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Versions: (draft-rosenberg-simple-simple) 00 01 02 03 04 05 06 07 08 09 RFC 6914

SIMPLE                                                      J. Rosenberg
Internet-Draft                                                     Cisco
Intended status: Informational                             July 26, 2007
Expires: January 27, 2008


 SIMPLE made Simple: An Overview of the IETF Specifications for Instant
   Messaging and Presence using the Session Initiation Protocol (SIP)
                      draft-ietf-simple-simple-00

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
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   This Internet-Draft will expire on January 27, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   The IETF has produced many specifications related to Presence and
   Instant Messaging with the Session Initiation Protocol (SIP).
   Collectively, these specifications are known as SIMPLE - SIP for
   Instant Messaging and Presence Leveraging Extensions.  This document
   serves as a guide to the SIMPLE suite of specifications.  It breaks
   them up into categories and explains what each is for and how they
   relate to each other.



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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Presence . . . . . . . . . . . . . . . . . . . . . . . . . . .  3
     2.1.  Core Protocol Machinery  . . . . . . . . . . . . . . . . .  4
     2.2.  Presence Documents . . . . . . . . . . . . . . . . . . . .  5
     2.3.  Privacy and Policy . . . . . . . . . . . . . . . . . . . .  6
     2.4.  Provisioning . . . . . . . . . . . . . . . . . . . . . . .  6
     2.5.  Optimizations  . . . . . . . . . . . . . . . . . . . . . .  8
   3.  Instant Messaging  . . . . . . . . . . . . . . . . . . . . . .  9
     3.1.  Page Mode  . . . . . . . . . . . . . . . . . . . . . . . .  9
     3.2.  Session Mode . . . . . . . . . . . . . . . . . . . . . . .  9
     3.3.  IM Chat Rooms  . . . . . . . . . . . . . . . . . . . . . .  9
     3.4.  IM Features  . . . . . . . . . . . . . . . . . . . . . . . 10
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   6.  Informative References . . . . . . . . . . . . . . . . . . . . 10
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13
   Intellectual Property and Copyright Statements . . . . . . . . . . 14
































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1.  Introduction

   The IETF has produced many specifications related to Presence and
   Instant Messaging with the Session Initiation Protocol (SIP) [1].
   Collectively, these specifications are known as SIMPLE - SIP for
   Instant Messaging and Presence Leveraging Extensions.  These
   specifications cover topics ranging from protocols for subscription
   and publication, to presence document formats, to protocols for
   managing privacy preferences.  The large number of specifications can
   make it hard to figure out exactly what exactly SIMPLE is, what
   specifications cover it, what functionality it provides, and how
   these specifications relate to each other.

   This document serves to address this problem.  It provides an
   enumeration of the protocols which make up the SIMPLE suite of
   specifications from IETF.  It categorizes them into related areas of
   functionality, and briefly explains the purpose of each and how the
   specifications relate to each other.  Each specification also
   includes a letter that designates its category in the standards track
   [34].  These values are:

   S: Standards Track (Proposed Standard, Draft Standard, or Standard)

   E: Experimental

   B: Best Current Practice

   I: Informational


2.  Presence

   SIMPLE provides for both presence and IM capabilities.  Though both
   of these fit underneath the broad SIMPLE umbrella, they are well
   separated from each other and are supported by different sets of
   specifications.  That is a key part of the SIMPLE story; presence is
   much broader than just IM, and it enables communications using voice
   and video along with IM.

   The SIMPLE presence specifications can be broken up into:

   o  The core protocol machinery, which provides the actual SIP
      extensions for subscriptions, notifications and publications

   o  Presence documents, which are XML documents that provide for rich
      presence and are carried by the core protocol machinery





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   o  Privacy and policy, which are documents for expressing privacy
      preferences about how those presence documents are to be shown (or
      not shown) to other users

   o  Provisioning, which describes how users manage their privacy
      policies, buddy lists and other pieces of information required for
      SIMPLE presence to work

   o  Optimizations, which are improvements in the core protocol
      machinery that were defined to improve the performance of SIMPLE,
      particularly on wireless links

2.1.  Core Protocol Machinery

   RFC 3265, SIP-Specific Event Notification (S):  RFC 3265 [2] defines
      the SUBSCRIBE and NOTIFY methods for SIP, forming the core of the
      SIP event notification framework.  To actually use the framework,
      extensions need to be defined for specific event packages.
      Presence is defined as an event package within this framework.
      Packages exist for other, non-presence related functions, such as
      message waiting indicators and dialog state changes.

