or forward one voice segment, then
multiple voice segments in a single message (if present) SHOULD be
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concatenated, and SHOULD NOT be discarded. It is RECOMMENDED that the
segments be concatenated in the same order as they were received.
5.4.4.1 Audio/Basic
An implementation compliant to this profile MAY send and MUST receive
Audio/BASIC [MIME?]. This encoding is the most widely supported voice
encoding in computer telephony and on the WEB. It requires the
minimum computation to create and is available on virtually all sound-
equipped computers. It is also the least compressed of the formats
with a data rate of 64 kbits/second. It is therefore an ideal encoding
for lightweight, well-connected message sending clients.
5.4.4.2 Audio/32KADPCM
An implementation compliant to this profile MAY send and MUST receive
Audio/32KADPCM [ADPCM]. This encoding is the required default for
VPIM V2 systems. This encoding is a moderately compressed encoding
with a data rate of 32 kbits/second using moderate processing
resources. Because the encoding has been in widespread use for over
20 years, there is believed to be no outstanding intellectual property
claims.
5.4.4.3 Audio/MS-GSM
An implementation compliant to this profile MAY send and MUST receive
Audio/MS-GSM [MSGSM]. This is a widely supported voice encoding in
the installed base of Microsoft Windows(TM) desktops. It provides
substantial compression at 13 kbits/second with substantial
processing.
5.4.4.4 Audio/G723.1
**** Recent discussions suggest this encoding should be dropped.
These discussions indicate the IPR issues are substantial and the
benefits over GSM are not sufficient to justify must receive status
****
An implementation compliant to this profile MAY send and MUST receive
Audio/G.723.1. This is a state-of-the-art voice encoding with high
compression at 6.8 kbits/second. This low bitrate provides better-
than-real-time download to clients connected over contemporary dial-up
Internet connections. This encoding requires substantial computing
resources to encode. The compression is encumbered by substantial
intellectual property claims that need to be considered.
5.4.4.5 Audio/wav
The Audio/wav is not an audio encoding per-se. It is a packaging of
an audio encoding into a Microsoft desktop-friendly wrapper. This
wrapping offers the benefit of being widely understood by helper
applications resident within a Microsoft Windows environment. When
the WAV packaging is used in conjunction with the mu-Law or GSM
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encoding, messages received by a non-VPIM aware client may be
minimally rendered.
While interpreting a WAV package offers little cost, the generation of
a WAV file may be difficult in many architectures. The WAV format is
difficult to create in a streaming environment because an accurate
length must be known and recorded at the beginning of the data stream.
For these reasons, VPIM Version 3 implementations MUST accept the WAV
packaging and MAY send the following codecs in the WAV packaging.
To promote maximum interoperability with desktop email clients and
audio helper applications, conforming systems MUST send only a single
audio segment per WAV file. To enable attachment-oriented desktop
clients to launch an audio helper application, conforming systems must
include a content-disposition header with a filename containing a
".wav" suffix.
For convenience, the WAV codec numbers for the four required codecs
are listed below.
+---------+----------------+-------------------+
|Codec | WAV Number | MIME Registration |
+---------+----------------+-------------------+
|G.726 | 0x0064 (100) | Audio/32kadpcm |
+---------+----------------+-------------------+
|G.711 | 0x0007 (7) | Audio/Basic |
+---------+----------------+-------------------+
|GSM 6.10 | 0x0031 (49) | Audio/MS-GSM |
+---------+----------------+-------------------+
|G723.1 | 0x0042 (66) | Audio/G723-1 |
+---------+----------------+-------------------+
5.4.4.6 Audio/X-wav
Applications wishing to send messages encoded in the WAV file format
SHOULD use the audio/wav. Conforming implementations should not send
Audio/X-wav
RECEPTION RULES
For backward compatibility with the installed base of wav file sending
systems, receiving implementation MUST treat the audio/X-wav content
the same as Audio/wav.
5.4.5 Proprietary Voice Formats
Use of any other encoding except the required codecs reduces
interoperability in the absence of explicit knowledge about the
capabilities of the recipient. A compliant implementation MAY use any
other encoding provided a unique identifier is registered with the
IANA prior to use (see [MIME4]). The voice encodings should be
registered as sub-types of Audio.
SEND RULES
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Proprietary voice encoding formats or other standard formats MAY be
sent under this profile provided the sender has a reasonable
expectation that the recipient will accept the encoding. In practice,
this requires explicit per-destination configuration information
maintained either in a directory, personal address book, or gateway
configuration tables.
RECEIVE RULES
Under the VPIM Version 3 profile, audio contents are considered the
primary information carrying contents of the message. Systems which
receive audio/* content types which they are unable to decode MUST
return the message to the originator with an NDN indicating media not
supported.
5.5 Other MIME Content Types
**** Clear up discard rules ****
Only the above specified contents are required to be supported within
a multipart/voice message by a receiving system. Other contents may
be included within the multipart/voice-message if the sender has a
reasonable expectation the recipient can receive the message.
