SIPPING                                                     J. Rosenberg
Internet-Draft                                               dynamicsoft
Expires: November 19, 2004 January 16, 2005                                 H. Schulzrinne
                                                     Columbia University
                                                           O. Levin, Ed.
                                                   Microsoft Corporation
                                                            May 21,
                                                           July 18, 2004

    A Session Initiation Protocol (SIP) Event Package for Conference

Status of this Memo

   This document is an Internet-Draft and is in full conformance with subject to all provisions
   of Section 10 section 3 of RFC 3667.  By submitting this Internet-Draft, each
   author represents that any applicable patent or other IPR claims of
   which he or she is aware have been or will be disclosed, and any of RFC2026.
   which he or she become aware will be disclosed, in accordance with
   RFC 3668.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at http://

   The list of Internet-Draft Shadow Directories can be accessed at

   This Internet-Draft will expire on November 19, 2004. January 16, 2005.

Copyright Notice

   Copyright (C) The Internet Society (2004).  All Rights Reserved.


   This document defines a conference event package for the Session
   Initiation Protocol (SIP) Events framework, along with a data format
   used in notifications for this package.  The conference package
   allows users to subscribe to a conference URI.  Notifications are
   sent about changes in the membership of this conference and
   optionally about changes in the state of additional conference

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4  5
   3.  Conference Event Package . . . . . . . . . . . . . . . . . . .  5  6
     3.1   Event Package Name . . . . . . . . . . . . . . . . . . . .  5  6
     3.2   SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . . .  5  6
     3.3   Subscription Duration  . . . . . . . . . . . . . . . . . .  5  6
     3.4   NOTIFY Bodies  . . . . . . . . . . . . . . . . . . . . . .  6  7
     3.5   Notifier Processing of SUBSCRIBE Requests  . . . . . . . .  6  7
     3.6   Notifier Generation of NOTIFY Requests . . . . . . . . . .  6  7
     3.7   Subscriber Processing of NOTIFY Requests . . . . . . . . .  7  8
     3.8   Handling of Forked Requests  . . . . . . . . . . . . . . .  7  8
     3.9   Rate of Notifications  . . . . . . . . . . . . . . . . . .  7  8
     3.10  State Agents . . . . . . . . . . . . . . . . . . . . . . .  7  8
   4.  Conference Data Format . . . . . . . . . . . . . . . . . . . .  9 10
     4.1   Conference Information . . . . . . . . . . . . . . . . . .  9 10
       4.1.1   User Element . . . . . . . . . . . . . . . . . . . . .  9 10   User Attributes  . . . . . . . . . . . . . . . . . 10 11   User Status Elements . . . . . . . . . . . . . . . 10 12   Media Stream Information  . . . . . . . . . . . . . 12 . . . 13
    Media Attributes . . . . . . . . . . . . . . . 13
    Media Elements . . . . . . . . . . . . . . . . 14   User Role  . . . . . . . . . . . . . . . . . . . . 14
       4.1.2   Sidebar Element  . . . . . . . . . . . . . . . . . . . 13 15
       4.1.3   Additional Conference Identifiers  . . . . . . . . . . 13 15
       4.1.4   Policy URIs  . . . . . . . . . . . . . . . . . . . . . 13 15
       4.1.5   Recording  . . . . . . . . . . . . . . . . . . . . . . 15
       4.1.6   Streaming  . . . . . . . . . . . . . . . . . . . . . . 16
     4.2   Constructing Coherent State  . . . . . . . . . . . . . . . 13 16
       4.2.1   User and Sidebar Updates .   The Algorithm  . . . . . . . . . . . . . . 14
       4.2.2   Conference and Policy Identifiers Updates . . . . . . 14 17
     4.3   Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 15 18
     4.4   Example  . . . . . . . . . . . . . . . . . . . . . . . . . 17 21
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 19 23
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 20 24
     6.1   conference Event Package Registration  . . . . . . . . . . 20 24
     6.2   application/conference-info+xml MIME Registration  . . . . 20 24
     6.3   URN Sub-Namespace Registration for
           urn:ietf:params:xml:ns:conference-info . . . . . . . . . . 20 24
     6.4   XML Schema Registration  . . . . . . . . . . . . . . . . . 21 25
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 22 26
   8.  Changes History  . . . . . . . . . . . . . . . . . . . . . . . 23 27
     8.1   Changes since -03 -04  . . . . . . . . . . . . . . . . . . . . 23 27
     8.2   Changes since -02 -03  . . . . . . . . . . . . . . . . . . . . 23 27
     8.3   Changes since -02  . . . . . . . . . . . . . . . . . . . . 27
     8.4   Changes since -01  . . . . . . . . . . . . . . . . . . . . 23 28
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 24 29
   9.1   Normative References . . . . . . . . . . . . . . . . . . . . 24 29
   9.2   Informative References . . . . . . . . . . . . . . . . . . . 24 29
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 25 30
       Intellectual Property and Copyright Statements . . . . . . . . 27 32

1.  Introduction

   The Session Initiation Protocol (SIP) [6] Events framework Events
   Framework [7] defines general mechanisms for subscribing to, and
   receiving notifications of, events within SIP networks.  It
   introduces the notion of a package, which is a specific
   "instantiation" of the events framework for a well-defined set of
   events.  Here, we define an event package for SIP conferences.  This
   package provides the conference notification service as outlined in
   the SIP conferencing framework [13]. [14].  As described there,
   subscriptions to a conference URI are routed to the focus that is
   handling the conference.  It acts as the notifier, and provides
   clients with updates on conference state.

   The information provided by this package is comprised of conference
   identifier(s), conference participants (optionally with their
   statuses and media description), conference sidebars, and conference
   policy URIs. URIs, etc.

