XCON Working Group M. Barnes
Internet-Draft Nortel
Expires: April 4, 2006 C. Boulton
Ubiquity Software Corporation
O. Levin
Microsoft Corporation
Oct 2005
A Framework and Data Model for Centralized Conferencing
draft-ietf-xcon-framework-02
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on April 4, 2006.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document defines the framework for Centralized Conferencing.
The framework allows participants using various call signaling
protocols, such as SIP, H.323, Jabber and PSTN, to exchange media in
a centralized unicast conference. The Centralized Conferencing
Framework defines logical entities and naming conventions, along with
Barnes, et al. Expires April 4, 2006 [Page 1]
Internet-Draft XCON Framework Oct 2005
a conferencing data model. The framework also outlines a set of
conferencing protocols, which are complementary to the call signaling
protocols, for building advanced conferencing applications. The
framework binds all the defined components together for the benefit
of builders of conferencing systems.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Centralized Conferencing Data Model . . . . . . . . . . . . . 10
5.1. Common Conference Information . . . . . . . . . . . . . . 11
5.2. Conference Template . . . . . . . . . . . . . . . . . . . 12
5.3. Conference policies . . . . . . . . . . . . . . . . . . . 12
6. Centralized Conferencing Constructs and Identifiers . . . . . 13
6.1. Conference Identifier . . . . . . . . . . . . . . . . . . 13
6.2. Conference Object . . . . . . . . . . . . . . . . . . . . 13
6.2.1. Conference Object Identifier . . . . . . . . . . . . . 15
6.3. Conference User Identifier . . . . . . . . . . . . . . . . 15
7. Conferencing System Realization . . . . . . . . . . . . . . . 15
7.1. Cloning Tree . . . . . . . . . . . . . . . . . . . . . . . 16
7.2. Ad-hoc Example . . . . . . . . . . . . . . . . . . . . . . 19
7.3. Advanced Example . . . . . . . . . . . . . . . . . . . . . 20
7.4. Scheduling a conference . . . . . . . . . . . . . . . . . 22
8. Conferencing Mechanisms . . . . . . . . . . . . . . . . . . . 25
8.1. Call Signaling . . . . . . . . . . . . . . . . . . . . . . 25
8.2. Notifications . . . . . . . . . . . . . . . . . . . . . . 25
8.3. Conference Control Protocol . . . . . . . . . . . . . . . 25
8.3.1. CPCP . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.3.2. CCCP . . . . . . . . . . . . . . . . . . . . . . . . . 27
8.3.3. CSCP . . . . . . . . . . . . . . . . . . . . . . . . . 27
8.3.4. NETCONF . . . . . . . . . . . . . . . . . . . . . . . 28
8.3.5. SOAP . . . . . . . . . . . . . . . . . . . . . . . . . 28
8.4. Floor Control . . . . . . . . . . . . . . . . . . . . . . 28
9. Conferencing Scenario Realizations . . . . . . . . . . . . . . 30
9.1. Conference Creation . . . . . . . . . . . . . . . . . . . 30
9.2. Participant Manipulations . . . . . . . . . . . . . . . . 32
9.3. Media Manipulations . . . . . . . . . . . . . . . . . . . 34
9.4. Sidebar Manipulations . . . . . . . . . . . . . . . . . . 35
9.5. Whispering or Private Messages . . . . . . . . . . . . . . 37
9.6. Conference Announcements and Recordings . . . . . . . . . 37
10. Relationships between SIPPING and Centralized Conferencing
Frameworks . . . . . . . . . . . . . . . . . . . . . . . . . . 37
11. Security Considerations . . . . . . . . . . . . . . . . . . . 38
11.1. Authorization . . . . . . . . . . . . . . . . . . . . . . 38
Barnes, et al. Expires April 4, 2006 [Page 2]
Internet-Draft XCON Framework Oct 2005
11.2. Security and Privacy of Identity . . . . . . . . . . . . . 39
11.3. Floor Control Server Authentication . . . . . . . . . . . 40
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 40
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 40
14. Changes since last Version . . . . . . . . . . . . . . . . . . 40
15. Appendix A - Conference Object Identifier . . . . . . . . . . 44
15.1. Conference Object URI Definition . . . . . . . . . . . . . 47
16. Appendix B - Conference User Identifier . . . . . . . . . . . 47
16.1. Conference User Definition . . . . . . . . . . . . . . . . 49
17. References . . . . . . . . . . . . . . . . . . . . . . . . . . 49
17.1. Normative References . . . . . . . . . . . . . . . . . . . 49
17.2. Informative References . . . . . . . . . . . . . . . . . . 49
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 53
Intellectual Property and Copyright Statements . . . . . . . . . . 54
Barnes, et al. Expires April 4, 2006 [Page 3]
Internet-Draft XCON Framework Oct 2005
1. Introduction
This document defines the framework for Centralized Conferencing.
The framework allows participants using various call signaling
protocols, such as SIP, H.323, Jabber, or PSTN, to exchange media in
a centralized unicast conference. Other than references to general
functionality (e.g., establishment and teardown), details of these
call signaling protocols are outside the scope of this document
The Centralized Conferencing Framework defines logical entities and
naming conventions, along with a conferencing data model. The
framework also outlines a set of conferencing protocols, which are
complementary to the call signaling protocols, for building advanced
conferencing applications.
The Centralized Conferencing Framework is compatible with the
functional model presented in the SIPPING Conferencing Framework [9].
Section 10 of this document discusses the relationship between the
Centralized Conferencing Framework and the SIPPING Conferencing
framework, in the context of the Centralized Conferencing model
presented in this document.
2. Conventions
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
described in BCP 14, RFC 2119 [1] and indicate requirement levels for
compliant implementations.
3. Overview
A centralized conference is an association of endpoints, called
conference participants, with a central endpoint, called a conference
Focus. The Focus has direct peer relationships with the participants
by maintaining a separate call signaling interface with each.
Consequently, in this centralized conferencing model, the call
signaling graph is always a star.
The most basic conference supported in this model would be an ad-hoc
unmanaged conference, which would not necessarily require any of the
functionality defined within this framework. For example, it could
be supported using basic SIP signaling functionality with a
participant serving as the Focus; the SIPPING Conferencing Framework
[9] together with the SIP Call Control Conferencing for User
Agents[15] documents address these types of scenarios.
Barnes, et al. Expires April 4, 2006 [Page 4]
Internet-Draft XCON Framework Oct 2005
In addition to the basic features, however, a conferencing system
supporting the centralized conferencing model proposed in this
framework document can offer richer functionality, by including
dedicated conferencing applications with explicitly defined
capabilities, reserved recurring conferences, along with providing
the standard protocols for managing and controlling the different
attributes of these conferences.
The core requirements for centralized conferencing are outlined in
[10]. These requirements are applicable for conferencing systems
using various call signaling protocols, including SIP. Additional
conferencing requirements are provided in [12], [13], and [14].
The centralizing conferencing system proposed by this framework is
built around a fundamental concept of a conference object. A
conference object provides the data representation of a conference
during each of the various stages of a conference (e.g., creation,
reservation, active, completed, etc.). A conference object is
accessed via the logical functional elements, with whom a
conferencing client interfaces, using the various protocols
identified in Figure 1. The functional elements defined for a
conferencing system described by the framework are a Conference
Control Server, Floor Control Server, any number of Foci and a
Notification Service. A Conference Control Protocol (CCP) provides
the interface between a conference and media control client and the
conference control server. A Binary Floor Control Protocol (BFCP)
provides the interface between a floor control client and the floor
control server. A call signaling protocol (e.g., SIP, H.323, PSTN,
etc.) provides the interface between a call signaling client and a
Focus. A notification protocol (e.g. SIP Notify) provides the
interface between the conferencing client and the Notification
Service.
A conferencing system can support a subset of the conferencing
functions depicted in the conferencing system logical decomposition
in Figure 1 and described in this document. However, there are some
essential components that would typically be used by most other
advanced functions, such as the Notification Service. For example,
the notification service is used to correlate information, such as
list of participants with their media streams, between the various
other components.
Barnes, et al. Expires April 4, 2006 [Page 5]
Internet-Draft XCON Framework Oct 2005
...................................................................
. Conferencing System .
. .
. +-----------------------------------------------------+ .
. | C o n f e r e n c e o b j e c t | .
. +-+---------------------------------------------------+ | .
. | C o n f e r e n c e o b j e c t | | .
. +-+---------------------------------------------------+ | | .
. | C o n f e r e n c e o b j e c t | | | .
. | | | | .
. | | |-+ .
. | |-+ .
. +-----------------------------------------------------+ .
. ^ ^ ^ | .
. | | | | .
. v v v v .
. +-------------------+ +--------------+ +-------+ +------------+.
. | Conference Control| | Floor Control| |Foci | |Notification|.
. | Server | | Server | | | |Service |.
. +-------------------+ +--------------+ +-------+ +------------+.
. ^ ^ ^ | .
..............|.................|...........|..........|...........
| | | |
|Conference |Binary |Call |Notification
|Control |Floor |Signaling |Protocol
|Protocol |Control |Protocol |
| |Protocol | |
| | | |
..............|.................|...........|..........|...........
. V V V V .
. +----------------+ +------------+ +----------+ +------------+.
. | Conference | | Floor | | Call | |Notification|.
. | and Media | | Control | | Signaling| | Client |.
. | Control | | Client | | Client | | |.
. | Client | | | | | | |.
. +----------------+ +------------+ +----------+ +------------+.
. .
. Conferencing Client .
...................................................................
Figure 1: Conferencing System Logical Decomposition.
The media graph of a conference can be centralized, decentralized, or
any combination of both and potentially differ per media type. In
the centralized case, the media sessions are established between a
media mixer controlled by the focus and each one of the participants.
In the decentralized (i.e., distributed) case, the media graph is a
Barnes, et al. Expires April 4, 2006 [Page 6]
Internet-Draft XCON Framework Oct 2005
multicast or multi-unicast mesh among the participants.
Consequently, the media processing (e.g., mixing) can be controlled
either by the focus alone or by the participants. The concepts in
this framework document clearly map to a centralized media model.