An implementation compliant with this profile MAY send additional
contents in a VPIM message. If an implementation receives a VPIM
message that contains content types not specified in this profile,
their handling is a local implementation issue (e.g. the unknown
contents MAY be discarded if they cannot be presented to the
recipient). Conversely, if an implementation receives a non-VPIM
message (i.e., without a multipart/voice-message content type) with
any of the contents defined in 5.4 & 5.5, it SHOULD deliver those
contents, but the full message handling is a local issue (e.g. the
unknown contents _or_ the entire message MAY be discarded).
Implementations MUST issue negative delivery status notifications to
the originator when any form of non-delivery to the recipient occurs.
The multipart contents defined below MAY be sent within a
multipart/voice message (with other noted contents below them as
required.) When multiple contents are present, they SHOULD be
presented to the user in the order that they appear in the message.
Several examples are given in Appendix B.
5.5.1 Image/Tiff
A common image encoding for facsimile, known as TIFF-F, is a
derivative of the Tag Image File Format (TIFF) and is described in
several documents. For the purposes of VPIM, the F Profile of TIFF
for Facsimile (TIFF-F) is defined in [TIFF-F] and the image/tiff MIME
content type is defined in [TIFFREG]. While there are several formats
of TIFF, only TIFF-F is profiled for use within a VPIM voice message.
Further, since the TIFF-F file format is used in a store-and-forward
mode with VPIM, the image MUST be encoded so that there is only one
image strip per facsimile page.
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SEND RULES
All VPIM implementations that support facsimile SHOULD generate TIFF-F
compatible facsimile contents in the image/tiff; application=faxbw
sub-type encoding by default. An implementation MAY send this fax
content in VPIM voice messages and MUST be able to recognize and
display it in received messages. If a fax message is received that
cannot be rendered to the user (e.g. the receiving VPIM system does
not support fax), then the system MUST return the message with a
negative delivery status notification with a media not supported
status code.
While any valid MIME body header MAY be used (e.g., Content-
Disposition to indicate the filename), none are specified to have
special semantics for VPIM and MAY be ignored. Note that the content
type parameter application=faxbw MUST be included in outbound
messages. However, inbound messages with or without this parameter
MUST be rendered to the user (if the rendering software encounters an
error in the file format, some form of negative delivery status
notification MUST be sent to the originator).
RECEIVE RULES
As with any non-voice attachment, a receiving system may accept a
voice message and discard the fax content. The recipient SHOULD be
notified of the dropped content. The sender of a message MAY be
notified of a partial message delivery by issuing a suitable MDN.
(details needed)
5.5.2 Multipart/Mixed
SEND RULES
Multipart/voice message provides the facilities for enclosing several
body parts in a single message. The semantics of using complex
hierarchy within a voice message is undefined and the use of such a
structure is discouraged.
RECEIVE RULES
Compliant systems MUST accept multipart/mixed body parts within a
multipart/voice messages. Systems may collapse the contents of the
multipart/mixed structure into the multipart/voice message itself.
From [MIME2]
5.5.3 Text/Plain
MIME requires support of the basic Text/Plain content type. This
content type has limited applicability within the voice messaging
environment. However, because VPIM is a MIME profile, MIME
requirements should be met.
SEND RULES
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Compliant VPIM implementations MAY send the Text/Plain content-type.
It should be understood that the textual information is not considered
a primary media within multipart/voice-message and may be discarded by
a receiving system.
RECEIVE RULES
Within a multipart/voice message, the text/plain content type MAY be
dropped from the message with a suitable advisory presented to the
recipient. The originator MAY be notified of a partial message
delivery by a suitable MDN.
Outside a Multipart/Voice message, compliant implementations MUST
accept Text/Plain messages, however, specific handling is left as an
implementation decision. From [MIME2]
There are several mechanisms that can be used to support text (once
accepted) on voice messaging systems including text-to-speech and
text-to-fax conversions. If no rendering of the text is possible
(i.e., it is not possible for the recipient to determine if the text
is a critical part of the message), the entire message MUST be
returned to the sender with a negative delivery status notification
and a media-unsupported status code.
5.5.4 Text/Informational
SEND RULES
The text/informational content type MAY be included as the first
section of a multipart/voice-message to explain the structure of a
VPIM Version 3 message, and optionally to instruct the recipient where
to download a suitable helper application or plug-in.
RECEPTION RULES
The display/playing of text/informational content type should be
suppressed for systems supporting VPIM Version 3 messages. The text
is intended for MIME-capable, but non-VPIM capable email clients as an
advisory.
5.6 Return and Notification Messages
VPIM delivery status notification messages (5.6.2) MUST be sent to the
originator of the message when any form of non-delivery of the subject
message or its components occurs. These error messages must be sent
to the return path (5.2.6) if present, otherwise, the From (5.2.1)
address may be used.