2.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   and "OPTIONAL" are to be interpreted as described in RFC 2119 [2] and
   indicate requirement levels for compliant implementations.

3.  Conference Event Package

   The conference event package allows a user to subscribe to a
   conference.  In SIP, conferences are represented by URIs.  These URIs
   route to a SIP user agent, called a focus, that is responsible for
   ensuring that all users in the conference can communicate with each
   other, as described in Conferencing Framework [13]. [14].  The focus has
   sufficient information about the state of the conference to inform
   subscribers about it.

   It is possible a participant in the conference may in fact be another
   focus.  In order to provide a more complete participant list, the
   focus MAY subscribe to the conference package of the other focus to
   discover the participant list in the cascaded conference.  This
   information can then be included in notifications by using of the
   "cascaded-focus" attribute as specified by this package.

   This section provides the details for defining a SIP Events package,
   as specified by RFC 3265 [7].

3.1  Event Package Name

   The name of this event package is "conference".  This package name is
   carried in the Event and Allow-Events header, as defined in RFC 3265

3.2  SUBSCRIBE Bodies

   A SUBSCRIBE for a conference package MAY contain a body.  This body
   defines a filter to apply to the subscription.  Filter documents are
   not specified in this document, and at the time of writing, are
   expected to be the subject of future standardization activity.

   A SUBSCRIBE for a conference package MAY be sent without a body.
   This implies the default subscription filtering policy.  The default
   policy is:
   o  Notifications are generated every time there is any change in the
      state of the conference.
   o  Notifications do not normally contain full state; rather, they
      only indicate the state that has changed.  The exception is a
      NOTIFY sent in response to a SUBSCRIBE.  These NOTIFYs contain the
      full state of the information requested by the subscriber.

3.3  Subscription Duration

   The default expiration time for a subscription to a conference is one
   hour.  Once the conference ends, all subscriptions to that particular
   conference are terminated, with a reason of "noresource" RFC 3265

3.4  NOTIFY Bodies

   As described in RFC 3265 [7], the NOTIFY message will contain bodies
   that describe the state of the subscribed resource.  This body is in
   a format listed in the Accept header field of the SUBSCRIBE, or a
   package-specific default if the Accept header field was omitted from

   In this event package, the body of the notification contains a
   conference information document.  This document describes the state
   of a conference.  All subscribers and notifiers MUST support the
   "application/conference-info+xml" data format described in Section 4.
   The subscribe request MAY contain an Accept header field.  If no such
   header field is present, it has a default value of "application/
   conference-info+xml".  If the header field is present, it MUST
   include "application/conference-info+xml", and MAY include any other
   types capable of representing dialog state.

   Of course, the notifications generated by the server MUST be in one
   of the formats specified in the Accept header field in the SUBSCRIBE

3.5  Notifier Processing of SUBSCRIBE Requests

   The conference information contains very sensitive information.
   Therefore, all subscriptions SHOULD be authenticated and then
   authorized before approval.  Authorization policy is at the
   discretion of the administrator, as always.  However, a few
   recommendations can be made.

   It is RECOMMENDED that all users in the conference be allowed to
   subscribe to the conference.

3.6  Notifier Generation of NOTIFY Requests

   Notifications SHOULD be generated for the conference whenever there
   is a change in the state in any of the information delivered to the

   The changes generally occur when a new participant joins (i.e.  gets
   "connected" to) or a participant leaves (i.e.  gets "disconnected"
   from) the conference.

   Subject to a local focus policy, additional changes in participant's
   status, changes in its media types, and other optional media
   attributes MAY be reported by the focus.

   Changes in sidebar rosters SHOULD be reported by the focus to their
   participants and MAY be reported to others, subject to local policy.

   Changes in conference identifiers and policy URIs SHOULD be reported
   by the focus to the conference participants.

3.7  Subscriber Processing of NOTIFY Requests

   The SIP Events framework expects packages to specify how a subscriber
   processes NOTIFY requests in any package specific ways, and in
   particular, how it uses the NOTIFY requests to contruct construct a coherent
   view of the state of the subscribed resource.

   Typically, the NOTIFY for the conference package will only contain
   information about those users whose state in the conference has
   changed.  To construct a coherent view of the total state of all
   users, a subscriber to the conference package will need to combine
   NOTIFYs received over time.

   Notifications within this package can convey partial information;
   that is, they can indicate information about a subset of the state
   associated with the subscription.  This means that an explicit
   algorithm needs to be defined in order to construct coherent and
   consistent state.  The details of this mechanism are specific to the
   particular document type.  See Section 4.2 for information on
   constructing coherent information from an application/
   conference-info+xml document.

3.8  Handling of Forked Requests

   By their nature, the conferences supported by this package are
   centralized.  Therefore, SUBSCRIBE requests for a conference should
   not generally fork.  Users of this package MUST NOT install more than
   a single subscription as a result of a single SUBSCRIBE request.

3.9  Rate of Notifications

   For reasons of congestion control, it is important that the rate of
   notifications not become excessive.  As a result, it is RECOMMENDED
   that the server not generate notifications for a single subscriber at
   a rate faster than once every 5 seconds.

