SIPPING                                                     J. Rosenberg
Internet-Draft                                               dynamicsoft
Expires: December 29, 2003 April 26, 2004                                   H. Schulzrinne
                                                     Columbia University
                                                           June 30,
                                                           O. Levin, Ed.
                                                   Microsoft Corporation
                                                        October 27, 2003

    A Session Initiation Protocol (SIP) Event Package for Conference
                                 State
                draft-ietf-sipping-conference-package-01
                draft-ietf-sipping-conference-package-02

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on December 29, 2003. April 26, 2004.

Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.

Abstract

   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, the state status of the
   dialogs that compose users'
   participation in the conference, and general information about the sidebars in the conference.

Table of Contents

   1.      Introduction . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.      Terminology  . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.      Conference Event Package . . . . . . . . . . . . . . . . . .  5
   3.1     Event Package Name . . . . . . . . . . . . . . . . . . . . .  5
   3.2   Event Package Parameters . . . . . . . . . . . . . . . . . .  5
   3.3     SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . . . .  6
   3.4  5
   3.3     Subscription Duration  . . . . . . . . . . . . . . . . . . .  6
   3.5  5
   3.4     NOTIFY Bodies  . . . . . . . . . . . . . . . . . . . . . . .  6
   3.6  5
   3.5     Notifier Processing of SUBSCRIBE Requests  . . . . . . . . .  7
   3.7  6
   3.6     Notifier Generation of NOTIFY Requests . . . . . . . . . . .  7
   3.8  6
   3.7     Subscriber Processing of NOTIFY Requests . . . . . . . . . .  7
   3.9  6
   3.8     Handling of Forked Requests  . . . . . . . . . . . . . . . .  8
   3.10  7
   3.9     Rate of Notifications  . . . . . . . . . . . . . . . . . . .  8
   3.11  7
   3.10    State Agents . . . . . . . . . . . . . . . . . . . . . . . .  8  7
   4.      Conference Data Format . . . . . . . . . . . . . . . . . . .  9  8
   4.1   Structute of the Format     Conference Information . . . . . . . . . . . . . . . . . .  9  8
   4.1.1 Conferencing Service Element . . . . . . . . . . . . . . . .  9
   4.1.2   User Element . . . . . . . . . . . . . . . . . . . . . . . . 10
   4.1.3 Status . . . . . . . . . . . . .  8
   4.1.1.1 User Statuses  . . . . . . . . . . . . . . 10
   4.1.4 Dialog . . . . . . . .  9
   4.1.1.2 Media Stream Information . . . . . . . . . . . . . . . . .  9
   4.1.2   Sidebar  . . 11
   4.1.5 Media Streams . . . . . . . . . . . . . . . . . . . . . . . 11 10
   4.2     Constructing Coherent State  . . . . . . . . . . . . . . . . 12 10
   4.3     Schema . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 11
   4.4     Example  . . . . . . . . . . . . . . . . . . . . . . . . . . 15 13
   5.      Security Considerations  . . . . . . . . . . . . . . . . . . 16 15
   6.      IANA Considerations  . . . . . . . . . . . . . . . . . . . . 17 16
   6.1     conference Event Package Registration  . . . . . . . . . . . 17 16
   6.2     application/conference-info+xml MIME Registration  . . . . . 17 16
   6.3     URN Sub-Namespace Registration for
           urn:ietf:params:xml:ns:conference-info . . . . . . . . . . . 18 17
   6.4     XML Schema Registration  . . . . . . . . . . . . . . . . . . 19 18
   7.      Acknowledgements . . . . . . . . . . . . . . . . . . . . . 19
   8.      Changes since -01  . . . . . . . . . . . . . . . . . . . . 20
           Normative References . . . . . . . . . . . . . . . . . . . . 21
           Informative References . . . . . . . . . . . . . . . . . . . 22
           Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 23 22
           Intellectual Property and Copyright Statements . . . . . . . 24 23

1. Introduction

   The Session Initiation Protocol (SIP) [3] Events framework [2]
   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. Packages have been
   defined for user presence [11], watcher information [12], and message
   waiting indicators [14], amongst others. Here, we define an
   event package for SIP conferences. This package provides the
   conference notification service as outlined in the SIP conferencing
   framework
   [15]. [9]. As described there, subscriptions to a conference URI
   are routed to the focus that is handling the conference. It acts as
   the notifer, and provides clients with updates on conference state.