   RFC 3856, A Presence Event Package for SIP (S):  RFC 3856 [3] defines
      an event package for indicating user presence through SIP.
      Through this package, a SIP user agent can ask to be notified of
      the presence state of a presentity (presence entity).  The content
      of the NOTIFY messages in this package are presence documents,
      discussed in Section 2.2

   RFC 4662, A Session Initiation Protocol (SIP) Event Notification
   Extension for Resource Lists (S):  RFC 4662 [4] defines an extension
      to RFC 3265 that allows a client to subscribe to a list of
      resources using a single subscription.  The server, called a
      Resource List Server (RLS) will "expand" the subscription and
      subscribe to each individual member of the list.  Its primary
      usage with presence is to allow subscriptions to "buddy lists".
      Without RFC 4662, a UA would need to subscribe to each presentity
      individually.  With RFC 4662, they can have a single subscription
      to all buddies.  A user can manage the entries in their buddy list
      using the provisioning mechanisms in Section 2.4.

   RFC 3903, SIP Extension for Event State Publication (S):  RFC 3903
      [5] defines the PUBLISH method.  With this method, a user agent
      can publish its current state for any event package, including the
      presence event package.  Once an agent publishes its presence
      state, the presence server would send notifications of this state
      change using RFC 3856.




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2.2.  Presence Documents

   Once a user has generated a subscription to presence using the core
   protocol machinery, they will receive notifications (SIP NOTIFY
   requests) which contain presence information.  That presence
   information is in the form of an XML presence document.  Several
   specifications have been defined to describe this document format,
   focusing on rich, multimedia presence.

   RFC 3863, Presence Information Data Format (S):  RFC 3863 [6] defines
      the baseline XML format for a presence document.  It defines the
      concept of a tuple as representing a basic communication modality,
      and defines a simple status for it (open or closed).

   RFC 4479, A Data Model for Presence (S):  RFC 4479 [7] extends the
      basic model in RFC 3863.  It introduces the concepts of devices
      and person status, and explains how these relate to each other.
      It describes how presence documents are used to represent states
      in communications systems in a consistent fashion.  More than RFC
      3863, it defines what a presence document is and what it means.

   RFC 4480, RPID: Rich Presence Extensions to PIDF (S):  RFC 4480 [8]
      adds many more attributes to the presence document schema,
      building upon the model in RFC 4479.  It allows for indications of
      activities, moods, places and place types, icons, and indications
      of whether a user is idle or not.

   RFC 4481, Timed Presence Extensions to the Presence Information Data
   Format (PIDF) to Indicate Status Information for Past and Future Time
   Intervals (S):  RFC 4481 [9] adds additional attributes to the
      presence document schema, again building upon the model in RFC
      4479.  It allows documents to indicate status for the future or
      the past.  For example, a user can indicate that they will be
      unavailable for voice communications from 2pm to 3pm, due to a
      meeting.

   RFC 4482, CIPID: Contact Information for the Presence Information
   Data Format (S):  RFC 4482 [10] adds attributes to the presence
      document schema for contact information, such as a vCard, display
      name, homepage, icon, or sound (such as the pronunciation of their
      name).

   RFC XXXX, Session Initiation Protocol (SIP) User Agent Capability
   Extension to Presence Information Data Format (PIDF) (S):  RFC XXXX
      [11] adds even more attributes to the presence document schema,
      this time to allow indication of capabilities for the user agent.
      For example, the extensions can indicate whether a UA supports
      audio and video, what SIP methods it supports, and so on.



