XCON H. Khartabil
Internet-Draft P. Koskelainen
Expires: April 12, 2005 A. Niemi
Nokia
October 12, 2004
The Conference Policy Control Protocol (CPCP)
draft-ietf-xcon-cpcp-01
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Copyright Notice
Copyright (C) The Internet Society (2004).
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
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conference policy data elements that enable a user to define a
conference policy.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions Used in This Document . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Structure of a Conference Policy document . . . . . . . . . . 5
4.1 MIME Type for CPCP XML Document . . . . . . . . . . . . . 5
4.2 Conference Root . . . . . . . . . . . . . . . . . . . . . 5
4.3 XML Document Description . . . . . . . . . . . . . . . . . 6
4.3.1 Conference Settings . . . . . . . . . . . . . . . . . 6
4.3.2 Conference Information . . . . . . . . . . . . . . . . 8
4.3.3 Conference Time . . . . . . . . . . . . . . . . . . . 9
4.3.4 Conference Dial-Out List . . . . . . . . . . . . . . . 10
4.3.5 Conference Refer List . . . . . . . . . . . . . . . . 11
4.3.6 Conference Media Streams . . . . . . . . . . . . . . . 11
4.3.7 Conference Authorization Rules . . . . . . . . . . . . 12
4.3.7.1 Conditions . . . . . . . . . . . . . . . . . . . . 12
4.3.7.1.1 Validity . . . . . . . . . . . . . . . . . . . 13
4.3.7.1.2 Identity . . . . . . . . . . . . . . . . . . . 14
4.3.7.1.2.1 Interpreting the <id> Element . . . . . . 15
4.3.7.1.3 Sphere . . . . . . . . . . . . . . . . . . . . 15
4.3.7.1.4 Conference Policy Identity . . . . . . . . . . 15
4.3.7.1.4.1 Matching Any Identity . . . . . . . . . . 15
4.3.7.1.4.2 Matching Identities in External Lists . . 15
4.3.7.1.5 Matching Pseudonymous Identities . . . . . . . 15
4.3.7.1.6 Matching Referred Identities . . . . . . . . . 16
4.3.7.1.7 Matching Invited Identities . . . . . . . . . 16
4.3.7.1.8 Matching Identities of Former Conference
Participants . . . . . . . . . . . . . . . . . 17
4.3.7.1.9 Matching Identities Currently in the
Conference . . . . . . . . . . . . . . . . . . 17
4.3.7.1.10 Matching Key Participant Identities . . . . . 17
4.3.7.1.11 Matching Identities on the Dial-out List . . . 17
4.3.7.1.12 Matching Identities on the Refer List . . . . 17
4.3.7.1.13 Floor ID . . . . . . . . . . . . . . . . . . . 17
4.3.7.1.14 Matching Participant Passcodes . . . . . . . . 17
4.3.7.1.15 Matching Passcodes . . . . . . . . . . . . . . 18
4.3.7.2 Actions . . . . . . . . . . . . . . . . . . . . . 19
4.3.7.2.1 Conference State Events . . . . . . . . . . . 19
4.3.7.2.2 Floor Control Events . . . . . . . . . . . . . 19
4.3.7.2.3 Conference Join Handling . . . . . . . . . . . 20
4.3.7.2.4 Dynamically Referring Users . . . . . . . . . 20
4.3.7.2.5 Dynamically Inviting Users . . . . . . . . . . 20
4.3.7.2.6 Dynamically Removing Users . . . . . . . . . . 21
4.3.7.2.7 Floor Request Handling . . . . . . . . . . . . 21
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4.3.7.3 Transformations . . . . . . . . . . . . . . . . . 22
4.3.7.3.1 Key Participant . . . . . . . . . . . . . . . 22
4.3.7.3.2 Floor Moderator . . . . . . . . . . . . . . . 22
4.3.7.3.3 Conference Information . . . . . . . . . . . . 22
4.3.7.3.4 Floor Holder . . . . . . . . . . . . . . . . . 22
4.3.7.3.5 Floor Requests . . . . . . . . . . . . . . . . 23
4.3.7.3.6 Providing anonymity . . . . . . . . . . . . . 23
4.4 XML Schema Extensibility . . . . . . . . . . . . . . . . . 23
4.5 XML Schema . . . . . . . . . . . . . . . . . . . . . . . . 24
5. Conference Policy Manipulation and Conference Entity
Behaviour . . . . . . . . . . . . . . . . . . . . . . . . . . 28
5.1 Overview of Operation . . . . . . . . . . . . . . . . . . 28
5.2 Use of External Lists . . . . . . . . . . . . . . . . . . 29
5.3 Communication Between Conference Entities . . . . . . . . 29
5.4 Manipulating Participant Lists . . . . . . . . . . . . . . 29
5.4.1 Expelling a Participant . . . . . . . . . . . . . . . 30
5.5 Re-joining a Conference . . . . . . . . . . . . . . . . . 31
6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
6.1 A Simple Conference Policy Document . . . . . . . . . . . 32
6.2 A Complex Conference Policy Document . . . . . . . . . . . 32
7. Security Considerations . . . . . . . . . . . . . . . . . . . 34
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36
8.1 XCAP Application Usage ID . . . . . . . . . . . . . . . . 36
8.2 application/conference-policy+xml MIME TYPE . . . . . . . 36
8.3 URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:conference-policy . . . . . . . . . 37
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 37