   The information provided by this package is broken into several
   general categories:

   General State: A small amount comprised of general conference state is
      provided, primarily for the purposes of bootstrapping access to
      other
   identifier, conference services, such as participants (optionally with their statuses
   and media types) and conference policy
      controls.

   Membership State: The members of sidebars.

2. Terminology

   In this document, the conference, and their state
      within the conference.

   Dialog State: The state of the dialogs for users connected to the
      conference.

   Media State: Information about what media users in the conference are
      receiving.

2. Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
   and "OPTIONAL" are to be interpreted as described in RFC 2119 [1] 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 [15]. [9]. The focus has sufficient information about the state of
   the conference to inform subscribers about it.

   This section provides the details for defining a SIP Events package,
   as specified by [2].

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 [2].

3.2 Event Package Parameters

   Two Event header field parameters are defined SUBSCRIBE Bodies

   A SUBSCRIBE for this package. The
   first is "recurse". The parameter has no values. When present, it
   informs a dialog package MAY contain a body. This body
   defines a filter to apply to the server that it should check whether any participants subscription. Filter documents are
   not specified in this document, and at the conference time of writing, are themselves
   expected to be the subject of future standardization activity.

   A SUBSCRIBE for a focus, and if so, generate dialog package MAY be sent without a
   subscription to their conference state with body. This
   implies the "recurse" attribute. default subscription filtering policy. The focus can determine whether a participant default policy
   is:

   o  Notifications are generated every time there is a focus based on any change in the
   presence
      state of the "isfocus" capability indication in the Contact header
   field provided by conference.

   o  Notifications do not normally contain full state; rather, they
      only indicate the participant [4]. state that has changed. The users reported exception is a
      NOTIFY sent in
   notifications from this recursed subscription are reported response to a SUBSCRIBE. These NOTIFYs contain the
   original subscriber. The result is that the list
      full state of users reported to the subscriber represents information requested by the complete user list even when cascaded
   conferences are used. subscriber.

3.3 Subscription Duration

   The second Event header field parameter is "type". Its value is default expiration time for a
   comma separated list of the types of conference information that are
   desired. This specification defines four values - "general",
   "membership", "dialog", and "basic-media". When any one of these is
   present, it means that the corresponding conference information is
   desired. The specific components of a conference information document
   corresponding to each of these values are described below. Additional
   values for this parameter MAY be defined by extensions to this
   package. Such extensions are anticipated to handle membership and
   media policy state.

   Both of these parameters MUST have the same value in a initial
   SUBSCRIBE request and any refreshes of the resulting subscription. In
   other words, their values are fixed for the duration of the
   subscription. The default meaning of the "type" parameter, when not
   present, is that the focus should send all information it has about
   the conference. When present, the type parameter MUST have at least
   one value.

   The BNF for these parameters is:

   recurse     = "recurse"
   type        = "type" EQUAL SWS DQUOTE conf-info *("," conf-info)
                   DQUOTE
                    ;; EQUAL, SWS, DQUOTE from RFC3261
   conf-info   = "general" | "membership" | "dialog" | "basic-media" |
                   token

   Example:

   Event: conference;recurse;type="membership,general"

3.3 SUBSCRIBE Bodies

   A SUBSCRIBE for a dialog 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 dialog 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, where that change is in a piece of
      information that the subscriber has indicated (using the "type"
      Event header field parameter) an interest in receiving.

   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.

3.4 Subscription Duration

   The default expiration time for a subscription to a conference is one
   hour. Once subscription to a conference is one
   hour. Once the conference ends, all subscriptions to that particular
   conference are terminated, with a reason of "noresource" [2].

3.5

3.4 NOTIFY Bodies

   As described in RFC 3265 [2], 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
   the SUBSCRIBE.

   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
   request.

3.6

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.