The concepts can also apply to the decentralized media case, however,
the details of such are left for future study.
Section 5 of this document provides more details on the conference
object. Section 6 provides an overview of the identifiers necessary
to address and manage the conference objects, instances and users
associated with a conferencing system. Section 7 of this document
describes how a conferencing system is logically built using the
defined data model and how the conference objects are maintained.
Section 8 describes the fundamental conferencing mechanisms and
provides a high level overview of the protocols. Section 9 then
provides realizations of various conferencing scenarios, detailing
the manipulation of the conference objects using the defined
protocols. Section 10 of this document summarizes the relationship
between this Centralized Conferencing Framework and the SIPPING
Conferencing Framework.
4. Terminology
This Centralized Conferencing Framework document generalizes, when
appropriate, the SIPPING Conferencing Framework [9] terminology and
introduces new concepts, as listed below. Further details and
clarification of the new terms and concepts are provided in the
subsequent sections of this document.
Active conference: The term active conference refers to a conference
cbject that has been created and activated via the allocation of
its identifiers (e.g., conference object identifier and conference
identifier) and the associated focus. An active conference is
created based on either a system default conference blueprint or a
specific conference reservation.
Call Signaling protocol: The call signaling protocol is used between
a participant and a focus. In this context, the term "call" means
a channel or session used for media streams.
Common conference information: The common conference information is
the data type (i.e., the XML schema) which is used to represent
the core set of information for a conference object. This core
information includes a common set of definitions for basic
conference features, such as conference identifiers, membership,
signaling, capabilities and media types, applicable to a wide
range of conferencing applications.
Barnes, et al. Expires April 4, 2006 [Page 7]
Internet-Draft XCON Framework Oct 2005
Conference blueprint: A conference blueprint is a static conference
object within a conferencing system, which describes a typical
conference setting supported by the system. A conference
blueprint is the basis for creation of dynamic conference objects.
A system may maintain multiple blueprints, each comprised of the
common conference information, along with any number of templates.
Conference control protocol (CCP): A conference control protocol
provides the interface for data manipulation and state retrieval
for the centralized conferencing data, represented by the
conference object.
Conference factory: A conference factory is a logical entity, that
generates upon request, unique URI(s) to identify and represent a
conference focus.
Conference identifier (ID): A conference identifier is a call
signaling protocol-specific URI that identifies a conference focus
and its associated conference instance.
Conference instance: A conference instance refers to an internal
implementation of a specific conference, represented as a set of
logical conference objects and associated identifiers.
Conference object: A conference object represents a conference at a
certain stage (e.g., description upon conference creation,
reservation, activation, etc.), which a conferencing system
maintains in order to describe the system capabilities and to
provide access to the services available for each object
independently. The conference object schema is comprised of two
distinct sub components; the common conference information and the
conference template(s).
Conference object identifier (ID): A conference object identifier is
a URI which uniquely identifies a conference object and is used by
a conference control protocol to access and modify the conference
information.
Conference policies: Conference policies collectively refers to a set
of rights, permissions and limitations pertaining to operations
being performed on a certain conference object.
Conference reservation: A conference reservation is a conference
object, which is created from either a system default or client
selected blueprint.
Conference state: The conference state reflects the state of a
conference instance and is represented using a specific, well-
defined schema.
Conferencing system: Conferencing system refers to a conferencing
solution based on the data model discussed in this framework
document and built using the protocol specifications referenced in
this framework document.
Barnes, et al. Expires April 4, 2006 [Page 8]
Internet-Draft XCON Framework Oct 2005
Conference template: The conference template refers to the data type
(i.e. the XML schema) which is used to represent the media or
application specific part of the conference object. This
information represents enhanced conferencing features or
capabilities, such as media mixers, and/or user interface
abstractions.
Floor: Floor refers to a set of data or resources associated with a
conference instance, for which a conference participant, or group
of participants, is granted temporary access.
Floor chair: A floor chair is a floor control protocol compliant
client, either a human participant or automated entity, who is
authorized to manage access to one floor and can grant, deny or
revoke access. The floor chair does not have to be a participant
in the conference instance.
Focus: A focus is a logical entity that maintains the call signalling
interface with each participating client and the conference object
representing the active state. As such, the focus acts as an
endpoint for each of the supported signaling protocols and is
responsible for all primary conference membership operations
(e.g., join, leave, update the conference instance) and for media
negotiation/maintenance between a conference participant and the
focus.
Media graph: The media graph is the logical representation of the
flow of media for a conference.
Media mixer: A media mixer is the logical entity with the capability
to combine media inputs of the same type, transcode the media and
distribute the result(s) to a single or multiple outputs. In this
context, the term "media" means any type of data being delivered
over the network using appropriate transport means, such as RTP/
RTCP (defined in RFC 3550[7]) or Message Session Relay Protocol
(defined in [25]).
Registered conference document : A standards track document (i.e.,
RFC) that defines and registers a conference template schema with
the appropriate organization (e.g., IANA). A registered
conference document also includes any complementary textual
information.
Role: A role provides the context for the set of conference
operations that a participant can perform. A default role (e.g.,
standard conference participant) will always exist, providing a
user with a set of basic conference operations. Based on system
specific authentication and authorization, a user may take on
alternate roles, such as conference moderator, allowing access to
a wider set of conference operations.
Sidebar: TBD.
Barnes, et al. Expires April 4, 2006 [Page 9]
Internet-Draft XCON Framework Oct 2005
Whisper: TBD.
5. Centralized Conferencing Data Model
The centralized conference data model is logically represented by the
conference object. A conference object is of type 'Conference object
type', which is comprised of two distinct components: the 'Common
conference information type' and the 'Conference template type', as
illustrated in Figure 2. Each of these types is extensible for
including potentially multiple sub-types.
+------------------------------------------------------+
| C o n f e r e n c e o b j e c t t y p e |
| |
| +--------------------------------------------------+ |
| | Common conference information type | |
| | | |
| | +----------------------------------------------+ | |
| | | Conference description (times, duration) | | |
| | +----------------------------------------------+ | |
| | +----------------------------------------------+ | |
| | | Membership (roles, capacity, names) | | |
| | +----------------------------------------------+ | |
| | +----------------------------------------------+ | |
| | | Signaling (protocol, direction, status) | | |
| | +----------------------------------------------+ | |
| | +----------------------------------------------+ | |
| | | Floor information | | |
| | +----------------------------------------------+ | |
| | +----------------------------------------------+ | |
| | | Sidebars, Etc. | | |
| | +----------------------------------------------+ | |
| | | |
| +--------------------------------------------------+ |
| +--------------------------------------------------+ |
| | Conference template type | |
| | | |
| | - Mixer algorithm, inputs, and outputs | |
| | - Floor controls | |
| | - User Control Interface | |
| | - User's View | |
| | - Etc. | |
| +--------------------------------------------------+ |
| |
+------------------------------------------------------+
Barnes, et al. Expires April 4, 2006 [Page 10]
Internet-Draft XCON Framework Oct 2005
Figure 2: Conference Object Type Decomposition.
In a system based on this conferencing framework, the same conference
object type is used for representation of a conference during
different stages of a conference, such as expressing conferencing
system capabilities, reserving conferencing resources or reflecting
the state of ongoing conferences. Thus, each of the two components
(i.e., the common conference information and the conference template)
may be optionally included in a particular conference object.
Section 7 describes the usage semantics of the conference objects.
The centralized conferencing data model defined in this framework has
no strict separation between conference membership, conference media
information and the related policies. The policies are an integral
part of the data model and are realized by local, system level
boundaries associated with specific data elements, such as the
membership, and by the ranges and limitations on other data elements.
Additional policy considerations for a system realization based on
this data model are discussed in Section 5.3. The integration of the
data in this model meets the requirement of many conference control
operations to enable synchronized access to the integral conference
policies, to the conference state as a whole, and for receiving
notifications about changes to either using the same interface.
The exact XML schema of the Conference Object, including the
organization of the Common Conference Information and the Conference
Templates, are detailed in separate documents [ref: TBD].
5.1. Common Conference Information
The common conference information section contains the core
information that is utilized in any conference and is independent of
the specific conference media nature (e.g., the mixing algorithms
performed, the advanced floor control applied, etc.). Typically,
participants with read-only access to the conference information
would be interested in this common conference information only.
The common conference information may be represented using the
conference-type as defined in [11]. The conference-type contains the
definitions for representation of the conference object capabilities,
membership, roles, call signaling and media status relevant to
different stages of the conference life-cycle.
New centralized conferencing specifications can extend the basic
conference-type and introduce additional data elements to be used
within the common conference information type.
Barnes, et al. Expires April 4, 2006 [Page 11]
Internet-Draft XCON Framework Oct 2005
5.2. Conference Template
The concept of a conference template is introduced to separate the
complexity and the details of the "mixer" and other enhanced
conferencing features from the common conference information and to
allow for easy user interface abstraction for advanced conferencing
systems.
Each conference template needs to be registered with IANA. The IANA
registration needs to point to an RFC having the text description of
the feature behavior and the XML definition allowing the feature
presentation, configuration, and management. The RFCs defining these
templates are referred to as a registered conference document.
Typically, a conference template would contain the information about
the specific media mixing details, the associated client roles and
the available floor controls. This information would allow
authorized clients to manipulate the mixer's behavior via the focus,
and the resultant distribution of the media to all or individual
participants. By doing so, a client can change its own state and/or
state of other participants in the conference.
A conference template can also include an abstract user interface
definition in terms of sliders, radio boxes, etc. for simplifying
user interaction with a specific non-trivial feature.
5.3. Conference policies
Conference policies collectively refers to a set of rights,
permissions and limitations pertaining to operations being performed
on a certain conference object.
The set of rights describes the read/write access privileges for the
conference object as a whole. This access would usually be granted
and defined in terms of giving the read-only or read-write access to
clients with certain roles in the conference. As such, the policies
represented by the set of rights aren't explicitly defined within the
data model, but rather are reflected in the system realization
(Section 7).