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2.3.  Privacy and Policy

   The rich presence capabilities defined by the specifications in
   Section 2.2 introduces a strong need for privacy preferences.  Users
   must be able to approve or deny subscriptions to their presence, and
   indicate what information such watchers can see.  In SIMPLE, this is
   accomplished through policy documents, uploaded to the presence
   server using the provisioning mechanisms in Section 2.4.

   RFC 4745, Common Policy: A Document Format for Expressing Privacy
   Preferences (S):  RFC 4745 [12] defines a general XML framework for
      expressing privacy preferences for both geolocation information
      and presence information.  It introduces the concepts of
      conditions, actions and transformations that are applied to
      privacy-sensitive data.  The common policy framework provides
      privacy-safety, a property by which network error or version
      incompatibilities can never cause more information to be revealed
      to a watcher than the user would otherwise desire.

   RFC XXXX, Presence Authorization Rules (S):  RFC XXXX [13] uses the
      framework of RFC 4745 to define a policy document format for
      describing presence privacy policies.  Besides basic yes/no
      approvals, this format allows a user to control what kind of
      information a watcher is allowed to see.

   RFC 3857, A Watcher Information Event Template Package for SIP (S):
      RFC 3857 [14], also known as watcherinfo, provides a mechanism for
      a user agent to find out what subscriptions are in place for a
      particular event package.  Though it was defined to be used for
      any event package, it has particular applicability for presence.
      It is used to provide reactive authorization.  With reactive
      authorization, a user gets alerted if someone tries to subscribe
      to their presence, so that they may provide an authorization
      decision.  Watcherinfo is used to provide the alert that someone
      has subscribed to a user's presence.

   RFC 3858, An Extensible Markup Language (XML) Based Format for
   Watcher Information (S):  RFC 3858 [15] is the companion to RFC 3857.
      It specifies the XML format of watcherinfo that is carried in
      notifications for the event template package in RFC 3857.

2.4.  Provisioning

   Proper operation of a SIMPLE presence system requires that several
   pieces of data are correctly managed by the users and provisioned
   into the system.  These include buddy lists (used by the resource
   list subscription mechanism in RFC 4662) and privacy policies (such
   as those described by the XML format in [13]).



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   In SIMPLE, management of this data is handled by the XML
   Configuration Access Protocol (XCAP) [16].  XCAP is used by the user
   agent to manipulate buddy lists, privacy policy, and other data that
   is represented by XML documents stored on a server.

   RFC 4825, The Extensible Markup Language (XML) Configuration Access
   Protocol (XCAP) (S):  RFC4825 [16] specifies XCAP.  XCAP is a usage
      of HTTP that allows a user agent to manipulate the contents of XML
      documents stored on a server.  It can be used to manipulate any
      kind of XML, and the protocol itself is independent of the
      particular schema of the data it is modifying.  XML schemas have
      been defined for buddy lists, privacy policies and offline
      presence status, allowing all of those to be managed by a user
      with XCAP.

   RFC XXXX, Extensions to the Session Initiation Protocol (SIP) User
   Agent Profile Delivery Change Notification Event Package for the
   Extensible Markup Language Language Configuration Access Protocol
   (XCAP) (S):  RFC XXXX [19] defines an extension to the SIP user agent
      configuration profile, allowing a user agent to learn about
      changes in its documents on an XCAP server.  With this mechanism,
      there can be a change made by someone else to a buddy list or
      privacy policy document, and a UA will find out that a new version
      is available.

   RFC XXXX, An Extensible Markup Language (XML) Document Format for
   Indicating A Change in XML Configuration Access  Protocol (XCAP)
   Resources (S):  RFC XXXX [20] defines an XML format for indicating
      changes in XCAP documents.  It makes use of an XML diff format
      defined in [21].  It is used in conjunction with [19] to alert a
      user agent of changes made by someone else to their provisioned
      data.

   RFC 4826, XML Formats for Representing Resource Lists (S):  RFC 4826
      [17] defines two XML document formats used to represent buddy
      lists.  One is simply a list of users (or more generally,
      resources), and the other defines a buddy list whose membership is
      composed of a list of users or resources.  These lists can be
      manipulated by XCAP, allowing a user to add or remove members from
      their buddy lists.  The buddy list is also accessed by the
      resource list server specified in RFC 4662 for processing resource
      list subscriptions.

