INTERNET-DRAFT Laile L. Di Silvestro Expires in 6 months Microsoft Corporation January 6, 1999 Goals for Voice Profile for Internet Messaging, Version 3 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 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 a "work in progress". To learn the current status of any Internet-Draft, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). This draft is being discussed by the Electronic Messagine Association VPIM work group. To subscribe to the mailing list, send a message to EMA Listserv Requests [listserv@listmail.ema.org] with the line "subscribe VPIM-L" in the body of the message. Internet Draft VPIM V3 Goals July 6, 1999 Table of contents: 1. Introduction 2. Goals for Voice Profile for Internet Messaging Version 3 2.1 Interoperability 2.2 Conformance to existing standards 2.3 Backward compatibility 2.4 Robustness 3. Interoperability goals for Voice Profile for Internet Messaging Version 3 3.1 Interoperability with desktop client applications 3.2 Interoperability with VPIM version 2 and version 3 voice messaging systems 3.3 Interoperability with VPIM version 3 unified messaging systems 3.4 Interoperability with traditional email servers 4. Acknowledgements 5. Copyright 6. Author's address 7. References Di Silvestro, Laile Expires 7/6/99 [Page 2] Internet Draft VPIM V3 Goals July 6, 1999 Abstract This document describes the goals of the Voice Profile for Internet Messaging (VPIM), Version 3 work group and establishes a baseline of desired functionality against which proposed MIME profiles for Internet voice messaging can be judged. The goals for VPIM version 3 are limited in scope and do not require any changes from the basic MIME flow defined by VPIM version 2. The primary goal for this version is to support interoperability with desktop clients. Other goals for this version of VPIM include expanded interoperability with unified messaging systems, backward compatibility, and conformance to Internet standards. This document does not include goals that were met fully by VPIM version 2. Different levels of desirability are indicated throughout the document. 1. Introduction Until recently, voice mail and call answering services were implemented as stand-alone proprietary systems. Today, standards such as the Voice Profile for Internet Mail (VPIM) enable interoperability between such systems over the Internet. VPIM [VPIM1] describes a messaging profile that standardizes the exchange of voice mail over an IP messaging network using ESMTP [ESMTP] and MIME [MIME1]. VPIM Version 2 [VPIM2] provides interoperability between voice messaging services only. With the trend toward integration of voice mail and email through unified messaging (UM), it is now necessary to define a new version of VPIM that supports the needs of unified messaging systems and desktop applications. Because the number of desktop boxes is growing rapidly and will soon approach the number of desktop telephones, it is especially important to consider the requirements of desktop email client applications. This document defines the goals for VPIM version 3 [VPIM3]. This standard will support the interchange of voice messages between voice mail systems, unified messaging systems, email servers, and desktop client applications. It will also expand the offerings of service providers by facilitating access to voice mail from a web client. 1.1 Terminology used within this document Within this document, different levels of desirability for a MIME profile for Internet voice messaging are indicated by different priorities, indicated in {braces}: {1} There is general agreement that this is a critical characteristic of any definition of VPIM version 3. {2} Most believe that this is an important characteristic of VPIM version 3. {3} There is general belief that this is a useful feature of VPIM version 3., but that other factors might override; a definition that does not provide this element is acceptable. Di Silvestro, Laile Expires 7/6/99 [Page 3] Internet Draft VPIM V3 Goals July 6, 1999 In addition, the following terms are used: "service" An operational service offered by a service provider. "application" A use of systems to perform a particular function. "terminal" The endpoint of a communication application. "goal" An objective of the standardization process. 2. Goals for Voice Profile for Internet Messaging version 3 VPIM must define the MIME profile and discard rules which will be used for the interchange of voice mail messages over the Internet, and must {1} meet the following goals: 2.1 Interoperability Enhanced interoperability is the primary goal of VPIM version 3. The profile must {1} enable interoperability between voice mail systems, unified messaging systems, Internet email servers, and desktop client applications. Such interoperability will require {1} support for the new media-agnostic systems, which combine multiple media types into a single message, as well as support for legacy voice mail and email systems. It will require {1} features to accommodate varying capabilities of the voice mail, unified messaging and email systems. It must also [1}, include new functionality to facilitate access to voice mail messages from desktop applications. Specific goals for interoperability are detailed in section 3.0. 