VPIM Receipt Notification messages (5.6.3) should be sent to the
sender specified in the Disposition-Notification-To header field
(5.2.14). The MDN should be sent after the message has been presented
to the recipient or if the message has somehow been disposed of
without being presented to the recipient (e.g. if it were deleted
before playing it).
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VPIM Notification messages may be positive or negative, and can
indicate delivery at the server or receipt by the client. However,
the notification MUST be contained in a multipart/report container
(5.5.4) and SHOULD contain a spoken error message.
5.6.1 Multipart/Report
The Multipart/Report is used for enclosing human-readable and machine
parsable notification (e.g. Message/delivery-status) body parts and
any returned message content. The multipart/report content-type is
used to deliver both delivery status reports indicating transport
success or failure and message disposition notifications to indicate
post-delivery events such as receipt notification. Compliant
implementations MUST use the Multipart/Report construct. Compliant
implementations MUST recognize and decode the Multipart/Report content
type and its components in order to present the report to the user.
From [REPORT]
Multipart/Report messages from VPIM implementations MAY include the
human-readable description of the error as a spoken audio/* content
(this speech MAY be made available to the notification recipient). As
well, VPIM implementations MUST be able to handle (and MAY generate)
Multipart/Report messages that encode the human-readable description
of the error as text. Note that per [DSN] the human-readable part
MUST always be present.
5.6.2 Message/Delivery-status
This MIME body part is used for sending machine-parsable delivery
status notifications. Compliant implementations MUST use the
Message/delivery-status construct when returning messages or sending
warnings. Compliant implementations MUST recognize and decode the
Message/delivery-status content type and present the reason for
failure to the sender of the message. From [DSN]
5.6.3 Message/Disposition-notification
This MIME body part is used for sending machine-parsable read-receipt
message disposition notifications. Conforming implementations SHOULD
use the Message/Disposition-notification construct when sending post-
delivery message status notifications. These MDNs, however, MUST only
be sent in response to the presence of the Disposition-notification-to
header in 5.2.14. Conforming implementations should recognize and
decode the Message/Disposition-notification content type and present
the notification to the user. From [MDN]
5.7 Forwarded Messages
VPIM version 2 explicitly supports the forwarding of voice and fax
content with voice or fax annotation. However, only the two
constructs described below are acceptable in a VPIM message. Since
only the first (i.e. message/rfc822) can be recognized as a forwarded
message (or even multiple forwarded messages), it is RECOMMENDED that
this construct be used whenever possible.
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Forwarded VPIM messages SHOULD be sent as a multipart/voice-message
with the entire original message enclosed in a message/rfc822 content
type and the annotation as a separate Audio/* or image/* body part.
If the RFC822 header fields are not available for the forwarded
content, simulated header fields with available information SHOULD be
constructed to indicate the original sending timestamp, and the
original sender as indicated in the "From" line. However, note that
at least one of "From", "Subject", or "Date" MUST be present. As
well, the message/rfc822 content MUST include at least the "MIME-
Version", and "Content-Type" header fields. From [MIME2]
In the event that forwarding information is lost through concatenation
of the original message and the forwarding annotation, such as must be
done in a gateway between VPIM and the AMIS voice messaging protocol,
the entire audio content MAY be sent as a single Audio/* segment
without including any forwarding semantics.
5.7.1 Message/RFC822
MIME requires support of the Message/RFC822 message encapsulation body
part. This body part is used within a multipart/voice-message to
forward complete messages (see 5.7) or to reply with original content
(see 5.7.1). From [MIME2]
RECEPTION RULES
May flatten structure if necessary to fit within the message structure
of the recipients voice mailbox.
5.8 Reply Messages
Replies to VPIM messages (and Internet mail messages) are addressed to
the address noted in the reply-to header (see 5.2.8) if it is present,
else the From address (see 5.2.1) is used. The vCard EMAIL attribute,
if present, SHOULD be the same as the reply-to address and may be the
same as the From address. It is expected that within legacy email
implementations, the voice message viewer application may need to
create a reply message without the benefit of the RFC822 headers. In
such a case, the vCard MAY be used to generate a reply to the sender.
RECEPTION RULES
Support of multiple originator header fields is often not possible on
voice messaging systems, so it may be necessary to choose only one
when gatewaying a VPIM message to another voice message system.
However, implementers should note that this may make it impossible to
send error messages and replies to their proper destinations.
In some cases, a reply message is not possible, such as with a message
created by telephone answering (i.e. classic voice mail). In this
case, the From field MUST contain the special address non-mail-
user@domain (see 5.1.2). A null ESMTP MAIL FROM address SHOULD also
be used in this case (see 6.1.2). A receiving VPIM system SHOULD NOT
offer the user the option to reply to this kind of message.