The permissions and limits, however, are specified as an integral
part of the conference object type, with data objects containing the
allowed ranges for other data objects (e.g., maximum number of
participants) and lists of clients allowed to perform certain
operations on a conference object. For example, the "allowed to
join" list of participants is consulted to decide who is allowed to
join. The entries in the list can specify the identity of an
individual user (joe@example.com), a role, a domain (*@example.com),
Barnes, et al. Expires April 4, 2006 [Page 12]
Internet-Draft XCON Framework Oct 2005
etc. For further details, refer to the detailed data model [ref:
TBD].
A more general rule mechanism, beyond the functionality provided by
the permissions and limits, is an item for future study.
6. Centralized Conferencing Constructs and Identifiers
This section provides details of the identifiers associated with the
centralized conferencing framework constructs and the identifiers
necessary to address and manage the clients associated with a
conferencing system. An overview of the allocation, characteristics
and functional role of the identifiers is provided.
6.1. Conference Identifier
The conference identifier (conference ID) is a call signaling
protocol-specific URI that identifies a specific conference focus and
its associated conference instance. A conference factory is one
method for generating a unique conference ID, to identify and address
a conference focus, using a call signaling interface. Details on the
use of a conference factory for SIP signaling can be found in [15].
The conference identifier can also be obtained using the conference
control protocol [Section 8.3] or other, including proprietary, out-
of-band mechanisms.
6.2. Conference Object
A Conference object provides the logical representation of a
conference iInstance in a certain stage, such as a conference
blueprint representing a conferencing system's capabilities, the data
representing a conference reservation, and the conference state
during an active conference. Each conference object is independently
addressable through the conference control protocol interface
[Section 8.3].
Figure 3 illustrates the relationships between the conference
identifier, the focus and the conference object ID within the context
of a logical conference instance, with the conference object
corresponding to an active conference.
A conference object representing a conference in the active state can
have multiple call signalling conference identifiers; for example,
for each call signalling protocol supported. There is a one-to-one
mapping between an active conference object and a conference focus.
The focus is addressed by explicitly associating unique conference
IDs for each signaling protocol supported by the active conference
Barnes, et al. Expires April 4, 2006 [Page 13]
Internet-Draft XCON Framework Oct 2005
object.
......................................................................
. Conference Instance .
. .
. .
. +---------------------------------------------------+ .
. | Conference Object Identifier | .
. | | .
. | | .
. +---------------------------------------------------+ .
. ^ ^ .
. | | .
. v | .
. ................................................... | .
. . Focus . | .
. . . | .
. . +----------------------------------+ . | .
. . |Conference Identifier (Protocol Y)| . | .
. . +------------------------------------+ | . | .
. . | Conference Identifier (PSTN) | | . | .
. . +--------------------------------------+ |-+ . | .
. . | Conference Identifier (SIP) | |^ . | .
. . | |-+| . | .
. . | |^ | . | .
. . +--------------------------------------+| | . | .
. ............^...............................|.|.... | .
. | | | | .
................|...............................|.|......|............
| | | |
|SIP | | |Conference
| PSTN | |Y |Control
| | | |Protocol
| +---------------+ | |
| | | |
| | | |
v v v v
+----------------+ +--------------+ +---------------+
| Conferencing | | Conferencing | | Conference |
| Client | | Client | | Client |
| 1 | | 2 | | X |
+----------------+ +--------------+ +---------------+
Figure 3: Identifier Relationships for an Active Conference.
Barnes, et al. Expires April 4, 2006 [Page 14]
Internet-Draft XCON Framework Oct 2005
6.2.1. Conference Object Identifier
In order to make each conference object externally accessible, the
conferencing system allocates a unique URI per distinct conference
object in the system. A conference control protocol includes the
conference object identifier in requests for directly manipulating a
particular conference object and for obtaining its current state.
The conference object identifier logically maps to other protocol
specific identifiers associated with the conference instance, such as
the BFCP 'confid'. A full description and semantics of how the
conference object identifier is created and used is defined in
Section 15.
6.3. Conference User Identifier
Each user within a conferencing system is allocated a unique
conference user identifier. The user identifier is used in
association with the conference object identifier to uniquely
identify a user within the scope of conferencing system. There is
also a requirement for identifying conferencing system users who may
not be participating in a conference instance. Examples of these
users would be a non participating 'Floor Control Chair' or 'Media
Policy Controller'. The conference user identifier is required in
conference control protocol requests to uniquely determine who is
issuing commands, so that appropriate policies can be applied to the
requested command. The conference user identifer is logically
associated with the other user identifiers assigned to the
conferencing client for other protocol interfaces, such as an
authenticated SIP user. A full description and semantics of the
conference user identifier is provided in Section 16
7. Conferencing System Realization
Implementations based on this centralized conferencing framework can
range from systems supporting ad-hoc conferences, with default
behavior only, to sophisticated systems with the ability to schedule
recurring conferences, each with distinct characteristics, being
integrated with external resource reservation tools, and providing
snapshots of the conference information at any of the stages of the
conference life-cycle.
A conference object is the logical representation of a conference
instance at a certain stage, such as capabilities description upon
conference creation, reservation, activation, etc., which a
conferencing system maintains in order to describe the system
capabilities and to provide access to the available services provided
by the conferencing system. Consequently, this centralized
Barnes, et al. Expires April 4, 2006 [Page 15]
Internet-Draft XCON Framework Oct 2005
conferencing framework does not mandate the actual usage of the
conference object, but rather defines the general cloning tree
concept and the mechanisms required for its realization, as described
in detail in Section 7.1.
Adhoc and advanced conferencing examples are provided in Section 7.2
and Section 7.3, with the latter providing additional description of
the Conference Object in terms of the stages of a conference, to
support scheduled and other advanced conference capabilities. The
scheduling of a conference based on these concepts and mechanisms is
then detailed in Section 7.4
As discussed in Section 5.3, there are conference policies implicit
in and derivable from the data in the conference objects and there
are also policies applying to the conference objects as a whole. In
the examples in this section, these latter policies are shown
logically associated with the conference objects, however, it is an
implementation specific mechansim as to how these policies are
managed and applied to the conference objects.
7.1. Cloning Tree
The concept defined in this section is a logical representation only,
as it is reflected through the centralized conferencing mechanisms:
the URIs and the protocols. Of course, the actual system realization
can differ from the presented model. The intent is to illustrate the
role of the logical elements in providing an interface to the data,
based on conferencing system and conferencing client actions, and
describe the resultant protocol implications
Any conference object in a conferencing system is created by either
being explicitly cloned from an existing parent object or being
implicitly cloned from a default system conference blueprint. A
conference blueprint is a static conference object used to describe a
typical conference setting supported by the system. Each system can
maintain multiple blueprints, typically each describing a different
conferencing type using the common conference information format,
along with any number of template definitions This document uses the
"cloning" metaphor instead of the "inheritance" metaphor because it
more closely fits the idea of object replication, rather than a data
type re-usage and extension concept.
The cloning operation needs to specify whether the link between the
parent and the child needs to be maintained in the system or not. If
no link between the parent and the child exists, the objects become
independent and are not impacted by any operations on the parent
object nor subject to any limitations of the parent object.
Barnes, et al. Expires April 4, 2006 [Page 16]
Internet-Draft XCON Framework Oct 2005
Once the new object is created, it can be addressed by a unique
conference object URI assigned by the system, as described in
Section 15 /[ref:TBD]. By default, the newly created object contains
all the data existing in the parent object. The newly created object
can expand the data it contains, within the schema types supported by
the parent. It can also restrict the read/write access to its
objects. However, unless the object is independent, it cannot relax
the access relative to its parent's access.
Any piece of data in the child object can be independently accessed
and, by default, can be independently modified without affecting the
parent data.
Unless the object is independent, the parent object can enforce a
different policy by marking certain data elements as "parent
enforceable". The values of these data elements can not be changed
by directly accessing the child object; neither can they be expanded
in the child object alone.
Figure 4 illustrates an example of a conference (Parent B), which is
created independent of its Parent (Parent A). Parent B creates two
child objects, Child 1 and Child 2. Any of the data elements of
Parent B can be modified (i.e. there are no "parent enforceable" data
elements) and depending upon the element, the changes will be
reflected in Child 1 and Child 2 , whereas changes to Parent A will
not impact the data elements of Parent B. Any "parent enforceable"
data elements as defined by Parent B cannot be modified in the child
objects.
Barnes, et al. Expires April 4, 2006 [Page 17]
Internet-Draft XCON Framework Oct 2005
+---+-----------------------+
| p | |
| o | P A R E N T A |
| l | |
| i | C O N F E R E N C E |
| c | |
| i | O B J E C T |
| e | |
+-s-+-----------------------+
|
\| /
\/ INDEPENDENT
/\
/| \
V
+---+-----------------------+
| p | |
| o | P A R E N T B |
| l | |
| i | C O N F E R E N C E |
| c | |
| i | O B J E C T |
| e | |
+-s-+-----------------------+
| |
| |
| ---------------------------
| |
V V
+---+-----------------------+ +---+-----------------------+
| p | | | p | |
| o | C H I L D 1 | | o | C H I L D 2 |
| i | | | l | |
| l | C O N F E R E N C E | | i | C O N F E R E N C E |
| i | | | c | |
| c | O B J E C T | | i | O B J E C T |
| i | | | e | |
+-s-+-----------------------+ +-s-+-----------------------+
Figure 4: The Cloning Tree.
Using the defined cloning model and its tools, the following sections
show examples of how different systems based on this framework can be
realized.
Barnes, et al. Expires April 4, 2006 [Page 18]
Internet-Draft XCON Framework Oct 2005
7.2. Ad-hoc Example
Figure 5 illustrates how an ad-hoc conference can be created and
managed in a conferencing system. A client can create a conference
by establishing a call signaling channel with a conference factory as
specified in Section 6.1. The conference factory can internally
select one of the system supported conference blueprints based on the
requesting client privileges and the media lines included in the SDP
body.
The selected blueprint with its default values is copied by the
server into a newly created conference object, referred to as an
'Active Conference'. At this point the conference object becomes
independent from its blueprint. A new conference object identifier,
a new conference identifier and a new focus are allocated by the
server.
