XCON H. Khartabil
Internet-Draft P. Koskelainen
Expires: January 14, 2005 A. Niemi
Nokia
July 16, 2004
The Conference Policy Control Protocol (CPCP)
draft-ietf-xcon-cpcp-xcap-01
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Abstract
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. It also defines an XML Configuration
Access Protocol (XCAP) application usage that may be used to store
and manipulate a conference policy.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions Used in This Document . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Structure of a Conference Policy document . . . . . . . . . . 6
4.1 MIME Type for CPCP XML Document . . . . . . . . . . . . . 6
4.2 Conference Root . . . . . . . . . . . . . . . . . . . . . 6
4.3 XML Document Description . . . . . . . . . . . . . . . . . 7
4.3.1 Conference Settings . . . . . . . . . . . . . . . . . 7
4.3.2 Conference Information . . . . . . . . . . . . . . . . 8
4.3.3 Conference Time . . . . . . . . . . . . . . . . . . . 9
4.3.4 Conference Authorization Rules . . . . . . . . . . . . 10
4.3.5 Conference Dial-Out List . . . . . . . . . . . . . . . 21
4.3.6 Conference Refer List . . . . . . . . . . . . . . . . 22
4.3.7 Conference Security Control . . . . . . . . . . . . . 22
4.3.8 Conference Floor Policy . . . . . . . . . . . . . . . 22
4.3.9 Conference Media Streams . . . . . . . . . . . . . . . 23
4.4 XML Schema Extensibility . . . . . . . . . . . . . . . . . 24
4.5 XML Schema . . . . . . . . . . . . . . . . . . . . . . . . 24
5. Conference Policy Manipulation and Conference Entity
Behaviour . . . . . . . . . . . . . . . . . . . . . . . . . . 30
5.1 Overview of Operation . . . . . . . . . . . . . . . . . . 30
5.2 Use of External Lists . . . . . . . . . . . . . . . . . . 31
5.3 Communication Between Conference Entities . . . . . . . . 31
5.4 Manipulating Participant Lists . . . . . . . . . . . . . . 31
5.4.1 Expelling a Participant . . . . . . . . . . . . . . . 32
5.5 Re-joining a Conference . . . . . . . . . . . . . . . . . 33
5.6 Floor Control Policy vs. Floor Control Protocol . . . . . 33
6. An XCAP Usage for Conference Policy Manipulation . . . . . . . 34
6.1 Application Unique ID . . . . . . . . . . . . . . . . . . 34
6.2 Resource Interdependencies . . . . . . . . . . . . . . . . 34
6.3 Additional Constraints . . . . . . . . . . . . . . . . . . 34
6.4 Naming Conventions . . . . . . . . . . . . . . . . . . . . 34
6.5 Authorization Policies . . . . . . . . . . . . . . . . . . 34
6.6 MIME Type for CPCP XML Document . . . . . . . . . . . . . 35
7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
7.1 An Example CPCP Document . . . . . . . . . . . . . . . . . 35
7.2 CPCP Manipulations Using XCAP . . . . . . . . . . . . . . 38
8. Security Considerations . . . . . . . . . . . . . . . . . . . 40
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 41
9.1 XCAP Application Usage ID . . . . . . . . . . . . . . . . 41
9.2 application/conference-policy+xml MIME TYPE . . . . . . . 41
9.3 URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:conference-policy . . . . . . . . . 42
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 43
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 43
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 43
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12.1 Normative References . . . . . . . . . . . . . . . . . . . . 43
12.2 Informative References . . . . . . . . . . . . . . . . . . . 44
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 45
Intellectual Property and Copyright Statements . . . . . . . . 46
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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. In some
cases, such as some ad-hoc scenarios described in [9], there is a
static conference policy which is not changed or manipulated during a
conference. This policy document may be given to a focus using a
number of transports. Mechanisms such as a web page or a voice
response system can also be used to manipulate conference policy
data.
However, in many cases it is useful to have standardised means to
manipulate conference policy elements such as access control lists.
The requirements for such protocol are defined in [8].