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5.9 Notification Messages
VPIM delivery status notification messages (5.6.2) MUST be sent to the
originator of the message when any form of non-delivery of the subject
message or its components occurs. These error messages must be sent
to the return path (5.2.6) if present, otherwise, the From (5.2.1)
address may be used.
VPIM Receipt Notification messages (5.6.3) should be sent to the
sender specified in the Disposition-Notification-To header field
(5.2.14), only after the message has been presented to the recipient
or if the message has somehow been disposed of without being presented
to the recipient (e.g. if it were deleted before playing it).
VPIM Notification messages may be positive or negative, and can
indicate delivery at the server or receipt by the client. However,
the notification MUST be contained in a multipart/report container
(5.5.4) and SHOULD contain a spoken error message.
If a VPIM system receives a message with contents that are not
understood (see 5.4 & 5.5), its handling is a local matter. A
delivery status notification SHOULD be generated if the message could
not be delivered because of unknown contents (e.g., on traditional
voice processing systems). In some cases, the message may be
delivered (with a positive DSN sent) to a mailbox before the
determination of rendering can be made.
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6. Message Transport Protocol
Messages are transported between voice mail machines using the
Internet Extended Simple Mail Transfer Protocol (ESMTP). All
information required for proper delivery of the message is included in
the ESMTP dialog. This information, including the sender and
recipient addresses, is commonly referred to as the message
"envelope". This information is equivalent to the message control
block in many analog voice messaging protocols.
ESMTP is a general-purpose messaging protocol, designed both to send
mail and to allow terminal console messaging. Simple Mail Transport
Protocol (SMTP) was originally created for the exchange of US-ASCII 7-
bit text messages. Binary and 8-bit text messages have traditionally
been transported by encoding the messages into a 7-bit text-like form.
[ESMTP] formalized an extension mechanism for SMTP, and subsequent
RFCs have defined 8-bit text networking, command streaming, binary
networking, and extensions to permit the declaration of message size
for the efficient transmission of large messages such as multi-minute
voice mail.
The following sections list ESMTP commands, keywords, and parameters
that are required and those that are optional for conformance to this
profile.
6.1 ESMTP Commands
6.1.1 HELO
Base SMTP greeting and identification of sender. This command is not
to be sent by compliant systems unless the more-capable EHLO command
is not accepted. It is included for compatibility with general SMTP
implementations. Compliant servers MUST implement the HELO command
for backward compatibility but clients SHOULD NOT send it unless EHLO
is not supported. From [SMTP]
6.1.2 MAIL FROM (REQUIRED)
Originating mailbox. This address contains the mailbox to which
errors should be sent. VPIM implementations SHOULD use the same
address in the MAIL FROM command as is used in the From header field.
This address is not necessarily the same as the message Sender listed
in the message header fields if the message was received from a
gateway or sent to an Internet-style mailing list. From [SMTP, ESMTP]
The MAIL FROM address SHOULD be stored in the local message store for
the purposes of generating a delivery status notification to the
originator. The address indicated in the MAIL FROM command SHOULD be
passed as a local system parameter or placed in a Return-Path: line
inserted at the beginning of a VPIM message. From [HOSTREQ]
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Since delivery status notifications MUST be sent to the MAIL FROM
address, the use of the null address ("<>") is often used to prevent
looping of messages. This null address MAY be used to note that a
particular message has no return path (e.g. a telephone answer
message). From [SMTP]
6.1.3 RCPT TO
Recipient's mailbox. The parameter to this command contains only the
address to which the message should be delivered for this transaction.
It is the set of addresses in one or more RCPT TO commands that are
used for mail routing. From [SMTP, ESMTP]
Note: In the event that multiple transport connections to multiple
destination machines are required for the same message, the set of
addresses in a given transport connection may not match the list of
recipients in the message header fields.
6.1.4 DATA
Initiates the transfer of message data. Support for this command is
required. Compliant implementations MUST implement the SMTP DATA
command for backwards compatibility. From [SMTP]
6.1.5 TURN
Requests a change-of-roles, that is, the client that opened the
connection offers to assume the role of server for any mail the remote
machine may wish to send. Because SMTP is not an authenticated
protocol, the TURN command presents an opportunity to improperly fetch
mail queued for another destination. Compliant implementations SHOULD
NOT implement the TURN command. From [SMTP]
6.1.6 QUIT
Requests that the connection be closed. If accepted, the remote
machine will reset and close the connection. Compliant
implementations MUST implement the QUIT command. From [SMTP]
6.1.7 RSET
Resets the connection to its initial state. Compliant implementations
MUST implement the RSET command. From [SMTP]
6.1.8 VRFY
Requests verification that this node can reach the listed recipient.