   RFC 4827, An Extensible Markup Language (XML) Configuration Access
   Protocol (XCAP) Usage for Manipulating Presence Document Contents
   (S):  RFC 4827 [18] defines an XCAP usage that allows a user to store
      an "offline" presence document.  This is a presence status that is
      used by a presence server when there are no presence documents



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      published for that user by any user agents currently running.

2.5.  Optimizations

   When running over wireless links, presence can be a very expensive
   service.  Notifications often get sent when the change is not really
   relevant to the watcher.  Furthermore, when a notification is sent,
   it contains the full presence state of the watcher, rather than just
   an indication of what changed.  Optimizations have been defined to
   address both of these cases.

   RFC 4660, Functional Description of Event Notification Filtering
   (S):  RFC 4660 [22] defines a mechanism that allows a watcher to
      include filters in its subscription.  These filters limit the
      cases in which notifications are sent.  It is used in conjunction
      with RFC 4661 [23] which specifies the XML format of the filters
      themselves.  The mechanism, though targeted for presence, can be
      applied to any SIP event package.

   RFC 4661, An Extensible Markup Language (XML)-Based Format for Event
   Notification Filtering (S):  RFC 4661 [23] defines an XML format used
      with the event notification filtering mechanism defined in RFC
      4660 [22].

   RFC XXXX, Presence Information Data format (PIDF) Extension for
   Partial Presence (S):  [25] defines a new XML format for representing
      changes in presence documents, called a partial PIDF document.
      This format contains an XML patch operation [21], that, when
      applied to the previous presence document, yields the new presence
      document.  The partial PIDF document is included in presence
      notifications when a watcher indicates that they support the
      format.

   RFC XXXX, Publication of Partial Presence Information (S):  RFC XXXX
      [24] defines a mechanism for publishing presence status using a
      partial PIDF document.

   RFC XXXX, An Extensible Markup Language (XML) Patch Operations
   Framework Utilizing XML Path Language (XPath) Selectors (S):  RFC
      XXXX [21] defines an XML structure for representing changes in XML
      documents.  It is a form of "diff", but specifically for XML
      documents.  It is used by several of the optimization mechanisms
      defined for SIMPLE.








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3.  Instant Messaging

   SIMPLE defines two modes of instant messaging.  These are page mode
   and session mode.  In page mode, instant messages are sent by sending
   a SIP request that contains the contents of the instant message.  In
   session mode, IM is viewed as another media type - along with audio
   and video - and an INVITE request is used to set up a session that
   includes IM as a media type.  While page mode is more efficient for
   one or two message conversations, session mode is more efficient for
   longer conversations since the messages are not sent through the SIP
   servers.  Furthermore, by viewing IM as a media type, all of the
   features available in SIP signaling - third party call control,
   forking, and so on, are available for IM.

3.1.  Page Mode

   RFC 3428, Session Initiation Protocol (SIP) Extension for Instant
   Messaging (S):  RFC 3428 [26] introduces the MESSAGE method, which
      can be used to send an instant message through SIP signaling.

3.2.  Session Mode

   RFC XXXX, The Message Session Relay Protocol (MSRP) (S):  RFC XXXX
      [27] defines a small text-based protocol for exchanging
      arbitrarily sized content of any time between users.  An MSRP
      session is set up by exchanging certain information, such as an
      MSRP URI, within SIP and SDP signaling.

   RFC 3862, Common Presence and Instant Messaging (CPIM): Message
   Format (S):  RFC 3862 [33] defines a wrapper around instant message
      content, providing meta-data such as the sender and recipient
      identity.  The CPIM format is carried in MSRP.

   RFC XXXX, Relay Extensions for the Message Sessions Relay Protocol
   (MSRP) (S):  RFC XXXX [28] adds support for relays to MSRP.  These
      relay servers receive MSRP messages and send them towards the
      destination.  They provide support for firewall and NAT traversal,
      and allow for features such as recording and inspection to be
      implemented.

