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Versions: 00 01                                                         
XCON                                                        H. Khartabil
Internet-Draft                                            P. Koskelainen
Expires: March 10, 2005                                         A. Niemi
                                                                   Nokia
                                                       September 9, 2004


             The Conference Policy Control Protocol (CPCP)
                        draft-ietf-xcon-cpcp-00

Status of this Memo

   By submitting this Internet-Draft, I certify that any applicable
   patent or other IPR claims of which I am aware have been disclosed,
   and any of which I become aware will be disclosed, in accordance with
   RFC 3668.

   Internet-Drafts are working documents of the Internet Engineering
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   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on March 10, 2005.

Copyright Notice

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

Abstract

   The Conference Policy is defined as the complete set of rules for a
   particular conference manipulated by the conference policy server.
   The Conferece Policy Control Protocol (CPCP) is the protocol used by
   clients to manipulate the conference policy.  This document describes
   the Conference Policy Control Protocol (CPCP).  It specifies an
   Extensible Markup Language (XML) Schema that enumerates the
   conference policy data elements that enable a user to define a
   conference policy.



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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  3
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   4.  Structure of a Conference Policy document  . . . . . . . . . .  4
     4.1   MIME Type for CPCP XML Document  . . . . . . . . . . . . .  4
     4.2   Conference Root  . . . . . . . . . . . . . . . . . . . . .  4
     4.3   XML Document Description . . . . . . . . . . . . . . . . .  5
       4.3.1   Conference Settings  . . . . . . . . . . . . . . . . .  5
       4.3.2   Conference Information . . . . . . . . . . . . . . . .  7
       4.3.3   Conference Time  . . . . . . . . . . . . . . . . . . .  8
       4.3.4   Conference Authorization Rules . . . . . . . . . . . .  9
       4.3.5   Conference Dial-Out List . . . . . . . . . . . . . . . 20
       4.3.6   Conference Refer List  . . . . . . . . . . . . . . . . 20
       4.3.7   Conference Media Streams . . . . . . . . . . . . . . . 21
     4.4   XML Schema Extensibility . . . . . . . . . . . . . . . . . 21
     4.5   XML Schema . . . . . . . . . . . . . . . . . . . . . . . . 22
   5.  Conference Policy Manipulation and Conference Entity
       Behaviour  . . . . . . . . . . . . . . . . . . . . . . . . . . 27
     5.1   Overview of Operation  . . . . . . . . . . . . . . . . . . 27
     5.2   Use of External Lists  . . . . . . . . . . . . . . . . . . 27
     5.3   Communication Between Conference Entities  . . . . . . . . 28
     5.4   Manipulating Participant Lists . . . . . . . . . . . . . . 28
       5.4.1   Expelling a Participant  . . . . . . . . . . . . . . . 28
     5.5   Re-joining a Conference  . . . . . . . . . . . . . . . . . 30
   6.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
     6.1   A Simple Conference Policy Document  . . . . . . . . . . . 30
     6.2   A Complex Conference Policy Document . . . . . . . . . . . 31
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 33
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 34
     8.1   XCAP Application Usage ID  . . . . . . . . . . . . . . . . 34
     8.2   application/conference-policy+xml MIME TYPE  . . . . . . . 34
     8.3   URN Sub-Namespace Registration for
           urn:ietf:params:xml:ns:conference-policy . . . . . . . . . 35
   9.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 36
   10.   Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 36
   11.   References . . . . . . . . . . . . . . . . . . . . . . . . . 36
   11.1  Normative References . . . . . . . . . . . . . . . . . . . . 36
   11.2  Informative References . . . . . . . . . . . . . . . . . . . 38
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 38
       Intellectual Property and Copyright Statements . . . . . . . . 40









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1.  Introduction

   The SIP conferencing framework [13] defines the mechanisms for
   multi-party centralized conferencing in a SIP environment.

   Existing SIP mechanisms allow users, for example, to join and leave a
   conference, as described in [9].  A centralised server, called focus,
   can expel and invite users, and may have proprietary access control
   lists and user privilege definitions.  This document defines an XML
   Schema in Section 4 that enumerates the conference policy data
   elements that enable a user to define a conference policy.  This
   policy document may be given to a focus using a number of transports
   that are outside the scope of this document.

   A focus conforming to this specification MUST support the XML object
   defined in Section 4.

2.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [2].

3.  Terminology

   This document uses terminology from [13].  Some additional
   definitions are introduced here.

   Conference authorization policy (CAP):  Conference authorization
      policy consists of an unordered set of rules, which control the
      permissions and privileges that are given to conference
      participants.

   Conference Policy Server (CPS):  Conference Policy Server.  See [13]

   Conference participant:  Conference participant is a user who has an
      on-going session (e.g.  SIP dialog) with the conference focus.

   Floor control:  Floor control is a mechanism that enables
      applications or users to gain safe and mutually exclusive or
      non-exclusive access to the shared object or resource in a
      conference.

   Dial-Out List (DL):  The Dial-out list (DL) is a list of users who
      the focus needs to invite to the conference.






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   Privileged user:  A privileged user is a user that has the right to
      manipulate parts or all of the conference policy XML document.

   Conference Policy URI:  The URI of conference policy.  It identifies
      the XML document.  The URI construction is specified in [10].

   Refer List (RL):  The Refer list (RL) is a list of users who the
      focus needs to refer to the conference.

   Sidebar:  A sub-conference of a main conference.


4.  Structure of a Conference Policy document

   The conference policy document is an XML [6] document that MUST be
   well-formed and MUST be valid.  The Conference policy documents MUST
   be based on XML 1.0 and MUST be encoded using UTF-8.  This
   specification makes use of XML namespaces for identifying conference
   policy 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 [15].
   This URN is:

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


4.1  MIME Type for CPCP XML Document

   The MIME type for the CPCP XML document is "application/
   conference-policy+xml".

4.2  Conference Root

   A conference policy document begins with the root element tag
   <conference>.  Other elements from different namespaces MAY be
   present for the purposes of extensibility.  Elements or attributes
   from unknown namespaces MUST be ignored.  The conference policy is
   build up using the following:

   o  The <settings> element: This element is mandatory and contains
      various conference settings.  It contains the conference URI(s),
      the maximum number of participants, the conference security level,
      and sidebar settings.  It can occur only once in the document.

   o  The <info> element: This element is optional and includes
      information describing the conference, that can be used, for
      example, search purposes.  This information can also be used in
      the session description when the focus is sending invitations.  It



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      can occur only once in the document.

   o  The <time> element: This optional element defines conference time
      information, namely elements defining start and stop times for a
      media mixing.

   o  The <authorization> element: This optional element is the
      conference authorisation rules.  It contains rules for users who
      can dial into the conference, users who are blocked from dialling
      in, amongst others.

   o  The <dialout-list> element: This optional element is for the
      dial-out list.  It contains URIs for users that the focus will
      invite to the conference.

   o  The <refer-list> element: This optional element is for the refer
      list.  It contains URIs for users that the focus will refer to the
      conference.

   o  The <ms> element: This optional element contains the media streams
      to be used in the conference.

   The elements are described in more detail in the forthcoming
   sections.

   A user may create a new conference at the CPS by placing a new
   conference policy document.  Depending on server policy and user
   privileges, the CPS may accept the creation, or it may reject it.

   A conference can be deleted permanently by removing the conference
   policy from the CPS, which consequently frees the resources.  When
   the user deletes a conference, the CPS MUST also delete all its
   sub-conferences ("sidebars") at a server.  Conference sidebars have
   unique URIs at the server.  Sidebars are created in [18].

4.3  XML Document Description

4.3.1  Conference Settings

   The <settings> element contains 2 sub-elements; the <conference-uri>
   element and the <max-participant-count> element.