3.7

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 types requested by delivered to the
   subscriber. For "membership", these

   The changes generally occur when a new participant joins, a
   participant leaves, and a dial-out attempt
   succeeds or fails. For "dialog", these changes occur when a dialog participant is
   created, terminated, or updated through put on-hold. Subject to a target refresh request. For
   "basic-media", these
   local focus policy, changes occur when in media types and other optional media
   attributes MAY be reported by the media types receive focus. In addition, creation and
   deletion of sidebars together with their rosters MAY be reported by a
   participant change. For "general", these changes occur when
   the
   conference policy protocol URIs change.

3.8 focus, subject to its local policy.

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 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 dialog 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.

3.9

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.

3.10

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.

3.11

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
   package.

4. Conference Data Format

   Conference information is an XML document [5] 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 [6], [4], using the namespace identifier 'ietf'
   defined by [7] [5] and extended by [8]. [6]. This URN is:

   urn:ietf:params:xml:ns:conference-info

   A conference information document begins with the root element tag
   "conference-info".

4.1 Structute of the Format Conference Information

   Conference information begins with the top level element
   "conference-info". This element has three mandatory attributes:

   version: This attribute allows the recipient of conference
      information documents to properly order them. Versions start at 0, 0
      and increment by one for each new document sent to a subscriber.
      Versions are scoped within a subscription. Versions MUST be
      representable using a 32 bit integer.

   state: This attribute indicates whether the document contains the
      full conference information, or whether it contains only the
      information that has changed since the previous document
      (partial).

   entity: This attribute contains the conference URI that identifies
      the conference being described in the document.

   The "conference-info" element has zero or more "conf-service"
   elements, which provide URIs for access conferencing services, such
   as media policy and conference policy control. This is followed by
   zero or more "user" sub-elements which contain information on the
   users in the conference.

4.1.1 Conferencing Service Element

   The "conf-service" element contains a URI that can be used to access
   some additional conferencing service. The element contains the
   following attributes:

   id: This attribute provides a unique identifier (unique within the
      context of the subscription) for the service. The attribute is
      mandatory.

   type: This attribute contains a string which indicates the type of
      service. Defined values are "conf-policy", to indicate that the
      URI is for manipulating the conference policy [17][18],
      "media-policy", to indicate that the URI is for manipulating the
      media policy [9], and "floor-control", to indicate that the URI is
      for access to floor control services [19]. The attribute is
      mandatory.

   There MUST only be one conf-service for each type of service.
   Additional service types may be defined in the future.

      OPEN ISSUE: Once a protocol becomes solidified, we will need to
      add some additional content here. For example, if XCAP [16] is
      used, the AUID should be provided here. We may want to move to a
      model where each service type is scoped within a unique XML element; that would
      allow for subscription. Versions MUST be
      represented using a 32 bit integer.

   state: This attribute indicates whether the schema to impose document contains the contraint on a single URI for
      each service type.

   The "conf-service" element is
      full conference information, or whether it contains only provided in notifications if the
   subscriber included
      information that has changed since the value of "general" previous document
      (partial).

   entity: This attribute contains the conference URI that identifies
      the conference being described in its "type" Event header
   field parameter.

4.1.2 User Element

   Each user the document.

   The "conference-info" element has zero or one "status" elements, indicating their
   status more "user" sub-elements
   which contain information on the users in the conference, zero or one "dialog" elements, indicating
   their dialog information, and conference. This is
   followed by zero or one "media-streams" elements,
   indicating their media reception information. more "sidebar" sub-elements which contain
   information on the sidebars in the conference.

4.1.1 User Element

   The user element has one mandatory attribute, "uri" that indicates
   the URI for the user in the conference. This is a logical identifier,
   not a machine specific one (i.e., its it's taken from the authenticated
   identity of the participant). 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.

4.1.3 Status

   The status element contains the display-name.

4.1.1.1 User Statuses

   Two optional status elements are defined: activity-status and history
   status. "Activity-status" provides information about user's current
   level of participation in the conference. "History-status", if
   present, provides information about the way the user joined or left
   the conference. Additional optional indication "is-on-dial-out-list"
   completes the information about the user membership in the
   conference.