3.3.  IM Chat Rooms

   In SIMPLE, IM multi-user chat, also known as chat-rooms, are provided
   using regular SIP conferencing mechanisms.  The framework for SIP
   conferencing [29] and conference control [30] describe how all SIP-
   based conferencing works, including joining and leaving, persistent
   and temporary conferences, floor control and moderation, and learning
   of conference membership, amongst other functions.  All that is



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   necessary are extensions to provide features that are specific to IM.

   RFC XXXX, Multi-party Instant Message (IM) Sessions Using the Message
   Session Relay Protocol (MSRP) (S):  RFC XXXX [31] defines how MSRP is
      used to provide support for nicknames and private chat within an
      IM conference.

3.4.  IM Features

   Several specifications have been written to provide IM-specific
   features for SIMPLE.  These include "is-typing" indications, allowing
   a user to know when their messaging peer is composing a response, and
   delivery notifications, allowing a user to know when their IM has
   been received.

   RFC 3994, Indication of Message Composition for Instant Messaging
   (S):  RFC 3994 [32] defines an XML format that can be sent in instant
      messages that indicates the status of message composition.  This
      provides the familiar "is-typing" indication in IM systems, but
      also supports voice, video and other message types.

   RFC XXXX, Instant Message Disposition Notification (S):  RFC XXXX
      [35] provides delivery notifications of IM receipt.  This allows a
      user to know with certainty that a message has been received.


4.  Security Considerations

   This specification is an overview of existing specifications, and
   does not introduce any security considerations on its own.


5.  IANA Considerations

   None.


6.  Informative References

   [1]   Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
         Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
         Session Initiation Protocol", RFC 3261, June 2002.

   [2]   Roach, A., "Session Initiation Protocol (SIP)-Specific Event
         Notification", RFC 3265, June 2002.

   [3]   Rosenberg, J., "A Presence Event Package for the Session
         Initiation Protocol (SIP)", RFC 3856, August 2004.



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   [4]   Roach, A., Campbell, B., and J. Rosenberg, "A Session
         Initiation Protocol (SIP) Event Notification Extension for
         Resource Lists", RFC 4662, August 2006.

   [5]   Niemi, A., "Session Initiation Protocol (SIP) Extension for
         Event State Publication", RFC 3903, October 2004.

   [6]   Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr, W., and
         J. Peterson, "Presence Information Data Format (PIDF)",
         RFC 3863, August 2004.

   [7]   Rosenberg, J., "A Data Model for Presence", RFC 4479,
         July 2006.

   [8]   Schulzrinne, H., Gurbani, V., Kyzivat, P., and J. Rosenberg,
         "RPID: Rich Presence Extensions to the Presence Information
         Data Format (PIDF)", RFC 4480, July 2006.

   [9]   Schulzrinne, H., "Timed Presence Extensions to the Presence
         Information Data Format (PIDF) to Indicate Status Information
         for Past and Future Time Intervals", RFC 4481, July 2006.

   [10]  Schulzrinne, H., "CIPID: Contact Information for the Presence
         Information Data Format", RFC 4482, July 2006.

   [11]  Lonnfors, M. and K. Kiss, "Session Initiation Protocol (SIP)
         User Agent Capability Extension to  Presence Information Data
         Format (PIDF)", draft-ietf-simple-prescaps-ext-07 (work in
         progress), July 2006.

   [12]  Schulzrinne, H., Tschofenig, H., Morris, J., Cuellar, J., Polk,
         J., and J. Rosenberg, "Common Policy: A Document Format for
         Expressing Privacy Preferences", RFC 4745, February 2007.

   [13]  Rosenberg, J., "Presence Authorization Rules",
         draft-ietf-simple-presence-rules-09 (work in progress),
         March 2007.

   [14]  Rosenberg, J., "A Watcher Information Event Template-Package
         for the Session Initiation Protocol (SIP)", RFC 3857,
         August 2004.

   [15]  Rosenberg, J., "An Extensible Markup Language (XML) Based
         Format for Watcher Information", RFC 3858, August 2004.