   <conference-uri> is a mandatory element.  It can occur more than once
   to accommodate multiple signaling protocols.  Once a conference URI
   is set, it MUST NOT be changed or removed for the duration of the
   conference.  Only one URI per protocol MUST be set.  URIs can be
   added at any time.




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   <max-participant-count> is an optional element.  It carries the
   maximum number of participants allowed in the conference.  When the
   maximum number of participants threshold is reached, no new users are
   not allowed to join until the number of participants decreases again.
   If using SIP, the server can reject a request to join (INVITE) with
   a "480 Temporarily Unavailable" response.  Alternatively, the sever
   may implement a waiting queue.

   <security-level> is an optional element.  It describes the security
   level that the creator of the conference wishes to have for the
   conference being created, including signalling and media.  There are
   4 security levels defined: none, low, medium, and high with medium
   being the default value if this element is absent.  Those levels are
   loosly defined here.  The interpretation of those levels and the
   security protocols applied is left as a local policy of the focus.  A
   focus may interpret those levels as follows:

   none:  No security is required for the signalling nor the media

   low:  Signalling and media integrity is required

   medium:  Signalling and media confidentiality is required

   high:  Signalling and media integrity and confidentiality are
      required


   <allow-sidebars> is an optional element with a boolean value
   indicating if sidebars are allowed in this conference or not.  The
   default value, if omitted, is "true" indicating that sidebars are
   allowed.

   <sidebar> is an element identifying a side bar.  Multiple <sidebar>
   elements can occur indicating multiple sidebars.  No <sidebar>
   elements appearing in a conference policy indicates that there are no
   sidebars currently for this conference.  A <sidebar> element contains
   a mandatory 'id' attribute that uniquely identifies the sidebar.  It
   also contains an <uri> element that hold the sidebar URI.  It can
   occur more than once to accommodate multiple signaling protocols.
   Once a sidebar URI is set, it MUST NOT be changed or removed for the
   duration of the conference.  Only one URI per protocol MUST be set.
   URIs can be added at any time.

   A sidebar MAY have its own policy.  This policy is created exactly in
   the same manner as any other conference.  The <policy> element in the
   <sidebar> element points to such policy.  If the <policy> element is
   omitted, the sidebar inherits the policy of the conference it is a
   sidebar of.



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   A conference is identified by one or more conference URIs, one for
   each call signaling protocol that is supported.  There must be at
   least one URI for a conference.  Conference URIs can be proposed by
   the creator of the conference policy, as it may be useful to have
   human-friendly name in some cases, or can be assigned by the CPS.  If
   the creator has proposed a conference URI, the server needs to decide
   whether to accept the name proposed by the client or not.  It does
   this determination by examining if the conference URI already exists
   or not.  If it exists, the CPS rejects the request to create the
   conference with that conference URI.  Similarly, the CPS rejects the
   request to create a conference with a conference URI for a signalling
   protocol it does not support.

   A Conference URI can be SIP, SIPS, TEL, or any supported URI scheme.
   The CPS MAY assign multiple conference URIs to a conference, one for
   each call signaling protocol that it supports.

   Sidebar URIs are subject to the same behaviour.

4.3.2  Conference Information

   The <info> element includes informative conference parameters which
   may be helpful describing the purpose of a conference, e.g.  for
   search purposes or for providing host contact information.  The
   <info> element has a special attribute 'xml:lang' to specify the
   language used in the contents of this element as defined Section 2.12
   of [6].

   Each conference has an optional <subject> element, which describes
   the current topic in a conference.  The optional <display-name>
   element is the display name of the conference, which usually does not
   change over time.

   <free-text> and <keywords> are optional elements.  They provide
   additional textual information about the conference.  This
   information can be made available to potential conference
   participants by means outside the scope of this document.  Examples
   of usage could be searching for a conference based on some keywords.

   The optional <web-page> element points to a URI where additional
   information about the conference can be found.

   The optional <host-info> element contains the <uri>, <e-mail> and
   <web-page> elements.  They give additional information about the user
   hosting the conference.  This information can, for example, be
   included into the SDP fields of the SIP INVITE requests sent by the
   focus.  The <uri> element is optional and can occur more than once.






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4.3.3  Conference Time

   The information related to conference time and lifetime is contained
   in the <time> element.  The conference may occur for a limited period
   of time (i.e.  bounded), or the conference may be unbounded (i.e.  it
   does not have a specified end time).  Bounded conferences may occur
   multiple times(e.g.  on weekly basis).

   The <time> element contains one or more <occurrence> elements each
   defining the time information of a single conference occurrence.
   Multiple <occurrence> elements MAY be used if a conference is active
   at multiple times; each additional <occurrence> element contains time
   information for a specific occurrence.

   For each occurrence, the <mixing-start-time> element specifies when
   conference media mixing starts.  the <mixing-stop-time> element
   specifies the time a conference media mixing stops.  If the
   <mixing-start-time> element is not present, it indicates that the
   conference media mixing starts immediately.  If the
   <mixing-stop-time> element is not present, it indicates that the
   conference occurrence is not bounded, i.e.  permanent unitl the
   conference policy is removed from the server.

   <mixing-start-time> and <mixing-stop-time> elements both have the
   mandatory 'require-participant' attribute.  This attribute has one of
   3 values: "none", "key-participant", and "participant".  For mixing
   start time, this attribute allows a privileged user to define when
   media mixing starts based on the latter of the mixing start time, and
   the time the first participant or key participant arrives.  If the
   value is set to "none", mixing starts according to the mixing start
   time.  For mixing stop time, this attribute allows a privileged user
   to define when media mixing stops based on the earlier of the mixing
   stop time, and the time the last participant or key participant
   leaves.  If the value is set to "none", mixing stops according to the
   mixing stop time.

   Users can be allowed to join a conference before the media mixing
   time starts and after a certain time.  A conference privileged user
   can indicate the time when users can join by populating the
   <can-join-after> element.  Similarly, a conference privileged user
   can define the time after which new users are not allowed to join the
   conference anymore.  This is done by populating the
   <must-join-before> element.

   It is possible to define the time when users or resources on the
   dial-out list and on the refer-list are requested to join the
   conference by using the <request-users> element.  It is also possible
   to define that the users and resources on the dial-out list and the



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   refer-list are requested to join the conference only after the first
   a participant or key participant has joined.  This is achieved with
   the 'require-participant' attribute.  A value of "none" indicates
   that the focus sends the requests immediately after the specified
   time has lapsed.

   The absence of this conference time information indicates that a
   conference starts immediately and terminates when the conference
   policy is removed.

   A running conference instance can be extended or stopped by modifying
   the conference time information.  Note that those conference times do
   not guarantee resources for the conference to be available.

   If a conference is in progress when deleted or stopped, the focus
   issues signalling requests to terminate all conference related
   sessions it has with participants.  In SIP, the focus issues BYE
   requests.

4.3.4  Conference Authorization Rules

   One of the key components of conference policy is the set of
   authorization rules that specify who is allowed to join a conference,
   see floors and request/grant them, subscribe to
   conference-information notifications and so on.  The unordered list
   of authorization rules together define the conference authorization
   policy

   The conference authorization rules are enclosed in the
   <authorization-rules> element and are formatted according to the XML
   schema defined in the common policy framework [1].  In the
   <authorization-rules> element, there can be multiple rules, each rule
   is represented by the <rule> element, each of which consist of three
   parts: conditions, actions and transformations.  Conditions determine
   whether a particular rule applies to a request.  Each action or
   transformation in the applied rule is a positive grant of permission
   to the conference participant.  The details of each specific element
   and attribute is described in [1].

   Asking the focus to allow certain users to join the conference is
   achieved by modifying an existing authorization rule or creating a
   new one.  The CPS then informs the focus of such change.