2.2 Conformance to existing standards It is the goal of VPIM version 3 to conform as closely as possible to existing standards while meeting the other goals defined in this document. - Restrictions: The profile should {2} impose as few restrictions as possible to existing Internet mail standards. In particular, it must {1} support all elements of RFC 822 [RFC822] except those that prevent the profile from meeting other VPIM version 3 goals. - Additions: The profile should {2} make as few additions as possible to existing internet mail standards. It should also {2} adhere to existing desktop standards in desktop-related areas such as file extensions. If it is necessary to define new MIME types or sub-types, the VPIM version 3 work group should {2} propose terms that are already standard or in common use in the desktop environment. 2.3 Backward compatibility It is a goal of this profile to assure backwards compatibility with VPIM version 2. Where this is not possible, it may be {2} necessary to clarify or revise version 2. VPIM version 3 must {1} comprise of superset of VPIM v2 features. It should {2} also provide define a minimal set of rules and status codes [CODES] for handling non-delivery of VPIM v3 messages. Di Silvestro, Laile Expires 7/6/99 [Page 4] Internet Draft VPIM V3 Goals July 6, 1999 2.4 Robustness VPIM v3 must {1} be usable in an environment in which there exist legacy gateways that do not understand MIME. Core features and critical data must {1} not be lost when messages pass through AMIS gateways [AMIS-A and AMIS-D]. VPIM version 3 should {2} allow interoperability with recipient devices and gateways which have limited buffering capabilities and cannot buffer all header information. 3. Interoperability goals for Voice Profile for Internet Messaging Version 3 To "support interoperability" means that a VPIM version 3 compliant sender attempting to send to a recipient will not fail because of incompatibility. It is essential {1} that VPIM version 3 support interoperability between most of the systems listed below, and desirable {3} to support all of them: - Desktop email client applications - VPIM version 2 and version 3 voice messaging systems - VPIM version 3 unified messaging systems - Traditional email servers Overall interoperability requires interoperability for all of the VPIM elements: critical body parts must {1} be preserved, essential information must be provided in a form that is accessible by the users {1}, status codes must {1} be understood, and operations that are standard for each system should {2} be supported. 3.1 Interoperability with desktop email applications Desktop email applications are typically text based. The ability to listen to, reply to, forward, and generate voice mail messages from a traditional desktop environment is a relatively new development. To accommodate current use and future developments in this area, VPIM version 3 must {1} provide features to support access to voice mail messages from the desktop and other email-reading devices. It would also be desirable {3} for it to support web access to voice mail from the desktop. VPIM version 3 should not {2} require desktop email applications to possess a large amount of processing power, and a base level implementation must {1} interoperate, even if it does not offer complex processing. It is therefore necessary {1} for VPIM version 3 to support a variety of codecs that meet differing processor and memory constraints. Codecs included in the VPIM version 3 specification should {2} meet the following criteria: - Availability on desktops: Codecs should {2} be available on most platforms (Windows, UNIX, Mac) - Multiple codecs: VPIM version 3 must {1} allow for range of codecs from low bit rate/high complexity to high bit rate/low complexity. Clients need choice in codec based on resources available (bandwidth and CPU). One codec is not suitable for all devices. Di Silvestro, Laile Expires 7/6/99 [Page 5] Internet Draft VPIM V3 Goals July 6, 1999 - Limited number of codecs: VPIM version 3 should {2} not specify more than 4 or 5 codecs or implementation may be delayed. -Source code availability -Decoding complexity: All codecs must {1} be low complexity to decode -Encoding complexity: Some of the codecs must {1} be low complexity to encode. - Bit rate: VPIM version 3 must {1} specify some codecs with low bit rate for devices (i.e., wireless) that do not have much space/bandwidth. -Voice Over IP support: VPIM version 3 should {2} specify at least one codec that supports Voice over IP implementations. Most desktop email applications and web clients are not capable of playing raw audio. To support "out-of-the box" playing of voice mail content, VPIM v3 must {1} support wav encapsulation of audio. To enable future support of other formats, VPIM version 3 should {2} provide identification of the codec used without requiring interpretation of an audio format. VPIM v3 may {3} allow audio encodings and formats that are not identified in the VPIM version 3 specification to support environments in which the sender is aware of the optimal encoding and format for the recipient. Performance and bandwidth issues make it desireable {3} to support streaming of VPIM version 3 audio to the desktop. VPIM version 3 may {3} explicitely support formats other than raw audio and wav to facilitate streaming. Because most email readers are text/html based and because many devices are not capable of recording audio content, VPIM v3 must {1} allow inclusion of text body parts in a voice message. VPIM version 3 should {2} not explicitly prohibit other media types, as long as critical content is identified and minimal discard rules are specified. To support devices that are not capable of playing audio, VPIM 3 should {2} define an optional informational text body part describing the content of the message and indicating how the audio content can be accessed. It is also a desktop requirement {1} to support attachments of any media type. VPIM version 3 must {1} specify discard rules for cases in which recipient can't render the attachments. 