While this functionality is also included in the RCPT TO command, VRFY
allows the query without beginning a mail transfer transaction. This
command is useful for debugging and tracing problems. Compliant
implementations MAY implement the VRFY command. From [SMTP]
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(Note that the implementation of VRFY may simplify the guessing of a
recipient's mailbox or automated sweeps for valid mailbox addresses,
resulting in a possible reduction in privacy. Various implementation
techniques may be used to reduce the threat, such as limiting the
number of queries per session.) From [SMTP]
6.1.9 EHLO
The enhanced mail greeting that enables a server to announce support
for extended messaging options. The extended messaging modes are
discussed in subsequent sections of this document. Compliant
implementations MUST implement the ESMTP command and return the
capabilities indicated later in this memo. From [ESMTP]
6.1.10 BDAT
The BDAT command provides a higher efficiency alternative to the
earlier DATA command, especially for voice. The BDAT command provides
for native binary transport of messages. Compliant implementations
SHOULD support binary transport using the BDAT command.[BINARY]
6.2 ESMTP Keywords
The following ESMTP keywords indicate extended features useful for
voice messaging.
6.2.1 PIPELINING
The "PIPELINING" keyword indicates ability of the receiving server to
accept new commands before issuing a response to the previous command.
Pipelining commands dramatically improves performance by reducing the
number of round-trip packet exchanges and makes it possible to
validate all recipient addresses in one operation. Compliant
implementations SHOULD support the command pipelining indicated by
this keyword. From [PIPE]
6.2.2 SIZE
The "SIZE" keyword provides a mechanism by which the SMTP server can
indicate the maximum size message supported. Compliant servers MUST
provide size extension to indicate the maximum size message that can
be accepted. Clients SHOULD NOT send messages larger than the size
indicated by the server. Clients SHOULD advertise SIZE= when sending
messages to servers that indicate support for the SIZE extension. From
[SIZE]
6.2.3 CHUNKING
The "CHUNKING" keyword indicates that the receiver will support the
high-performance binary transport mode. Note that CHUNKING can be
used with any message format and does not imply support for binary
encoded messages. Compliant implementations MAY support binary
transport indicated by this capability. From [BINARY]
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6.2.4 BINARYMIME
The "BINARYMIME" keyword indicates that the SMTP server can accept
binary encoded MIME messages. Compliant implementations MAY support
binary transport indicated by this capability. Note that support for
this feature requires support of CHUNKING. From [BINARY]
6.2.5 DSN
The "DSN" keyword indicates that the SMTP server will accept explicit
delivery status notification requests. Compliant implementations MUST
support the delivery notification extensions in [DRPT].
6.2.6 ENHANCEDSTATUSCODES
The "ENHANCEDSTATUSCODES" keyword indicates that an SMTP server
augments its responses with the enhanced mail system status codes
[CODES]. These codes can then be used to provide more informative
explanations of error conditions, especially in the context of the
delivery status notification format defined in [DSN]. Compliant
implementations SHOULD support this capability. From [STATUS]
6.3 ESMTP Parameters - MAIL FROM
6.3.1 BINARYMIME
The current message is a binary encoded MIME messages. Compliant
implementations SHOULD support binary transport indicated by this
parameter. From [BINARY]
6.3.2 RET
The RET parameter indicates whether the content of the message should
be returned. Compliant systems SHOULD honor a request for returned
content. From [DRPT]
6.3.3 ENVID
The ENVID keyword of the SMTP MAIL command is used to specify an
"envelope identifier" to be transmitted along with the message and
included in any DSNs issued for any of the recipients named in this
SMTP transaction. The purpose of the envelope identifier is to allow
the sender of a message to identify the transaction for which the DSN
was issued. Compliant implementations MAY use this parameter. From
[DRPT]
Should use the original email address of the sender in this field.
This is less an envelope ID and more of a billing ID.
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6.4 ESMTP Parameters - RCPT TO
6.4.1 NOTIFY
The NOTIFY parameter indicates the conditions under which a delivery
report should be sent. Compliant implementations MUST honor this
request. From [DRPT]
6.4.2 ORCPT
The ORCPT keyword of the RCPT command is used to specify an "original"
recipient address that corresponds to the actual recipient to which
the message is to be delivered. If the ORCPT esmtp-keyword is used,
it MUST have an associated esmtp-value, which consists of the original
recipient address, encoded according to the rules below. Compliant
implementations MAY use this parameter. From [DRPT]
6.5 ESMTP - SMTP Downgrading
The ESMTP extensions suggested or required for conformance to VPIM
fall into two categories. The first category includes features which
increase the efficiency of the transport system such as SIZE,
BINARYMIME, and PIPELINING. In the event of a downgrade to a less
functional transport system, these features can be dropped with no
functional change to the sender or recipient.
The second category of features is transport extensions in support of
new functions. DSN and EnhancedStatusCodes provide essential
improvements in the handling of delivery status notifications to bring
email to the level of reliability expected of Voice Mail. To ensure a
consistent level of service across an intranet or the global Internet,
it is essential that VPIM compliant ESMTP support the ESMTP DSN
extension at all hops between a VPIM originating system and the
recipient system. In the situation where a `downgrade' is unavoidable
a relay hop may be forced (by the next hop) to forward a VPIM message
without the ESMTP request for positive delivery status notification.