3.10  State Agents

   Conference state is ideally maintained in the element in which the
   conference resides.  Therefore, the elements that maintain the
   conference are the ones best suited to handle subscriptions to it.
   Therefore, the usage of state agents is NOT RECOMMENDED for this

4.  Conference Data Format

   Conference information is an XML document that MUST be well-formed
   and SHOULD be valid.  Dialog information documents MUST be based on
   XML 1.0 and MUST be encoded using UTF-8.  This specification makes
   use of XML namespaces for identifying dialog information documents
   and document fragments.  The namespace URI for elements defined by
   this specification is a URN [3], using the namespace identifier
   'ietf' defined by [4] and extended by [1].  This URN is:


   A conference information document begins with the root element tag

4.1  Conference Information

   Conference information begins with the top level element
   "conference-info".  This element has three mandatory and one optional attributes:
   version: This mandatory attribute allows the recipient of conference
      information documents to properly order them.  Versions start at 0
      and increment by one for each new document sent to a subscriber.
      Versions are scoped within a subscription.  Versions MUST be
      represented using a 32 bit integer.
   state: This mandatory attribute indicates whether the document
      contains the full conference information, or whether it contains
      only the information that has changed since the previous document
   entity: This mandatory attribute contains the conference URI that
      identifies the conference being described in the document.
   recording: This optional attribute indicates whether the conference
      is being recorded at this moment ("on") or not ("off").

   The "conference-info" element has zero or more "user" sub-elements
   which contain information on the users in the conference.  This is
   followed by zero or more "sidebar" sub-elements which contain
   information on the sidebars in the conference.  This is followed by
   zero or more "conf-uri" sub-elements which contain information on
   additional URIs that the conference can be accessed by.  This is
   followed by zero or more "policy-uri" sub-elements which contain
   information on additional URIs that the conference policies can be
   accessed by.  This is followed by "recording" and "streaming"
   elements describing recording and streaming statuses of the

4.1.1  User Element  User Attributes

   The user element has one mandatory attribute, "uri" that indicates
   the URI for the user in the conference.  This is a logical
   identifier, which corresponds to the authenticated identity of the
   participant.  The "uri" attribute MUST be unique in the user element
   list because it is used as the key in partial notifications about
   users' state.

   If a conference participant has more than a single signaling dialog
   associated with the conference, the conference focus MAY present the
   user's aggregated information (e.g.  the statuses) and display all
   its media streams under a single user element.

   Note, that the optional element "dialog-uri" "instance" of "media-stream" "media" (see below) MAY
   be used in this case to specify the actual signaling dialog for each
   media stream.

   An anonymous participant in a conference SHOULD be represented by an
   anonymous URI generated by the focus.  For multiple anonymous
   participants, the focus must ensure that each anonymous URI is
   unique.  The guidelines for generating anonymous URIs in RFC 3323 [8]
   should be followed.  For example,

   "Anonymous1" <sip:anonymous1@anonymous.invalid>

    could be used for a participant requesting privacy.

   The optional attribute "display-name" contains a display name for the
   user.  The standard "xml:lang" language attribute can also be present
   to indicate the language of the display-name.

   The optional attribute "cascaded-focus" contains a conference URI
   (different from the main conference URI) for users that are connected
   to the main conference as a result of focus cascading.  In accordance
   with the SIP conferencing framework [13], [14], this package allows for
   representation of peer-to-peer (i.e.  "flat") focus cascading only.
   The actual cascading graph can not be deduced from the information
   provided in the package alone.  Advanced applications can construct
   the graph by subscribing to both this package and the Dialog Package
   [15] of the cascaded foci and correlating the relevant information.

   If the main conference "state" is "full", the state of its user(s)
   MUST "full".  If the main conference "state" is "partial", the state
   of its user(s) MAY be either "partial" or "full".  User Status Elements

   Three optional status elements are defined: status, joining-mode, and
   o  "status": provides information about user's current level of
      participation in the conference.
   o  "joining-mode": if present, provides information about the way the
      user joined the conference.
   o  "disconnection-reason": if present, provides information about the
      way the user left the conference.

   The following statuses are defined for the "status" element:
   connected: The user is a participant in the conference.  Depending on
      the media policies, he/she can send and receive media to and from
      other participants.
   disconnected: The user is not a participant in the conference and no
      active dialog exists between the user and the focus.
   on-hold: Active SIP dialog exists between a user and a focus, but
      user is "on-hold" for this conference, i.e.  neither he/she is
      "hearing" the conference mix, nor is his/her media being mixed in
      the conference.  As an example, the user has asked to join the
      conference using SIP, but his/her participation is pending based
      on moderator approval.  In the meantime he/she is hearing
      music-on-hold or some other kind of related content.
   muted-via-focus: Active SIP dialog exists between a user and a focus
      and the user can "listen" to the conference, but user's media is
      not being mixed into the conference.  Note that sometimes a subset
      of user media streams can be muted by focus (such as poor quality
      video) while others (such as voice or IM) can still be active.  In
      this case, it is RECOMMENDED that the "aggregated" user
      connectivity "status" reflects the status of the mostly active
   blocked: User is denied from ever participating in this conference.
   pending: User is not yet in the session, but it is anticipated that
      he/she will join in the near future.
   calling: User is being called by the focus.
   ringing: An PSTN ALERTING or SIP 180 Ringing was returned for the
      outbound call, user is being alerted.
   dialing-in: User is dialing into the conference, not yet in the
      roster (probably being authenticated).
   disconnecting: Focus is in the process of disconnecting user (either
      DISCONNECT or BYE was sent to the user's device).
   removed: This status is used to remove the user from the roster using
      partial notifications mechanism.

   Note that the defined transient states (e.g., calling, ringing, etc.)
   could generate a lot of notifications.  Implementations MAY choose
   not to generate notifications on these to all participants if it will
   generate too much traffic.

   The following statuses are defined for the "joining-mode" element:
   dialed-in: The user dialed into the conference, i.e.  sent INVITE to
      the focus, which resulted in successful dialog establishment.
   dialed-out: The focus has brought the user into the conference by
      sending a successful INVITE to the user.
   focus-owner: The user is the focus for this conference.  This status
      is used only when a participant UA acts as a conference focus
      being identified by its own AOR or GRUU. focus.

