SIMPLE                                                      J. Rosenberg
Internet-Draft                                                     Cisco
Intended status: Informational                         November 13, 2007
Expires: May 16, 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-01

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   By submitting this Internet-Draft, each author represents that any
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   This Internet-Draft will expire on May 16, 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 . . . . . . . . . . . . . . . . . . . . . . .  7
     2.5.  Optimizations  . . . . . . . . . . . . . . . . . . . . . .  8
   3.  Instant Messaging  . . . . . . . . . . . . . . . . . . . . . .  9
     3.1.  Page Mode  . . . . . . . . . . . . . . . . . . . . . . . .  9
     3.2.  Session Mode . . . . . . . . . . . . . . . . . . . . . . .  9
     3.3.  IM Chat Rooms  . . . . . . . . . . . . . . . . . . . . . . 10
     3.4.  IM Features  . . . . . . . . . . . . . . . . . . . . . . . 10
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   6.  Informative References . . . . . . . . . . . . . . . . . . . . 11
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14
   Intellectual Property and Copyright Statements . . . . . . . . . . 16
































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1.  Introduction

   The IETF has produced many specifications related to Presence and
   Instant Messaging with the Session Initiation Protocol (SIP)
   [RFC3261].  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
   [RFC2026].  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 [RFC3265]
      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 [RFC3856]
      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 [RFC4662] 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
      [RFC3903] 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 [RFC3863]
      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 [RFC4479] 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
      [RFC4480] 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 [RFC4481] 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 [RFC4482] 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
      [I-D.ietf-simple-prescaps-ext] adds even more attributes to the
      presence document schema, this time to allow indication of



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      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.

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 [RFC4745] 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
      [I-D.ietf-simple-presence-rules] 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 [RFC3857], 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 [RFC3858] 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.






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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
   [I-D.ietf-simple-presence-rules]).

   In SIMPLE, management of this data is handled by the XML
   Configuration Access Protocol (XCAP) [RFC4825].  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 [RFC4825] 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 [I-D.ietf-sip-xcap-config] 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 [I-D.ietf-simple-xcap-diff] defines an XML
      format for indicating changes in XCAP documents.  It makes use of
      an XML diff format defined in [I-D.ietf-simple-xml-patch-ops].  It
      is used in conjunction with [I-D.ietf-sip-xcap-config] 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
      [RFC4826] 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



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      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 [RFC4827] 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 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 [RFC4660] 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 [RFC4661] 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 [RFC4661] defines an XML format
      used with the event notification filtering mechanism defined in
      RFC 4660 [RFC4660].

   RFC XXXX, Presence Information Data format (PIDF) Extension for
   Partial Presence (S):  [I-D.ietf-simple-partial-pidf-format] defines
      a new XML format for representing changes in presence documents,
      called a partial PIDF document.  This format contains an XML patch
      operation [I-D.ietf-simple-xml-patch-ops], 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
      [I-D.ietf-simple-partial-publish] defines a mechanism for
      publishing presence status using a partial PIDF document.




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   RFC XXXX, An Extensible Markup Language (XML) Patch Operations
   Framework Utilizing XML Path Language (XPath) Selectors (S):  RFC
      XXXX [I-D.ietf-simple-xml-patch-ops] 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.

   RFC XXXX, The Presence-Specific Static Dictionary for Signaling
   Compression (Sigcomp) (S):  [I-D.garcia-simple-presence-dictionary]
      defines a dictionary for usage with Signaling Compression
      (Sigcomp) [RFC3320] to improve the compressability of presence
      documents.


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 [RFC3428] introduces the MESSAGE method,
      which can be used to send an instant message through SIP
      signaling.

   RFC XXXX, Multiple-Recipient MESSAGE Requests in the Session
   Initiation Protocol (SIP) (S):  [I-D.ietf-sip-uri-list-message]
      defines a mechanism whereby a client can send a single SIP MESSAGE
      to multiple recipients.  This is accomplished by including the
      list of recipients as an object in the body, and having a network
      server send a copy to each recipient.

3.2.  Session Mode

   RFC 4975, The Message Session Relay Protocol (MSRP) (S):  RFC 4975
      [RFC4975] 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



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      MSRP URI, within SIP and SDP signaling.

   RFC 3862, Common Presence and Instant Messaging (CPIM): Message
   Format (S):  RFC 3862 [RFC3862] 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 4976, Relay Extensions for the Message Sessions Relay Protocol
   (MSRP) (S):  RFC 4976 [RFC4976] 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 [RFC4353] and conference control
   [I-D.ietf-xcon-framework] 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 necessary are
   extensions to provide features that are specific to IM.

   RFC XXXX, Multi-party Instant Message (IM) Sessions  the Message
   Session Relay Protocol (MSRP) (S):  RFC XXXX [I-D.ietf-simple-chat]
      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 [RFC3994] 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
      [I-D.ietf-simple-imdn] provides delivery notifications of IM
      receipt.  This allows a user to know with certainty that a message
      has been received.



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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

   [RFC3261]  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.

   [RFC3265]  Roach, A., "Session Initiation Protocol (SIP)-Specific
              Event Notification", RFC 3265, June 2002.

   [RFC3856]  Rosenberg, J., "A Presence Event Package for the Session
              Initiation Protocol (SIP)", RFC 3856, August 2004.