Section 6 of this document describes one such protocol for the
real-time manipulation of conference policy. An XML Configuration
Access Protocol (XCAP) [10] application usage is defined which meets
the requirements in [8] to store and manipulate a conference policy
object.
XCAP has many advantages in its use for conference policy control
protocol. It is a HTTP 1.1 based protocol that allows clients to
read, write, modify and delete application data stored in XML format
at a server. XCAP maps XML document elements and attributes to HTTP
URIs that can be directly accessed by HTTP. One application area
which has already adopted XCAP is the manipulation of event lists
[11].
A focus conforming to this specification MUST support the XML object
defined in Section 4 . For manipulation of the the XML object, the
system MAY support the XCAP usage defined in Section 6.
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.
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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)
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 manipulate parts
or all of the conference policy settings.
CPS XCAP URI
The URI of the XCAP server that is used to create the
conference. The URI construction is specified in [10]. It is
referred to in XCAP as the host part.
Conference Policy URI
The URI of conference policy. In XCAP, it is the CPS XCAP URI
along with the abs_path. It identifies the XML document. The
URI construction is specified in [10].
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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. 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)
and the maximum number of participants. It can occur only once
in the document.
o The <info> element: This element is optional and includes
information describing the conference, e.g. for 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
conference.
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
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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 <security-control> element: This optional element is for
security control. It contains conference security level and
passwords.
o The <ms> element: This optional element contains the media streams
to be used in the conference.
o The <fp> element: This optional element is for the floor control
policy.
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 at the CPS. Depending on server policy
and user privileges, the CPS may accept the creation.
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.
4.3 XML Document Description
4.3.1 Conference Settings
The mandatory <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.
<max-participant-count> is optional. 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
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implement a waiting queue.
<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.
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 it 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 optional <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
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information. The <info> element MUST have 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 several elements. It gives
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.
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 a
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, though media
mixing will not become active until the <mixing-start-time>.
<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
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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
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. See Section 4.2 for more details.
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 occur.
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
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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
<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
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 Identity
4.3.4.1.1.1 Interpreting the <id> Element
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.?
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4.3.4.1.1.2 Matching Any Identity
The <any> element is used to match any participant. This allows a
conference to be open to anyone.
4.3.4.1.1.3 Matching Unauthenticated Identities
The <unauthenticated> element is used to match unauthenticated
participants. That is, participants that have provided no
authenticated identity to the conference focus.
4.3.4.1.1.4 Matching AnonymousIdentities
The <anonymous> element is used to match participants that have
provided an authenticated identity to the conference focus, but have
requested anonymity in the conference itself.
4.3.4.1.1.5 Matching Referred Identities
The <has-been-referred> element can be used to match those
participants that the focus has referred to the conference.
4.3.4.1.1.6 Matching Invited Identities
The <has-been-invited> element can be used to match those
participants that the focus has invited into the conference.
4.3.4.1.1.7 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.
4.3.4.1.1.8 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.
4.3.4.1.1.9 Matching Key Participant Identities
The <key-participant> element can be used to match those participants
that are key participants of a conference.
4.3.4.1.1.10 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.
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4.3.4.1.1.11 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.
4.3.4.1.1.12 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.
4.3.4.1.1.13 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
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:
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<rule id="2">
<conditions>
<identity>
<id>358401234567</id>
</identity>
<pin>67890</pin>
</conditions>
<actions>
<join-handling>allow</join-handling>
</actions>
<transformations/>
</rule>
4.3.4.1.1.14 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.
OPEN ISSUE: Is a simple block/allow sufficient here, or should the
subscription handling be similar to e.g. presence, and have three
states (block, confirm, allow), or possibly even four states
(block, confirm, polite-block, allow)?
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.
OPEN ISSUE: Is a simple block/allow sufficient here, or should the
subscription handling be similar to e.g. presence, and have three
states (block, confirm, allow), or possibly even four states
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(block, confirm, polite-block, allow)?
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:
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.
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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.
4.3.4.2.6 Modifying Conference setting
The <allow-modify-settings> element represents a boolean action. If
set to TRUE, the identity is allowed to modify the conference
settings in the conference policy. If set to FALSE, any
modifications to the conference settings are rejected.