During the conference lifetime, an authorized client can manipulate
the conference object, such as adding participants, using the
Conference Control Protocol [Section 8.3].
+---+-----------------------+
| p | |
| o | System Default |
| l | |
| i | Conference |
| c | |
| i | Blueprint |
| e | |
+-s-+-----------------------+
|
\| /
\/
/\
/| \
V
+---+-----------------------+
| p | |
| o | Active |
| l | |
| i | Conference |
| c | |
| i | |
| e | |
+-s-+-----------------------+
Barnes, et al. Expires April 4, 2006 [Page 19]
Internet-Draft XCON Framework Oct 2005
Figure 5: Conference Ad-hoc Creation and Lifetime.
7.3. Advanced Example
Figure 6 illustrates how a recurring conference can be specified
according to system capabilities, scheduled, reserved, and managed in
a conferencing system. A client would first query a conferencing
system for its capabilities. This can be done by requesting a list
of the conference blueprints the system supports. Each blueprint
contains a specific combination of capabilities and limitations of
the conference server in terms of supported media types (e.g., audio,
video, text, or combinations of these), participant roles, maximum
number of participants of each role, availability of floor control,
controls available for participants, availability and type of
sidebars, the definitions and names of media streams, etc.
A client may need to query any templates in the blueprints that it
doesn't understand and then make a decision on compatibility.
Interface hints need to be included as per [21]. The client then
selects which specific templates to use and retrieves the templates
from the server itself, rather than from a centralized repository.
The selected blueprint with its default values is cloned by the
client into a newly created conference object, referred to as a
conference reservation, that specifies the resources needed from the
system for this conference instance. At this point the conference
reservation becomes independent from its blueprint. The client can
also change the default values, within the system ranges, and add
additional information, such as the list of participants and the
conference start time, to the conference reservation.
At this point the client can ask the conference server to create new
conference reservations by attaching the conference reservation to
the request. As a result, the server can allocate the needed
resources, create the additional conference objects for the child
conference reservations and allocate the conference object
identifiers for all - the original conference reservation and for
each child conference reservation.
From this point on, any authorized client is able to access and
modify each of the conference objects independently. By default,
changes to an individual child conference reservation will affect
neither the parent conference reservation, from which it was created,
nor its siblings.
On the other hand, some of the conference sub-objects, such as the
maximum number of participants and the participants list, can be
defined by the system as parent enforceable. As a result, these
Barnes, et al. Expires April 4, 2006 [Page 20]
Internet-Draft XCON Framework Oct 2005
objects can be modified by accessing the parent conference
reservation only. The changes to these objects can be applied
automatically to each of the child reservations, subject to local
policy.
+---+-----------------------+
| p | |
| o | Selected |
| l | |
| i | Conference |
| c | |
| i | Blueprint |
| e | |
+-s-+-----------------------+
|
\| /
\/
/\
/| \
V
+---+-----------------------+
| p | |
| o | Conference |
| l | |
| i | Reservation |
| c | |
| i | |
| e | |
+-s-+-----------------------+
| | |
| | |
| | |
| | |
+---|--|--V-----------------+
+-+---|--V------------------+ |
+-+-+---V-------------------+ | |
| p | | | |
| o | Child Conference | | |
| l | | | |
| i | Reservation | | |
| c | | | |
| i | | |-+
| e | |-+
+-s-+-----------------------+
Figure 6: Advanced Conference Definition, Creation, and Lifetime.
Barnes, et al. Expires April 4, 2006 [Page 21]
Internet-Draft XCON Framework Oct 2005
When the time comes to schedule the conference reservation, either
via the system determination that the 'start' time has been reached
or via client invocation, an active conference is cloned based on the
conference reservation. As in the adhoc example, the active
conference is independent from the parent and changes to the
conference reservation will not impact the active conference. Any
desired changes must be targeted towards the active conference. An
example of this interaction is shown in Section 9.1
7.4. Scheduling a conference
The capability to schedule conferences forms an important part of the
conferencing system solution. An individual conference reservation
typically has a specified 'start' and 'end' time, with the times
being specified relative to a single specified 'fixed' time (e.g.,
'start' = 09.00 GMT, 'end'= 'start'+2), subject to system
considerations. In most advanced conferencing solutions it is
possible to not only schedule an individual occurrence of a
conference reservation, but also schedule a series of related
conferences (e.g., a weekly meeting that starts on Thursday at 09.00
GMT).
To be able to achieve such functionality, a conferencing system needs
to be able to appropriately schedule and maintain conference
reservations that form part of a recurring conference. The mechanism
proposed in this document makes use of the 'Internet Calendaring and
Scheduling Core Object' specification defined in RFC2445[8] in union
with the concepts introduced in Section 5 for the purpose of
achieving advanced conference scheduling capability.
Figure 7 illustrates a simplified view of a client interacting with a
conferencing system. The client is using the Conference Control
Protocol (Section 8.3) to add a new conference reservation to the
conferencing system by interfacing with the conference control
server. A CCP request contains a valid conference reservation and
reference by value to an 'iCal' object which contains scheduling
information about the conference (e.g., start time, end time).
Barnes, et al. Expires April 4, 2006 [Page 22]
Internet-Draft XCON Framework Oct 2005
+--------------+ +-------Conferencing System-----------------+
| Generic ICAL | | |
| Resource | | ..Conference Instance.... |
+--------------+ | . . +-----------+|
^ ^ | . +-------------------+ . | Conference||
| | | . |Conference Objects |<--| Control ||
| ----------------->. +-------------------+ . | Server ||
| | . . +-----------+|
| | ......................... ^ |
| | ^ | |
+-----|--------------+ | | |
| v | | |
| +--------------+ | | |
| | Resource |<------------------+ | |
| | Scheduler | | |
| +--------------+ | |
| | |
+---------------------------------------------------------|------+
|
|
+-Request-+
| |
+----+ |
|ICAL| |
+----+----+
|
|
|
Conference Control|
Protocol |
|
+-------------+
| Conferencing|
| Client |
+-------------+
Figure 7: Resource Scheduling
A CCP request to create a new conference reservation is validated,
including the associated iCal object, and the resultant conference
reservation is created. The conference reservation is uniquely
represented within the conferencing system by a conference object
identifier (e.g., xcon:hd87928374) as introduced in Section 6.2 and
defined in [ref:TBD]. This unique URI is returned to the client and
can be used to reference the conference reservation, if any future
manipulations are required (e.g., alter start time), using a CCP
request.
Barnes, et al. Expires April 4, 2006 [Page 23]
Internet-Draft XCON Framework Oct 2005
The previous example explains how a client creates a basic conference
reservation using an iCal reference in association with a conference
control protocol. Figure 7 can also be applied when explaining how a
series of conferences are scheduled in the system. The description
is almost identical with the exception that the iCal definition that
is included in a CCP request represents a series of recurring
conference instances (e.g., conference start time, end time, occur
weekly). The conferencing system will treat this request the same as
the first example. The CCP request will be validated, along with the
associated iCal object, and the conference reservation is created.
The conference reservation and its conference object ID created for
this example represent the entire series of recurring conference
instances rather than a single Conference. If the client uses the
conference object ID provided and a CCP request to adjust the
conference reservation, every conference instance in the series will
be altered. This includes all future occurrences, such as a
conference scheduled as an infinite series, subject to the
limitations of the available calendaring interface.
A conferencing system that supports the scheduling of a series of
conference instances should also be able to support manipulation
within a specific range of the series. A good example is a
conference reservation that has been scheduled to occur every Monday
at 09.00 GMT. For the next three weeks only, the meeting has been
altered to occur at 10.00 GMT in an alternative venue. With Figure 7
in mind, the client will construct a CCP request whose purpose is to
modify the existing conference reservation for the recurring
conference instance. The client will include the conference object
ID provided by the conferencing system to explicitly reference the
conference reservation within the conferencing system. A CCP request
will contain all the required changes to the conference reservation
(e.g., change of venue).
The conferencing system matches the incoming CCP request to the
existing conference reservation but identifies that the associated
iCal object only refers to a range of the existing series. The
conferencing system creates a child, by cloning the original
conference reservation, to represent the altered conference instances
within the series. The cloned child object is not independent of the
original parent object, thus preventing any potential conflicts in
scheduling (e.g., a change to the whole series 'start time'). The
cloned conference reservation, representing the altered series of
conference instances, has its own associated conference object ID
which is returned to the client using a CCP response. This
conference object ID is then used by the client to make any future
alterations on the newly defined sub-series. This process can be
repeated any number of times as the newly returned conference object
ID representing an altered (cloned) series of conference instances,
Barnes, et al. Expires April 4, 2006 [Page 24]
Internet-Draft XCON Framework Oct 2005
can itself be manipulated using a CCP request for the newly created
conference object ID . This provides a flexible approach to the
scheduling of recurring conference instances.
8. Conferencing Mechanisms
8.1. Call Signaling
The focus is the central component of the conference. Participants
interface with the focus using an appropriate call signaling
protocol. Participants request to establish or join a conference
using the call interface. After checking the applicable policies, a
focus then either accepts the request, sends a progress indication
related to the status of the request (e.g., for a parked call while
awaiting moderator approval to join) or rejects that request using
the call signaling interface.
During an active conference, a Conference Control Protocol
[Section 8.3] can be used to affect the conference state. For
example, CCP requests to add and delete participants are communicated
to the focus and checked against the conference policies. If
approved, the participants are added or deleted using the call
signaling to/from the focus.
8.2. Notifications
A conferencing system is responsible for implementing a Conference
Notification Service. The Conference Notification Service provides
updates about the conference instance state to authorized parties,
including participants. A model for notifications using SIP is
defined in [11].
The conference user identifier and associated role are used by the
conferencing system to filter the notifications such that they
contain only information that is allowed to be sent to that user.
8.3. Conference Control Protocol
The conference control protocol provides for data manipulation and
state retrieval for the centralized conferencing data, represented by
the conference object. The details of the conference control
protocol are detailed in separate documents [references TBD].