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 37
11. Normative References . . . . . . . . . . . . . . . . . . . . 38
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 39
Intellectual Property and Copyright Statements . . . . . . . . 41
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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: A conference participant is a user who has
an on-going session (e.g. SIP dialog) with the conference focus.
Key participant: A key participant is a user whose participantion in
the conference is required for the conference to take place as
s/he can be the note taker, the person with whom a debate is
taking place, etc. A key participant may be required to be in a
conference before the conference starts and may be required for
the conference not to end.
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
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conference.
Dial-Out List (DL): The Dial-out list (DL) is a list of users who
the focus needs to invite to the conference.
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 according to schemas, including
extension schemas, available to the validater and applicable to the
XML document. 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,
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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
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 <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.
o The <ruleset> 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.
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.
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<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.
<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.
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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.
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
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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.
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. If the conference policy was modified so that that
last key participant is now a normal conference participant, and the
conference requires a kep participant to continue; that conference
MUST terminate.
The following is an example that states a conference mixing will not
start before a key participant joins but the mixing will stop as soon
as the last participant (no neccesarily the last key participant)
leaves.
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<time>
<occurrence>
<mixing-start-time required-participant="key-participant">
2004-12-17T09:30:00-05:00</mixing-start-time>
<mixing-stop-time required-participant="participant">
2004-12-17T12:30:00-05:00</mixing-stop-time>
</occurrence>
</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
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 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
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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
4.3.5 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. In a
different paradiam, this could also mean that the focus sends an SMS
or an email to the referred user. This list can be updated during
the conference lifetime so it can be used for 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 4.3.4.
4.3.6 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 [17].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
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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.
4.3.7 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 <ruleset>
element and are formatted according to the XML schema defined in the
common policy framework [1]. In the <ruleset> 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
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.
4.3.7.1 Conditions
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4.3.7.1.1 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>
4.3.7.1.2 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 4.3.7.1.2.1),
the <any> element (Section 4.3.7.1.4.1), the <external-list> element
(Section 4.3.7.1.4.2), 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.
4.3.7.1.2.1 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.?
4.3.7.1.3 Sphere
The <sphere> element has no meaning in the context of conference
policy and MUST be ignored if present.
4.3.7.1.4 Conference Policy Identity
4.3.7.1.4.1 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 an identity. It differs
from the <domain> element in that the domain part is needed in the
identity since it has no domain to refer to.