   The following statuses are defined:

   active: defined for the activity-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. 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.

   The following statuses are defined for the history-status element:

   dialed-in: The user is dialed into the conference, i.e. sent INVITE to
      the focus, which resulted in an active successful dialog with establishment.

   dialed-out: The focus has brought the focus. user into the conference by
      sending a successful INVITE to the user.

   departed: The user sent a BYE, thus leaving the conference.

   booted: The user was sent a BYE by the conference host, focus, booting them him/her out of
      the conference.

   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.

   The "status" element is only provided in notifications if the
   subscriber included the value of "membership" in its "type" Event
   header field parameter.

4.1.4 Dialog

   The dialog element is defined in [13]. It is presented from the
   viewpoint of the focus. The "dialog" element is only provided in
   notifications if the subscriber included the value of "dialog" in its
   "type" Event header field parameter.

4.1.5

4.1.1.2 Media Streams

   The "media-streams" Stream Information

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

   Each "media-stream" element indicates the media streams stream that the user
   is currently connected to. Here, "connected to" implies that a user
   has a media line in their SDP [20] which is associated with a media
   stream managed by the focus (see Section 2.1 of [9]). [10]. With this definition, a user is
   connected to a media stream even if they are not sending any media.

   The "media-streams" element has zero or more "media-stream"
   sub-elements. The value of the "media-stream" element is an
   identifier, unique within the conference, which identifies the media
   stream that a user is connected to [9]. The "media-stream" element
   also has a mandatory "media-type" attribute
   which identifies the media type (audio, (e.g. audio, video, message and
   application) and MUST have one of the media
   stream. values registered for "media"
   of SDP [10].

   The "media-streams" "media-stream" element is only provided in notifications if has also an optional "proto" sub-element,
   which MUST has the
   subscriber included value registered for "proto" of SDP [10]).

   An optional "ssrc" sub-element, if present, carries the value of "basic-media" in its "type" Event SSRC
   (RTP/RTCP [8]) as generated by the user for the stream it sends.

   When an RTP mixer generates a CSRC list according to RTP/RTCP [8], it
   inserts a list of the SSRC identifiers of the sources that
   contributed to the generation of a particular packet into the RTP
   header field parameter.

      OPEN ISSUE: This needs of that packet. "An example application is audio conferencing
   where a mixer indicates all the talkers whose speech was combined to be aligned with
   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)."

4.1.2 Sidebar

   The sidebar element has one attribute - "entity" that indicates the
   URI which identifiers the sidebar. A sidebar has zero or more users
   that are of type "user-type" as the final media policy
      mechanisms done in xcon. If we wish this draft to proceed
      independently, we should probably remove any notion users of media
      information. the main conference are.

4.2 Constructing Coherent State

   The conference information subscriber maintains a table for the list
   of users in the conference. The table contains a row for each user.
   Each row is indexed by a URI, present in the "uri" attribute of the
   "user" element. The contents of each row contain the state of that
   user as conveyed in the document.

   The subscriber also maintains a
   table for the service URIs in the conference. This table contains a
   row for each service type. Each row is indexed by a token, present in
   the "id" attribute of the "conf-service" element. The contents of the
   row contain the URI and type of that service.

   Both tables are associated with a 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.

   The 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 contents of both tables are the table is flushed.
   They are It
   is repopulated from the document. A new row in the user table is
   created for each "user" element, and a new row in the conferencing
   services table is created for each "conf-service" element. 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 tables. table.
   For each "user" element in the document, the subscriber checks to see
   whether a row exists for that user in the user table. This check is
   done by comparing the URI in the "uri" attribute of the "user"
   element with the URI associated with the row. If the user doesn't
   exist in the table, a row is added, and its state is set to the
   information from that "user" element. If the user does exist, its
   state is updated to be the information from that "user" element. If a
   row is updated or created, such that its state is now disconnected,
   booted, failed or departed, that entry MAY be removed from the table
   at any time.