[Editor's note: The remaining paragraphs and subsections of this
section should be removed from this document once the WG reaches
consensus and a high level overview of the requirements for the
conference control protocol should be provided here. However, until
Barnes, et al. Expires April 4, 2006 [Page 25]
Internet-Draft XCON Framework Oct 2005
the WG reaches that consensus (and agrees the fundamental
requirements) it seems premature to remove these details from this
document.]
The proposals for the conference control protocol under discussion
span from data manipulation (management-like) protocols (CPCP and
NETCONF) to semantic-oriented (CCCP and CSCP) . Details of the
proposed protocols are in the sections below. The following
paragraphs summarize the fundamental issues around the selection of
the protocol(s). [Editor's Note: Discussion Point 5 on the XCON WG
mailing list].
It is recognized that semantic manipulations make for a cleaner
protocol design, with the disadvantage that extensions to the
underlying data model require extensions to the protocol used to
manipulate it. Syntactic manipulations allow for extensions to the
data model without requiring protocol extensions, with the
disadvantage that the server generally has to infer intent from data
manipulations instead of having intent explicitly signaled.
It is worth noting that one portion of the data to be manipulated,
the Common Conference Information, will not be extended, and would
naturally lend itself to semantic manipulation. Another part of the
data, the Conference Template, is intended to be extended, and would
naturally lend itself to syntactic manipulation. However, there has
been a stated desire to use a single protocol (and presumably a
single mode of operation within this protocol) to manipulate all
conference object state (common and template).
The third statement in the paragraph above makes the first two
solution options mutually exclusive. A proposal was made that by
allowing more than one protocol, a hybrid approach could be taken
such that CPCP and CSCP can both be used, since they are based on
other protocols that are likely to be supported by the clients (XCAP
and BFCP, respectively). However, the very rough consensus of the WG
supports a single protocol for Conference Control and SOAP has most
recently been put forth as that protocol. A basic overview of SOAP
in the context of Conference control is provided in Section 8.3.5
8.3.1. CPCP
A Conference Policy Control Protocol (CPCP) is a data manipulation
protocol being proposed as a standard means of storing and
manipulating the conference policy. According to CPCP, the
conference policy is comprised of the rules associated with a
specific conference instance. Requirements for the CPCP are defined
in the CPCP Requirements document [13]. The Conference Policy
Control Protocol document [17] defines the XML Schema for the
Barnes, et al. Expires April 4, 2006 [Page 26]
Internet-Draft XCON Framework Oct 2005
conference policy data elements.
The privileges as to which users are allowed to read and/or
manipulate a specific conference instance are defined in a separate
Extensible Markup Language (XML) Schema[19]. This schema is based on
the common policy model being used for geographic privacy information
and for presence information.
A separate document [18] proposes XCAP as one protocol mechanism for
storing and manipulating this conferencing policy data. XCAP is a
HTTP 1.1 based protocol that allows clients to read, write, modify
and delete application data stored in XML format on a server. One of
the main advantages of XCAP is that it maps XML document elements and
attributes to HTTP URIs that can be directly accessed by HTTP.
8.3.2. CCCP
A Centralized Conferencing Control Protocol [20] is a semantic-
oriented protocol defined to allow participants or otherwise
authorized entities to directly manipulate an active conference
instance. CCCP is defined as a set of transactions issued over a
reliable transport protocol. A transaction consists of a Request
carrying the required information in an XML body and a corresponding
Response carrying an appropriate XML body.
CCCP requests are submitted to the CCCP server and can be prioritized
and queued, based on the CCCP client Role and the requested
primitives. CCCP requires no single lock per document, and the CCCP
server can locally implement an optimization strategy independent of
CCCP client behavior.
8.3.3. CSCP
A Conference State Change protocol [26] is a client server protocol
used to change the state of a conference object. CSCP extends the
BFCP protocol [16] with new commands. A client sends the server a
request representing a sequence of commands. Each command can set,
get, add, or delete a single field in the conference object. Changes
to the conference object are performed on a hierarchal set of
elements and unique attributes within those elements. A series of
changes can be pipelined in a single BFCP message. The server
executes each action in series. If one of them fails, the server
returns an error for the action that failed and does not execute any
of the actions after that. Each individual action is atomic but the
pipelined series is not.
The item to which a command applies is specified by a unique ID and,
where appropriate, attribute name. The ID is an unsigned 32 bit
Barnes, et al. Expires April 4, 2006 [Page 27]
Internet-Draft XCON Framework Oct 2005
integer called the Element ID. The server discovery of the Element
ID is outside of CSCP. Typically this is done by using the
conference notification service per Section 8.2. Each field in the
data received in the notification contains a unique field ID
attribute that can be used in BFCP requests.
8.3.4. NETCONF
The Network Configuration (NETFCONF) protocol [27] defines a simple
mechanism through which a network device can be managed,
configuration data information can be retrieved, and new
configuration data can be uploaded and manipulated. The protocol
allows the device to expose a full, formal, application programming
interface (API).
NETCONF is proposed as the mechanism for object content manipulation
and state retrieval for the centralized conferencing data. NETCONF
provides a flexible configuration retrieval mechanism, with
extensibility. It allows for incremental configuration and commits.
NETCONF supports stored configurations (e.g., for startup, running,
etc.). It also supports XPath and subtree filtering. With NETCONF,
there are no constraints on the configuration content.
8.3.5. SOAP
The SOAP protocol is fundamentally an XML messaging scheme, capable
of supporting remote procedure calls. SOAP defines a simple message
format composed of a "header" and a "body" contained within an
"envelope". The "header" contains meta-information relating to the
message, and can be used to indicate such things as store-and-forward
behaviour or transactional characteristics. In addition, SOAP
encoding is optimized for ease of automated deserialization.
SOAP is proposed as the mechanism for object content manipulation and
state retrieval for the centralized conferencing data. In general,
SOAP is a good fit for Conference Control, essentially because of its
remote procedure call characteristics and its inherently synchronous
and client-driven nature.
8.4. Floor Control
A floor control protocol allows an authorized client to manage access
to a specific floor and to grant, deny or revoke access of other
conference users to that floor. Floor control is not a mandatory
mechanism for a conferencing system implementation but provides
advanced media input control features for conference users. A
mechanism for floor control within a conferencing system is defined
in the Binary Floor Control Protocol specification [16]. [Editor's
Barnes, et al. Expires April 4, 2006 [Page 28]
Internet-Draft XCON Framework Oct 2005
note: Evaluation of an alternative proposal, as a stand alone draft,
for using Templates as the means for correlating Floor Control
identifiers has been proposed. If/when this work is done, it needs
to be introduced and referenced here].
Within this framework, a client supporting floor control needs to
obtain information for connecting to a floor control server to enable
it to issue floor requests. This connection information can be
retrieved using information provided by mechanisms such as
negotiation using the SDP[2] offer/answer[5] exchange on the
signaling interface with the focus. Section 11.3 provides a
discussion of client authentication of a floor control server.
As well as the client to the floor control server connection
information, a client wishing to interact with a floor control server
requires access to additional information. This information
associates floor control interactions with the appropriate floor
instance. Once a connection has been established and authenticated
(see [16] for authentication details), a specific floor control
message requires detailed information to uniquely identify a
conference, a user and a floor.
The conference is uniquely identifed by the conference object ID per
Section 6.2.1. This conference object ID must be included in all
floor control messages. When the SDP model is used as described in
[24] this identifier maps to the 'confid' SDP attribute.
Each authorized user associated with a conference object is uniquely
represented by a conference user ID per Section 6.3. This conference
user ID must be included in all floor control messages. When using
SDP offer/answer exchange to negotiate a Floor control connection
with the focus using the call signaling interface, the unique
conference identifier is contained in the 'userid' SDP attribute, as
defined in [24]
A media session witin a conferencing system can have any number of
floors (0 or more) that are represented by the conference identifer.
When using SDP offer/answer exchange to negotiate a floor control
connection with the focus using the call signaling interface, the
unique conference identifier is contained in the 'floorid' SDP
attribute, as defined in [24] e.g., a=floorid:1 m-stream:10 . Each
'floorid' attribute, representing a unique floor, has an 'm-stream'
tag containing one or more identifiers. The identifiers represent
individual SDP media sessions (as defined using 'm=' from SDP) using
the SDP 'Label' attribute as defined in [23].
Barnes, et al. Expires April 4, 2006 [Page 29]
Internet-Draft XCON Framework Oct 2005
9. Conferencing Scenario Realizations
This section addresses how advanced conferencing scenarios, many of
which have been described in [14], are realized using this
centralized conferencing framework. The objective of this section is
to further illustrate the model, mechanisms and protocols presented
in the previous sections and also serves to validate that the model,
mechanisms and protocols are sufficient to support advanced
conferencing scenarios.
9.1. Conference Creation
There are different ways to create a conference. A participant can
create a conference using call signaling means only, such as SIP and
detailed in [15]. For a conferencing client to have more flexibility
in defining the charaterisitics and capabilities of a conference, a
conferencing client would implement a conference control protocol
client. By using a conference control protocol, the client can
determine the capabilities of a conferencing system and its various
resources.
Figure 8 provides an example of one client "Alice" determining the
conference blueprints available for a particular conferencing system
and creating a conference based on the desired blueprint. It should
be noted that not all entities impacted by the request are shown in
the diagram (e.g., Focus), but rather the emphasis is on the new
entities introduced by this centralized conferencing framework.