   If the conference is long-lasting, it is possible that new rules are
   added all the time but old rules are almost never removed (some of
   them are overwritten, though).  This leads easily to the situation
   that the conference policy contains many unnecessary rules which are
   not really needed anymore.  Therefore, there is a need to delete



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   rules.  This can be achieved by removing that portion of the policy.

   Conflicting rules may exist (for example, both allowed and blocked
   action is defined for same target).  The common policy directives [1]
   dictate the behaviour in such situations.

   This section outlines the new conditions, actions and transformations
   for conference authorization policy.

4.3.4.1  Conditions

4.3.4.1.1  Validity

   The <validity> element, as defined in  the common policy framework
   [1], expresses the rule validity period by two attributes, a starting
   and a ending time.  Times are expressed in XML dateTime format.
   Expressing the lifetime of a rule implements a garbage collection
   mechanism.  A rule maker might not have always access to the
   conference policy server to remove some rules which grant
   permissions.  Hence this mechanisms allows to remove or invalidate
   granted permissions automatically without further interaction between
   the rule maker and the conference policy server.

   To give a real life example, there are often meetings where
   management are allowed to join the first half of the conference and
   engineers are only allowed to join the conference during the second
   half of that meeting to report technical findings, etc.  Two rules
   can be set in this scenario, the first rules allows the managers to
   join the conference without specifying a validity contraint.  The
   second rule allows engineers to join an hour into the conference.
   The following example demostrates this.  The meeting starts at 9:30
   and ends at 12:30.  The manager can join at any time while the
   engineer cannot only join before 10:30 (Note that the example is
   simplified for clarity).

















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     <rule id="1">
       <conditions>
         <identity>
           <id>manager@example.com</id>
         </identity>
       </conditions>
       <actions>
         <join-handling>allow</join-handling>
       </actions>
       <transformations/>
     </rule>
     <rule id="2">
       <conditions>
         <validity>
           <from>2004-12-17T10:30:00-05:00</from>
           <to>2004-12-17T12:30:00-05:00</to>
         </validity>
         <identity>
           <id>engineeer@example.com</id>
         </identity>
       </conditions>
       <actions>
         <join-handling>allow</join-handling>
       </actions>
       <transformations/>
     </rule>
     ...
     <time>
       <occurrence>
         <mixing-start-time required-participant="participant">
           2004-12-17T09:30:00-05:00</mixing-start-time>
         <mixing-stop-time required-participant="none">
           2004-12-17T12:30:00-05:00</mixing-stop-time>
       </occurrence>
     </time>



4.3.4.1.2  Identity

   The <identity> element is already defined in the common policy
   framework [1]The presence of the <identity> element is a condition
   requires any identity within it to be authenticated before a rule is
   applied to it.  This includes the <id> element (Section 4.3.4.1.2.1),
   the <any> element (Section 4.3.4.1.2.2), the <external-list> element
   (Section 4.3.4.1.2.4), their exceptions, and any future extension
   that carries an identity.  The absence of the <identity> element with
   in a condition indicated that the rule applies to all unauthenticated



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   identities.  That is participants that have provided no authenticated
   identity to the conference focus.

4.3.4.1.2.1  Interpreting the <id> Element

   As earlier indicated, the <identity> element is already defined in
   the common policy framework [1].  However, the rules for interpreting
   the identities in <id> elements are left for each application to
   define separately.  This document, however, does not define the rules
   for interpreting identities in <id> elements in conferencing
   applications since those interpretation rules are signalling protocol
   specific.

      OPEN ISSUE: Do we need to state more than this? How are identities
      derived from users that join using POTS, H.323, etc.?


4.3.4.1.2.2  Matching Any Identity

   The <any> element is used to match any participant.  This allows a
   conference to be open to any authenticated user.  Just as for the
   <domain> element in <identity> element, The <any> element contains a
   list of <except> elements and allows to implement a simple blacklist
   mechanism.  The <except> element contains the identity.  It differs
   from the <domain> element in that the domain part is needed in the
   identity since it has not domain to refer to.

4.3.4.1.2.3  Matching Pseudonymous Identities

   The <pseudonymous> element is used to match participants that have
   provided an authenticated identity to the conference focus, but have
   requested pseudonymity in the conference itself.  A user requests
   pseudonymity by authenticating himself to the conference focus and
   providing an pseudonym in the signalling protocol (for example, using
   the From-header of a SIP reqeust).  A rule allowing pseudonymous
   users to join looks like the following:



        <rule id="4">
                <conditions>
                        <pseudonymous>
                </conditions>
                <actions>
                        <join-handling>allow</join-handling>
                </actions>
                <transformations/>
        </rule>



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   The <pseudonymous> element can be combined with the <identity>
   element to provide the focus with a rule on what to do when a
   specific identity is authenticated and that identity is requesting
   pseudonymity through the signalling protocol.  An example of such a
   rule follows:



   <rule id="4">
     <conditions>
       <identity>
         <id>alice@example.com</id>
       </identity>
       <pseudonymous>
     </conditions>
     <actions>
       <join-handling>allow</join-handling>
     </actions>
     <transformations/>
   </rule>


4.3.4.1.2.4  Matching Identities in External Lists

   The <external-list> element can be used to match those participants
   that are part of a resource list that is created externally.  Section
   5.2 talks about the use of this condition in more detail.

4.3.4.1.2.5  Matching Referred Identities

   The <has-been-referred> element can be used to match those
   participants that the focus has referred to the conference.

4.3.4.1.2.6  Matching Invited Identities

   The <has-been-invited> element can be used to match those
   participants that the focus has invited into the conference.

4.3.4.1.2.7  Matching Identities of Former Conference Participants

   The <has-been-in-conference> element can be used to match those
   participants that have joined the conference in the past.

4.3.4.1.2.8  Matching Identities Currently in the Conference

   The <is-in-conference> element can be used to match those
   participants that are currently participating in the conference.



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4.3.4.1.2.9  Matching Key Participant Identities

   The <key-participant> element can be used to match those participants
   that are key participants of a conference.

4.3.4.1.2.10  Matching Identities on the Dial-out List

   The <is-on-dialout-list> element can be used to match those
   participants that are on the dial-out list.

4.3.4.1.2.11  Matching Identities on the Refer List

   The <is-on-refer-list> element can be used to match those
   participants that are on the refer list.

4.3.4.1.2.12  Floor ID

   The <floor-id> element can be used to assign users as floor
   moderators.  It MUST be used in conjunction with the <id> element
   that identifies the floor moderator.  The <floor-id> element carries
   the floor ID of the floor that the user is a moderator of.  The
   transformation <is-floor-moderator> is used to assert that the user
   identified using the <id> condition is the floor moderator of the
   floor identified in the <floor-id> condition.

   The <floor-id> element is also used with the <floor-request-handling>
   element (Section 4.3.4.2.6) to set rules on who is allowed to request
   a floor.

4.3.4.1.2.13  Matching PIN Codes

   The <pin> element can be used to match those participants that are
   have knowledge on a PIN code for the conference.  For example:



        <rule id="1">
                <conditions>
                        <pin>12345</pin>
                </conditions>
                <actions>
                        <join-handling>allow</join-handling>
                </actions>
                <transformations/>
        </rule>


   So the condition is the PIN.  If any user knows the PIN, ignoring



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   their identity, the user is allowed to join.