4.3.7.1.4.2 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. The
<external-list> element contains a list of <except> elements and
allows to implement a simple blacklist mechanism. The <except>
element contains an identity.Section 5.2 talks about the use of this
condition in more detail.
4.3.7.1.5 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
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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>
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>
4.3.7.1.6 Matching Referred Identities
The <has-been-referred> element can be used to match those
participants that the focus has referred to the conference.
4.3.7.1.7 Matching Invited Identities
The <has-been-invited> element can be used to match those
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participants that the focus has invited into the conference.
4.3.7.1.8 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.
4.3.7.1.9 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.
4.3.7.1.10 Matching Key Participant Identities
The <key-participant> element can be used to match those participants
that are key participants of a conference.
4.3.7.1.11 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.
4.3.7.1.12 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.
4.3.7.1.13 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 4.3.7.2.7) to set rules on who is allowed to request
a floor.
4.3.7.1.14 Matching Participant Passcodes
The <participant-passcode> element can be used to match those
participants that are have knowledge on a passcode for the
conference. For example:
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<rule id="3">
<conditions>
<participant-passcode/>
</conditions>
<actions>
<join-handling>allow</join-handling>
</actions>
<transformations/>
</rule>
So the condition is the participant passcode. If any user knows the
passcode, the user is allowed to join.
A focus need not care if a user using a passcode to join is calling
from a PSTN or an IP phone. For example: Using a SIP phone, a SIP
INVITE request arrives directly at the focus. The focus examines the
identity and discovers that there are no rules allowing this identity
to join. The focus also determines that there are no rules
explicitly prohibiting this identity from joining. The focus in this
case decides to challenge the identity for a passcode, if there is a
rule that allows users with a passcode knowledge to join. If no such
rule exists, the focus would not challenge for a passcode.
For PSTN users, the system can be set up for an IVR system to prompt
the user for a passcode before forwarding the request to the focus.
The focus does not need to care if there is an IVR system or not. It
can apply the same procedure as above. It checks if there are any
the rules allowing or denying the identity access. In this case, the
identity is the GW. If no rules exist for that identity but an
general passcode rule does, then the focus would challenge the GW/IVR
for the passcode.
A focus can challenge for the passcode using, for example, a HTTP
Digest challenge. The username, passcode and realm need to be
assigned and distributed is a manner that is outside the scope of
this document. Mutliple passcodes can be assigned to multiple users.
4.3.7.1.15 Matching Passcodes
In some cases, key participants are assigned a different passcode
than normal participants. The <key-participant-passcode> element can
be used to match those key participants that are have knowledge on a
key participant passcode for the conference. For example:
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<rule id="3">
<conditions>
<key-participant-passcode/>
</conditions>
<actions>
<join-handling>allow</join-handling>
</actions>
<transformations>
<is-key-participant/>
</transformations>
</rule>
So the condition is the key participant passcode. If any user knows
that passcode, that user is allowed to join and is made a key
participant. Again, a focus need not care if a user using a passcode
to join is calling from a PSTN or an IP phone. Section 4.3.7.1.14
has more details.
It is important that the focus has a unique identity for each user
joining from a PSTN phone via a gateway. It is not enough that one
identity to be assigned to all users joining from the same gateway
since key participants have more control over conference duration, if
the conference mixing times are key participant dependant. See
Section 4.3.3 for details. It might be required that a gateway maps
the telephone number of the PSTN phone into the IP signalling
protocol header that usually carries the asserted identity or a user.
4.3.7.2 Actions
4.3.7.2.1 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.
4.3.7.2.2 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.
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If this element is undefined, it has a value of FALSE, causing the
subscription to floor control events to be rejected.
4.3.7.2.3 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:
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.
4.3.7.2.4 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.
4.3.7.2.5 Dynamically Inviting Users
The <allow-invite-users-dynamically> element represents a boolean
action. If set to TRUE, the identity is allowed to instruct the
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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
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.
