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Voice Messaging Client Behaviour

The information below is for an old version of the document that is already published as an RFC.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 4024.
Authors Janusz Maruszak , Glenn Parsons
Last updated 2015-10-14 (Latest revision 2001-07-24)
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Informational
Stream WG state (None)
Document shepherd (None)
IESG IESG state Became RFC 4024 (Informational)
Action Holders
Consensus boilerplate Unknown
Telechat date (None)
Responsible AD Ned Freed
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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.  
     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 draft documents valid for a maximum of six months and may be updated, 
     replaced, or obsoleted by other documents at any time. It is inappropriate 
     to use Internet- Drafts as reference material or to cite them other than 
     as "work in progress."  
     The list of current Internet-Drafts can be accessed at  
     The list of Internet-Draft Shadow Directories can be accessed at 

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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 
     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 
     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 
     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 
     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 
     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 
     Phone: +1-416-597-7517 

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     Glenn Parsons  
     Nortel Networks  
     P.O. Box 3511, Station C 
     Ottawa, ON  K1Y 4H7 
     Phone: +1-613-763-7582  
     Fax: +1-416-597-7005 
     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 
     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 

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