If this element is undefined it has a value of FALSE, causing the
modifications to be rejected.
4.3.4.2.7 Modifying Conference Information
The <allow-modify-information> element represents a boolean action.
If set to TRUE, the identity is allowed to modify the conference
information in the conference policy. If set to FALSE, any
modifications to the conference information are rejected.
If this element is undefined it has a value of FALSE, causing the
modifications to be rejected.
4.3.4.2.8 Modifying Conference Time
The <allow-modify-time> element represents a boolean action. If set
to TRUE, the identity is allowed to modify the conference time in
the conference policy. If set to FALSE, any modifications to the
conference time are rejected.
If this element is undefined it has a value of FALSE, causing the
modifications to be rejected.
4.3.4.2.9 Modifying Authorization rules
The <allow-modify-authorization-rules> element represents a boolean
action. If set to TRUE, the identity is allowed to modify the
authorization rules of a conference in the conference policy. If set
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to FALSE, any modifications to the rules are rejected.
If this element is undefined it has a value of FALSE, causing the
modifications to be rejected.
4.3.4.2.10 Modifying Conference Dial-out List
The <allow-modify-dol> element represents a boolean action. If set
to TRUE, the identity is allowed to modify the conference dial-out
list in the conference policy. If set to FALSE, any modifications to
the dial-out list are rejected.
If this element is undefined it has a value of FALSE, causing the
modifications to be rejected.
4.3.4.2.11 Modifying Conference Refer List
The <allow-modify-rl> element represents a boolean action. If set to
TRUE, the identity is allowed to modify the conference refer list in
the conference policy. If set to FALSE, any modifications to the
refer list are rejected.
If this element is undefined it has a value of FALSE, causing the
modifications to be rejected.
4.3.4.2.12 Modifying Conference Security Control
The <allow-modify-sc> element represents a boolean action. If set to
TRUE, the identity is allowed to modify the conference security
control settings in the conference policy. If set to FALSE, any
modifications to the security control settings are rejected.
If this element is undefined it has a value of FALSE, causing the
modifications to be rejected.
4.3.4.2.13 Modifying Conference Floor Policy
The <allow-modify-fp> element represents a boolean action. If set to
TRUE, the identity is allowed to modify the conference floor policy
in the conference policy. If set to FALSE, any modifications to the
floor policy are rejected.
If this element is undefined it has a value of FALSE, causing the
modifications to be rejected.
4.3.4.2.14 Modifying Conference media streams
The <allow-modify-ms> element represents a boolean action. If set to
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TRUE, the identity is allowed to modify the conference media streams
in the conference policy. If set to FALSE, any modifications to the
media streams are rejected.
If this element is undefined it has a value of FALSE, causing the
modifications to be rejected.
4.3.4.2.15 Creating Sidebars
The <allow-sidebar> element represents a boolean action. If set to
TRUE, the identity is allowed to create and manipulate a sidebar by
creating and modifying a <sidebar> element in a conference policy.
If set to FALSE, any sidebar creation and manipulation is rejected.
If this element is undefined it has a value of FALSE, causing the
modifications to be rejected.
4.3.4.2.16 Modifying Conference Dial-in List
The conference dial-in list is virtual and is not represented by a
physical list in the conference policy. It is rather a collection of
authorization rules that allow users to join a conference. The
<allow-modify-dil> element represents a boolean action. If set to
TRUE, the identity is allowed to create an authorization rule in the
conference policy that give a user a join handling of "allow" (See
Section 4.3.4.2.3. If set to FALSE, any modifications to
authorization rules are rejected.
If this element is undefined it has a value of FALSE, causing the
modifications to be rejected.
4.3.4.2.17 Authenticating a User
The <authenticate> element defines the mechanism used by the
conference focus to authenticate a user. This element is an
enumerated integer type, with defined values of:
none: This action instructs the focus not to authenticate the user.
This action has a value of zero and it is the lowest value of the
<authenticate-user> element. This action is the default action
taken in the absence of any other actions.
asserted-id: This action instructs the focus to authenticate the
user by asserting their identity using means outside the scope of
this document (for example, using digest-AKA). This action has a
value of one.