   The following statuses are defined for the disconnection-reason
   departed: The user sent a BYE, thus leaving the conference.
   booted: The user was sent a BYE by the focus, booting him/her out of
      the conference.  Alternatively, the user tried to dial into to
      conference without success because was rejected by the focus
      according to local policy decisions.
   failed: The server tried to bring the user into the conference, but
      its attempt to contact the specific user resulted in a non-200
      class final response.  Alternatively, the user tried to dial into
      the conference without success due to technical reasons.  Media Stream Information

   Each user has zero or more "media-stream" "media" sub-elements.

   Each "media-stream" "media" element indicates the media stream that the user is currently
   connected to.  Here, "connected to" implies that a user has a media
   line in his/her SDP [11] [12] document(s).  With this definition, a user
   is connected to a media stream even if he/she is not sending any
   media.  Media Attributes

   The "media-stream" "media" element has a mandatory "media-type" attribute which
   identifies the media type (e.g.  audio, video, message and
   application) and MUST have one of the values registered for "media"
   of SDP [11]. [12].

   The "media-stream" optional "id" attribute serves as a unique reference to a "media"
   element within the "user" element.  It MUST be included for each
   "media" element for all notifications if the focus uses "partial"
   user notifications for this conference.  Otherwise, the  "id"
   attribute MAY be omitted.

   If the user "state" is "full", the state of its "media" element(s)
   MUST be "full".  If the user "state" is "partial", the state of its
   "media" element(s) MAY be either "partial" or "full".  Media Elements

   The "media" element has also an optional "proto" sub-element, which
   MUST has the value registered for "proto" of SDP [11]. [12].

   An optional "ssrc" sub-element, if present, carries the value of SSRC
   (defined in RTP/RTCP [10]) as generated by the user for the stream it

   When an RTP mixer generates a CSRC list according to RTP/RTCP [10],
   it inserts a list of the SSRC identifiers of the sources that
   contributed to the generation of a particular packet into the RTP
   header of that packet.  "An example application is audio conferencing
   where a mixer indicates all the talkers whose speech was combined to
   produce the outgoing packet, allowing the receiver to indicate the
   current talker, even though all the audio packets contain the same
   SSRC identifier (that of the mixer)."

   An optional "info" sub-element, if present, carries a human readable
   description for this stream populated by the focus.  The value of
   this element corresponds to the information media attribute "i" in
   SDP [11]. [12].

   An optional "label" sub-element, if present, carries a unique
   identifier for this stream among all streams in the conference and is
   assigned by the focus.  The value of this element corresponds to the
   "label" media attribute in SDP [11] [12] and defined in [17]. [18].

   An optional "dialog-id" "instance" sub-element, if present, carries a URI, which
   MUST uniquely identify the signaling dialog being used for
   establishing of this media stream.  In SIP, for example, values of
   Contact URI or GRUU [16] [17] can be used for this purpose.  It is
   RECOMMENDED to include the "dialog-id" "instance" information for every user that
   has more than a single dialog associated with the conference.  This
   element SHOULD NOT be included for an anonymous participant.

4.1.2  Sidebar Element

   The sidebar

   An optional "status" sub-element, if present, is used to remove
   "media" elements during partial notifications.

   Optional "snd-status" and "rcv-status" sub-elements, if present,
   describe the status of media streams in each direction.  User Role

   The optional "role" element has conveys the role of the user in the
   conference, e.g.  participant, presenter, panelist, host, etc.
   User's role MAY change dynamically in the course of the conference.
   Also, a user MAY have more than a single role in one attribute - time.

   This document does not define fixed values for the "role" element,
   instead it is expected that conferencing applications will define
   custom-fit roles by templates.

4.1.2  Sidebar Element

   The sidebar element is of the general "conference-type" and MAY use
   all the attributes and elements defined by it.  Typically, only the
   "entity", which carries uniquely identifies the
   URI identifying sidebar, and the "user"
   elements will be useful to present to the majority of the
   participants in the conference.

   The "conference-type" mandatory attributes MUST be included for each
   sidebar.  This

   The value of the "version" attribute is meaningless for "sidebar"
   elements and MUST be ignored because it is always overruled by the
   "version" attribute of the main "conference-info".

   If the main conference "state" is "full", the state of its sidebar(s)
   MUST be "full".  If the main conference "state" is "partial", the
   state of its sidebar(s) MAY be either "full" or "partial".

   The "entity" URI attribute MUST be unique among the sidebar
   identifiers of the same conference.  Attribute "entity" is used as
   the key for "sidebar" elements in partial notifications about sidebars of a

   A sidebar has zero or more users of "user-type". for

4.1.3  Additional Conference Identifiers

   In addition to the Conference URI present in the "entity" attribute,
   a conference MAY have additional URIs of various types.  Connecting
   to these URIs will result in joining to the same conference.

4.1.4  Policy URIs

   A policy URI specifies where and how a certain policy pertaining to
   the conference can be accessed.  The actual policy name and usage is
   deduced from the URI schema name.

   An example for the "policy-uri" usage is inclusion of the URI of the
   CPCP [15]. [16].  A subscriber to the Conference package can use the Policy
   URI to access and modify the conference policy.

4.2  Constructing Coherent State

   Conference information is associated with a version number.  The
   version number MUST be initialized with

4.1.5  Recording

   In many cases, legal regulations require conference providers to
   announce to the value of participants that a specific conference is being

   In addition to the "version"
   attribute from recording "status" information, the "conference-info" "recording"
   element in MAY include the first document
   received.  Each time a new document is received, URIs specifying the location and the format
   of the recorded data.  Typically, the recorded data becomes available
   after the conference ends.  Multiple URIs can be provided, for
   example, specifying different content types.  For Web-Page embedded
   media, a plain HTTP URI MAY be provided.