   A combination of the <identity> condition and the <pin>  condition
   creates the possibility of assigning users personal PIN codes  to
   enable them to join a conference.  For example:



        <rule id="2">
                <conditions>
                        <identity>
                                <id>358401234567</id>
                        </identity>
                        <pin>67890</pin>
                </conditions>
                <actions>
                        <join-handling>allow</join-handling>
                </actions>
                <transformations/>
        </rule>


4.3.4.1.2.14  Matching Passwords

   The <password> element can be used to match those participants that
   are have knowledge on a password for the conference.  For example:



        <rule id="3">
                <conditions>
                        <password>pass1</password>
                </conditions>
                <actions>
                        <join-handling>allow</join-handling>
                </actions>
                <transformations/>
        </rule>


   So the condition is the password.  If any user knows the password,
   ignoring their identity, the user is allowed to join.

   A combination of the <identity> condition and the <password>
   condition creates the possibility of assigning users personal
   passwords to enable them to join a conference.  For example:





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        <rule id="4">
                <conditions>
                        <identity>
                                <id>alice@example.com</id>
                        </identity>
                        <password>pass2</password>
                </conditions>
                <actions>
                        <join-handling>allow</join-handling>
                </actions>
                <transformations/>
        </rule>


4.3.4.2  Actions

4.3.4.2.1  Conference State Events

   The <allow-conference-state> element represents a boolean action.  If
   set to TRUE, the focus is instructed to allow the subscription to
   conference state events, such as the SIP Event Package for Conference
   State [14].  If set to FALSE, the subscription to conference state
   events would be rejected.

   If this element is undefined it has a value of TRUE, causing the
   subscription to conference state events to be accepted.

4.3.4.2.2  Floor Control Events

   The <allow-floor-events> element represents a boolean action.  If set
   to TRUE, the focus is instructed to accept the subscription to floor
   control events.  If set to FALSE, the focus is instructed to reject
   the subscription.

   If this element is undefined, it has a value of FALSE, causing the
   subscription to floor control events to be rejected.

4.3.4.2.3  Conference Join Handling

   The <join-handling> element defines the actions used by the
   conference focus to control conference participation.  This element
   defines the action that the focus is to take when processing a
   particular request to join a conference.  This element is an
   enumerated integer type, with defined values of:







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   block:  This action instructs the focus to deny access to the
      conference.  This action has a value of zero and it is the lowest
      value of the <join-handling> element.  This action is the default
      action taken in the absence of any other actions.

   confirm:  This action instructs the focus to place the participant on
      a pending list (e.g., by parking the call on a music-on-hold
      server), awaiting moderator input for further actions.  This
      action has a value of one.

   allow:  This action instructs the focus to accept the conference join
      request and grant access to the conference within the instructions
      specified in the transformations of this rule.  This action has a
      value of two.

   Note that placing a value of block for this element doesn't guarantee
   that a participant is blocked from joining the conference.  Any other
   rule that might evaluate to true for this participant that carried an
   action whose value was higher than block would automatically grant
   confirm/allow permission to that participant.

4.3.4.2.4  Dynamically Referring Users

   The <allow-refer-users-dynamically> element represents a boolean
   action.  If set to TRUE, the identity is allowed  to instruct the
   focus to refer a user to the conference without modifying the
   refer-list (in SIP terms, the identity is allowed to send a REFER
   request to the focus which results in the focus sending a REFER
   request to the user the referrer wishes to join the conference).  If
   set to FALSE, the refer request is rejected.

   If this element is undefined it has a value of FALSE, causing the
   refer to be rejected.

4.3.4.2.5  Dynamically Inviting Users

   The <allow-invite-users-dynamically> element represents a boolean
   action.  If set to TRUE, the identity is allowed  to instruct the
   focus to invite a user to the conference without modifying the
   dial-out list (in SIP terms, the identity is allowed to send a REFER
   request to the focus which results in the focus sending an INVITE
   requested to the user the referrer wishes to join the conference).
   If set to FALSE, the refer request is rejected.

   If this element is undefined it has a value of FALSE, causing the
   refer to be rejected.





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4.3.4.2.6  Floor Request Handling

   The <floor-request-handling> element defines the actions used by the
   conference focus to control floor requests.  This element defines the
   action that the focus is to take when processing a particular request
   to a floor within a conference.  This element is an enumerated
   integer type, with defined values of:


   block:  This action instructs the focus to deny the floor request.
      This action has a value of zero and it is the lowest value of the
      <floor-request-handling> element.  This action is the default
      action taken in the absence of any other actions.

   confirm:  This action instructs the focus to allow the request.  The
      focus then uses the defined floor algorithm to further allow of
      deny the floor.  The algorithms used are outside the scope of this
      document.

   Note that placing a value of block for this element doesn't guarantee
   that a participant is blocked from joining the conference.  Any other
   rule that might evaluate to true for this participant that carried an
   action whose value was higher than block would automatically grant
   confirm/allow permission to that participant.

4.3.4.3  Transformations

4.3.4.3.1  Key Participant

   When the <is-key-participant> element is set to TRUE, the joining
   participant is denoted as a key participant.  If set to FALSE, the
   participant is not denoted as a key participant.

   If this element is undefined, it has a value of FALSE, causing no key
   participant status to be given to the participant.

4.3.4.3.2  Floor Moderator

   When the <is-floor-moderator> element is set to TRUE, the joining
   conference participant is denoted as floor moderator, meaning that
   they are privileged to control the floor in the conference.  If set
   to FALSE, floor moderator privileges are not given to the conference
   participant.

   If this element is undefined, it has a value of FALSE, causing no
   floor moderator privileges to being granted.





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4.3.4.3.3  Conference Information

   The <show-conference-info> element is of type boolean transformation.
   If set to TRUE, conference information is shown to the conference
   participant.  If set to FALSE, conference information is not shown to
   the participant.

   The <show-conference-info> element controls whether information in
   the <settings>, <time> and <info> elements may be made available
   publicly.  For example, an application at a conference server might
   list the ongoing conferences on web page, or it may allow searching
   for conferences based on the keywords listed in the <Conference-info>
   element.  Not setting this transformation to any users instructs the
   application not to reveal any such information to any user.  However,
   information in other elements, such as <dialout-list>, should not be
   seen by anyone else other than a privileged user, even with this
   transformation enabled for a user.

   If this element is undefined, it has a value of FALSE, causing no
   conference information to being shown.

4.3.4.3.4  Floor Holder

   The <show-floor-holder> element is of type boolean transformation.
   If set to TRUE, the conference participant is able to see who is
   currently holding the floor.  If set to FALSE, the participant is not
   able to see the floor holder.

   If this element is undefined, it has a value of FALSE, causing the
   floor holder not be shown to the participant.

4.3.4.3.5  Floor Requests

   The <show-floor-requests> element is of type boolean transformation.
   If set to TRUE, the conference participant is able to see the floor
   requests.  If set to FALSE, the conference participant is not able to
   see floor requests.

   If this element is undefined, it has a value of FALSE, causing the
   floor requests to not being seen by the conference participant.

4.3.4.3.6  Providing anonymity

   A rule can be set that provides anonymity to a specific identity.  In
   this case, the focus provides to the rest of the participants an
   anonymous identity for that user, for example anonymous1.  This can
   be achieved by using the <provide-anonymity> element.  It is a
   boolean transformation.  If set to TRUE, the conference participants



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   will see an anonymous identity for the user whose identity is present
   in the conditions.  An example of such rule follows:



   <rule id="4">
     <conditions>
       <identity>
         <id>alice@example.com</id>
       </identity>
     </conditions>
     <actions>
       <join-handling>allow</join-handling>
     </actions>
     <transformations>
       <provide-anonymity>
     </transformation>
   </rule>


   If this element is undefined, it has a value of FALSE, causing the
   identity to be revealed.

4.3.5  Conference Dial-Out List

   The dial-out list (DL) is a list of user URIs that the focus uses to
   learn who to invite to join a conference.  This list can be created
   at conference policy creation time or updated during the conference
   lifetime so it can be used for mid-conference invites (and
   mass-invites) as well.