   [RFC4662]  Roach, A., Campbell, B., and J. Rosenberg, "A Session
              Initiation Protocol (SIP) Event Notification Extension for
              Resource Lists", RFC 4662, August 2006.

   [RFC3903]  Niemi, A., "Session Initiation Protocol (SIP) Extension
              for Event State Publication", RFC 3903, October 2004.

   [RFC3863]  Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr,
              W., and J. Peterson, "Presence Information Data Format
              (PIDF)", RFC 3863, August 2004.

   [RFC4479]  Rosenberg, J., "A Data Model for Presence", RFC 4479,
              July 2006.

   [RFC4480]  Schulzrinne, H., Gurbani, V., Kyzivat, P., and J.
              Rosenberg, "RPID: Rich Presence Extensions to the Presence
              Information Data Format (PIDF)", RFC 4480, July 2006.

   [RFC4481]  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.

   [RFC4482]  Schulzrinne, H., "CIPID: Contact Information for the



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              Presence Information Data Format", RFC 4482, July 2006.

   [I-D.ietf-simple-prescaps-ext]
              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.

   [RFC4745]  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.

   [I-D.ietf-simple-presence-rules]
              Rosenberg, J., "Presence Authorization Rules",
              draft-ietf-simple-presence-rules-10 (work in progress),
              July 2007.

   [RFC3857]  Rosenberg, J., "A Watcher Information Event Template-
              Package for the Session Initiation Protocol (SIP)",
              RFC 3857, August 2004.

   [RFC3858]  Rosenberg, J., "An Extensible Markup Language (XML) Based
              Format for Watcher Information", RFC 3858, August 2004.

   [RFC4825]  Rosenberg, J., "The Extensible Markup Language (XML)
              Configuration Access Protocol (XCAP)", RFC 4825, May 2007.

   [RFC4826]  Rosenberg, J., "Extensible Markup Language (XML) Formats
              for Representing Resource Lists", RFC 4826, May 2007.

   [RFC4827]  Isomaki, M. and E. Leppanen, "An Extensible Markup
              Language (XML) Configuration Access Protocol (XCAP) Usage
              for Manipulating Presence Document Contents", RFC 4827,
              May 2007.

   [I-D.ietf-sip-xcap-config]
              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.

   [I-D.ietf-simple-xcap-diff]
              Rosenberg, J., "An Extensible Markup Language (XML)
              Document Format for Indicating A Change  in XML



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              Configuration Access Protocol (XCAP) Resources",
              draft-ietf-simple-xcap-diff-05 (work in progress),
              March 2007.

   [I-D.ietf-simple-xml-patch-ops]
              Urpalainen, J., "An Extensible Markup Language (XML) Patch
              Operations Framework Utilizing XML  Path Language (XPath)
              Selectors", draft-ietf-simple-xml-patch-ops-03 (work in
              progress), August 2007.

   [RFC4660]  Khartabil, H., Leppanen, E., Lonnfors, M., and J. Costa-
              Requena, "Functional Description of Event Notification
              Filtering", RFC 4660, September 2006.

   [RFC4661]  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.

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

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

   [RFC3428]  Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C.,
              and D. Gurle, "Session Initiation Protocol (SIP) Extension
              for Instant Messaging", RFC 3428, December 2002.

   [RFC4975]  Campbell, B., Mahy, R., and C. Jennings, "The Message
              Session Relay Protocol (MSRP)", RFC 4975, September 2007.

   [RFC4976]  Jennings, C., Mahy, R., and A. Roach, "Relay Extensions
              for the Message Sessions Relay Protocol (MSRP)", RFC 4976,
              September 2007.

   [RFC4353]  Rosenberg, J., "A Framework for Conferencing with the
              Session Initiation Protocol (SIP)", RFC 4353,
              February 2006.

   [I-D.ietf-xcon-framework]
              Barnes, M., "A Framework for Centralized Conferencing",
              draft-ietf-xcon-framework-09 (work in progress),



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Internet-Draft             Simple Made Simple              November 2007


              August 2007.

   [I-D.ietf-simple-chat]
              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.

   [RFC3994]  Schulzrinne, H., "Indication of Message Composition for
              Instant Messaging", RFC 3994, January 2005.

   [RFC3862]  Klyne, G. and D. Atkins, "Common Presence and Instant
              Messaging (CPIM): Message Format", RFC 3862, August 2004.

   [RFC2026]  Bradner, S., "The Internet Standards Process -- Revision
              3", BCP 9, RFC 2026, October 1996.

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

   [I-D.garcia-simple-presence-dictionary]
              Garcia-Martin, M., "The Presence-Specific Static
              Dictionary for Signaling Compression  (Sigcomp)",
              draft-garcia-simple-presence-dictionary-06 (work in
              progress), August 2007.

   [RFC3320]  Price, R., Bormann, C., Christoffersson, J., Hannu, H.,
              Liu, Z., and J. Rosenberg, "Signaling Compression
              (SigComp)", RFC 3320, January 2003.

   [I-D.ietf-sip-uri-list-message]
              Garcia-Martin, M. and G. Camarillo, "Multiple-Recipient
              MESSAGE Requests in the Session Initiation Protocol
              (SIP)", draft-ietf-sip-uri-list-message-01 (work in
              progress), January 2007.














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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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