4.1.6  Streaming

   The "streaming" element, if present, specifies whether the conference
   output is being streamed (to general public, for example), in what
   streaming format, and at what (e.g.  multicast) addresses it can be
   listened at.  RTSP [11] is an example of such streaming protocol.

4.2  Constructing Coherent State

   The conference information is described by a hierarchal XML structure
   with the root element "conference-info".  The root element is the
   only element in the schema that carries meaningful version number for
   all the elements in the document.  The whole conference information
   is associated with this version number.

   The version number MUST be initialized with the value of the
   "version" attribute from the "conference-info" element in the first
   document received.  Each time a new document is received, the value
   of the local version number, and the "version" attribute in the new
   document, are compared.  If the value in the new document is one
   higher than the local version number, the local version number is
   increased by one, and the document is processed.  If the value in the
   document is more than one higher than the local version number, the
   local version number is set to the value in the new document, the
   document is processed, and the subscriber SHOULD generate a refresh
   request to trigger a full state notification.  If the value in the
   document is less than the local version, the document is discarded
   without processing.

   Further processing of the conference information document depends on
   whether it contains full or partial state.  If it contains full
   state, indicated by the value of the "state" attribute in the
   "conference-info" element, the whole local content is flushed and
   repopulated from the document.

   If the document contains partial state, as indicated by the value of
   the "state" attribute in the "conference-info" element, the document
   is used to update the local content as described below.

   The conference information is described by a means of a root element:
   "conference-info", which

   All sub-elements in the "conference-info" hierarchal XML structure
   can be comprised of elements classified in two groups: those that carry relatively small
   amount of four main
   types: "user-type", "sidebar-type", "conf-ids-type", data and
   "policy-ids-type".  Updates from partial notifications MUST be
   implemented as those that can potentially carry a set of atomic operations on elements lot of these types

4.2.1  User and Sidebar Updates

   The conference package subscriber maintains two tables: one for data.
   During partial notifications, the
   list light elements are updated as
   atomic pieces of users and another for data.  On the list other hand, elements that can carry a
   substantial amount of sidebars in data have the conference.
   Each table contains a row for each user or each sidebar
   correspondingly.  Each row general "state" attribute
   attached to them.  That is indexed by a URI key, present in the
   "uri" order to support partial notifications
   for their content.

   A "state" attribute of the "user" a child element or in the "entity" attribute of
   the "sidebar" element correspondingly.  The contents document MUST adhere to
   its parent "state".  It means that if the parent's "state" is "full",
   the state of each row
   contain its children MUST be "full".  If the parent's "state" is
   "partial", the state of that user its children MAY be either "partial" or a sidebar as conveyed in the


   For elements with optional "state" attribute, if the document attribute is not
   included for an update (i.e.  contains partial state), element, it means that the element's state is "full".

   For a parent element with "state", its sub-elements with possible
   multiple appearances under the parent have keys that uniquely
   identify each element among others in the same list.

4.2.1  The Algorithm

   The conference package subscriber locally maintains a local element
   for each
   table element in the schema and a table for each "element with
   key(s)" in the schema.  The tables are indexed by the key(s) defined
   in schema for the element.

   Starting from outer elements in the received document,

   1.  If the parent element (i.e.  "user" or "sidebar") contains full state, the element is
   replaced with the new information as a whole.

   2.  Otherwise, if the parent element contains partial state,

   2.1 For elements with keys, the subscriber compares the keys received
   in the update with the keys in the local tables.

   2.1.1 If a key doesn't exist in the local table, a row is added, and
   its content is set to the element information from the update.

   2.1.2 Otherwise, if a key of the same value does exist, for each
   sub-element in the row content is replaced
   with the received information.

   If a row algorithm is updated or created such that user's state becomes
   "disconnected", that entry MAY be removed applied from the table at any time.
   If a row is updated or created such that a sidebar element doesn't
   contain any users, that sidebar step 2.2.

   2.2 For each atomic element MAY be removed from received in the table
   at any time.

4.2.2  Conference and Policy Identifiers Updates

   In order to support additional conference features, schema, the conference
   package subscriber SHOULD locally maintain two additional
   informational elements: "conf-ids" and "policy-ids".  The content of
   each contains element is
   replaced with the new information as a list of URIs for additional conference identifiers or whole.  Also, for policy protocols (correspondingly) applicable to this conference.

   If each
   non-atomic element received in the document is an update (i.e.  contains partial state), and one schema with either no "state"
   attribute included or both of the elements exist in the update, state attribute is set to "full", the element(s) is/are
   element is replaced with the new information as a whole.

   2.2.1 If the updated or created element carries the "removed" status,
   that element SHOULD be removed from the local content.  If the
   element is updated or created, such that it is empty, that element
   MAY be removed from the local content at any time.

   2.3 For each non-atomic element with the state attribute set to
   "partial", the algorithm is applied recursively starting from step 2.

4.3  Schema

   <?xml version="1.0" encoding="UTF-8" ?>
   <xs:schema targetNamespace="urn:ietf:params:xml:ns:conference-info" xmlns:tns="urn:ietf:params:xml:ns:conference-info" xmlns:xs="" xmlns="urn:ietf:params:xml:ns:conference-info" elementFormDefault="qualified" attributeFormDefault="unqualified">
    This import brings in the XML language attribute xml:lang
     <xs:import namespace="" schemaLocation="" />

   <xs:element name="conference-info">

   <xs:complexType> name="conference-info" type="tns:conference-type"/>

   <xs:simpleType name="state-type">
    <xs:restriction base="xs:string">
           <xs:enumeration value="full" />
           <xs:enumeration value="partial" />

