Network Working Group Janusz Maruszak
Internet Draft Nortel Networks
Document: <draft-ema-vpim-cb-02.txt> Glenn Parsons
Category: Informational Nortel Networks
July 18, 2001
Voice Messaging Client Behaviour
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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Table of Contents
1. Abstract.....................................................3
2. Conventions used in this document............................3
3. Introduction.................................................3
4. Message Icon.................................................4
4.1 Proposed Mechanism..........................................4
5. Sender's Number Column.......................................4
5.1 Proposed Mechanism..........................................4
6. Message Size.................................................5
6.1 Proposed Mechanism..........................................5
7. Media Viewer.................................................6
7.1 Proposed Mechanism..........................................7
8. Mark Message as Read.........................................7
8.1 Proposed Mechanism..........................................7
9. Security Considerations......................................7
10. References..................................................8
11. Acknowledgments.............................................8
12. Author's Addresses..........................................8
13. Full Copyright Statement....................................9
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1. Abstract
This document defines the expected behaviour of a client to various
aspects of a VPIM message or any voice and/or fax message.
2. Conventions used in this document
In examples, "C:" and "S:" indicate lines sent by the client and server
respectively.
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 [4].
3. Introduction
As Internet messaging evolves into unified messaging, the term "e-mail" no
longer refers to text-only messages. Today's "e-mail" are often multi-
media. That is, they can have numerous non-text parts. These parts can be
attachments or can contain voice and/or fax.
Each of voice, fax, and text have their own distinct characteristics, which
are intuitive to the user. For example, each of these message types
require a different media viewer (text editor for text, audio player for
voice, and image viewer for fax), and the dimensions of message size are
also different for all three (kilobytes for text, seconds for voice, and
pages for fax). As a result, a message that includes more than one of
these in its parts is termed a mixed media message.
How the messaging client responds to, and acts on these differences is
termed "Client Behaviour". This is dependant on the concept of "Message-
Context" [2] (previously called primary content), which defines whether the
message is a voice mail, fax, or text message. The client can utilize this
header to determine the appropriate client behaviour for a particular
message.
Traditionally, a messaging "client" referred to some sort of visual
interface (or GUI -
graphical user interface) that was presented on the
users computer. However, as messaging evolves to unified communications
the actual form of the messaging client is expected to change. TodayËs
email can often be viewed on wireless devices with very limited screens or
even "viewed" over a telephone (i.e., listening to email as you would
listen to voice mail through a TUI -
telset user interface).
The intent of this document is to be general and refer to all types of
messaging clients, as the userËs expectation of behaviour based on the
type of message is not expected to change. However, some of the following
concepts may tend towards the more common GUI client.
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4. Message Icon
The preferred method to distinguish between voice, fax, and text messages
on a GUI client is with a visual cue, or icon. A similar voice prompt or
"earcon" would be used for TUI clients.
As it is possible for the message to contain more than one media type, the
icon should describe the primary message content, as defined by the
"Message-Context" header. Obvious choices for the icon/message pairs would
be a telephone for a voice message, a fax machine for a fax message, and an
envelope for a text mail message. Similarly obvious for the earcons would
be short spoken prompts like "voice message".
This could be taken a step further, and have the GUI icon change to
indicate that the message has been read as is currently done in some email
clients (others do not change the icon but merely bold the message in the
message list to indicate it is unread). For example, a telephone with the
receiver off-hook could indicate that the voice message has been played. A
fax machine with paper at the bottom, as opposed to the top, would show
that the fax had been viewed. Finally, an open envelope indicates that a
text message has been read.
4.1 Proposed Mechanism
As the choice of icon is determined by the primary message type, the client
should obtain this information from the "Message-Context " message header.
This header is defined in [2].
5. Sender's Number Column
As is the case with most email GUI clients today, important message
information is organized into columns when presented to the user in a the
summary message list. TUIs often present even briefer aummaries to the user
at the beginning of the session. Typical columns in the GUI client include
the message subject, and the date the message was received.
Another important piece of information for the user is the origin of the
message. For a voice or fax message, the origin is typically a telephone
or fax machine respectively, each of which has an associated telephone
number. This telephone number is critical to the user if they wish to
return the call. This should be presented accurately to the user (without
making it an email address).
5.1 Proposed Mechanism
Instead of forcing the telephone number into an email address, a new
Internet message header can be used to hold the originating telephone
number [3]. If the message is indicated as being a voice or fax message
per [2], the client should extract the number, and display it to the user
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in a separate column. As this header is defined to only hold the digits of
the telephone number, it is left to the client to add any separating
characters (e.g. "-").
6. Message Size
In the cases of large attachments, small clients (e.g., PDA) and slow links
(e.g., wireless) there is also a need for the client to see the length of
the message in a suitable format before opening it.
Currently, message size is normally given in kilobytes (kB). This is
sufficient for plain text messages, but while it may give a hint as to how
good the compression algorithm is, kB is not very useful in knowing the
size of a voice and/or fax message. Instead, the size should give an
indication of the length of the message, i.e. the duration (in seconds) of
a voice message, and the number of pages of a fax. Again, the message may
contain multiple types, so the size displayed should be that of the primary
content type, per [2].
6.1 Proposed Mechanisms
There are three suggested methods to relay this information, of them, the
first method is favoured:
6.1.1 MIME Header Content-Duration as described in RFC 2424 [5]
For voice messages, the Content-Duration field of the main audio/* body
part (as indicated by content-disposition per [1]) should be displayed as
the length of the message. If there are several audio parts, an
implementation may display the message size as an aggregate of the length
of each.