   Similarly, for each each "conf-service" element in the document, the
   subscriber checks to see whether a row exists for that service in the
   service table. This check is done by comparing the id in the "id"
   attribute of the "conf-service" element with the id associated with
   the row. If the service doesn't exist in the table, a row is added,
   and its URI and type are set to be the information from the
   "conf-service" element. Since it is not expected that this
   information will change during the lifetime of the conference, there
   is no way to indicate removal of a service.

      OPEN ISSUE: Is this really the right way to bootstrap these URIs?
      The information really is static, and placing it in an event
      package will result in a waste of bandwidth during full-state
      updates.

4.3 Schema

   <?xml version="1.0" encoding="UTF-8"?> encoding="UTF-8" ?>
   <xs:schema targetNamespace="urn:ietf:params:xml:ns:conference-info" xmlns:tns="urn:ietf:params:xml:ns:conference-info" xmlns:xs="http://www.w3.org/2001/XMLSchema"
     xmlns:di="urn:ietf:params:xml:ns:dialog-info" xmlns="urn:ietf:params:xml:ns:conference-info" elementFormDefault="qualified" attributeFormDefault="unqualified">
   <!--
    This import brings in the XML language attribute xml:lang--> xml:lang
     -->
     <xs:import namespace="http://www.w3.org/XML/1998/namespace"
       schemaLocation="http://www.w3.org/2001/03/xml.xsd"/>
     <!-- This import brings in the dialog-info element dialog-->
     <xs:import namespace="urn:ietf:params:xml:ns:dialog-info"
       schemaLocation="dialog-info.xsd"/> schemaLocation="http://www.w3.org/2001/03/xml.xsd" />

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

   <xs:complexType>
   <xs:sequence>
     <xs:element name="conf-service" type="tns:conf-serviceType"
              minOccurs="0" maxOccurs="unbounded"/>
           <xs:element name="user" type="user-type" minOccurs="0" maxOccurs="unbounded"/> maxOccurs="unbounded" />
     <xs:element name="sidebar" type="sidebar-type" minOccurs="0" maxOccurs="unbounded" />
     <xs:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded"/> maxOccurs="unbounded" />
   </xs:sequence>
     <xs:attribute name="version" type="xs:nonNegativeInteger"
              use="required"/> use="required" />
     <xs:attribute name="state" use="required">
       <xs:simpleType>
        <xs:restriction base="xs:string">
           <xs:enumeration value="full"/> value="full" />
           <xs:enumeration value="partial"/> value="partial" />
        </xs:restriction>
       </xs:simpleType>
     </xs:attribute>

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

   </xs:complexType>
   </xs:element>

   <xs:complexType name="user-type">
    <xs:sequence>
     <xs:element name="status" type="tns:status-type" minOccurs="0"/> name="activity-status" type="tns:activity-status-type" minOccurs="0" />
     <xs:element ref="di:dialog" minOccurs="0"/> name="history-status" type="tns:history-status-type" minOccurs="0" />
     <xs:element name="media-streams" minOccurs="0">
           <xs:complexType name="media-status-type">
             <xs:sequence> name="is-on-dial-out-list" type="xs:boolean" minOccurs="0" />
     <xs:element name="media-stream" type="tns:media-stream-type" minOccurs="0" maxOccurs="unbounded"/> maxOccurs="unbounded" />
     <xs:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded"/>
             </xs:sequence>
           </xs:complexType>
         </xs:element> maxOccurs="unbounded" />
     </xs:sequence>

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

   </xs:complexType>

   <xs:complexType name="media-stream-type">
       <xs:simpleContent>
         <xs:extension base="xs:string"> name="sidebar-type">
    <xs:sequence>
     <xs:element name="user" type="user-type" minOccurs="0" maxOccurs="unbounded" />
     <xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded" />
    </xs:sequence>

     <xs:attribute name="media-type" type="tns:mimetypes"
             use="required"/>
         </xs:extension>
       </xs:simpleContent> name="entity" type="xs:anyURI" use="required" />
   </xs:complexType>
     <xs:simpleType name="mimetypes">
       <xs:restriction base="xs:string">
         <xs:enumeration value="audio"/>
         <xs:enumeration value="video"/>
         <xs:enumeration value="message"/>
         <xs:enumeration value="application"/>
       </xs:restriction>
     </xs:simpleType>