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shared-secret: This action instructs the focus to authenticate the
user using a shared secret (for example, using digest). This
action has a value of two.
certificate: This action instructs the focus to authenticate the
user using a certificate (for example, using PGP). This action
has a value of three.
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.
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.
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If this element is undefined, it has a value of FALSE, causing no
conference information to being shown.
OPEN ISSUE: Do we require more granularity for this element?
Perhaps an enumerated integer type, with defined levels of
information about the conference, or a set of boolean
transformations, each granting a single piece of conference
information, like the ability to see "sidebar" elements?
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.
4.3.5 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. The <target> element includes the mandatory 'uri'
attribute. The <target> element can be extended.
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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
mid-conference refers as well.
The <refer-list> element is optional and identical to the
<dialout-list> element in Section 4.3.5.
4.3.7 Conference Security Control
The conference security currently encompasses one aspects: the
integrity and confidentiality of the signalling messages.
The conference security settings start with the optional
<security-control> element.
We define two mechanisms for securing the signaling between users and
the focus: TLS and S/MIME. TLS is used to provide transport layer
security on a hop-by-hop basis. According to SIP [5], using SIPS URI
scheme in a request signifies that TLS must be used to secure each
hop over which the request is forwarded until the request reaches the
SIP entity responsible for the domain portion of the Request-URI.
The <security-mechanism> element inside the <security-control>
element has 2 boolean attributes: 'tls' and 's-mime'. When the 'tls'
attribute is set to "true" (thus implying the use of SIPS URI scheme,
if SIP is used as the signaling protocol), it is required that TLS is
used end-to-end. In other words, TLS must be used also on the last
hop between the entity responsible for the domain portion of the
Request-URI and the conference policy server.
If end-to-end confidentiality of entire signalling protocol messages
is not required by the conference policy, but it is required that the
message bodies within the signalling protocol messages are encrypted,
the 's-mime' attribute must have a value "true".
TLS and S/MIME may be required independent of each other. In other
words, it may be required to use neither, one, or both depending on
the settings of these attributes.
4.3.8 Conference Floor Policy
The absence of the <floor-policy> element from an XML document
indicates that the conference does not have a floor.
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One or more <floor> elements can appear in the <floor-policy>
element. The number of those elements indicates how many floors the
conference can have. The <floor> element contains the required
'floor-control' attribute that uniquely identifies a floor and
indicates the floor control protocol URI. It also contains the
required boolean attribute 'moderator-controlled' that indicates if
the floor is moderator controlled or not.
A floor can be used for one or more media streams; the mandatory
<media-streams> element can contain zero or more of the <video>,
<audio>, <application>, <data> ,<control>, <message>, and <text>
elements indicating the media of the floor. Other media types can be
defined by extensions. Each media stream is identified with the
'media-id' attribute. This attribute is mandatory and MUST be unique
for all media streams in a conference. It is used to correlate the
conference media stream in Section 4.3.9 with the ones for a floor.
It is also used to correlate the media streams used in the signalling
protocols with those in the conference policy, used, for example, in
SDP "i" field [19].
A floor can be controlled using many algorithms; the mandatory
<algorithm> element MUST contain one and only of the
<moderator-controlled>, <fcfs>, and <random> elements indicating the
algorithm.
The <max-floor-users> element in the <floor> element is optional and,
if present, dictates the maximum number of users who can have the
floor at one time. The optional <moderator-uri> indicates the URI of
the moderator. It MUST be set if the attribute moderator-controlled
is set to "true".
4.3.9 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 [18].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. The details of media manipulation are
defined elsewhere. User with sufficient privileges is allowed to
create, modify and delete the media policy (e.g. add new media
types).
The definition starts with the optional <media-streams> element.
This element lists the media streams allowed for this conference.
The format of this mirrors that of the <media-streams> element in
floor policy in Section 4.3.8. The absence of this element indicates
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that the conference will use media according to the focus local
policy.