   <xs:complexType name="conference-type">

     <xs:element name="user" type="user-type" minOccurs="0" maxOccurs="unbounded" />
     <xs:element name="sidebar" type="sidebar-type" type="conference-type" minOccurs="0" maxOccurs="unbounded" />
     <xs:element name="conf-ids" type="conf-ids-type" minOccurs="0" maxOccurs="1" />
     <xs:element name="policy-ids" type="policy-ids-type" minOccurs="0" maxOccurs="1" />
     <xs:element name="recording" type="recording-type" minOccurs="0" maxOccurs="1" />
     <xs:element name="streaming" type="streaming-type" minOccurs="0" maxOccurs="1" />
     <xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded" />

     <xs:attribute name="version" type="xs:nonNegativeInteger" use="required" /> use="required"/>
     <xs:attribute name="state" use="required">
        <xs:restriction base="xs:string">
           <xs:enumeration value="full" />
           <xs:enumeration value="partial" />
     </xs:attribute>   type="tns:state-type"        use="required"/>
     <xs:attribute name="entity"  type="xs:anyURI" use="required" />
     <xs:attribute name="recording" type="tns:recording-type" use="optional" />             use="required"/>
     <xs:anyAttribute />

   <xs:complexType name="user-type"> name="conf-ids-type">
     <xs:element name="status" type="tns:status-type" minOccurs="0" />
     <xs:element name="joining-mode" type="tns:joining-mode-type" minOccurs="0" />
     <xs:element name="disconnection-reason" type="tns:disconnection-reason-type" minOccurs="0" />
     <xs:element name="media-stream" type="tns:media-stream-type" name="conf-uri" type="xs:anyURI" minOccurs="0" maxOccurs="unbounded" />
     <xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded" />

     <xs:attribute name="uri" type="xs:anyURI" use="required" />
     <xs:attribute name="display-name" type="xs:string" use="optional" />
     <xs:attribute ref="xml:lang" use="optional" />
     <xs:attribute name="cascaded-focus" type="xs:anyURI" use="optional" />

    <xs:anyAttribute />

   <xs:complexType name="sidebar-type"> name="policy-ids-type">
     <xs:element name="user" type="user-type" name="policy-uri" type="xs:anyURI" minOccurs="0" maxOccurs="unbounded" />
     <xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded" />

     <xs:attribute name="entity" type="xs:anyURI" use="required"

    <xs:anyAttribute />

   <xs:complexType name="conf-ids-type"> name="recording-type">
     <xs:element name="conf-uri" name="uri" type="xs:anyURI" minOccurs="0" maxOccurs="unbounded" />
     <xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded" />

    <xs:attribute name="status" type=="stream-status-type" use="required"/>
    <xs:anyAttribute />

   <xs:complexType name="policy-ids-type"> name="streaming-type">
     <xs:element name="policy-uri" name="uri" type="xs:anyURI" minOccurs="0" maxOccurs="unbounded" />
     <xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded" />

    <xs:attribute name="status" type="stream-status-type" use="required"/>
    <xs:anyAttribute />

   <xs:complexType name="media-stream-type"> name="user-type">
     <xs:element name="proto" type="xs:string" minOccurs="0" /> name="status" type="tns:user-status-type" minOccurs="0"/>
     <xs:element name="ssrc" type="xs:nonNegativeInteger" minOccurs="0" /> name="joining-mode" type="tns:user-joining-mode-type" minOccurs="0"/>
     <xs:element name="info" type="xs:string" minOccurs="0" /> name="disconnection-reason" type="tns:user-disconnection-reason-type" minOccurs="0"/>
     <xs:element name="label" type="xs:string" name="media" type="tns:media-type" minOccurs="0" /> maxOccurs="unbounded"/>
     <xs:element name="dialog-id" type="xs:anyURI" name="role" type="xs:string" minOccurs="0" /> maxOccurs="unbounded"/>
     <xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded" /> maxOccurs="unbounded"/>


    <xs:attribute name="media" name="uri"          type="xs:anyURI"   use="required"/>
    <xs:attribute name="display-name" type="xs:string" use="required"   use="optional"/>
    <xs:attribute ref="xml:lang"                         use="optional"/>
    <xs:attribute name="cascaded-focus" type="xs:anyURI" use="optional"/>
    <xs:attribute name="state" type="tns:state-type"     use="optional"/>
    <xs:anyAttribute />


   <xs:simpleType name="status-type"> name="user-status-type">
    <xs:restriction base="xs:string">
     <xs:enumeration value="connected" /> value="connected"/>
     <xs:enumeration value="disconnected" /> value="disconnected"/>
     <xs:enumeration value="on-hold" /> value="on-hold"/>
     <xs:enumeration value="muted-by-focus" /> value="muted-via-focus"/>
     <xs:enumeration value="blocked"/>
     <xs:enumeration value="pending"/>
     <xs:enumeration value="calling"/>
     <xs:enumeration value="ringing"/>
     <xs:enumeration value="dialing-in"/>
     <xs:enumeration value="disconnecting"/>
     <xs:enumeration value="removed"/>

   <xs:simpleType name="joining-mode-type"> name="user-joining-mode-type">
    <xs:restriction base="xs:string">
     <xs:enumeration value="dialed-in" />
     <xs:enumeration value="dialed-out" />
     <xs:enumeration value="focus-owner" />

   <xs:simpleType name="disconnection-reason-type"> name="user-disconnection-reason-type">
    <xs:restriction base="xs:string">
     <xs:enumeration value="departed" />
     <xs:enumeration value="booted" />
     <xs:enumeration value="failed" />

   <xs:complexType name="media-type">
     <xs:element name="proto"      type="xs:string"             minOccurs="0"/>
     <xs:element name="ssrc"       type="xs:nonNegativeInteger" minOccurs="0"/>
     <xs:element name="info"       type="xs:string"             minOccurs="0"/>
     <xs:element name="label"      type="xs:string"             minOccurs="0"/>
     <xs:element name="instance"   type="xs:anyURI"             minOccurs="0"/>
     <xs:element name="status"     type="tns:media-status-type" minOccurs="0"/>
     <xs:element name="snd-status" type="tns:stream-status-type" minOccurs="0"/>
     <xs:element name="rcv-status" type="tns:stream-status-type" minOccurs="0"/>
     <xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded"/>