3.2 Interoperability with VPIM version 2 and version 3 voice messaging systems Voice messaging systems are generally implemented as special-purpose machines that interface to a telephone switch and provide call answering and voice messaging services. VPIM version 2 was designed to support interoperability between such systems and remains the best messaging profile for the purpose. Di Silvestro, Laile Expires 7/6/99 [Page 6] Internet Draft VPIM V3 Goals July 6, 1999 To support interoperability between VPIM voice messaging systems and other compliant systems, VPIM version 3 must {1} have a simple minimum set of required features that will guarantee interoperability, as well as provision for additional functionality that may be supported by more capable systems. Support for this additional functionality requires {1} a mechanism for identifying essential content and status codes indicating that a message could not be delivered due to capability differences. It should {2} also include a minimum set of discard rules. The requirement for interoperability with VPIM version 2 voice messaging systems has strong implications for the specification of standard audio encoding and format. Interoperability must {1} be able to depend on the receiving system supporting the VPIM version 2 32KADPCM codec [ADPCM and G726] , and must not {1} depend on the receiving system supporting any additional VPIM version 3 codecs or audio formats. To ensure interoperability between VPIM version 2 and version 3 systems, it may [3] be desirable to revise the VPIM version 2 specification to include new status codes and discard rules. 3.3 Interoperability with VPIM version 3 unified messaging systems Unified messaging solutions typically leverage common store, directory, and transport layers to provide greater interoperability and accessibility to a variety of media content. They support creation of and access to voicemail, email, and fax messages from a single user interface. Most unified messaging systems preserve the notion of a primary media type with multiple message components that convey essential information. Because unified messaging clients have varying capabilities, these components may have a different media type than the message. It is also common for unified messaging systems to permit forwarding and replying to messages of one type as an attachment to a message of another type. To accommodate the common functionality of unified messaging systems, VPIM version 3 must {1} support the inclusion of body parts of a type other than the primary content type. It must {1} also support the embedding of VPIM messages as attachments to messages of another type (such as multipart/mixed), as well as the embedding of messages of another type as attachments to VPIM messages. To provide interoperability with systems that cannot handle a particular content type, VPIM version 3 must {1} provide a mechanism for identifying essential body parts and should {2} define media specific status codes and strings to handle non-delivery of essential body parts. Di Silvestro, Laile Expires 7/6/99 [Page 7] Internet Draft VPIM V3 Goals July 6, 1999 3.4 Interoperability with traditional email servers VPIM version 3 must {1} interoperate consistently with the current Internet mail environment. If VPIM version 3 messages arrive in users' mailboxes, it is required {1} that the standard interoperate successfully with common user practices for mail messages: storing them in databases, retransmission, forwarding, creation of mail digests, and replying to messages using non-audio equipment. 4. Acknowledgements The author gratefully acknowledges the input and feedback provided by the members of the VPIM version 3 work group including Kevin Chestnut, Bernard Elliot, Holly Grabowski, Glen Parsons, and Greg Vaudreuil. The author also appreciates the contributions of Eric Schultz in reviewing this document. 5. Copyright Copyright (C) The Internet Society, 1997. 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." 6. Author's address Laile L. Di Silvestro Microsoft Corporation One Microsoft Way, MS 34/3308 Redmond, WA 98073 lailed@microsoft.com Di Silvestro, Laile Expires 7/6/99 [Page 8] Internet Draft VPIM V3 Goals July 6, 1999 7. References [ADPCM] G. Vaudreuil and G. Parsons, "Toll Quality Voice - 32 kbit/s ADPCM: MIME Sub-type Registration", Work In Progress, , 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. [CODES] Vaudreuil, G. "Enhanced Mail System Status Codes", RFC 1893, 01/15/1996. [DISP] R. Troost and S. Dorner, Communicating Presentation Information in Internet Messages: The Content-Disposition Header, RFC 2183, August 1997 [DRPT] Moore, K. "SMTP Service Extensions for Delivery Status Notifications", RFC 1891, 01/15/1996 [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). [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. [REPORT] Vaudreuil, G., "The Multipart/Report Content Type for the Reporting of Mail System Administrative Messages", RFC 1892, 01/15/1996. [RFC822] Crocker, D., "Standard for the Format of ARPA Internet Text Messages", STD 11, RFC 822, UDEL, August 1982. [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. [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. Di Silvestro, Laile Expires 7/6/99 [Page 9] Internet Draft VPIM V3 Goals July 9, 1999 [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. [VPIM3] Vaudreuil, Greg, "Voice Profile for Internet Mail, Version 2", ", Work In Progress, , December 1998