It is RECOMMENDED that the downgrading system should continue to
attempt to deliver the message, but MUST send an appropriate delivery
notification to the originator, e.g. the message left an ESMTP host
and was sent (unreliably) via SMTP.
7. Conformance Requirements
<To be completed>
8. Security Considerations
8.1 General Directive
This document is a profile of existing Internet mail protocols. To
maintain interoperability with Internet mail, any security to be
provided should be part of the Internet security infrastructure,
rather than a new mechanism or some other mechanism outside of the
Internet infrastructure.
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8.2 Threats and Problems
Both Internet mail and voice messaging have their own set of threats
and countermeasures. As such, this specification does not create any
security issues not already existing in the profiled Internet mail and
voice mail protocols themselves. This section attends only to the set
of additional threats that ensue from integrating the two services.
8.2.1 Spoofed sender
The actual sender of the voice message might not be the same as that
specified in the Sender or From header fields of the message content
header fields or the MAIL FROM address from the SMTP envelope. In a
tightly constrained environment, sufficient physical and software
controls may be able to ensure prevention of this problem. In
addition, the recognition of the sender's voice may provide confidence
of the sender's identity irrespective of that specified in Sender or
From. It should be recognized that SMTP implementations do not
provide inherent authentication of the senders of messages, nor are
sites under obligation to provide such authentication.
8.2.2 Unsolicited voice mail
Assigning an Internet mail address to a voice mailbox opens the
possibility of receiving unsolicited messages (either text or voice
mail). Traditionally voice mail systems operated in closed
environments and were not susceptible to unknown senders. Voice mail
users have a higher expectation of mailbox privacy and may consider
such messages as a security breach. Many Internet mail systems are
choosing to block all messages from unknown sources in an attempt to
curb this problem.
8.2.3 Message disclosure
Users of voice messaging systems have an expectation of a level of
message privacy that is higher than the level provided by Internet
mail without security enhancements. This expectation of privacy by
users SHOULD be preserved as much as possible.
8.3 Security Techniques
Sufficient physical and software control may be acceptable in
constrained environments. Further, the profile specified in this
document does not in any way preclude the use of any Internet object
or channel security protocol to encrypt, authenticate, or non-
repudiate the messages.
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References
[8BIT] Klensin, J., Freed, N., Rose, M., Stefferud, E., D. Crocker,
"SMTP Service Extension for 8bit-MIMEtransport" RFC 1426, United
Nations University, Innosoft International, Inc., Dover Beach
Consulting, Inc., Network Management Associates, Inc., The Branch
Office, February 1993.
[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.
[BINARY] Vaudreuil, G., "SMTP Service Extensions for Transmission of
Large and Binary MIME Messages", RFC 1830, October 1995.
[CODES] Vaudreuil, G. "Enhanced Mail System Status Codes", RFC 1893,
01/15/1996.
[MIMEDIR] F. Dawson, T. Howes, & M. Smith, "A MIME Content-Type for
Directory Information", Work In Progress, <draft-ietf-asid-mime-
direct-06.txt>, March 1998
[DISP] R. Troost and S. Dorner, Communicating Presentation Information
in Internet Messages: The Content-Disposition Header, RFC 2183,
August 1997
[DNS1] Mockapetris, P., "Domain names - implementation and
specification", RFC1035, Nov 1987.
[DNS2] Mockapetris, P., "Domain names - concepts and facilities", RFC
1034, Nov 1987.
[DRPT] Moore, K. "SMTP Service Extensions for Delivery Status
Notifications", RFC 1891, 01/15/1996
[DSN] Moore, K., Vaudreuil, G., "An Extensible Message Format for
Delivery Status Notifications", RFC 1894, 01/15/1996.
[DUR] G. Parsons and G. Vaudreuil, "Content Duration MIME Header
Definition", Work In Progress, <draft-ema-vpim-dur-02.txt>, November
1997.
[E164] CCITT Recommendation E.164 (1991), Telephone Network and ISDN
Operation, Numbering, Routing and Mobile Service - Numbering Plan
for the ISDN Era.
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[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).
[HOSTREQ] Braden, R., "Requirements for Internet Hosts -- Application
and Support", STD 3, RFC 1123, October 1989.
[LANG] Alvestrand,H., "Tags for the Identification of Languages", RFC
1766, Mar 1995
[MDN] Fajman, Roger, "An Extensible Message Format for Message
Disposition Notifications" Work In Progress, <draft-ietf-receipt-mdn-
08.txt>, January 1998
[MIB II] M. Rose, "Management Information Base for Network Management of
TCP/IP-based internets: MIB-II", RFC 1158, May 1990.
[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.
[PIPE] Freed, N., Cargille, A., "SMTP Service Extension for Command
Pipelining" RFC 1854, October 1995.
