Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


Network Working Group G. Parsons Request for Comments: 4024 Nortel Networks Category: Informational J. Maruszak

                                                             July 2005
                 Voice Messaging Client Behaviour

Status of This Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2005).


 This document defines the expected behaviour of a client to various
 aspects of a Voice Profile for Internet Mail (VPIM) message or any
 voice and/or fax message.

Table of Contents

 1.  Introduction..................................................  2
 2.  Conventions Used in This Document.............................  2
 3.  Message Icon..................................................  3
     3.1.  Proposed Mechanism......................................  3
 4.  Sender's Number Column........................................  3
     4.1.  Proposed Mechanism......................................  4
 5.  Message Size..................................................  4
     5.1.  Proposed Mechanism......................................  4
 6.  Media Viewer..................................................  5
     6.1.  Proposed Mechanism......................................  6
 7.  Mark Message as Read..........................................  6
     7.1.  Proposed Mechanism......................................  6
 8.  Security Considerations.......................................  7
 9.  Informative References........................................  7
 10. Acknowledgments...............................................  8

Parsons & Maruszak Informational [Page 1] RFC 4024 Voice Messaging Client Behaviour July 2005

1. 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
 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
 How the messaging client responds to, and acts on these differences
 is termed "Client Behaviour".  This is dependent 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.  Today's 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 user's 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.

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",
 document are to be interpreted as described in RFC-2119 [4].

Parsons & Maruszak Informational [Page 2] RFC 4024 Voice Messaging Client Behaviour July 2005

3. 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

3.1. 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].

4. 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 summaries
 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
 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).

Parsons & Maruszak Informational [Page 3] RFC 4024 Voice Messaging Client Behaviour July 2005

4.1. 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 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., "-").

5. 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].

5.1. Proposed Mechanisms

 There are three suggested methods to relay this information, of them,
 the first method is favored:

5.1.1. 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.

Parsons & Maruszak Informational [Page 4] RFC 4024 Voice Messaging Client Behaviour July 2005

5.1.2. Message length indicated as a parameter of an Existing

      RFC 2045 [7] 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.
 Content-Type Header Field example:
 Content-Type=audio/*; length=50
 Content-Type=image/tiff; pages=3

5.1.3. Message length indicated as part of an existing RFC 2822 [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)

6. 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

Parsons & Maruszak Informational [Page 5] RFC 4024 Voice Messaging Client Behaviour July 2005

 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

6.1. 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].

7. 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

7.1. 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

Parsons & Maruszak Informational [Page 6] RFC 4024 Voice Messaging Client Behaviour July 2005

8. 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.

9. Informative References

 [1]  Vaudreuil, G. and G. Parsons, "Voice Profile for Internet Mail -
      version 2 (VPIMv2)", RFC 3801, June 2004.
 [2]  Burger, E., Candell, E., Eliot, C., and G. Klyne, "Message
      Context for Internet Mail", RFC 3458, January 2003.
 [3]  Parsons, G. and J. Maruszak, "Calling Line Identification for
      Voice Mail Messages", RFC 3939, December 2004.
 [4]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
      Levels", BCP 14, RFC 2119, March 1997.
 [5]  Vaudreuil, G. and G. Parsons, "Content Duration MIME Header
      Definition", RFC 3803, June 2004.
      RFC 3501, March 2003.
 [7]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
      Extensions (MIME) Part One: Format of Internet Message Bodies",
      RFC 2045, November 1996.
 [8]  Burger, E., "Critical Content Multi-purpose Internet Mail
      Extensions (MIME) Parameter", RFC 3459, January 2003.
 [9]  Resnick, P., "Internet Message Format", RFC 2822, April 2001.
 [10] Parsons, G., "IMAP Voice Extensions", Work in Progress, June

Parsons & Maruszak Informational [Page 7] RFC 4024 Voice Messaging Client Behaviour July 2005

10. Acknowledgments

 This work was inspired by the discussion of "Proposed Mechanisms" for
 IMAP that were detailed in a since expired work in progress entitled
 "IMAP Voice Extensions" [10].  The authors would like to acknowledge
 all those who contributed to that document.  In addition, Cheryl
 Kinden, Derrick Dunne, and Jason Collins assisted in the editing of
 previous revisions of this document.

Author's Addresses

 Glenn Parsons
 Nortel Networks
 P.O. Box 3511, Station C
 Ottawa, ON  K1Y 4H7
 Phone: +1-613-763-7582
 Fax: +1-613-967-5060
 Janusz Maruszak
 Phone: +1-416-885-0221

Parsons & Maruszak Informational [Page 8] RFC 4024 Voice Messaging Client Behaviour July 2005

Full Copyright Statement

 Copyright (C) The Internet Society (2005).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an

Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at ietf-


 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Parsons & Maruszak Informational [Page 9]

/data/webs/external/dokuwiki/data/pages/rfc/rfc4024.txt · Last modified: 2005/07/08 18:24 by

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki