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SIMPLE                                                      J. Rosenberg
Internet-Draft                                               jdrosen.net
Intended status: Informational                         February 16, 2013
Expires: August 20, 2013


 SIMPLE made Simple: An Overview of the IETF Specifications for Instant
   Messaging and Presence using the Session Initiation Protocol (SIP)
                      draft-ietf-simple-simple-09

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
   categorizes the specifications and explains what each is for and how
   they relate to each other.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on August 20, 2013.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


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.  Federation . . . . . . . . . . . . . . . . . . . . . . . .  8
     2.6.  Optimizations  . . . . . . . . . . . . . . . . . . . . . .  8
   3.  Instant Messaging  . . . . . . . . . . . . . . . . . . . . . .  9
     3.1.  Page Mode  . . . . . . . . . . . . . . . . . . . . . . . .  9
     3.2.  Session Mode . . . . . . . . . . . . . . . . . . . . . . . 10
     3.3.  IM Chat Rooms  . . . . . . . . . . . . . . . . . . . . . . 10
     3.4.  IM Features  . . . . . . . . . . . . . . . . . . . . . . . 11
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   7.  Informative References . . . . . . . . . . . . . . . . . . . . 11
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 15


























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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 6665, SIP-Specific Event Notification (S):  RFC 6665 [RFC6665]
      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 [RFC3856]
      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, below.

   RFC 4662, A Session Initiation Protocol (SIP) Event Notification
   Extension for Resource Lists (S):  RFC 4662 [RFC4662] defines an
      extension to RFC 6665 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, below.

   RFC 5367, Subscriptions to Request-Contained Resource Lists in the
   Session Initiation Protocol (SIP) (S):  [RFC5367] is very similar to
      RFC 4662.  It allows a client to subscribe to a list of resources
      using a single subscription.  However, with this mechanism, the
      list is included within the body of the SUBSCRIBE request.  In RFC
      4662, it is provisioned ahead of time on the server.



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   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.

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):  [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):  [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):  [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):  [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):  [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).




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   RFC 5196, Session Initiation Protocol (SIP) User Agent  Capability
   Extension to Presence Information Data Format (PIDF) (S):  [RFC5196]
      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.

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):  [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 5025, Presence Authorization Rules (S):  [RFC5025] 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):
      [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):  [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 [RFC5025]).

   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] 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 5875, An Extensible Markup Language (XML) Configuration Access
   Protocol (XCAP) Diff Event Package (S):  [RFC5875] 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 5874, An Extensible Markup Language (XML) Document Format for
   Indicating A Change in XML Configuration Access  Protocol (XCAP)
   Resources (S):  [RFC5874] defines an XML format for indicating
      changes in XCAP documents.  It makes use of an XML diff format
      defined in [RFC5261].  It is used in conjunction with [RFC5875] to
      alert a user agent of changes made by someone else to their
      provisioned data.

   RFC 4826, XML Formats for Representing Resource Lists (S):  [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 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.



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   RFC 4827, An Extensible Markup Language (XML) Configuration Access
   Protocol (XCAP) Usage for Manipulating Presence Document Contents
   (S):  [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.  Federation

   Federation refers to the interconnection of different presence and
   instant messaging systems for the purposes of communications.
   Federation can be between domains or within a domain.  A document has
   been developed which describes how presence and IM federation works.

   RFC 5344, Presence and Instant Messaging Peering Use Cases (I):
      [RFC5344] describes a basic set of presence and instant messaging
      use cases for federating between providers.

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

   RFC 5262, Presence Information Data format (PIDF)  Extension for
   Partial Presence (S):  [RFC5262] defines a new XML format for
      representing changes in presence documents, called a partial PIDF
      document.  This format contains an XML patch operation [RFC5261],
      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.



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   RFC 5263, SIP Extension for Partial Notification of Presence
   Information (S):  [RFC5263] defines a mechanism for receiving
      notifications that contain partial presence documents.

   RFC 5264, Publication of Partial Presence Information  (S):
      [RFC5264] defines a mechanism for publishing presence status using
      a partial PIDF document.

   RFC 5261, An Extensible Markup Language (XML) Patch  Operations
   Framework Utilizing XML Path Language (XPath) Selectors (S):
      [RFC5261] 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 5112, The Presence-Specific Static Dictionary for Signaling
   Compression (Sigcomp) (S):  [RFC5112] defines a dictionary for usage
      with Signaling Compression (Sigcomp) [RFC3320] to improve the
      compressability of presence documents.

   RFC 6446, Session Initiation Protocol (SIP) Event Notification
   Extension for Notification Rate Control (S):  [RFC6446] This document
      specifies mechanisms for adjusting the rate of SIP event
      notifications.  These mechanisms can be applied in subscriptions
      to all SIP event packages.


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





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   RFC 5365, Multiple-Recipient MESSAGE Requests in the  Session
   Initiation Protocol (SIP) (S):  [RFC5365] 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):  [RFC4975]
      defines a small text-based protocol for exchanging arbitrarily
      sized content of any kind 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):  [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):  [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.