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
o The <target> 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 <security-control> element to allow new security setting for a
conference to be introduced into
o The <algorithm> element in <floor-policy> to allow new algorithms
to be introduced into how a floor is granted
o The <floor> element in <floor-policy> to allow extensions to floor
policy for a floor
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">
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<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="Target" minOccurs="0"/>
<xs:element name="refer-list" type="Target" minOccurs="0"/>
<xs:element name="security-control" type="ConferenceSC" minOccurs="0"/>
<xs:element name="floor-policy" type="ConferenceFloorPolicy" 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" minOccurs="1" maxOccurs="unbounded"/>
<xs:element name="max-participant-count" type="xs:nonNegativeInteger" 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>
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<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>
<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>
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</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="identity" substitutionGroup="condition">
<xs:complexType>
<xs:choice>
<xs:element name="id" type="xs:anyURI"/>
<xs:sequence>
<xs:element name="domain" type="xs:string"/>
<xs:sequence minOccurs="0">
<xs:element name="except" type="xs:anyURI" 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:anyURI" maxOccurs="unbounded"/>
</xs:sequence>
</xs:sequence>
</xs:choice>
</xs:complexType>
</xs:element>
<xs:element name="unauthenticated" type="xs:string" substitutionGroup="condition"/>
<xs:element name="anonymous" 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" substitutionGroup="action">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="block"/>
<xs:enumeration value="allow"/>
<xs:enumeration value="confirm"/>
</xs:restriction>
</xs:simpleType>
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</xs:element>
<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="allow-modify-settings" type="xs:boolean" substitutionGroup="action"/>
<xs:element name="allow-modify-information" type="xs:boolean" substitutionGroup="action"/>
<xs:element name="allow-modify-time" type="xs:boolean" substitutionGroup="action"/>
<xs:element name="allow-modify-authorization-rules" type="xs:boolean" substitutionGroup="action"/>
<xs:element name="allow-modify-dol" type="xs:boolean" substitutionGroup="action"/>
<xs:element name="allow-modify-rl" type="xs:boolean" substitutionGroup="action"/>
<xs:element name="allow-modify-sc" type="xs:boolean" substitutionGroup="action"/>
<xs:element name="allow-modify-fp" type="xs:boolean" substitutionGroup="action"/>
<xs:element name="allow-modify-ms" type="xs:boolean" substitutionGroup="action"/>
<xs:element name="allow-sidebar" type="xs:boolean" substitutionGroup="action"/>
<xs:element name="allow-modify-dil" type="xs:boolean" substitutionGroup="action"/>
<xs:element name="authenticate" substitutionGroup="action">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="none"/>
<xs:enumeration value="digest-aka"/>
<xs:enumeration value="digest"/>
</xs:restriction>
</xs:simpleType>
</xs:element>
<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"/>
<!-- Target -->
<xs:complexType name="Target">
<xs:sequence>
<xs:element name="target" minOccurs="0" maxOccurs="unbounded">
<xs:complexType>
<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>
</xs:element>
</xs:sequence>
</xs:complexType>
<!-- Security Control (SC) -->
<xs:complexType name="ConferenceSC">
<xs:sequence>
<xs:element name="security-mechanism">
<xs:complexType>
<xs:attribute name="tls" type="xs:boolean" default="false"/>
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<xs:attribute name="s-mime" type="xs:boolean" default="false"/>
</xs:complexType>
</xs:element>
<xs:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
<!-- Conference Floor Control Policy -->
<xs:complexType name="ConferenceFloorPolicy">
<xs:sequence>
<xs:element name="floor" maxOccurs="unbounded">
<xs:complexType>
<xs:sequence>
<xs:element name="media-streams" type="ConferenceMediaStreams"/>
<xs:element name="algorithm">
<xs:complexType>
<xs:sequence>
<xs:element name="moderator-controlled" minOccurs="0"/>
<xs:element name="fcfs" minOccurs="0"/>
<xs:element name="random" minOccurs="0"/>
<xs:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="max-floor-users" type="xs:nonNegativeInteger" minOccurs="0" default="1"/>
<xs:element name="moderator-URI" type="xs:anyURI" minOccurs="0"/>
<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="floor-control" type="xs:anyURI"/>
<xs:attribute name="moderator-controlled" type="xs:boolean" default="false"/>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
<!-- Conference Media Streams -->
<xs:complexType name="ConferenceMediaStreams">
<xs:sequence>
<xs:element name="video" type="Media" minOccurs="0" maxOccurs="unbounded"/>
<xs:element name="audio" type="Media" minOccurs="0" maxOccurs="unbounded"/>
<xs:element name="application" type="Media" minOccurs="0" maxOccurs="unbounded"/>
<xs:element name="data" type="Media" minOccurs="0" maxOccurs="unbounded"/>
<xs:element name="control" type="Media" minOccurs="0" maxOccurs="unbounded"/>
<xs:element name="message" type="Media" minOccurs="0" maxOccurs="unbounded"/>
<xs:element name="text" type="Media" minOccurs="0" maxOccurs="unbounded"/>
<xs:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
<!-- Start/Stop time -->
<xs:complexType name="StartStopTime">
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<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>
<!-- Sidebar -->
<xs:complexType name="Sidebar">
<xs:sequence>
<xs:element name="uri" type="xs:anyURI" minOccurs="1" 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>
<!-- Media -->
<xs:complexType name="Media">
<xs:attribute name="media-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 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
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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.
