Network Working Group G. Parsons Internet Draft J.K. Wong Document: Nortel Networks Category: Informational June 2002 Unified Messaging Support for Diverse Clients 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 http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract This document describes an architecture for unified multimedia messaging -- capable of supporting clients of varying capabilities but based on extending existing IETF Internet Mail standards and infrastructure. Parsons & Wong Expires: 01/01/03 1 Unified Messaging Support for Diverse Clients June 2002 Table of Contents 1. Abstract 3 2. Conventions used in this document 3 3. Introduction 3 4. Internet Mail and Messaging 4 4.1 Mail Server 4 4.2 Message Format 4 4.3 Client Access 4 5. Profiles 5 5.1 Voice (VPIMv2) 5 5.2 Fax 5 5.3 TUI 5 5.4 WUI 6 6. Security Considerations 6 7. References 7 8. Acknowledgments 8 9. Author's Addresses 8 10. Full Copyright Statement 9 Parsons & Wong Expires: 01/01/03 2 Unified Messaging Support for Diverse Clients June 2002 1. Abstract This document describes an architecture for unified multimedia messaging -- capable of supporting clients of varying capabilities but based on extending existing IETF Internet Mail standards and infrastructure. 2. Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC-2119. 3. Introduction The architecture proposed in this document arises from two recent trends in Internet messaging Ï one may be referred to as evolution towards "unified messaging" and the other is the increasing support for terminals of varying capabilities. "Unified messaging" appears to have a number of different meanings. The unified messaging in this discussion is the Internet unified messaging from [UMREQ]. Internet unified messaging provides a single infrastructure, mailbox and set of interfaces for a user to get, respond to and manipulate all of their messages, no matter what the media or source. [UMREQ] gives a set of requirements for Internet unified messaging. A subset of these requirements germane to the discussion here is the need to reuse existing email protocols, maintain their existing semantics and the semantics of the current email entities (e.g. MTAs, UAs, etc.) The Internet is evolving toward the support of new devices less powerful than traditional computers as hosts for messaging clients (e.g., PDAs, cellular phones, tablet computers, etc.) In particular, [UMISS] gives the requirements for a telephone based client with a telephone user interface (TUI). We will refer to a client based on a cellular phone or wireless enabled PDA as having a wireless user interface (WUI). The architecture presented in the rest of this document is an infrastructure for unified messaging based on extending existing messaging standards and infrastructure and capable of supporting clients of varying capabilities such as TUIs and WUIs. Parsons & Wong Expires: 01/01/03 3 Unified Messaging Support for Diverse Clients June 2002 4. Internet Mail and Messaging This section reviews very briefly protocols supporting the existing architecture for Internet Mail and outlines an approach to extending this architectureØs capabilities without modifying its existing semantics. 4.1 Mail Server [RFC2821] specifies the most recent version (currently an IETF proposed standard that resulted from the DRUMS WG) of SMTP which is the transport protocol between messaging servers. This document includes a description of the extension model for the SMTP protocol. |------| |------| | | SMTP | | |server|---------------------|server| | | | | |------| |------| 4.2 Message Format [RFC2822] gives the current message and header format (also a proposed standard). A series of five MIME RFCs [RFC2045 to RFC2049](draft standards except RFC2048 BCP) extend the Internet mail system to allow the transport of general media beyond just restricted text including contents generated by other applications. It also allows messages to have multi-part bodies consisting of mixed media types. 4.3 Client Access Messaging clients communicate with messaging servers using either the POP3 [RFC1939] (standard) or the IMAP4 [RFC2060] (proposed standard) protocols. The POP3 protocol assumes a simple message delivery functionality on the part of the mail server. IMAP4 requires that the server can act as a remote store of messages for a client this is an important feature for diverse client support. The message store is in the form of multiple mailboxes which the client can manipulate. Neither protocol defines message posting which is specified by SMTP. |------| |-------| pop3 | | |client1|-----------| | |-------| | | |server| |-------| imap4 | | |client2|-----------| | |-------| | | |------| Parsons & Wong Expires: 01/01/03 4 Unified Messaging Support for Diverse Clients June 2002 5. Profiles A variety of client and server types other than traditional email can be supported. The clients may be adapted for host restrictions such as limited processing power, message store, display window size, etc. Alternatively clients may be adapted for different functionality (e.g. voice mail, fax, etc.). Servers may support optional mail features that would allow better handling of different media ((e.g. voice mail, fax, video, etc.). A useful way to identify features that would be important to support for a particular application is to define a profile of Internet Mail for that application. 5.1 Voice (VPIMv2) These profiles [RFC2421 to RFC2424] (proposed standards) enable the transport of voice messages using the internet mail system. One of the drivers for this work was support of IP transport for voice mail systems. As voice mail clients are accustomed to a higher degree of responsiveness and certainty as to message delivery, the functionality added by VPIMv2 includes Message Disposition Notification and Delivery Status Message as well as the addition of voice media to multi-part message bodies. 5.2 Fax This set of profiles [RFC2301 to RFC2306] (proposed standards) enables the transport of fax using the internet mail system. This work defined the image/tiff MIME type. Support for fax clients also required extensions to Message Delivery Notification. 