     <xs:attribute name="media"  type="xs:string"             use="required"/>
     <xs:attribute name="id"     type="nonNegativeInteger"    use="optional"/>
     <xs:attribute name="state"  type="tns:state-type"        use="optional"/>
     <xs:anyAttribute />


   <xs:simpleType name="recording-type"> name="media-status-type">
    <xs:restriction base="xs:string">
     <xs:enumeration value="on" value="removed" />

   <xs:simpleType name="stream-status-type">
    <xs:restriction base="xs:string">
     <xs:enumeration value="on"/>
     <xs:enumeration value="off"/>
     <xs:enumeration value="off" value="muted" />


4.4  Example

   The following is an example conference information document:

   <?xml version="1.0" encoding="utf-8" ?>
   <conference-info version="0" state="full" entity="" recording="on"> entity="">
         <user uri="" display-name="Bob Jones">
       <media-stream media-type="audio">
          <proto> RTP/AVP </proto>
          <ssrc> 583398 </ssrc>
               <media media="audio">
         <user uri="" display-name="Barbara Jones">
         <user uri="" display-name="Bill Minelli">

         <sidebar version="0" state="full" entity="">
               <user uri=""> uri="" />
               <user uri=""> uri="" />


         <recording status="on">


   This conference currently has three users, two of which are in a
   sidebar conversation.  The conference is being recorded.  There are
   additional means to join the conference either by phone using tel URI
   [14] or by H.323 protocol using H.323 URL [12]. [13].

5.  Security Considerations

   Subscriptions to conference state can reveal very sensitive
   information.  For this reason, the document recommends authentication
   and authorization, and provides guidelines on sensible authorization

   Since the data in notifications is sensitive as well, end-to-end SIP
   encryption mechanisms using S/MIME SHOULD be used to protect it.

   Since a focus provides participants identity information using this
   event package, participant privacy needs to be taken into account.  A
   focus MUST support requests by participants for privacy.  Privacy can
   be indicated by the conference policy - for every participant or
   select participants.  It can also be indicated in the session
   signaling.  In SIP this can be done using the Privacy header field
   described in RFC 3323 [8].  For a participant requesting privacy, no
   identity information SHOULD be revealed by the focus such as a URI
   (e.g.  the Address of Record, Contact, or GRUU).  For these cases,
   the anonymous URI generation method outlined in section "User
   Element" of this document MUST be followed.

6.  IANA Considerations

   This document registers a SIP event package, a new MIME type,
   application/conference-info+xml, a new XML namespace, and a new XML

6.1  conference Event Package Registration

   This specification registers an event package, based on the
   registration procedures defined in RFC 3265 [7].  The following is
   the information required for such a registration:
   Package Name: conference
   Package or Template-Package: This is a package.
   Published Document: RFC XXXX (Note to RFC Editor: Please fill in XXXX
      with the RFC number of this specification).
   Person to Contact: Jonathan Rosenberg,

6.2  application/conference-info+xml MIME Registration
   MIME media type name: application
   MIME subtype name: conference-info+xml
   Mandatory parameters: none
   Optional parameters: Same as charset parameter application/xml as
      specified in RFC 3023 [5].
   Encoding considerations: Same as encoding considerations of
      application/xml as specified in RFC 3023 [5].
   Security considerations: See Section 10 of RFC 3023 [5] and Section 5
      of this specification.
   Interoperability considerations: none.
   Published specification: This document.
   Applications which use this media type: This document type has been
      used to support SIP conferencing applications.
   Additional Information:
      Magic Number: None
      File Extension: .cif or .xml
      Macintosh file type code: "TEXT"
   Personal and email address for further information: Jonathan
      Rosenberg, <>
   Intended usage: COMMON
   Author/Change controller: The IETF.

6.3  URN Sub-Namespace Registration for

   This section registers a new XML namespace, as per the guidelines in

   URI: The URI for this namespace is
   Registrant Contact: IETF, SIPPING working group, <>,
      Jonathan Rosenberg <>.

   <?xml version="1.0"?>
   <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
   <html xmlns="">
     <meta http-equiv="content-type"
     <title>Conference Information Namespace</title>
     <h1>Namespace for Conference Information</h1>
     <p>See <a href="[[[URL of published RFC]]]">RFCXXXX</a>.</p>

6.4  XML Schema Registration

   This specification registers a schema, as per the guidelines in in
      URI: please assign.
      Registrant Contact: IETF, SIPPING Working Group
      (, Jonathan Rosenberg (
      XML: The XML can be found as the sole content of Section 4.3.

7.  Acknowledgements

   The authors would like to thank Dan Petrie, Sean Olson, thank Dan Petrie, Sean Olson, Alan
   Johnston, and Rohan Mahy for their comments and inputs.

8.  Changes History

8.1  Changes since -04
   o  "Sidebar-type" has been removed.  "Sidebar" conference element is
      defined using the general "conference-type".
   o  "Recording" conference attribute has been replaced with
      "recording" and "streaming" elements within "conference-type".
      New "recording-type" and "streaming-type" have been introduced.
   o  Attribute "state" has been added to "user-type".
   o  Element "media-stream" within "user-type" has been renamed to
   o  Element "role" within "user-type" has been introduced.
   o  The following statuses have been added to "user-status-type":
      blocked, pending, calling, ringing, dialing-in, disconnecting,
   o  User status "muted-by-focus" has been renamed to
   o  Attributes "id" and Alan
   Johnston for their comments "state" have been added to "media-type".
   o  Elements "status", "snd-status" and inputs.