   RFC 6135, An Alternative Connection Model for the Message Session
   Relay Protocol (MSRP) (S):  [RFC6135] Allows clients to negotiate
      which endpoint in a session will establish the MSRP connection.
      Without this specification, the client generating the SDP offer
      would initiate the connection.

   RFC 6714, Connection Establishment for Media Anchoring (CEMA) for the
   Message Session Relay Protocol (MSRP) (S):  [RFC6714] allows
      middleboxes to anchor the MSRP connection, without the need for
      middleboxes to modify the MSRP messages, and thus also enables a
      secure end-to-end MSRP communication in networks where such
      middleboxes are deployed.

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 [RFC5239] 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



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

   draft-ietf-simple-chat, Multi-party Chat Using the Message Session
   Relay Protocol (MSRP) (S):  [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):  [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 5438, Instant Message Disposition Notification (S):  [RFC5438]
      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.  Acknowledgements

   Thanks to Vijay Gurbani, Barry Leiba, Stephen Hanna, and Salvatore
   Loreto for their review and comments.


7.  Informative References

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.



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              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              June 2002.

   [RFC6665]  Roach, A., "SIP-Specific Event Notification", RFC 6665,
              July 2012.

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

   [RFC5196]  Lonnfors, M. and K. Kiss, "Session Initiation Protocol
              (SIP) User Agent Capability Extension to Presence
              Information Data Format (PIDF)", RFC 5196, September 2008.

   [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.

   [RFC5025]  Rosenberg, J., "Presence Authorization Rules", RFC 5025,
              December 2007.

   [RFC3857]  Rosenberg, J., "A Watcher Information Event Template-



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              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.

   [RFC5875]  Urpalainen, J. and D. Willis, "An Extensible Markup
              Language (XML) Configuration Access Protocol (XCAP) Diff
              Event Package", RFC 5875, May 2010.

   [RFC5874]  Rosenberg, J. and J. Urpalainen, "An Extensible Markup
              Language (XML) Document Format for Indicating a Change in
              XML Configuration Access Protocol (XCAP) Resources",
              RFC 5874, May 2010.

   [RFC5261]  Urpalainen, J., "An Extensible Markup Language (XML) Patch
              Operations Framework Utilizing XML Path Language (XPath)
              Selectors", RFC 5261, September 2008.

   [RFC5263]  Lonnfors, M., Costa-Requena, J., Leppanen, E., and H.
              Khartabil, "Session Initiation Protocol (SIP) Extension
              for Partial Notification of Presence Information",
              RFC 5263, September 2008.

   [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.

   [RFC5264]  Niemi, A., Lonnfors, M., and E. Leppanen, "Publication of
              Partial Presence Information", RFC 5264, September 2008.

   [RFC5262]  Lonnfors, M., Leppanen, E., Khartabil, H., and J.



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              Urpalainen, "Presence Information Data Format (PIDF)
              Extension for Partial Presence", RFC 5262, September 2008.

   [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.

   [RFC5239]  Barnes, M., Boulton, C., and O. Levin, "A Framework for
              Centralized Conferencing", RFC 5239, June 2008.

   [I-D.ietf-simple-chat]
              Niemi, A., Garcia, M., and G. Sandbakken, "Multi-party
              Chat Using the Message Session Relay Protocol (MSRP)",
              draft-ietf-simple-chat-18 (work in progress),
              January 2013.

   [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.

   [RFC5438]  Burger, E. and H. Khartabil, "Instant Message Disposition
              Notification (IMDN)", RFC 5438, February 2009.

   [RFC5112]  Garcia-Martin, M., "The Presence-Specific Static
              Dictionary for Signaling Compression (Sigcomp)", RFC 5112,
              January 2008.

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

   [RFC5365]  Garcia-Martin, M. and G. Camarillo, "Multiple-Recipient



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              MESSAGE Requests in the Session Initiation Protocol
              (SIP)", RFC 5365, October 2008.

   [RFC5344]  Houri, A., Aoki, E., and S. Parameswar, "Presence and
              Instant Messaging Peering Use Cases", RFC 5344,
              October 2008.

   [RFC6714]  Holmberg, C., Blau, S., and E. Burger, "Connection
              Establishment for Media Anchoring (CEMA) for the Message
              Session Relay Protocol (MSRP)", RFC 6714, August 2012.

   [RFC5367]  Camarillo, G., Roach, A., and O. Levin, "Subscriptions to
              Request-Contained Resource Lists in the Session Initiation
              Protocol (SIP)", RFC 5367, October 2008.

   [RFC6135]  Holmberg, C. and S. Blau, "An Alternative Connection Model
              for the Message Session Relay Protocol (MSRP)", RFC 6135,
              February 2011.

   [RFC6446]  Niemi, A., Kiss, K., and S. Loreto, "Session Initiation
              Protocol (SIP) Event Notification Extension for
              Notification Rate Control", RFC 6446, January 2012.


Author's Address

   Jonathan Rosenberg
   jdrosen.net

   Email: jdrosen@jdrosen.net
   URI:   http://www.jdrosen.net




















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