   Asking the focus to invite (add) a user into the conference is
   achieved by adding that user's URI to the Dial-Out List (DL).  The
   CPS then triggers the focus to send the conference invitation, eg:
   SIP INVITE as needed.  Similarly, a user can be removed from the
   Dial-out list by removing the URI from the dial-out list.

   The <dialout-list> element is optional and includes zero or more
   <target> elements and zero or more <external> elements.  Those two
   elements includes the mandatory 'uri' attribute.  The use of the
   <external> element is described in more detail in Section 5.2

4.3.6  Conference Refer List

   The Refer List (RL) contains a list of resources that the focus needs
   to refer to the conference.  In SIP, this is achieved by the focus
   sending a REFER request to those potential participants.  This list
   can be updated during the conference lifetime so it can be used for



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   mid-conference refers as well.

   The Refer List differs from the Dial-out list in that the dial-out
   list contains a list of resources that the focus will initiate a
   session with.  The resources on the refer list, on the other had, are
   expected to initiate the session establishment towards the focus
   themselves.  It is also envisioned that difference users will have
   different access rights to those lists and therefore a separation
   between the two is needed.

   The <refer-list> element is optional and identical to the
   <dialout-list> element in Section 4.3.5.

4.3.7  Conference Media Streams

   Media policy is an integral part of the conference policy.  It
   defines e.g.  what kind of media topologies exist in the conference.
   Media policy is documented in [20].This document does not define
   media policy, but instead enables the user to specify the media
   streams a conference has.  This is used by the focus to know what
   media streams to invite users with and what media streams it should
   accept from dialling in users.  Media can be added to or removed from
   a conference by a privileged user before or during a conference
   occurance.  This might result in the focus modifying the session it
   has with each participant.  In SIP, this means re-issuing and INVITE
   request modifying the session description (SDP).

   The definition starts with the optional <media-streams> element.
   This element lists the media streams allowed for this conference.  It
   can contain at most one of each media type using the <video>,
   <audio>, <message> and <text> elements.

4.4  XML Schema Extensibility

   The schema as be extended at multiple places:

   o  The <conference> element to enable more conference policy
      information to be added

   o  The <settings> element to allow for future conference settings to
      be defined

   o  The <info> element to allow further conference and host
      information to be conveyed

   o  The <occurrence> element to allow further conference timing
      information




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   o  The <target> element and the <external> element in <dialout-list>
      and <refer-list> to allow  extensions on the behaviour of the
      focus.  For example, how many times to retry inviting a user

   o  The <media-streams> element to allow introduction of new media
      streams

   o  The <sidebar> element to allow introduction of new sidebar
      information


4.5  XML Schema


   <?xml version="1.0" encoding="UTF-8"?>
   <xs:schema targetNamespace="urn:ietf:params:xml:ns:conference-policy" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns="urn:ietf:params:xml:ns:conference-policy" elementFormDefault="qualified">
        <!-- This import brings in the XML language attribute xml:lang-->
        <xs:import namespace="http://www.w3.org/XML/1998/namespace" schemaLocation="http://www.w3.org/2001/xml.xsd"/>
        <!-- The root Conference Element -->
        <xs:element name="conference">
                <xs:complexType>
                        <xs:sequence>
                                <xs:element name="settings" type="ConferenceSettings"/>
                                <xs:element name="info" type="ConferenceInfo" minOccurs="0"/>
                                <xs:element name="time" type="ConferenceTime" minOccurs="0"/>
                                <xs:element name="authorization-rules" type="ConferenceAuthorizationRules" minOccurs="0"/>
                                <xs:element name="dailout-list" type="UserList" minOccurs="0"/>
                                <xs:element name="refer-list" type="UserList" minOccurs="0"/>
                                <xs:element name="media-streams" type="ConferenceMediaStreams" minOccurs="0"/>
                                <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
                        </xs:sequence>
                </xs:complexType>
        </xs:element>
        <!-- Conference Settings -->
        <xs:complexType name="ConferenceSettings">
                <xs:sequence>
                        <xs:element name="conference-uri" type="xs:anyURI" maxOccurs="unbounded"/>
                        <xs:element name="max-participant-count" type="xs:nonNegativeInteger" minOccurs="0"/>
                        <xs:element name="security-level" type="SecurityLevel" default="medium" minOccurs="0"/>
                        <xs:element name="allow-sidebars" type="xs:boolean" default="true" minOccurs="0"/>
                        <xs:element name="sidebar" type="Sidebar" minOccurs="0" maxOccurs="unbounded"/>
                        <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
                </xs:sequence>
        </xs:complexType>
        <!-- Conference Info -->
        <xs:complexType name="ConferenceInfo">
                <xs:sequence>
                        <xs:element name="subject" type="xs:string" minOccurs="0"/>



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                        <xs:element name="display-name" type="xs:string" minOccurs="0"/>
                        <xs:element name="free-text" type="xs:string" minOccurs="0"/>
                        <xs:element name="keywords" minOccurs="0">
                                <xs:simpleType>
                                        <xs:list itemType="xs:string"/>
                                </xs:simpleType>
                        </xs:element>
                        <xs:element name="web-page" type="xs:anyURI" minOccurs="0"/>
                        <xs:element name="host-info" minOccurs="0">
                                <xs:complexType>
                                        <xs:sequence>
                                                <xs:element name="uri" type="xs:anyURI" minOccurs="0" maxOccurs="unbounded"/>
                                                <xs:element name="e-mail" type="xs:anyURI" minOccurs="0"/>
                                                <xs:element name="web-page" type="xs:anyURI" minOccurs="0"/>
                                        </xs:sequence>
                                </xs:complexType>
                        </xs:element>
                        <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
                </xs:sequence>
                <xs:attribute ref="xml:lang"/>
        </xs:complexType>
        <!-- Conference time -->
        <xs:complexType name="ConferenceTime">
                <xs:sequence>
                        <xs:element name="occurrence" minOccurs="0" maxOccurs="unbounded">
                                <xs:complexType>
                                        <xs:sequence>
                                                <xs:element name="mixing-start-time" type="StartStopTime" minOccurs="0"/>
                                                <xs:element name="mixing-stop-time" type="StartStopTime" minOccurs="0"/>
                                                <xs:element name="can-join-after" type="xs:dateTime" minOccurs="0"/>
                                                <xs:element name="must-join-before" type="xs:dateTime" minOccurs="0"/>
                                                <xs:element name="request-users" type="StartStopTime" minOccurs="0"/>
                                                <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
                                        </xs:sequence>
                                </xs:complexType>
                        </xs:element>
                </xs:sequence>
        </xs:complexType>
        <!-- Conferenece Authorisation -->
        <xs:complexType name="ConferenceAuthorizationRules">
                <xs:sequence>
                        <xs:element name="rule" type="ruleType" minOccurs="0" maxOccurs="unbounded"/>
                </xs:sequence>
        </xs:complexType>
        <xs:complexType name="ruleType">
                <xs:sequence>
                        <xs:element name="conditions" minOccurs="0">
                                <xs:complexType>