5.3 TUI Traditional voice mail clients have telephone-based (TUI) clients. To enable a TUI based client to support media types other than voice, (i.e. become a unified messaging client) additional functionality needs to be added [UMISS] to the client access protocols. E.g. a command to forward an undownloaded message would be useful in the handling of long text messages where text-to-speech (TTS) may be awkward. In the diagram below, this might require IMAP to be augmented to a form of IMAP+. The design of IMAP+ would require careful consideration. |----------| |------------------------------| | client | | UM server | | | | | | |------| | DTMF | |------| IMAP+ |--------| | | | TUI | |-------| | UA |----------| server | | | |------| | voice | |------| |--------| | |----------| |------------------------------| Parsons & Wong Expires: 01/01/03 5 Unified Messaging Support for Diverse Clients June 2002 5.4 WUI Wireless-based (WUI) clients (e.g. wireless enabled PDAs, cell phones, etc.) can be considered in an analogous manner to the TUI above. However, the WUI offers the potential of simultaneous voice and data (with a limited screen size) interfaces that leads to a more complex architecture. The first step would be a compilation of the requirements which a WUI would force on a client access protocol to allow for a useful form of unified messaging. (E.g. in the diagram below, what are the requirements on IMAP++ to allow for useful unified messaging with a WUI.) |----------| |---------------------------| | client | | UM server | | | voice-band | | | |------|~|----------------------|~|----| IMAP++ |--------| | | | | | | | UA |---------| | | | | WUI | |-----------| | |----| | | | | | | |----| | IMAP++ | | server | | | | |------| UA |~|----------| ~ ~ ~ | | | | |------| |----| | | |--------| | | | | | |----------------------| |---------------------------| The extended mail client access protocol (IMAP++) is seen as the application level protocol to be used over the air to the wireless device. Other architectures have proposed the use of more wireless specific message formats and/or application level protocols. See for instance [MMS] (this presentation overviews the 3GPP approach to a Multimedia Messaging Service(MMS)). To handle Internet Mail, this service requires messages to be transformed from native formats into specialized formats and protocols. As a result of the potentially complex interactions that can occur given the splitting of the UA function between the client and the server, the design of IMAP++ will require additional consideration. The presentation of use-cases in a future revision of this draft will explore some of the possible complexities. This may result in the identification that enhancements or profiles are needed to additional Internet Mail protocols in order to support the WUI. 6. Security Considerations Security considerations would be specific to the profiles supported. Parsons & Wong Expires: 01/01/03 6 Unified Messaging Support for Diverse Clients June 2002 7. References [UMREQS] Burger, E, "Internet Unified Messaging Requirements", , February 2002 [UMISS] Vaudreuil, Greg "Messaging profile for telephone-based Messaging clients", , February 2002 [RFC2821] Klensin, J., Editor " Simple Mail Transfer Protocol", RFC 2821, April 2001 [RFC2822] Resnick, P., Editor "Internet Message Format", RFC 2822, April 2001. [RFC2045] Freed, N. and Borenstein, N. "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC2045, November 1996 [RFC2046] Freed, N. and Borenstein, N. "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", RFC2046, November 1996 [RFC2047] Moore, K. "Multipurpose Internet Mail Extensions (MIME) Part Three: Message Header Extensions for Non-ASCII Text", RFC2047, November 1996 [RFC2048] Freed,N., Klensin, J., Postel, J. "Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures", RFC2048, November 1996 [RFC2049] Freed, N. and Borenstein, N. "Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples", RFC2049, November 1996 [RFC1939] Myers, J., Rose, M. "Post Office Protocol - Version 3", RFC1939, May 1996 Ï also STD:53 [RFC2060] Crispin, M. "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1", RFC2060, December 1996 [RFC2421] Vaudreuil, G., Parsons, G. "Voice Profile for Internet Mail - version 2", RFC2421, September 1998 [RFC2422] Vaudreuil, G., Parsons, G. "Toll Quality Voice - 32 kbit/s ADPCM MIME Sub-type Registration", RFC2422, September 1998 [RFC2423] Vaudreuil, G., Parsons, G. "VPIM Voice Message MIME Sub- type Registration", RFC2423, September 1998 [RFC2424] Vaudreuil, G., Parsons, G. "Content Duration MIME Header Definition", RFC2424, September 1998 Parsons & Wong Expires: 01/01/03 7 Unified Messaging Support for Diverse Clients June 2002 [RFC2301] McIntyre, L., Zilles, S., Buckley, R., Venable, D., Parsons, G., Rafferty, J. "File Format for Internet Fax", RFC2301, March 1998 [RFC2302] Parsons, G., Rafferty, J. Zilles, S. "Tag Image File Format (TIFF) - image/tiff MIME Sub-type Registration", RFC2302, March 1998 [RFC2303] Allocchio, C. "Minimal PSTN address format in Internet Mail", RFC 2303, March 1998 [RFC2304] Allocchio, C. "Minimal FAX address format in Internet Mail", RFC2304, March 1998 [RFC2305] Toyoda, K., Ohno, H., Murai, J., Wing, D. "A Simple Mode of Facsimile Using Internet Mail", RFC2305, March 1998 [RFC2306] Parsons, G., Rafferty, J. "Tag Image File Format (TIFF) - F Profile for Facsimile", RFC2306, March 1998 [MMS] Leuca, I. "Multimedia Messaging Service", Presentation to the VPIM WG, IETF53 Proceedings, April 11, 2002 8. Acknowledgments 9. Author's Addresses Glenn Parsons Nortel Networks P.O. Box 3511, Station C Ottawa, ON K1Y 4H7 Phone: +1-613-763-7582 Email: gparsons@nortelnetworks.com Jin Kue Wong Nortel Networks P.O. Box 3511, Station C Ottawa, ON K1Y 4H7 Phone: +1-613-763-2515 Email: jkwong@nortelnetworks.com Parsons & Wong Expires: 01/01/03 8 Unified Messaging Support for Diverse Clients June 2002 10. Full Copyright Statement Copyright (C) The Internet Society (2002). 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. Parsons & Wong Expires: 01/01/03 9