For fax messages a new MIME Header, Content-Page-Length, could be defined,
similar to Content-Duration with the exception that number of pages would
be specified, rather than number of seconds. (e.g. Content-Page-Length:3).
This would be created at origination.
6.1.2 Message length indicated as a parameter of an existing Content-Type
Header Field
This would be created at the source. This proposed method would allow the
message length to be passed to the client by default in IMAP. Again the
client would have to choose between the main voice message length or an
aggregate message length for display.
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Content-Type Header Field example:
Content-Type=audio/*; length=50
Content-Type=image/tiff; pages=3
6.1.3 Message length indicated as part of an existing RFC822 [9] Header
Field
This field would be created at the source and may include message length
information, but because it is part of the message headers, it could also
be amended on reception (by a local process). This method would allow the
message length to be passed to any client by default and not require any
client modification. If used, this field would indicate the aggregate
length of all attachments.
The advantage of this mechanism is that no new headers are required and it
works with existing clients. The downside is that it overloads the subject
field.
Subject Header Field example:
Subject=Voice Message (0:04)
Subject=Fax Message (3p)
Subject=Voice Message (0:14) with Fax (1p)
7. Media Viewer
When a message is initially opened, the client should, by default, open
the proper media viewer to display the primary message content. That is,
an audio player for voice messages, an image viewer for fax, and a text
editor for text messages. Note that on a TUI, the viewer would render the
media to sound (which would have varying effect depending on the media and
available process).
Where there is more than one body part, obviously the appropriate viewer
should be used depending on which body part the user has selected.
In the case where several viewers are available for a single media type,
the user should be prompted to select the desired viewer on the first
occasion that the message type is encountered. That viewer should then
become the default viewer for that media type. The user should have the
ability to change the default viewer for a media type at any time.
Note that it is possible that the media viewer may not be part of the
client or local to the host of the client. For example, a user could
select to play a voice message from a GUI and the message is played over a
telephone (perhaps because the user has no desktop speakers).
Additionally, a user listening to a unified messaging inbox over a TUI
could chose to print a particular message to a nearby fax machine.
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7.1 Proposed Mechanism
As mentioned, the default viewer displayed to the user should be the
appropriate one for the primary message type. The client is able to
determine the primary message type from the "Message-Context" message
header per [2].
8. Mark Message as Read
Obviously, the user must be able to know which messages they have read, and
which are unread. This feature would also control the message icon or
earcon as mentioned in section 1.
With the proliferation of voice and fax messages, clients should only
indicate that these messages are read when the primary body part has been
read. For example, a voice message should not be indicated as read until
the audio part has been played. The default is currently to mark a message
read, when the first body part (typically text) is viewed.
8.1 Proposed Mechanism
Implementation of this feature on most clients is a local issue.
For example, in the case of IMAP4 [6], these clients should only set the
\SEEN flag after the first attachment of the primary content type has been
opened. That is, if the message context is voice message, the \SEEN flag
would be set after the primary voice message (indicated by content-
disposition [1] or content-criticality [8]) is opened.
9. Security Considerations
The desirable client behaviours described here are intended to provide the
user with a better client experience. However, supporting the proposed
behaviours described in this document does not make a client immune from
the risks of being a mail client. That is, the client is not responsible
for the format of the message received, it only interprets. As a result,
messages could be spoofed or masqueraded to look like a message they are
not to elicit a desired client behaviour. This could be used to fool the
end user, for example, into thinking a message was a voice message
(because of the icon) when it was not.
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10. References
1. Parsons, G., Vaudreuil, G., "Voice Profile for Internet Mail - version
2", draft-ietf-vpim-vpimv2r2-03.txt, June 2001, Work in Progress.
2. Burger, E., Candell, E., Klyne, G., Eliot, C., "Message Context for
Internet Mail", draft-ietf-vpim-hint-07.txt, June 2001, Work in Progress
3. Parsons & Maruszak, "Calling Line Identification for VPIM Messages",
draft-ema-vpim-clid-02.txt, June 2001, Work in Progress
4. Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997
5. Vaudreuil, G., Parsons, G., "Content Duration MIME Header Definition",
RFC2424, September 1998
6. Crispin, M., "Internet Message Access Protocol - Version 4rev1", RFC
2060, December 1996
7. Freed, N., Borenstein, N., "Multipurpose Internet Mail Extensions
(MIME) Part One: Format of Internet Message Bodies", RFC 2045, November
1996
8. Burger, E., "Critical Content of Internet Mail" <draft-burger-vpim-cc-
04.txt>, June 2001, Work in Progress.
9. Resnick, P., "Internet Message Format", RFC 2822, April 2001.
11. Acknowledgments
This work was inspired by the discussion of "Proposed Mechanisms" for IMAP
that were detailed in a since expired draft (draft-ema-vpim-imap-01.txt).
The authors would like to acknowledge all those who contributed to that
document. In addition, Cheryl Kinden, Derrick Dunne and Jason Maruszak
assisted in the editing of previous revisions of this document.
12. Author's Addresses
Janusz Maruszak
Nortel Networks
522 University Avenue
Toronto, ON M5G 1W7
Canada
Phone: +1-416-597-7517
Email: marusj@nortelnetworks.com
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Glenn 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
13. Full Copyright Statement
Copyright (C) The Internet Society (2001). All Rights Reserved.
This document and translations of it may be copied and furnished to
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distributed, in whole or in part, without restriction of any kind,
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may not be modified in any way, such as by removing the copyright notice
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The limited permissions granted above are perpetual and will not be
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DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO
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PARTICULAR PURPOSE.
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Datatracker
draft-ema-vpim-cb-02
This is an older version of an Internet-Draft that was ultimately published as RFC 4024.
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