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                                        <xs:sequence>
                                                <xs:element ref="condition" minOccurs="0" maxOccurs="unbounded"/>
                                        </xs:sequence>
                                </xs:complexType>
                        </xs:element>
                        <xs:element name="actions" minOccurs="0">
                                <xs:complexType>
                                        <xs:sequence>
                                                <xs:element ref="action" minOccurs="0" maxOccurs="unbounded"/>
                                        </xs:sequence>
                                </xs:complexType>
                        </xs:element>
                        <xs:element name="transformations" minOccurs="0">
                                <xs:complexType>
                                        <xs:sequence>
                                                <xs:element ref="transformation" minOccurs="0" maxOccurs="unbounded"/>
                                        </xs:sequence>
                                </xs:complexType>
                        </xs:element>
                </xs:sequence>
                <xs:attribute name="id" type="xs:string" use="required"/>
        </xs:complexType>
        <xs:element name="condition" abstract="true"/>
        <xs:element name="action" abstract="true"/>
        <xs:element name="transformation" abstract="true"/>
        <xs:element name="validity" substitutionGroup="condition">
                <xs:complexType>
                        <xs:all>
                                <xs:element name="from" type="xs:dateTime"/>
                                <xs:element name="to" type="xs:dateTime"/>
                        </xs:all>
                </xs:complexType>
        </xs:element>
        <xs:element name="identity" substitutionGroup="condition">
                <xs:complexType>
                        <xs:choice>
                                <xs:element name="id" type="xs:string" maxOccurs="unbounded"/>
                                <xs:sequence>
                                        <xs:element name="domain" type="xs:string"/>
                                        <xs:sequence minOccurs="0">
                                                <xs:element name="except" type="xs:string" maxOccurs="unbounded"/>
                                        </xs:sequence>
                                </xs:sequence>
                                <xs:sequence>
                                        <xs:element name="any" type="xs:string"/>
                                        <xs:sequence minOccurs="0">
                                                <xs:element name="except" type="xs:string" maxOccurs="unbounded"/>
                                        </xs:sequence>



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                                </xs:sequence>
                                <xs:sequence>
                                        <xs:element name="external-list" type="xs:string"/>
                                        <xs:sequence minOccurs="0">
                                                <xs:element name="except" type="xs:string" maxOccurs="unbounded"/>
                                        </xs:sequence>
                                </xs:sequence>
                        </xs:choice>
                </xs:complexType>
        </xs:element>
        <xs:element name="pseudonymous" type="xs:string" substitutionGroup="condition"/>
        <xs:element name="has-been-referred" type="xs:string" substitutionGroup="condition"/>
        <xs:element name="has-been-invited" type="xs:string" substitutionGroup="condition"/>
        <xs:element name="has-been-in-conference" type="xs:string" substitutionGroup="condition"/>
        <xs:element name="is-in-conference" type="xs:string" substitutionGroup="condition"/>
        <xs:element name="key-participant" type="xs:string" substitutionGroup="condition"/>
        <xs:element name="is-on-dialout-list" type="xs:string" substitutionGroup="condition"/>
        <xs:element name="is-on-refer-list" type="xs:string" substitutionGroup="condition"/>
        <xs:element name="floor-id" type="xs:anyURI" substitutionGroup="condition"/>
        <xs:element name="pin" type="xs:anyURI" substitutionGroup="condition"/>
        <xs:element name="password" type="xs:anyURI" substitutionGroup="condition"/>
        <xs:element name="allow-conference-state" type="xs:boolean" substitutionGroup="action"/>
        <xs:element name="allow-floor-events" type="xs:boolean" substitutionGroup="action"/>
        <xs:element name="join-handling" type="JoinHandling" substitutionGroup="action"/>
        <xs:element name="allow-refer-users-dynamically" type="xs:boolean" substitutionGroup="action"/>
        <xs:element name="allow-invite-users-dynamically" type="xs:boolean" substitutionGroup="action"/>
        <xs:element name="floor-request-handling" type="xs:boolean" substitutionGroup="action"/>
        <xs:element name="is-key-participant" type="xs:boolean" substitutionGroup="transformation"/>
        <xs:element name="is-floor-moderator" type="xs:boolean" substitutionGroup="transformation"/>
        <xs:element name="show-conference-info" type="xs:boolean" substitutionGroup="transformation"/>
        <xs:element name="show-floor-holder" type="xs:boolean" substitutionGroup="transformation"/>
        <xs:element name="show-floor-requests" type="xs:boolean" substitutionGroup="transformation"/>
        <xs:element name="provide-anonymity" type="xs:boolean" substitutionGroup="transformation"/>
        <!-- User List -->
        <xs:complexType name="UserList">
                <xs:sequence>
                        <xs:element name="target" type="Target" minOccurs="0" maxOccurs="unbounded"/>
                        <xs:element name="external" type="Target" minOccurs="0" maxOccurs="unbounded"/>
                </xs:sequence>
        </xs:complexType>
        <!-- Conference Media Streams -->
        <xs:complexType name="ConferenceMediaStreams">
                <xs:sequence>
                        <xs:element name="video" type="xs:string" minOccurs="0"/>
                        <xs:element name="audio" type="xs:string" minOccurs="0"/>
                        <xs:element name="message" type="xs:string" minOccurs="0"/>
                        <xs:element name="text" type="xs:string" minOccurs="0"/>
                        <xs:any namespace="##other" processContents="lax" minOccurs="0"/>



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                </xs:sequence>
        </xs:complexType>
        <!-- Target  -->
        <xs:complexType name="Target">
                <xs:sequence>
                        <xs:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded"/>
                </xs:sequence>
                <xs:attribute name="uri" type="xs:anyURI" use="required"/>
        </xs:complexType>
        <!-- Start/Stop time -->
        <xs:complexType name="StartStopTime">
                <xs:simpleContent>
                        <xs:extension base="xs:dateTime">
                                <xs:attribute name="required-participant" use="required">
                                        <xs:simpleType>
                                                <xs:restriction base="xs:string">
                                                        <xs:enumeration value="key-participant"/>
                                                        <xs:enumeration value="participant"/>
                                                        <xs:enumeration value="none"/>
                                                </xs:restriction>
                                        </xs:simpleType>
                                </xs:attribute>
                        </xs:extension>
                </xs:simpleContent>
        </xs:complexType>
        <!-- Security Level -->
        <xs:simpleType name="SecurityLevel">
                <xs:restriction base="xs:string">
                        <xs:enumeration value="none"/>
                        <xs:enumeration value="low"/>
                        <xs:enumeration value="medium"/>
                        <xs:enumeration value="high"/>
                </xs:restriction>
        </xs:simpleType>
        <!-- Join Handling -->
        <xs:simpleType name="JoinHandling">
                <xs:restriction base="xs:string">
                        <xs:enumeration value="block"/>
                        <xs:enumeration value="allow"/>
                        <xs:enumeration value="confirm"/>
                </xs:restriction>
        </xs:simpleType>
        <!-- Sidebar -->
        <xs:complexType name="Sidebar">
                <xs:sequence>
                        <xs:element name="uri" type="xs:anyURI" maxOccurs="unbounded"/>
                        <xs:element name="policy" type="xs:anyURI" minOccurs="0"/>
                        <xs:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded"/>



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                </xs:sequence>
                <xs:attribute name="id" type="xs:string" use="required"/>
        </xs:complexType>
   </xs:schema>


5.  Conference Policy Manipulation and Conference Entity Behaviour

5.1  Overview of Operation

   This document assumes that the user knows the location of conference
   policy serve, the details of that discovery are beyond the scope of
   this document.

   CPCP allows clients to manipulate the conference policy at the
   conference policy server (CPS).  CPS is able to inform the focus
   about changes in conference policy, if necessary.  For example, if
   new users are added to the dial-out list, then conference policy
   server informs the focus which makes the invitations as requested.

   Some assumptions about the conferencing architecture are made.
   Clients always connect to the conference policy server (CPS) when
   they perform manipulation operations.  It is assumed that the CPS
   informs other conferencing entities, such as focus, the floor control
   server and the mixer directly or via the focus.  For example, if user
   A wants to expel user B from an ongoing conference, user A must first
   manipulate the conference policy data.  The CPS then communicates
   that change to the focus to perform the operation.