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 manipulation URI in an element that carries a URI. 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.
In 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
reference is ignored.
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.
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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:
<rule id="2">
<conditions>
<identity>
<uri>bob@example.com</uri>
</identity>
</conditions>
<actions>
<join-handling>block</join-handling>
</actions>
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<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.
5.6 Floor Control Policy vs. Floor Control Protocol
Conference floor control is an optional feature provided by a
separate floor control protocol (FCP). However, creating a floor and
defining a floor policy belongs to CPCP. Moreover, setting some key
floor parameters, such as floor moderator in moderator controlled
floor policy, belongs to CPCP. FCP only defines how to request,
grant, deny and revoke a floor within given floor policy.
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For example, in a typical conference the privileged conference user
uses CPCP for creating a floor for audio plane, defining the floor
policy as "moderator-controlled" and appointing one user - possibly
himself - to act as a floor moderator governing the access to the
floor.
When the floor has been created and a floor moderator has been
assigned, the floor moderator gets notifications from the focus and
is able to accept or deny floor requests from the conference users.
Note that FCP does not create media streams (just the virtual floor
attached to media), as media streams are created using CPCP. The
details of FCP are beyond the scope of this draft.
6. An XCAP Usage for Conference Policy Manipulation
6.1 Application Unique ID
XCAP requires application usages to define a unique application usage
ID (AUID) in either the IETF tree or a vendor tree. This
specification defines the "conference-policy" AUID within the IETF
tree, via the IANA registration in Section 9.
6.2 Resource Interdependencies
The conference policy server MAY fill the conference URI(s), but the
client MUST propose a conference URI. If the CPS does not allow
assignments of URIs by the client, it rejects the request with a
"409" response and SHOULD include a body in the response detailing
the error. XCAP Base document [10] section 7.2.1 explains how such a
response body is constructed. The CPS MAY assign multiple conference
URIs to a conference, one for each call signaling protocol that it
supports. Section 4.3.1 discusses this is more detail.
Sidebar URIs are subject to the same behaviour.
6.3 Additional Constraints
These are defined within the XML structure definition.
6.4 Naming Conventions
There are no naming conventions that need to be defined for this
application usage.
6.5 Authorization Policies
A server can allow privileged users to modify documents that they
don't own. The establishment and indication of such policies is done
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by setting the authorization rules as described in Section 4.3.4.
6.6 MIME Type for CPCP XML Document
The MIME type for the CPCP XML document is defined in Section 4.1
7. Examples
The following is an example of a document compliant to the schema:
Below is an example how to create a conference:
7.1 An Example CPCP 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 conference allows side-bars
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
o Alice will be invited to join the conference while Sarah will be
referred to the conference.
o No TLS, will be used but S/MIME is required.
o PIN code is set to 13579 and password is set to abcd1234.
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o One floor is created for audio and a first-come-first-serve
policy.