Barnes, et al. Expires April 4, 2006 [Page 30]
Internet-Draft XCON Framework Oct 2005
+--------------------------------+
| Conferencing System |
"Alice" | +------------+|
+--------+ | | ||
| |CCP Request <blueprints> | +-----------+ | ||
| Client |-------------------------->|Conference | |Conference ||
| |<--------------------------|Control |~~~>|Blueprint(s)||
+--------+CCP Response<blueprintA, | |Server | | ||
... | +-----------+ +------------+|
blueprintZ, | |
confUserID> | |
"Alice" |
+--------+ | |
| |CCP Request <reserve, | +------------+|
| | blueprintAConfObjID,| +-----------+ | ||
| Client |-------------------------->|Conference | |Conference ||
| | confUserID> | |Control |~~~>|BlueprintA ||
| |<--------------------------|Server | | ||
| |CCP Response | | | +------------+|
+--------+ <reservationConfObjID, | | | \|/ |
confID> | | | /|\ |
| | | V |
| | | +------------+|
| | |~~~>|Conference ||
| | | |Reservation ||
| +-----------+ +------------+|
"Alice" | | |
+--------+ | | |
| |CCP Request <add, | V |
| |reservationConfObjID, | +-----------+ +------------+|
| Client |-------------------------->|Conference | |Active ||
| | confID,confUserID> | |Control |~~~>|Conference ||
| |<--------------------------|Server | | ||
| |CCP Response | | | +------------+|
+--------+ <activeConfObjID, | | | |
confID> | +-----------+ |
+--------------------------------+
Figure 8: Client Creation of Conference using Blueprints
Upon receipt of the Conference Control Protocol request for
blueprints, the conferencing system would first authenticate "Alice"
(and allocate a conference user identifier, if necessary) and then
Barnes, et al. Expires April 4, 2006 [Page 31]
Internet-Draft XCON Framework Oct 2005
ensure that "Alice" has the appropriate authority based on system
policies to receive any blueprints supported by that system. Any
blueprints that "Alice" is authorized to use are returned in a
response, along with the conference user ID.
Upon receipt of the Conference Control Protocol response containing
the blueprints, "Alice" determines which blueprint to use for the
conference to be created. "Alice" creates a conference object based
on the blueprint (i.e., clones) and modifies applicable fields, such
as membership list and start time. "Alice" then sends a request to
the conferencing system to create a conference reservation based upon
the updated blueprint.
Upon receipt of the Conference Control Protocol request to "reserve"
a conference based upon the blueprint in the request, the
conferencing system ensures that blueprint received is a valid
blueprint (i.e. the values of the various field are within range).
The conferencing system determines the appropriate read/write access
of any users to be added to a conference based on this blueprint
(using membership, roles, etc.). The conferencing system uses the
received blueprint to clone a conference reservation. The
conferencing system also reserves or allocates a conference ID to be
used for any subsequent protocol requests from any of the members of
the conference. The conferencing system maintains the mapping
between this conference ID and the conference object ID associated
with the reservation through the conference instance.
Upon receipt of the conference control protocol response to reserve
the conference, "Alice" can now create an active conference using
that reservation or create additional reservations based upon the
existing reservations. In this example, "Alice" has reserved a
meetme conference bridge. Thus, "Alice" provides the conference
information, including the necessary conference ID, to desired
participants. When the first participant, including "Alice",
requests to be added to the conference, an active conference and
focus are created. The focus is associated with the conference ID
received in the request. Any participants that have the authority to
manipulate the conference would receive the conference object
identifier of the active conference in the response.
9.2. Participant Manipulations
There are different ways to affect a participant state in a
conference. A participant can join and leave the conference using
call signaling means only, such as SIP. This kind of operation is
called "1st party signaling" and does not affect the state of other
participants in the conference.
Barnes, et al. Expires April 4, 2006 [Page 32]
Internet-Draft XCON Framework Oct 2005
Limited operations for controlling other conference participants (a
so called "3rd party control") through the Focus, using call
signaling only, may also be available for some signaling protocols.
For example, "Conferencing for SIP User Agents" [15] shows how SIP
with REFER can be used to achieve this functionality.
In order to perform richer conference control a user client needs to
implement a conference control protocol client. By using a
conference control protocol, the client can affect its own state,
state of other participants, and state of various resources (such as
media mixers) which may indirectly affect the state of any of the
conference participants.
Figure 9 provides an example of one client "Alice" impacting the
state of another client "Bob". This example assumes an established
conference. In this example, "Alice" wants to add "Bob" to the
conference.
It should be noted that not all entities impacted by the request are
shown in the diagram (e.g., Focus), but rather the emphasis is on the
new entities introduced by this centralized conferencing framework.
+--------------------------------+
| Conferencing System |
"Alice" | +---------+--+|
+--------+ | |policies | ||
| |CCP Request < | +-----------+ +---------+ ||
| Client |-------------------------->|Conference | | Active ||
| | Conference Object ID, | |Control |~~~>|Conference ||
+--------+ Add, "Bob" > | |Server | | ||
| +-----------+ +-------+ ||
| |"Alice"| ||
"Bud" | ' ' '|
+--------+ NOTIFY <"Bob"="added"> |+------------+ ' ' '|
| |<-------------------------|Notification|<~~~| ||
| Client |. . ||Service | +-------+ ||
+--------+--+ . || | |"Bob" | ||
| |<----------------------| | +-------+----+|
| Client |NOTIFY <"Bob"="added">|+------------+ |
+--------+ +--------------------------------+
"Bob"
Barnes, et al. Expires April 4, 2006 [Page 33]
Internet-Draft XCON Framework Oct 2005
Figure 9: Client Manipulation of Conference - Add a party
Upon receipt of the Conference Control Protocol request to "add" a
party ("Bob") in the specific conference as identified by the
conference object ID, the conferencing system ensures that "Alice"
has the appropriate authority based on the policies associated with
that specific conference object to perform the operation. The
conferencing system must also determine whether "Bob" is already a
user of this conferencing system or whether he is a new user.
If "Bob" is a new user for this conferencing system, a Conference
User Identifier is created for Bob. Based upon the addressing
information provided for "Bob" by "Alice", the call signaling to add
"Bob" to the conference is instigated through the Focus.
Once the call signaling indicates that "Bob" has been successfully
added to the specific conference, per updates to the state, and
depending upon the policies, other participants (including "Bob") may
be notified of the addition of "Bob" to the conference via the
Conference Notification Service.
9.3. Media Manipulations
There are different ways to manipulate the media in a conference. A
participant can change its own media streams by, for example, sending
re-INVITE with new SDP content using SIP only. This kind of
operations is called "1st party signaling" and they do not affect the
state of other participants in the conference.
In order to perform richer conference control a user client needs to
implement a conference control protocol client. By using a
conference control protocol, the client can manipulate the state of
various resources, such as media mixers, which may indirectly affect
the state of any of the conference participants.
Figure 10 provides an example of one client "Alice" impacting the
media state of another client "Bob". This example assumes an
established conference. In this example, the client, "Alice" whose
Role is "moderator" of the conference, wants to mute "Bob" on a
medium-size multi-party conference, as his device is not muted (and
he's obviously not listening to the call) and background noise in his
office environment is disruptive to the conference.
It should be noted that only entities impacted by the request are
shown in the diagram (e.g., there is no Focus shown).
Barnes, et al. Expires April 4, 2006 [Page 34]
Internet-Draft XCON Framework Oct 2005
+--------------------------------+
| Conferencing System |
"Alice" | +---------+--+|
+--------+ | |policies | ||
| |CCP Request < | +-----------+ +---------+ ||
| Client |-------------------------->|Conference | |Active ||
| | Conference Object ID, | |Control |~~~>|Conference ||
+--------+ Mute, "Bob" > | |Server | | ||
| +-----------+ +-------+ ||
| |"Alice"| ||
| ' ' '|
+--------+ NOTIFY <"Bob"=mute"> |+------------+ ' ' '|
| |<-------------------------|Notification|<~~~| ||
| Client |. . ||Service | +-------+ ||
+--------+--+ . || | |"Bob" | ||
| |<----------------------| | +-------+----+|
| Client | NOTIFY <"Bob"=mute">|+------------+ |
+--------+ +--------------------------------+
Figure 10: Client Manipulation of Conference - Mute a party
Upon receipt of the Conference Control Protocol request to "mute" a
party ("Bob") in the specific conference as identified by the
conference object ID, the Conference Server ensures that "Alice" has
the appropriate authority based on the policies associated with that
specific conference object to perform the operation. "Bob's" status
is marked as "recvonly" and the Conference Template of the Conference
Object (if included) is updated to reflect that "Bob's" media is not
to be "mixed" with the conference media.
Depending upon the policies, other participants (including "Bob") may
be notified of this change via the Conference Notification Service.
9.4. Sidebar Manipulations
A sidebar can be viewed as a separate Conference instance that only
exists within the context of a parent conference instance. Although
viewed as an independent conference instance, it can not exist
without a parent. A sidebar is created using the same mechanisms
employed for a standard conference as described in Section 7.1.
A conference object representing a sidebar is created by cloning the
parent associated with the existing conference and updating any
information specific to the sidebar. A sidebar conference object is
Barnes, et al. Expires April 4, 2006 [Page 35]
Internet-Draft XCON Framework Oct 2005
implicitly linked to the parent conference object (i.e. it is not an
independent object) and is associated with the parent conference
object identifier as as shown in Figure 11. A conferencing system
manages and enforces the parent and appropriate localized
restrictions on the sidebar conference object (e.g., no members from
outside the parent conference instance can join, sidebar conference
can not exist if parent conference is terminated, etc.).
+--------------+
| Conference |
| Object |
| Identifier |
+--------------+
|
|
|
+---------------------+---------------------+
| | |
+-------+-------+ +-------+-------+ +-------+-------+
| Sidebar | | Sidebar | | Sidebar |
| Conference | | Conference | | Conference |
| Object | | Object | | Object |
| Identifier | | Identifier | | Identifier |
+-------+-------+ +-------+-------+ +---------------+
Figure 11: Conference Object Mapping.
Figure 11 illustrates the relationship between a conference object
and associated Sidebar conference objects within a conferencing
system. Each Sidebar conference object has a unique conference
object Identifier as described in Section 6.2.1. The main conference
object identifier acts as a top level identifier for associated
sidebars.
A sidebar conference object Identifier follows many of the concepts
outlined in the cloning tree model described in Section 7.1. A
Sidebar conference object contains a subset of members from the
original Conference object. Properties of the sidebar conference
object can be manipulated by a Conference Control Protocol
(Section 8.3) using the unique conference object identifier for the
sidebar. It is also possible for the top level conference object to
enforce policy on the sidebar object (similar to parent enforceable
as discussed in Section 7.1).