   [16]  Rosenberg, J., "The Extensible Markup Language (XML)
         Configuration Access Protocol (XCAP)", RFC 4825, May 2007.




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   [17]  Rosenberg, J., "Extensible Markup Language (XML) Formats for
         Representing Resource Lists", RFC 4826, May 2007.

   [18]  Isomaki, M. and E. Leppanen, "An Extensible Markup Language
         (XML) Configuration Access Protocol (XCAP) Usage for
         Manipulating Presence Document Contents", RFC 4827, May 2007.

   [19]  Petrie, D., "Extensions to the Session Initiation Protocol
         (SIP) User Agent Profile  Delivery Change Notification Event
         Package for the Extensible Markup Language Language
         Configuration Access Protocol (XCAP)",
         draft-ietf-sip-xcap-config-00 (work in progress), October 2006.

   [20]  Rosenberg, J., "An Extensible Markup Language (XML) Document
         Format for Indicating A Change  in XML Configuration Access
         Protocol (XCAP) Resources", draft-ietf-simple-xcap-diff-05
         (work in progress), March 2007.

   [21]  Urpalainen, J., "An Extensible Markup Language (XML) Patch
         Operations Framework Utilizing XML  Path Language (XPath)
         Selectors", draft-ietf-simple-xml-patch-ops-02 (work in
         progress), March 2006.

   [22]  Khartabil, H., Leppanen, E., Lonnfors, M., and J. Costa-
         Requena, "Functional Description of Event Notification
         Filtering", RFC 4660, September 2006.

   [23]  Khartabil, H., Leppanen, E., Lonnfors, M., and J. Costa-
         Requena, "An Extensible Markup Language (XML)-Based Format for
         Event Notification Filtering", RFC 4661, September 2006.

   [24]  Lonnfors, M., "Publication of Partial Presence Information",
         draft-ietf-simple-partial-publish-06 (work in progress),
         February 2007.

   [25]  Lonnfors, M., "Presence Information Data format (PIDF)
         Extension for Partial Presence",
         draft-ietf-simple-partial-pidf-format-08 (work in progress),
         November 2006.

   [26]  Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C., and
         D. Gurle, "Session Initiation Protocol (SIP) Extension for
         Instant Messaging", RFC 3428, December 2002.

   [27]  Campbell, B., "The Message Session Relay Protocol",
         draft-ietf-simple-message-sessions-19 (work in progress),
         February 2007.




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   [28]  Jennings, C., "Relay Extensions for the Message Sessions Relay
         Protocol (MSRP)", draft-ietf-simple-msrp-relays-10 (work in
         progress), December 2006.

   [29]  Rosenberg, J., "A Framework for Conferencing with the Session
         Initiation Protocol (SIP)", RFC 4353, February 2006.

   [30]  Barnes, M., "A Framework for Centralized Conferencing",
         draft-ietf-xcon-framework-08 (work in progress), May 2007.

   [31]  Niemi, A. and M. Garcia-Martin, "Multi-party Instant Message
         (IM) Sessions Using the Message Session Relay  Protocol
         (MSRP)", draft-ietf-simple-chat-00 (work in progress),
         June 2007.

   [32]  Schulzrinne, H., "Indication of Message Composition for Instant
         Messaging", RFC 3994, January 2005.

   [33]  Klyne, G. and D. Atkins, "Common Presence and Instant Messaging
         (CPIM): Message Format", RFC 3862, August 2004.

   [34]  Bradner, S., "The Internet Standards Process -- Revision 3",
         BCP 9, RFC 2026, October 1996.

   [35]  Burger, E. and H. Khartabil, "Instant Message Disposition
         Notification", draft-ietf-simple-imdn-04 (work in progress),
         May 2007.


Author's Address

   Jonathan Rosenberg
   Cisco
   Edison, NJ
   US

   Phone: +1 973 952-5000
   Email: jdrosen@cisco.com
   URI:   http://www.jdrosen.net












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Internet-Draft             Simple Made Simple                  July 2007


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