4.3.7.2.6 Dynamically Removing Users
The <allow-remove-users-dynamically> element represents a boolean
action. If set to TRUE, the identity is allowed to instruct the
focus to remove a user from the conference without modifying the
ruleset (in SIP terms, the identity is allowed to send a REFER
request to the focus which results in the focus sending an BYE
request to the user the referrer wishes to leave 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.
4.3.7.2.7 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.
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4.3.7.3 Transformations
4.3.7.3.1 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.
4.3.7.3.2 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.
4.3.7.3.3 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.
4.3.7.3.4 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
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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.
4.3.7.3.5 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.
4.3.7.3.6 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
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.
4.4 XML Schema Extensibility
The schema as be extended at multiple places:
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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
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:cr="urn:ietf:params:xml:ns:common-policy" xmlns="urn:ietf:params:xml:ns:conference-policy" xmlns:xs="http://www.w3.org/2001/XMLSchema" 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"/>
<!-- This import brings in the common-policy-->
<xs:import namespace="urn:ietf:params:xml:ns:common-policy"/>
<!-- 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="dialout-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:element ref="cr:ruleset"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<!-- Conference Settings -->
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<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"/>
<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>
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</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
<!-- 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"/>
</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"/>
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<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"/>
</xs:sequence>
<xs:attribute name="id" type="xs:string" use="required"/>
</xs:complexType>
<!-- Conferenece Authorisation -->
<xs:element name="cp-identity" substitutionGroup="cr:condition">
<xs:complexType>
<xs:choice>
<xs:sequence>
<xs:element name="any"/>
<xs:sequence minOccurs="0">
<xs:element name="except" type="xs:string"
maxOccurs="unbounded"/>
</xs:sequence>
</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="cr:condition"/>
<xs:element name="has-been-referred" type="xs:string" substitutionGroup="cr:condition"/>
<xs:element name="has-been-invited" type="xs:string" substitutionGroup="cr:condition"/>
<xs:element name="has-been-in-conference" type="xs:string" substitutionGroup="cr:condition"/>
<xs:element name="is-in-conference" type="xs:string" substitutionGroup="cr:condition"/>
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<xs:element name="key-participant" type="xs:string" substitutionGroup="cr:condition"/>
<xs:element name="is-on-dialout-list" type="xs:string" substitutionGroup="cr:condition"/>
<xs:element name="is-on-refer-list" type="xs:string" substitutionGroup="cr:condition"/>
<xs:element name="floor-id" type="xs:anyURI" substitutionGroup="cr:condition"/>
<xs:element name="participant-passcode" substitutionGroup="cr:condition"/>
<xs:element name="key-participant-passcode" substitutionGroup="cr:condition"/>
<xs:element name="allow-conference-state" type="xs:boolean" substitutionGroup="cr:action"/>
<xs:element name="allow-floor-events" type="xs:boolean" substitutionGroup="cr:action"/>
<xs:element name="join-handling" type="JoinHandling" substitutionGroup="cr:action"/>
<xs:element name="allow-refer-users-dynamically" type="xs:boolean" substitutionGroup="cr:action"/>
<xs:element name="allow-invite-users-dynamically" type="xs:boolean" substitutionGroup="cr:action"/>
<xs:element name="allow-remove-users-dynamically" type="xs:boolean" substitutionGroup="cr:action"/>
<xs:element name="floor-request-handling" type="xs:boolean" substitutionGroup="cr:action"/>
<xs:element name="is-key-participant" type="xs:boolean" substitutionGroup="cr:transformation"/>
<xs:element name="is-floor-moderator" type="xs:boolean" substitutionGroup="cr:transformation"/>
<xs:element name="show-conference-info" type="xs:boolean" substitutionGroup="cr:transformation"/>
<xs:element name="show-floor-holder" type="xs:boolean" substitutionGroup="cr:transformation"/>
<xs:element name="show-floor-requests" type="xs:boolean" substitutionGroup="cr:transformation"/>
<xs:element name="provide-anonymity" type="xs:boolean" substitutionGroup="cr:transformation"/>
</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 [16]
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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
4.3.7.1.4.2) and the <external> element in both, the dialout list
(Section 4.3.4) and the refer list (Section 4.3.5). 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
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
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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
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:
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<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:
<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.