[Editor's Note: this needs more detail - especially around cloning
tree, including an example scenario such as a sidebar which still
Barnes, et al. Expires April 4, 2006 [Page 36]
Internet-Draft XCON Framework Oct 2005
receives the visual media from the main conference, but has audio
within the sidebar. The example would use some of the mechanisms
shown in previous sections (e.g. create a new sidebar conference,
cloned from the existing active conference, manipulate the media, add
participants.]
9.5. Whispering or Private Messages
[Editor's Note: TBD. Once we get full agreement on terminology and
the basic ideas in the other sections, we'll tackle this.]
9.6. Conference Announcements and Recordings
[Editor's note: TBD. Use Cullen's comments on the previous version
of the doc .]
10. Relationships between SIPPING and Centralized Conferencing
Frameworks
The SIPPING Conferencing Framework [9] provides an overview of a wide
range of centralized conferencing solutions known today in the
conferencing industry. The document introduces a terminology and
logical entities in order to systemize the overview and to show the
common core of many of these systems. The logical entities and the
listed scenarios in the SIPPING Conferencing Framework are being used
to illustrate how SIP [4] can be used as a signaling means in these
conferencing systems. SIPPING Conferencing Framework does not define
new conference control protocols to be used by the general
conferencing system. It uses only basic SIP [4], the SIP
Conferencing for User Agents [15], and the SIPPING Conference Package
[9] for basic SIP conferencing realization.
This centralized conferencing framework document defines a particular
centralized conferencing system and the logical entities implementing
it. It also defines a particular data model and refers to the set of
protocols (beyond call signaling means) being defined by the XCON WG
to be used among the logical entities for implementing advanced
conferencing features. The purpose of the XCON working group and
this framework is to achieve interoperability between the logical
entities from different vendors for controlling different aspects of
advanced conferencing applications.
The logical entities defined in the two frameworks are not intended
to be mapped one-to-one. The two frameworks differ in the
interpretation of the internal conferencing system decomposition and
the corresponding operations. Nevertheless, the basic SIP [4], the
SIP Conferencing for User Agents [15], and the SIPPING Conference
Barnes, et al. Expires April 4, 2006 [Page 37]
Internet-Draft XCON Framework Oct 2005
Package [9] are fully compatible with both Framework documents.
11. Security Considerations
There are a wide variety of potential attacks related to
conferencing, due to the natural involvement of multiple endpoints
and the many, often user-invoked, capabilities provided by the
conferencing system. Examples of attacks include the following: an
endpoint attempting to listen to conferences in which it is not
authorized to participate, an endpoint attempting to disconnect or
mute other users, and theft of service, by an endpoint, in attempting
to create conferences it is not allowed to create.
There are several issues surrounding security of this conferencing
framework. One set of issues involves securing the actual protocols
and the associated authorization mechanisms. This first set of
issues should be addressed in the specifications specific to the
protocols described in Section 8. The protocols used for
manipulation and retrieval of confidential information MUST support a
confidentiality and integrity mechanism. Similar requirements apply
for the floor control protocols. Section 11.3 discusses an approach
for client authentication of a floor control server.
There are also security issues associated with the authorization to
perform actions on the conferencing system to invoke specific
capabilities. Section 5.3 discusses the policies associated with the
conference object to ensure that only authorized entities are able to
manipulate the data to access the capabilities. The final set of
issues involves the privacy and security of the identity of a user in
the conference, which is discussed in Section 11.2
11.1. Authorization
Many policy authorization decisions are based on the identity of the
user or the role that a user may have. There are several ways that a
user might authenticate its identity to the system. The conferencing
system may know about specific users and assign passwords to the
users. The users may also be authenticated by knowing a particular
conference ID and a PIN for it. Sometimes, a PIN is not required and
the conference ID is used as a shared secret. The call signaling
means can provide a trusted form of the user identity or it might
just provide a hint of the possible identity and the user still needs
to provide some authentication to prove it has the identity that was
provided as a hint in the call signaling. This may be in the form of
an IVR system or other means. The goal for the conferencing system
is to figure out a user identity and a role for any attempt to send a
request to the conferencing system.
Barnes, et al. Expires April 4, 2006 [Page 38]
Internet-Draft XCON Framework Oct 2005
When a conferencing system presents the identity of authorized users,
it may choose to provide information about the way the identity was
proven to or verified by the system. A user may also come as a
completely unauthenticated user into the system - this fact needs
also be communicated to interested parties.
When guest users interact with the system, it is often in the context
of a particular conference. In this case, the user may provide a PIN
or a password that is specific to the conferences and authenticates
the user to take on a certain role in that conference. The guest
user can then perform actions that are allowed to any user with that
role.
The term password is used to mean the usual, that is to say a
reasonable sized, in number of bits, hard to predict shared secret.
Today users often have passwords with more than 30 bits of randomness
in them. PIN is a special password case - a shared secret that is
only numeric and often contains a fairly small number of bits (often
as few as 10 bits). When conferencing systems are used for audio on
the PSTN, there is often a need to authenticate using a PIN.
Typically if the user fails to provide the correct PIN a few times in
a row, the PSTN call is disconnected. The rate of making the calls
and getting to the point to enter a PIN makes it fairly hard to do an
exhaustive search of the PIN space even for 4 digit PINs. When using
a high speed interface to connect to a conferencing system, it is
often possible to do thousands of attempts per second and the PIN
space could quickly be searched. Because of this, it is not
appropriate to use PINs for authorization on any of the interfaces
that provide fast queries or many simultaneous queries.
11.2. Security and Privacy of Identity
This conferencing system has an idea of the identity of a user but
this does not mean it can reveal this identity to other users, due to
privacy considerations. Users can set select various options for
revealing their identity to other users. A user can be "hidden" such
that other users can not see they are involved in the conference, or
they can be "anonymous" such that users can see that another user is
there, but not see the identity of the user, or they can be "public"
where other users can see their identity. If there are multiple
"anonymous" users, other parties will be able to see them as
independent "anonymous" parties and will be able to tell how many
"anonymous" parties are in the conference. Note, that the visibility
to other participants is dependent on their roles. For example,
users' visibility (including "anonymous" and "hidden") may be
displayed to the moderator or administrator, subject to a
conferencing system's local policies. "Hidden" status is often used
by robot participants of a conference (e.g., call recording) and is
Barnes, et al. Expires April 4, 2006 [Page 39]
Internet-Draft XCON Framework Oct 2005
also used in many call center situations.
11.3. Floor Control Server Authentication
Clients can authenticate a floor control server using the TLS
certificates. Requests submitted on a successfully created
connection between the client and floor control server may
additionally require digest authentication within the BFCP protocol
to authenticate the floor control client to the server. For this to
take place, a shared secret needs to be exchanged between the floor
control client/server entities. This can be achieved out of band
using a mechanism such as the 'k=' SDP attribute. The shared secret
can also be exchanged using un-specified 'out of band' mechanisms.
When using Digest authentication of floor control client messages the
exchange of an active 'Nonce' is also required. This can be achieved
using a BFCP request response interaction as defined in BFCP (A
request is submitted without a Nonce TLV and the server generates an
error response with either an Error Code 7 (DIGEST TLV Required) or 6
(Invalid Nonce) containing the valid nonce). The BFCP 'Nonce' value
can also be obtained 'out of band' using information provided in the
offer/answer exchange. As with the other SDP Floor attributes
referenced in this section and defined in [24], the 'nonce' attribute
can be inserted in the SIP response e.g., a=nonce:dhsa8hd0dwqj.
[Editor's Note: May need more specifics on fetching from the
conference object the credentials required for BFCP. This includes
the conference id, user id, and password.]
12. IANA Considerations
This is an informational draft, with no IANA considerations required.
13. Acknowledgements
This document is a result of architectural discussions among IETF
XCON working group participants. The authors would like to thank
Henning Schulzrinne for the "Conference Object Tree" proposal and
general feedback, Cullen Jennings for providing input for the
"Security Considerations" section and Keith Lantz, Dave Morgan, Oscar
Novo, Roni Even, Umesh Chandra and Avshalom Houri for their reviews
and constructive input.
14. Changes since last Version
Changes from WG 01 to 02::
Barnes, et al. Expires April 4, 2006 [Page 40]
Internet-Draft XCON Framework Oct 2005
- Editorial nits -i.e. consistent terminology, capatilization, etc.
- Revamped abstract and introduction
- Global removal of XCON as a qualifier (we had previously done this
in a previous version with all the identifiers).
- Global change of "call control signalling" to "call signaling"
- Moved the terminology section after the Overview section:
- - Modified the definitions to be more concise and per some of
Henning's recommendations.
- - Added definitions for blueprint and conference reservation.
- Clarified the definition of policy and added more explicit text as
to how policy is accomplished via the data model and system
realization (section 4.3 and 6.1)
- Removed the Editor's note/text in section 4 about the options for
the schema; added a reference to a TBD schema document.
- Section 5:
- - clarified the identifiers. Kept the logical definition as
"identifiers", although most will be realized as URIs.
- - deleted the section on conference instance.
- - removed the term "umbrella" from sections conference User and
conference object identifier sections
- - moved alot of detail from Conference User Identifier and
conference Object Identifier sections into appendices, and added
additional detail, that will become the basis for separate documents.
- In section 6:
- - added a bit of explanation as to the intent of the cloning tree
model - it's not implementation binding, but rather to illustrate the
data model and context for the protocol interactions.
- - removed the term copying altogether. Cloning is the model and
the idea is that the cloned object contains data indentical to the
parent when it was created (whether it gets "copied" or whatever from
the parent is an implementation issue).
Barnes, et al. Expires April 4, 2006 [Page 41]
Internet-Draft XCON Framework Oct 2005
- - introduce the blueprint concept in section 6.1 prior to its
implied usage in 6.2 and 6.3.
- - removed the usage of the term occurrence (which is just a child
reservation).
- Removed security related details from Floor Control section and
moved those to the security section. As a result removed most of the
editorial notes from the front of the Floor control section and
integrated the remaining ones inline into that section, where the
resolution should be documented.