[REPORT] Vaudreuil, G., "The Multipart/Report Content Type for the
Reporting of Mail System Administrative Messages", RFC 1892,
01/15/1996.
[REQ] S. Bradner, "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March 1997.
[RFC822] Crocker, D., "Standard for the Format of ARPA Internet Text
Messages", STD 11, RFC 822, UDEL, August 1982.
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Internet Draft VPIM V3 August 20, 1999
[SIZE] Klensin, J, Freed, N., Moore, K, "SMTP Service Extensions for
Message Size Declaration" RFC 1870, United Nations University,
Innosoft International, Inc., November 1995.
[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.
[TIFF-F] G. Parsons and J. Rafferty, "Tag Image File Format:
Application F", <draft-ietf-fax-tiff-09.txt>, February 1998.
[TIFFREG] G. Parsons, J. Rafferty & S. Zilles, "Tag Image File Format:
image/tiff - MIME sub-type registraion", RFC????, ??? 1998.
[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.
[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.
[X.400] Hardcastle-Kille, S., "Mapping between X.400(1988) / ISO 10021
and RFC 822", RFC 1327, May 1992.
9. Acknowledgments
The author's would like to offer a special thanks to the Lucent
Internal design team consisting of Gordon Brunsen, Ralph Costantini,
Cliff Didcock, Greg Vaudreuil and Michael Wilson from whom the
outlines of the VPIM V3 proposal originated.
The author's would like to recognise the EMA voice messaging
committee, especially Kevin Chestnut, Bernhard Elliot, and Holly
Gabrowski who provided critical review and initial support to get this
project rolling.
The EMA hosts the VPIM web page at http://www.ema.org/vpim.
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10. Copyright Notice
"Copyright (C) The Internet Society (1998). 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."
11. Authors' Addresses
Glenn W. Parsons
Nortel Networks
P.O. Box 3511, Station C
Ottawa, ON K1Y 4H7
Canada
Phone: +1-613-763-7582
Fax: +1-613-763-4461
EMail: GParsons@NortelNetworks.com
Gregory M. Vaudreuil
Lucent Technologies,
Octel Messaging Division
17080 Dallas Parkway
Dallas, TX 75248-1905
United States
Phone/Fax: +1-972-733-2722
Email: GregV@Lucent.Com
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12. Appendix A - VPIM Requirements Summary
<to be created>
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13. Appendix B - Example Voice Messages
The following is a full-featured VPIM V3 message designed by the
sending system to be as broadly compatable with desktop email clients
as possible. This message includes a message attributes of urgent,
private, and read-receipt request.
VPIM Message:
To: +19725551212@mycompany.com
To: +16135551234@mycompany.com
From: "Parsons, Glenn" <+12145551234@mycompany.com>
Date: Mon, 26 Aug 93 10:20:20 -0700 (CDT)
MIME-Version: 1.0 (Voice 3.0)
Content-type: Multipart/Voice-Message; Version=3.0;
Boundary="MessageBoundary"
Content-Transfer-Encoding: 7bit
Message-ID: 123456789@VM2.mycompany.com
Disposition-Notification-To: <+12145551234@mycompany.com>
Sensitivity: Private
Importance: High
--MessageBoundary
Content-type: Audio/WAV; codec=49
Content-Transfer-Encoding: Base64
Content-Disposition: inline; voice=Voice-Message
Content-Language: en-US
Content-ID: part1@VM2-4321
glslfdslsertiflkTfpgkTportrpkTpfgTpoiTpdadasssdasddasdasd
(This is a sample of the base-64 Spoken Message data)
fgdhgddlkgpokpeowrit09==
--MessageBoundary
Content-type: text/directory; charset=us-ascii; profile=vCard
Content-Transfer-Encoding: 7bit
BEGIN:VCARD
N:Parsons;Glenn;;Mr.;
EMAIL;TYPE=INTERNET:+12145551234@mycompany.com
TEL:+1-214-555-1234
SOUND;TYPE=32KADPCM;ENCODING=B;
kdsfkaskflkkasdf
- Base-64 spoken name content -
sdfsdfsdfsdfsfsfsdf=
REV:19951031T222710Z
VERSION: 3.0
END:VCARD
--MessageBoundary-
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The following is a simple VPIM V3 message including a PowerPoint
attachment destined to another voice messaging server on a local high-
bandwidth Intranet. The example uses the mu-law voice encoding since
there is little need to expend the CPU to encode the message in a
smaller form.