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>
<allow-sidebar>true</allow-sidebar>
</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 >
<security-control>
<security-mechanism tls="false" s-mime="true"/>
<pin>13579</pin>
<password>abcd1234</password>
</security-control>
<floor-policy>
<floor floor-control="fcp://example.com/floorabc" moderator-controlled="false">
<media-streams>
<audio media-id="2"/>
</media-streams>
<algorithm>
<fcfs/>
</algorithm>
<max-floor-users>1</max-floor-users>
</floor>
</floor-policy>
<media-streams>
<video media-id="1"/>
<audio media-id="2"/>
</media-streams>
</conference>
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7.2 CPCP Manipulations Using XCAP
1. Creating a Conference
Continuing with the example from Section 7.1, Alice's client uses
XCAP to transport the conference policy to the conference policy
server
PUT
http://xcap.example.com/services/conferences/users/Alice/conference.xml HTTP/1.1 Content-Type:application/conference-policy+xml
Content-Type: application/conference-policy+xml
[conference policy from Section 7.1 goes here.
At exactly 2004-12-17T09:30:00-05:00, the focus sends SIP INVITE
request to Alice and a SIP REFER request to Sarah. At
2004-12-17T09:25:00-05:00, SIP INVITE requests can be accepted from
anyone at domain example.com. Any attempts to join the conference by
users in other domains are rejected.
2. Expelling a User
After the conference has started, Alice decides to expel Bob who has
joined the conference. So she modifies the authorization rule that
allows everyone at example.com to join:
PUT
http://xcap.example.com/services/conferences/users/Alice/conference.xml/~~/conference/authorization-rules/rule[@id=""]/conditions/identity/ HTTP/1.1
Content-Type:text/plain
<identity>
<domain>example.com</domain>
<except>bob@example.com</except>
</identity>
At this point, the focus sends a SIP BYE request to Bob ending Bob's
participation in the conference. This also guarantees that Bob
cannot rejoin the conference since he is explicitly blocked. Any
attempt Bob makes in rejoining the conference will fail.
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3. Allowing An Expelled Participant To Join Again
Continuing with the example above, Alice now decides to allow Bob to
join again after a period of time. She does so by rewriting parts of
the rule that blocks him from joining.
PUT
http://xcap.example.com/services/conferences/users/Alice/conference.xml/~~/conference/authorization-rules/rule[@id=""]/conditions/identity/ HTTP/1.1
Content-Type:text/plain
<identity>
<domain>example.com</domain>
</identity>
Bob can now rejoin the conference by sending a SIP INVITE request.
4. Allowing Sarah to Refer Users
Alice now decides that Sarah can ask the focus to refer users to the
conference:
PUT
http://xcap.example.com/services/conferences/users/Alice/conference.xml/~~/conference/authorization-rules/rule[@id="3"] HTTP/1.1
Content-Type:text/plain
<rule id="3">
<conditions>
<identity>
<uri>sarah@example.com</uri>
</identity>
</conditions>
<actions>
<allow-refer-users-dynamically>true</allow-refer-users-dynamically>
</actions>
<transformations/>
</rule>
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5. Removing A Conference
Alice now decides she no longer wants this conference to exist and
therefore deletes the conference:
DELETE
http://xcap.example.com/services/conferences/users/Alice/conference.xml
As a result of this action, the focus sends SIP BYE requests to all
current participants in the conference. The conference server
terminates the focus thereafter.
8. 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 PIN code, password of
the conference, 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
control settings for a conference. This can happen because the
conference policy it self 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 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
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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.
9. IANA Considerations
9.1 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.
9.2 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 9 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:
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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
9.3 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
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10. Contributors
Jose Costa-Requena
Simo Veikkolainen
Teemu Jalava
11. Acknowledgements
The authors would like to thank Markus Isomaki, Adam Roach, Eunsook
Kim, Roni Evan and the IETF XCON working group for their feedback and
suggestions.
12. References
12.1 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,
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",
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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.
[16] Franks, J., "HTTP Authentication: Basic and Digest Access
Authentication", RFC 2617, June 1999.
[17] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
12.2 Informative References
[18] Jennings, C. and B. Rosen, "Media Mixer Control for XCON",
draft-jennings-xcon-media-control-00 (work in progress),
February 2004.
[19] 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.
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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
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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Khartabil, et al. Expires January 14, 2005 [Page 46]