   User privileges are defined in [19]

5.2  Use of External Lists

   External lists MAY be used in a conference policy.  They can be used
   in the dial-out list, the refer-list and the authorization policy.
   An external list is a list of resources created by means outside the
   scope of this document.

   A privileged user of the conference policy uses an external list by
   placing its URI in an conference policy element that is dedicated to
   carrying external list URIs.  The external list URI is the URI used
   to manipulate the list and not the URI used to signal to the list.
   There are three such elements documented in this memo: the
   <external-list> element in the authorization rules (Section
   4.3.4.1.2.4) and the <external> element in both, the dialout list
   (Section 4.3.5) and the refer list (Section 4.3.6).  At the time the
   focus needs to activate the policy surrounding the URI, the focus
   fetches the URIs for the members of the external list using the list



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   URI.  For example, a conference creator creates a conference and
   places the URI of an external list in the dial-out list.  At some
   point, the focus needs to invite using on the dial-out list to join
   the conference.  It is at that moment that the focus retrieves the
   members of the external list.  It then sends INVITE (in SIP terms) to
   the members of that external list.  This results in all participants
   connected to one focus.

   It can happen that the external list is not accessible at the time
   the focus requires it.  In this case, the external list is ignored,
   and in the case of an authorization rule, that rule fails.

   There are also cases where the external list has been manipulated.
   It is outside the scope of this document how the focus can learn of
   such manipulation.  But if is does, it reacts in a similar manner as
   it would have if the list was local and has been modified.

   If an external list contains a reference to yet another list, that
   referenced list is also fetched if the focus has not already done so.
   This is to avoid list loops.

5.3  Communication Between Conference Entities

   The communication between different (logical) conferencing elements
   is beyond the scope of this document.  It can be expected that in
   most cases CPS includes also those logical functions.

5.4  Manipulating Participant Lists

   A user with sufficient privileges is allowed to perform user
   management operations, such as adding a new user to the conference or
   expelling a user from the conference.  These operations are performed
   by modifying the conference policy at the conference policy server.
   After authorising the user to do such manipulations, the conference
   policy server communicates the change to the focus.  The focus reacts
   by performing singlling operations such as sending SIP INVITE, BYE or
   REFER.

5.4.1  Expelling a Participant

   Expelling a user is performed by a privileged user creating or
   manipulating an existing authorization rule and setting that user's
   <join-handling> action to "block>.  The focus reacts by terminating
   the session with that participant, such as a sending SIP BYE request.

   Care must be taken since if one rules allows a user to join and one
   blocks a user from joining, the result in that the user is allowed to
   join.  For example, Bob can join a conference since an authorization



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   rule has been defined to allow everyone at example.com:




        <rule id="1">
                <conditions>
                        <identity>
                                <domain>example.com</domain>
                        </identity>
                </conditions>
                <actions>
                        <join-handling>allow</join-handling>
                </actions>
                <transformations/>
        </rule>


   Setting the following rule will not block Bob from joining nor will
   it expel him since the above rule overrides it:




        <rule id="2">
                <conditions>
                        <identity>
                                <uri>bob@example.com</uri>
                        </identity>
                </conditions>
                <actions>
                        <join-handling>block</join-handling>
                </actions>
                <transformations/>
        </rule>


   So, in order to expel Bob, the original rule has to be modified using
   the <except> element:












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        <rule id="1">
                <conditions>
                        <identity>
                                <domain>example.com</domain>
                                <except>bob@domain.com</except>
                        </identity>
                </conditions>
                <actions>
                        <join-handling>allow</join-handling>
                </actions>
                <transformations/>
        </rule>


5.5  Re-joining a Conference

   Participants can drop out of a conference for many reasons including:
   client crash, out of coverage, had to leave for a while.  It might be
   of interest to enable that user to re-join the conference.  To allow
   that, participants that have departed the conference gracefully can
   only re-join if a privileged user has added an authorization rule
   allowing them to join.  Participants that have departed the
   conference ungracefully (eg: crash) require a special behaviour from
   the focus .  The focus is aware when a user has not gracefully
   departed a conference (for example; it did not receive a SIP BYE
   request and media is no longer being received).  If this is the case,
   the focus is required to re-issue the invitation or referral to that
   user after a pre-configured unit of time.

6.  Examples

6.1  A Simple Conference Policy Document

   The simplist of a conference policy document contains the conference
   URI, a dial-out list, and the media.  An example looks like
   this:















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   <?xml version="1.0" encoding="UTF-8"?>
   <conference xmlns="urn:ietf:params:xml:ns:conference-policy" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
        <settings>
                <conference-uri>sip:myconference@example.com</conference-uri>
        </settings>
        <dailout-list>
                <target uri="sip:bob@example.com"/>
                <target uri="sip:alice@example.com"/>
                <target uri="sip:john@example.com"/>
                <target uri="sip:robert@example.com"/>
        </dailout-list>
        <media-streams>
                <audio/>
        </media-streams>
   </conference>


6.2  A Complex Conference Policy Document

   Alice creates a conference with the follows policy:


   o  Conference URIs are suggested to be sip:myconference@example.com
      and tel:+3581234567.

   o  Maximum number of participants in the conference is 10.

   o  The security level for the conference is medium.

   o  The conference allows sidebars

   o  Media mixing starts at the latter of 9:30 am and the first
      participant arrives

   o  Media mixing sends at 12:30 pm.  The conference does not need a
      key participant to continue.

   o  Users can join 5 minutes before media mixing starts and cannot
      join half an hour before media mixing ends.

   o  Users are requested to join a conference (invited and referred) 5
      minutes before the conference starts and no participant nor
      key-participant is needed for this action to take place.

   o  Everyone at the domain example.com is allowed to join and can
      subscribe to the conference state event package.

   o  Alice is a key participant



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   o  Alice will be invited to join the conference while Sarah will be
      referred to the conference.

   o  Two media are made available in the conference:audio and video.

   The resulting CPCP document looks like





   <?xml version="1.0" encoding="UTF-8"?>
   <conference xmlns="urn:ietf:params:xml:ns:conference-policy" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
        <settings>
                <conference-uri>sip:myconference@example.com</conference-uri>
                <max-participant-count>10</max-participant-count>
                <allow-sidebars>true</allow-sidebars>
        </settings>
        <info xml:lang="en-us">
                <subject>What's happening tonight</subject>
                <display-name>Party Goer's</display-name>
                <free-text>John and Peter will join the conference soon</free-text>
                <keywords>party nightclub beer</keywords>
                <host-info>
                        <uri>sip:Alice@example.com</uri>
                        <uri>tel:+3581234567</uri>
                        <e-mail>mailto:Alice@example.com</e-mail>
                        <web-page>http://www.example.com/users/Alice</web-page>
                </host-info>
        </info>
        <time>
                <occurrence>
                        <mixing-start-time required-participant="participant">2004-12-17T09:30:00-05:00</mixing-start-time>
                        <mixing-stop-time required-participant="none">2004-12-17T12:30:00-05:00</mixing-stop-time>
                        <can-join-after>2001-12-17T09:25:00-05:00</can-join-after>
                        <must-join-before>2004-12-17T12:00:00-05:00</must-join-before>
                        <request-users required-participant="none">2001-12-17T09:30:00-05:00</request-users>
                </occurrence>
        </time>
        <authorization-rules>
                <rule id="1">
                        <conditions>
                                <identity>
                                        <domain>example.com</domain>
                                </identity>
                        </conditions>
                        <actions>
                                <allow-conference-state>true</allow-conference-state>



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                                <join-handling>allow</join-handling>
                        </actions>
                        <transformations/>
                </rule>
                <rule id="2">
                        <conditions>
                                <identity>
                                        <id>alice@example.com</id>
                                </identity>
                        </conditions>
                        <actions/>
                        <transformations>
                                <is-key-participant>true</is-key-participant>
                        </transformations>
                </rule>
        </authorization-rules>
        <dailout-list>
                <target uri="sip:bob@example.com"/>
        </dailout-list>
        <refer-list>
                <target uri="sip:sarah@example.com"/>
        </refer-list>
        <media-streams>
                <video/>
                <audio/>
        </media-streams>
   </conference>


7.  Security Considerations

   A conference document may contain information that is highly
   sensitive.  Its delivery to the conference server needs to happen
   strictly, paying special attention to integrity and confidentiality.
   Reading the document is also a security concern since the conference
   policy contains sensitive information like the topic of the
   conference, who is allowed to join and the URIs of the users that can
   participate.