VPIM Message:
To: +19725551212@mycompany.com
To: +16135551234@mycompany.com
From: "Parsons, Glenn" <+12145551234@mycompany.com>
Date: Mon, 26 Aug 93 10:20:20 -0700 (CDT)
MIME-Version: 1.0 (Voice 3.0)
Content-type: Multipart/Voice-Message; Version=3.0;
Boundary="MessageBoundary"
Content-Transfer-Encoding: 7bit
Message-ID: 123456789@VM2.mycompany.com
--MessageBoundary
Content-type: Audio/BASIC
Content-Transfer-Encoding: Base64
Content-Disposition: inline; voice=Voice-Message
Content-Language: en-US
Content-ID: part1@VM2-4321
glslfdslsertiflkTfpgkTportrpkTpfgTpoiTpdadasssdasddasdasd
(This is a sample of the base-64 Spoken Message data)
fgdhgddlkgpokpeowrit09==
--MessageBoundary
Content-type: Application/Octet-Stream; filename=howdy.ppt
Content-Transfer-Encoding: Base=64
glslfdslsertiflkTfpgkTportrpkTpfgTpoiTpdadasssdasddasdasd
(This is a sample of the base-64 encoded PowerPoint Presentation
fgdhgddlkgpokpeowrit09==
--MessageBoundary
Content-type: text/directory; charset=us-ascii; profile=vCard
Content-Transfer-Encoding: 7bit
BEGIN:VCARD
N:Parsons;Glenn;;Mr.;
EMAIL;TYPE=INTERNET:+12145551234@mycompany.com
TEL:+1-217-555-1234
SOUND;TYPE=32KADPCM;ENCODING=B;
kdsfkaskflkkasdf
- Base-64 spoken name content -
sdfsdfsdfsdfsfsfsdf=
REV:19951031T222710Z
VERSION: 3.0
END:VCARD
--MessageBoundary-
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If the receiving voice mail machine cannot store a PowerPoint
presentation, it may discard the attachment and provide notification
to the recipient that there was an attachment that could not be
delivered.
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14. Appendix C - Example Error Voice Processing Error Codes
The following common voice processing errors and their corresponding
status codes are given as examples. Text after the error codes are
intended only for reference to describe the error code.
Implementations should provide implementation specific informative
comments after the error code rather than the text below.
Error condition RFC 1893 Error codes
----------------------------- --------------------------------
Analog delivery failed 4.4.0 Persistent connection error
because remote system is busy - other
Analog delivery failed 4.4.1 Persistent protocol error
because remote system is - no answer from host
ring-no-answer
Remote system did not answer 5.5.5 Permanent protocol error
AMIS-Analog handshake ("D" in - wrong version
response to "C" at connect
time)
Mailbox does not exist 5.1.1 Permanent mailbox error
- does not exist
Mailbox full or over quota 4.2.2 Persistent mailbox error
- full
Disk full 4.3.1 Persistent system error
- full
Command out of sequence 5.5.1 Permanent protocol error
- invalid command
Frame Error 5.5.2 Permanent protocol error
- syntax error
Mailbox does not support FAX 5.6.1 Permanent media error
- not supported
Mailbox does not support TEXT 5.6.1 Permanent media error
- not supported
Sender is not authorized 5.7.1 Permanent security error
- sender not authorized
Message marked private, but 5.3.3 Permanent system error
system is not private capable - not feature capable
Destination does not support 5.5.0 Permanent protocol error
Version 3, not delivered
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15. Appendix D - Example Voice Processing Disposition Types
The following common voice processing disposition conditions and their
corresponding MDN Disposition (which contains the disposition mode,
type and modifier, if applicable) are given as examples. Implementers
should refer to [MDN] for a full description of the format of message
disposition notifications.
Notification event MDN Disposition mode, type & modifier
------------------------------ -------------------------------------
Message played by recipient, manual-action/MDN-sent-automatically;
receipt automatically returned displayed
Message deleted from mailbox manual-action/MDN-sent-automatically;
by user without listening deleted
Message cleared when mailbox manual-action/MDN-sent-automatically;
deleted by admin deleted/mailbox-terminated
Message automatically deleted automatic-action/
when older than administrator MDN-sent-automatically; deleted/
set threshold expired
Message processed, however manual-action/MDN-sent-automatically;
audio encoding unknown - processed/error
unable to play to user Error: unknown audio encoding
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16. Appendix F - Change History: RFC 2421 (VPIM V2) to this Document
The updated profile in this document is based on the Lucent experience
planning implementations for the diverse portfolio of voice messaging
and unified messaging products. This version of the profile is
significantly different from the previous described in [VPIM2]. The
changes are categorized as general, content, transport and compliance.
They are detailed below:
1. General
- a refined multipart/voice-message definition
- Addition of three new must-receive audio encodings. These are
GSM, G.723.1, and mu-law.
- Changed the Voice version to Version 3
- Various editorial updates to improve readability. Separated send
rules from reception rules.
- Clarified the behavior upon reception of unrecognized content
types expected with the interworking between voice and unified
messaging systems.
2. Content
- Changed handling of received lines by a gateway to SHOULD NOT
delete in a gateway. In gateways to systems such as AMIS, it is
not possible to preserve this information. It is intended that
such systems be able to claim conformance.
- Changed the encoding of spoken name in vCards from "by-reference"
to "inline".
3. Transport
-
4. Compliance
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