   <xs:complexType name="conf-serviceType">
       <xs:simpleContent>
         <xs:extension base="xs:anyURI"> name="media-stream-type">
    <xs:sequence>
     <xs:element name="proto" type="xs:string" minOccurs="0" />
     <xs:element name="ssrc" type="xs:nonNegativeInteger" minOccurs="0" />
     <xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded" />
    </xs:sequence>
     <xs:attribute name="id" name="media" type="xs:string" use="required"/>
           <xs:attribute name="type" type="tns:typeType" use="required"/>
         </xs:extension>
       </xs:simpleContent> use="required" />
   </xs:complexType>

   <xs:simpleType name="typeType"> name="activity-status-type">
    <xs:restriction base="xs:string">
     <xs:enumeration value="conf-policy"/> value="connected" />
     <xs:enumeration value="media-policy"/> value="disconnected" />
     <xs:enumeration value="floor-control"/> value="on-hold" />
    </xs:restriction>
   </xs:simpleType>

   <xs:simpleType name="status-type"> name="history-status-type">
    <xs:restriction base="xs:string">
     <xs:enumeration value="active"/> value="dialed-in" />
     <xs:enumeration value="departed"/> value="dialed-out" />
     <xs:enumeration value="booted"/> value="departed" />
     <xs:enumeration value="failed"/> value="booted" />
     <xs:enumeration value="failed" />
    </xs:restriction>
   </xs:simpleType>

   </xs:schema>

4.4 Example

   The following is an example conference information document:

   <conference-info version="0" state="full" entity="sip:conf233@example.com">
     <user uri="sip:jdrosen@example.com" display-name="Jonathan Rosenberg">
       <status>active</status>
       <media-streams> uri="sip:bob@example.com" display-name="Bob Jones">
       <activity-status>connected</activity-status>
       <history-status>dialed-in</history-status>
       <media-stream media-type="audio">8hha7</media-stream>
       </media-streams> media-type="audio"
          <proto> RTP/AVP <proto>
          <ssrc> 583398 <ssrc>
       </media-stream>
     </user>

     <user uri="sip:barbara@example.com" display-name="Barbara Jones">
       <activity-status>on-hold</activity-status>
     </user>

     <user uri="sip:hgs@example.com" display-name="Henning Schulzrinne">
       <status>active</status> uri="sip:bill@example.com" display-name="Bill Minelli">
       <activity-status>on-hold</activity-status>
     </user>

     <sidebar entity="sip:conf233.1@example.com">
       <user>uri="sip:barbara@example.com"</user>
       <user>uri="sip:bill@example.com"</user>
     </sidebar>

   </conference-info>

   This document describes a conference with two three users, both two of which
   are active. in a sidebar conversation.

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
   policies.

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

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
   schema.

6.1 conference Event Package Registration

   This specification registers an event package, based on the
   registration procedures defined in RFC 3265 [2]. 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, jdrosen@jdrosen.net.

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 [10]. [7].

   Encoding considerations: Same as encoding considerations of
      application/xml as specified in RFC 3023 [10]. [7].

   Security considerations: See Section 10 of RFC 3023 [10] [7] 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, <jdrosen@jdrosen.net>

   Intended usage: COMMON

   Author/Change controller: The IETF.

6.3 URN Sub-Namespace Registration for
    urn:ietf:params:xml:ns:conference-info

   This section registers a new XML namespace, as per the guidelines in
   [8].
   [6].

   URI: The URI for this namespace is
      urn:ietf:params:xml:ns:conference-info.

   Registrant Contact: IETF, SIPPING working group, <sipping@ietf.org>,
      Jonathan Rosenberg <jdrosen@jdrosen.net>.

   XML:

   BEGIN
   <?xml version="1.0"?>
   <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
             "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
   <html xmlns="http://www.w3.org/1999/xhtml">
   <head>
     <meta http-equiv="content-type"
        content="text/html;charset=iso-8859-1"/>
     <title>Dialog
     <title>Conference Information Namespace</title>
   </head
   <body>
     <h1>Namespace for Dialog Conference Information</h1>
     <h2>urn:ietf:params:xml:ns:conference-info</h2>
     <p>See <a href="[[[URL of published RFC]]]">RFCXXXX</a>.</p>
   </body>
   </html>
   END

6.4 XML Schema Registration

   This specification registers a schema, as per the guidelines in in
   [8].
   [6].