8.  Changes History

8.1 "rcv-status" have been added
      to "media-type".
   o  Element "dialog-id" has been renamed to "instance".
   o  "Constructing Coherent State" section has been updated to include
      user and media partial notifications.

8.2  Changes since -03
   o  "Constructing Coherent State" section has been updated.
   o  In order to support partial notifications, two placeholders
      "conference-ids" and "policy-ids" (for "conf-uri" and "policy-uri"
      elements, correspondingly) are created.
   o  Discussion and security considerations regarding anonymous
      participation have been added.
   o  Optional elements "dialog-uri", "info" and "label" per media
      stream are added.


8.3  Changes since -02
   o  State "muted-by-focus" is added to user's status.
   o  Optional conference attribute "recording" is added.
   o  Policy URI placeholder (i.e.  element "policy-uri") is created.
   o  Example's syntax is corrected.
   o  Optional attribute "cascaded-focus" URI per user is added.
   o  Optional additional conference identifiers (i.e.  element
      "conf-uri") are added.
   o  In order to cover all possible cases, participant's status is
      expressed using three optional statuses: "status", "joining-mode"
      and "disconnection-reason".  That is instead of "activity-status",
      "history-status" and "is-on-dial-out-list".


8.4  Changes since -01
   o  Package parameters are removed.  Decision about performing
      "recursive" membership algorithm is perceived as a focus local
   o  General information (i.e.  pointers to additional available
      services) is removed.  The defined XML schema can be extended in
      future to include those when XCON work matures.
   o  Dialog information is removed.  It can be obtained by direct
      subscription to a dialog package of a participant.
   o  Media stream information is aligned with SDP definitions (media
      and proto) and SSRC attribute is added.
   o  Participant's status is expressed using two optional statuses:
      "activity" and "history".  Optional "is-on-a-dial-out-list"
      indication is added.
   o  Normative references to XCON work are removed.
   o  Optional sidebar rosters are added.

9.  References

9.1  Normative References

   [1]   Mealling, M., "The IETF XML Registry",
         draft-mealling-iana-xmlns-registry-05 (work in progress), June

   [2]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", BCP 14, RFC 2119, March 1997.

   [3]   Moats, R., "URN Syntax", RFC 2141, May 1997.

   [4]   Moats, R., "A URN Namespace for IETF Documents", RFC 2648,
         August 1999.

   [5]   Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC
         3023, January 2001.

   [6]   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.

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

   [8]   Peterson, J., "A Privacy Mechanism for the Session Initiation
         Protocol (SIP)", RFC 3323, November 2002.

   [9]   Camarillo, G., Eriksson, G., Holler, J. and H. Schulzrinne,
         "Grouping of Media Lines in the Session Description Protocol
         (SDP)", RFC 3388, December 2002.

   [10]  Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson,
         "RTP: A Transport Protocol for Real-Time Applications", STD 64,
         RFC 3550, July 2003.

9.2  Informative References

   [11]  Schulzrinne, H., Rao, A. and R. Lanphier, "Real Time Streaming
         Protocol (RTSP)", RFC 2326, April 1998.

   [12]  Handley, M. and V. Jacobson, "SDP: Session Description
         Protocol", RFC 2327, April 1998.


   [13]  Levin, O., "H.323 Uniform Resource Locator (URL) Scheme
         Registration", RFC 3508, April 2003.


   [14]  Rosenberg, J., "A Framework for Conferencing with the Session
         Initiation Protocol",
         draft-ietf-sipping-conferencing-framework-02 (work in
         progress), October 2003.

   [14] June 2004.

   [15]  Rosenberg, J. and H. Schulzrinne, "An INVITE Inititiated Dialog
         Event Package for the Session Initiation  Protocol (SIP)",
         draft-ietf-sipping-dialog-package-04 (work in progress),
         February 2004.


   [16]  Koskelainen, P. and H. Khartabil, "Requirements for Conference
         Policy Control Protocol", draft-ietf-xcon-cpcp-reqs-03 (work in
         progress), April 2004.


   [17]  Rosenberg, J., "Obtaining and Using Globally Routable User
         Agent (UA) URIs (GRUU) in the  Session Initiation Protocol
         (SIP)", draft-ietf-sip-gruu-01 draft-ietf-sip-gruu-02 (work in progress), February July 2004.


   [18]  Levin, O. and G. Camarillo, "SDP Media Label", "The SDP (Session Description
         Protocol) Label Attribute",
         draft-levin-mmusic-sdp-media-label-00 (work in progress),
         May July

Authors' Addresses

   Jonathan Rosenberg
   600 Lanidex Plaza
   Parsippany, NJ  07054

   Phone: +1 973 952-5000

   Henning Schulzrinne
   Columbia University
   M/S 0401
   1214 Amsterdam Ave.
   New York, NY  10027

   Orit Levin (editor)
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA  98052


Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   intellectual property
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation RFC documents can be
   found in BCP-11. BCP 78 and BCP 79.

   Copies of
   claims of rights IPR disclosures made available for publication to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementors implementers or users of this
   specification can be obtained from the IETF Secretariat. on-line IPR repository at

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which that may cover technology that may be required to practice implement
   this standard.  Please address the information to the IETF Executive

Full Copyright Statement

   Copyright (C) The Internet Society (2004).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose at

Disclaimer of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assignees. Validity

   This document and the information contained herein is are provided on an

Copyright Statement

   Copyright (C) The Internet Society (2004).  This document is subject
   to the rights, licenses and restrictions contained in BCP 78, and
   except as set forth therein, the authors retain all their rights.


   Funding for the RFC Editor function is currently provided by the
   Internet Society.