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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:
<?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"
xmlns:cr="urn:ietf:params:xml:ns:common-policy">
<settings>
<conference-uri>sip:myconference@example.com</conference-uri>
</settings>
<dialout-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"/>
</dialout-list>
<media-streams>
<audio/>
</media-streams>
<cr:ruleset/>
</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
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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
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"
xmlns:cr="urn:ietf:params:xml:ns:common-policy">
<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>
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<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>
<dialout-list>
<target uri="sip:bob@example.com"/>
</dialout-list>
<refer-list>
<target uri="sip:sarah@example.com"/>
</refer-list>
<media-streams>
<video/>
<audio/>
</media-streams>
<cr:ruleset>
<cr:rule id="1">
<cr:conditions>
<cr:identity>
<cr:domain>example.com</cr:domain>
</cr:identity>
</cr:conditions>
<cr:actions>
<allow-conference-state>true</allow-conference-state>
<join-handling>allow</join-handling>
</cr:actions>
<cr:transformations/>
</cr:rule>
<cr:rule id="2">
<cr:conditions>
<cr:identity>
<cr:id>alice@example.com</cr:id>
</cr:identity>
</cr:conditions>
<cr:actions/>
<cr:transformations>
<is-key-participant>true</is-key-participant>
</cr:transformations>
</cr:rule>
</cr:ruleset>
</conference>
7. Security Considerations
A conference policy document may contain information that is highly
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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. A user impersonating another may make changes to a
conference policy. This can happen because the conference policy may
have a companion conference policy provileges document that 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 the
conference policy document (pretending to be someone else), s/he can
manipulate parts of the conference policy under a false identity.
Some of the things that a malicious user can do include: giving
himself floor moderation, removing users from lists, removing rules
for certain identities, 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.
Passcodes are generated and distributed by means outside the scope of
this document. The distribution mechanism MUST be secure. If
distributed via email, it is recommented that the emails are signed
and ecrypted.
External lists are have also potential of abuse. A focus bringing in
identities to a conference using an external list MUST make sure that
the list is created an maintained in a secure manner. It is NOT
RECOMMENDED for a focus to use external lists that are not within its
trust domain.
A focus accepting a user requesting pseudonymity into a conference
may result in a user impersonating another. The imporsonation cannot
be detectable by the focus and may cause other users that rely of a
user interface providing names of participants to be misinformed. Of
course the focus does not rely on the pseudonym to authenticate a
user. A conference creator needs to be careful when creating such
rules allowing pseudonymity. A safer rule to have is for the
conference policy itself to provide the transformation
<provide-pseudonymity>. this, however, requires the user to ask the
creator or a privileged user, out of band, to provide such rule that
gives that user pseudonymity.
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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].
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
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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:
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, Cullen Jennings,
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Rohan Mahy and the IETF XCON working group for their feedback and
suggestions.
11 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,
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
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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.
[16] Khartabil, H. and A. Niemi, "Privileges for Manipulating a
Conference Policy",
draft-ietf-xcon-conference-policy-privileges-00 (work in
progress), September 2004.
[17] Jennings, C. and B. Rosen, "Media Mixer Control for XCON",
draft-jennings-xcon-media-control-00 (work in progress),
February 2004.
[18] Rosen, B. and A. Johnson, "SIP Conferencing: Sub-conferences
and Sidebars", draft-rosen-xcon-conf-sidebars-01 (work in
progress), July 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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