   Manipulations of the conference policy have similar security issues.
   Users with relevant privileges can manipulate parts of the conference
   policy giving themselves and others privileges to manipulate the
   conference policy, including the dial-out list and the security level
   settings for a conference.  This can happen because the conference
   policy itself carries the identities and the authorization rules that
   apply to those identities.  Those authorization rules carry the
   privileges that certain identities have.  If an unauthorized user
   gets access to this document (pretending to be someone else), s/he



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   can manipulate those rules giving himself and other unauthorized
   users access to the conference policy.  S/he can also manipulate
   other parts of the conference policy under a false identity.  Some of
   the things that a malicious user can do include: denying users
   certain privileges, giving himself floor moderation, removing users
   from lists, removing rules for certain identities, giving privileges
   to other malicious users, changing the media streams and changing
   conference time.  Therefore, it is very important that only
   authorized clients are able to manipulate the conference policy.  Any
   conference policy transport protocol MUST provide authentication,
   confidentiality and integrity.

   In the case that XCAP is used to create and manipulate a conference
   policy, the XCAP base specification mandates that all XCAP servers
   MUST implement HTTP Authentication: Basic and Digest Access
   Authentication [16].  Furthermore, XCAP servers MUST implement HTTP
   over TLS [17].  It is recommended that administrators of XCAP servers
   use an HTTPS URI as the XCAP root services URI, so that the digest
   client authentication occurs over TLS.  By using these means, XCAP
   client and server can ensure the confidentiality and integrity of the
   XCAP created conference policy document  and its manipulation
   operations, and that only authorized clients are allowed to perform
   them.

8.  IANA Considerations

8.1  XCAP Application Usage ID

   This section registers a new XCAP Application Usage ID (AUID)
   according to the IANA procedures defined in..

   Name of the AUID: conference-policy
   Description: Conference policy application manipulates conference
   policy at a server.

8.2  application/conference-policy+xml MIME TYPE

   MIME media type: application

   MIME subtype name: conference-policy+xml

   Mandatory parameters: none

   Optional parameters: Same as charset parameter application/xml as
   specified in RFC 3023 [7].

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



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   Security considerations: See section 10 of RFC 3023 [7] and section
   Section 8 of this document.

   Interoperability considerations: none.

   Published specification: This document.

   Applications which use this media type: This document type has been
   used to support conference policy manipulation for SIP based
   conferencing.

   Additional information:

   Magic number: None

   File extension: .cl or .xml

   Macintosh file type code: "TEXT"

   Personal and email address for further information: Petri Koskelainen
   (petri.koskelainen@nokia.com)

   Intended Usage: COMMON

   Author/change controller: The IETF

8.3  URN Sub-Namespace Registration for
    urn:ietf:params:xml:ns:conference-policy

   This section registers a new XML namespace, as per guidelines in URN
   document [15].

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

   Registrant Contact: IETF, XCON working group, Petri Koskelainen
   (petri.koskelainen@nokia.com)

   XML:












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   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>Conference Policy Namespace</title>
   </head>
   <body>
     <h1>Namespace for Conference Policy</h1>
     <h2>application/conference-policy+xml</h2>
     <p>See <a href="[[[URL of published RFC]]]">RFCXXXX</a>.</p>
   </body>
   </html>
   END


9.  Contributors

      Jose Costa-Requena

      Simo Veikkolainen

      Teemu Jalava


10.  Acknowledgements

   The authors would like to thank Markus Isomaki, Adam Roach, Eunsook
   Kim, Roni Evan, Alan Johnston, Hannes Tschofenig and the IETF XCON
   working group for their feedback and suggestions.

11.  References

11.1  Normative References

   [1]   Schulzrinne, H., Tschofenig, H., Cuellar, J., Polk, J. and J.
         Rosenberg, "Common Policy", Internet-Draft
         I-D.ietf-geopriv-common-policy, February 2004.

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

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

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



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         August 1999.

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

   [6]   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.

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

   [8]   Koskelainen, P. and H. Khartabil, "Requirements for conference
         policy control protocol", draft-ietf-xcon-cpcp-req-01 (work in
         progress), January 2004.

   [9]   Johnston, A. and O. Levin, "Session Initiation Protocol Call
         Control - Conferencing for User Agents",
         draft-ietf-sipping-cc-conferencing-03 (work in progress),
         February 2004.

   [10]  Rosenberg, J., "The Extensible Markup Language (XML)
         Configuration Access Protocol (XCAP)",
         draft-ietf-simple-xcap-02 (work in progress), February 2004.

   [11]  Rosenberg, J., "An Extensible Markup Language (XML)
         Configuration Access Protocol (XCAP) Usage for Presence Lists",
         draft-ietf-simple-xcap-list-usage-02 (work in progress),
         February 2004.

   [12]  Rosenberg, J., "A Session Initiation Protocol (SIP) Event
         Package for Modification Events for the Extensible Markup
         Language (XML) Configuration Access Protocol (XCAP) Managed
         Documents", draft-ietf-simple-xcap-package-01 (work in
         progress), February 2004.

   [13]  Rosenberg, J., "A Framework for Conferencing with the Session
         Initiation Protocol",
         draft-ietf-sipping-conferencing-framework-01 (work in
         progress), October 2003.

   [14]  Rosenberg, J., Shulzrinne, H. and O. Levin, "A Session
         Initiation Protocol (SIP) Event Package for Conference State",
         draft-ietf-sipping-conference-package-03, February 2004.

   [15]  Mealling, M., "The IETF XML Registry", RFC 3688, January 2004.




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   [16]  Franks, J., "HTTP Authentication: Basic and Digest Access
         Authentication", RFC 2617, June 1999.

   [17]  Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.

11.2  Informative References

   [18]  Rosen, B., "SIP Conferencing: Sub-conferences and Sidebars",
         draft-rosen-xcon-conf-sidebars-00 (work in progress), July
         2004.

   [19]  Khartabil, H. and A. Niemi, "Privileges for Manipulating a
         Conference Policy",
         draft-ietf-xcon-conference-policy-privileges-00 (work in
         progress), September 2004.

   [20]  Jennings, C. and B. Rosen, "Media Mixer Control for XCON",
         draft-jennings-xcon-media-control-00 (work in progress),
         February 2004.

   [21]  Handly, M., Eriksson, G., Jacobson, V. and C. Perkins,
         "Grouping of Media Lines in SDP", draft-ietf-mmusic-sdp-new-18
         (work in progress), June 2004.


Authors' Addresses

   Hisham Khartabil
   Nokia
   P.O. Box 321
   Helsinki  FIN-00045
   Finland

   EMail: hisham.khartabil@nokia.com


   Petri Koskelainen
   Nokia
   P.O. Box 100 (Visiokatu 1)
   Tampere  FIN-33721
   Finland

   EMail: petri.koskelainen@nokia.com








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   Aki Niemi
   Nokia
   P.O. Box 100
   NOKIA GROUP, FIN  00045
   Finland

   Phone: +358 50 389 1644
   EMail: aki.niemi@nokia.com











































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