      URI: please assign.

      Registrant Contact: IETF, SIPPING Working Group
      (sipping@ietf.org), Jonathan Rosenberg (jdrosen@jdrosen.net).

      XML: The XML can be found as the sole content of Section 4.3.

7. Acknowledgements

   The authors would like to thank Dan Petrie and Sean Olson for their
   comments.

8. Changes since -01

   o  Package parameters are removed. Decision about performing
      "recursive" membership algorithm is perceived as a focus local
      policy.

   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.

Normative References

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

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

   [3]  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.

   [4]   Rosenberg, J., "Indicating User Agent Capabilities in the
         Session Initiation Protocol  (SIP)",
         draft-ietf-sip-callee-caps-00 (work in progress), June 2003.

   [5]   Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler,
         "Extensible Markup Language (XML) 1.0 (Second Edition)", W3C
         REC REC-xml-20001006, October 2000.

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

   [7]

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

   [8]

   [6]  Mealling, M., "The IETF XML Registry",
        draft-mealling-iana-xmlns-registry-05 (work in progress), June
        2003.

   [9]   Mahy, R. and N. Ismail, "Media Policy Manipulation in the
         Conference Policy Control Protocol",
         draft-mahy-xcon-media-policy-control-00 (work in progress),
         June 2003.

   [10]

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

Informative References

   [11]  Rosenberg, J., "A Presence Event Package for the Session
         Initiation Protocol (SIP)", draft-ietf-simple-presence-10 (work
         in progress), January 2003.

   [12]  Rosenberg, J., "A Watcher Information Event Template-Package
         for the Session Initiation  Protocol (SIP)",
         draft-ietf-simple-winfo-package-05 (work in progress), January
         2003.

   [13]  Rosenberg, J. and H.

   [8]  Schulzrinne, "An INVITE Inititiated Dialog
         Event Package for the Session Initiation  Protocol (SIP",
         draft-ietf-sipping-dialog-package-01 (work in progress), March
         2003.

   [14]  Mahy, R., "A Message Summary H., Casner, S., Frederick, R. and Message Waiting Indication
         Event Package for the  Session Initiation V. Jacobson,
        "RTP: A Transport Protocol (SIP)",
         draft-ietf-sipping-mwi-03 (work in progress), for Real-Time Applications", RFC
        3550, July 2003.

   [15]

Informative References

   [9]   Rosenberg, J., "A Framework for Conferencing with the Session
         Initiation Protocol",
         draft-ietf-sipping-conferencing-framework-00 (work in
         progress), May 2003.

   [16]  Rosenberg, J., "The Extensible Markup Language (XML)
         Configuration Access Protocol  (XCAP)",
         draft-ietf-simple-xcap-00 (work in progress), June 2003.

   [17]  Koskelainen, P. and H. Khartabil, "An Extensible Markup
         Language (XML) Configuration Access Protocol (XCAP)  Usage for
         Conference Policy Manipulation",
         draft-koskelainen-xcon-xcap-cpcp-usage-00 (work in progress),
         June 2003.

   [18]  Levin, O., "Conference Policy Control Protocol for Centralized
         Conferencing", draft-levin-xcon-cpcp-00 (work in progress),
         June 2003.

   [19]  Wu, X., "Use of Session Initiation Protocol (SIP) and Simple
         Object Access  Protocol (SOAP) for Conference Floor Control
         Protocol (SOAP) for Conference Floor Control",
         draft-wu-sipping-floor-control-04 (work in progress), March
         2003.

   [20]

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

Authors' Addresses

   Jonathan Rosenberg
   dynamicsoft
   600 Lanidex Plaza
   Parsippany, NJ  07054
   US

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

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

   EMail: schulzrinne@cs.columbia.edu
   URI:   http://www.cs.columbia.edu/~hgs

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

   EMail: oritl@microsoft.com

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