- Section 8:
- - Added new example 8.1 - conference creation
- - Added a placeholder for a more detailed example to the sidebar
section to show a sidebar which has some media specifically
associated with the sidebar (i.e. audio), yet still use the main
conference for other media (visual presentation).
- Section 11: As a result of adding additional information to the
security section, divided this section into subsections for clarity.
Changes from WG 00 to 01::
- Section 2 (Conventions and Terminology). Slight modifications to
definitions of Call (control) signaling, Conference Identifer,
Conference Instance, Conference Object.
- Section 2 (Conventions and Terminology).Renaming of term
"Registered Template Definition" to "Registered Conference Document"
(per agreement at interim meeting).
- Section 3 (Next to the last paragraph on the media model).
Clarified the text such that it doesn't read that the focus performs
media mixing. Changed "focus" to "media mixer controlled by the
focus" in the 2nd sentence and "performed" to "controlled" in the
4th.
- Section 5. Rearranged the sub-sections a bit for better flow.
First describe the Conference ID, then the Conference Instance,
followed by the Conference Object, with the Conference Object
Identifer described in a subsection of the Conference Object section.
Added a diagram showing the relationship between Conference
Identifer/Focus and Conference Object Identifier, within the context
of a Conference Instance to the Conference Object section.
Barnes, et al. Expires April 4, 2006 [Page 42]
Internet-Draft XCON Framework Oct 2005
- Section 6.1 (Cloning Tree). Rewording to clarify which operations
apply to independent objects (and non-independent).
- Section 6.3 (Advanced Example). Added additional text with regards
to future conferences, introducing the concept of infinite series
(which would be limited by calendaring interface).
- Section 7.3 (Conference Control Protocol). Updated to include
reference to SOAP option.
- Section 8.3 (sidebars) - reworded 1st paragraph to be more explicit
about the XCON FW constructs used.
Changes from individual 02 to WG 00:
- few minor editorial changes
- Section 2. Removed second sentence of definition of Conference ID,
as that's now included/described in context in new Identifier
section.
- Section 3. Clarified that TBD in Figure 1 is "Conference Control
Protocol" (per Keith's comment to be more explicit).
- Section 4.1. Identifiers. Moved this to a new section (
Section 6).
- New section for Identifiers ( Section 6), thus all section
references beyond 4 are incremented in the new version.
- Section 4. Since section 4.1 was removed, section 4.2 became the
body text for section 4.
- Section 4.2. Added "Floor Information" to Figure 2 as part of
Common Conference Information, also added "Floor Control" to
Conference Template (per text and Cullen's draft).
- Section 4.5. Conference policies. Reworded to not introduce new
terms, but use the general terms identified in the 1st paragraph.
- Section 5.2. Removed "Instance" from "Active Conference Instance"
in Figure 4.
- Section 5.3. Added text clarifying that templates are retrieved
from server (not central repository) (per DP3 conclusion).
- Section 5.4. Added text that there is a single time and that the
times are all relative the one time (per DP1 conclusion).
Barnes, et al. Expires April 4, 2006 [Page 43]
Internet-Draft XCON Framework Oct 2005
- Section 5.4. Added text clarifying that changes to a series impact
"all future occurrences (per DP1 discussion/conclusion).
- Section 6.3 - Added subsections for discussion of CSCP and NETCONF
as the CCP.
- Section 6.4 - Floor Control. Removed Editor's notes 2 and 3.
Condensed the text only slightly, but added explicit references to
new identifier section.
- Section 6.4.1 Moved to new Identifier section ( Section 6)
- Section 7.1 - moved example to 7.2. Included a new (more
appropriate example) in 7.1, although this may be too basic.
- Section 7.3 - added some proposed text for Sidebars.
15. Appendix A - Conference Object Identifier
[Editors Note: This appendix will be incorporated in a separate
specification in the next release of this document and will include
all relevant detail.]
The conference object URI can be viewed as a key to accessing a
specific conference object. It is used by the Conference Control
Protocol as described in Section 8.3 to access, manipulate and delete
a conference object associated with a specific conference instance.
A conference object identifier is provided to the Conference Control
Client to enable such functions to be carried out. This can either
be returned through the Conference Control Protocol while creating a
conference object, be provided by the conference notification service
or through out-of-band mechanisms (e.g. E-Mail).
[Editors Note: Previous section to be expanded and more detail
included. It also needs to link up with other drafts and explicitly
reference.]
A centralized conferencing system, as defined in the Conference
Framework [ref] has potential to expose a range of interfaces and
protocols. It is also possible that future centralized conferencing
enhancements might place requirements to provide further additional
protocols and interfaces. A conference object can consist and be
associated with many identifiers that are in some way related to a
conference object. Good examples include the Binary Floor Control
Protocol (BFCP)[24] and call signaling protocols, such as SIP. Each
use unique identifiers to represent a protocol instance associated
with a conference object.
Barnes, et al. Expires April 4, 2006 [Page 44]
Internet-Draft XCON Framework Oct 2005
A conferencing system may maintain a relationship between the
conference object URIs and the identifiers associated with each of
the complementary centralized conferencing protocols (e.g., call
signaling protocols, BFCP, etc.). To facilitate the maintenance of
these relationships, the conference object URI acts as a top level
identifier within the conferencing system for the purpose of
identifying the interfaces for these other protocols. This implicit
binding provides a structured mapping of the various protocols with
the associated conference object identifier. Figure 12 illustrates
the relationship between the identifiers used for the protocols
within this framework and the general conference object identifier.
+--------------+
| Conference |
| Object |
| Identifier |
+------+-------+
|
|
|
+-----------------+---------------+
| |
+-------+---------+ +-------+-------+
|CSP Conference ID| | BFCP 'confid' |
+-----------------+ +---------------+
Figure 12: Conference Object Mapping.
In Figure 12, the conference object identifier acts as the top level
key in the identification process. The call signaling protocols have
an associated conference ID representation in the form of URIs. The
binary floor control protocol, as defined in [24], defines the
'conf-id' identifier which represents a conference instance within
floor control. When created within the conferencing system, the
'conf-id' has a 1:1 mapping to the unique conference object
Identifier. Operations associated with the Conference Control
Protocols are directly associated with the conference object, thus
the primary identifier associated with these protocols is the
conference object identifier. The mappings between additional
protocols/interface is not strictly 1:1 and does allow for multiple
occurrences. For example, multiple call signaling protocols will
each have a representation that is implicitly linked to the top level
conference object identifier, for example, H323 and SIP URIs that
represent a conference instance. It should be noted that a
conferencing system is free to structure such relationships as
required and this information is just included as a guideline that
Barnes, et al. Expires April 4, 2006 [Page 45]
Internet-Draft XCON Framework Oct 2005
can be used.
The following example illustrates the representation and
relationships that might occur in a typical conference instance. The
table in Figure 13 lists a typical conference instance and related
properties.
+----------------------+------------------------+----------------------+
| Conf Obj URI | CSP URI | BFCP Conf-ID |
+----------------------+------------------------+----------------------+
| xcon:Ji092i | sip:Ji092i@example.com | Ji092i |
| | tel:+44(0)2920930033 | |
| | h323:Ji092i@example.com| |
+----------------------+------------------------+----------------------+
Figure 13: Conference Table Representation
The information from Figure 13 can then be applied to the
representation introduced in Figure 12. This results in Figure 14.
+--------------+
| Conference |
| Object |
| Identifier |
+--------------+
| xcon:Ji092i |
+------+-------+
|
|
|
+-----------------+---------------+
| |
+-----------+-----------+ +-------+-------+
| CSP Conference IDs | | BFCP 'confid' |
+-----------------------+ +---------------+
|h323:Ji092i@example.com| | Ji092i |
|tel:+44(0)2920930033 | +-------+-------+
|sip:Ji092i@example.com | |
+-----------------------+ +-------|-------+
| BFCP 'floorid |
+---------------+
| UEK78d |
| 09cnJk |
+---------------+
Barnes, et al. Expires April 4, 2006 [Page 46]
Internet-Draft XCON Framework Oct 2005
Figure 14: Conference Tree Representation
Further elements can be added to the tree representation in Figure 14
to enable a complete representation of a conference instance within a
conferencing system.
This style of association can be applied to any supplementary
protocols or conferencing mechanisms that are applied to the
centralized conferencing model defined in this document as long as a
unique reference per conference instance is available that can be
mapped to a conference object.
15.1. Conference Object URI Definition
[Editors Note: When the appendix split from the Framework document,
full URI definition will be included.
16. Appendix B - Conference User Identifier
[Editors Note: This appendix will be incorporated in a separate
specification in the next release of this document and will include
all relevant detail.]
Each user within a conferencing system is allocated a unique
conference user identifier. The user identifier is used in
association with the conference object identifier defined in
Section 15, and by the conference control protocol to uniquely
identify a user within the scope of conferencing system. The
conference control protocol uses the user identifier to uniquely
determine who is issuing commands. Appropriate policies can then be
applied to the requested command.
As with the conference object identifier, a number of supplementary
user identifiers defined in other protocols are used within a
conference instance. Such user identifiers can be associated with
this conference user identifier and enable the conferencing system to
correlate and map these multiple authenticated user identities to the
single user identifier.
Figure 15 illustrates an example using the conference user identifier
in association with the user identity defined for BFCP and SIP Digest
user identity as defined in RFC3261[4], which would be used when SIP
is the call signaling protocol. It should be noted that a
conferencing system is free to structure such relationships as
required and this information is just included as a guideline that
can be used.
Barnes, et al. Expires April 4, 2006 [Page 47]
Internet-Draft XCON Framework Oct 2005
+---------------+
| Conference |
| User |
| Identifier |
+-------+-------+
|
|
|
+---------------+---------------+
| |
+-------+-------+ +-------+-------+
| BFCP | | SIP Digest |
| 'UserID' | | Username |
+---------------+ +-------+-------+
Figure 15: Conference User Identifier
Within a conferencing system, a user is identified by a single
conference user identifier. Any additional conferencing mechanisms
that contain a protocol specific user ID can be associated with the
conference user identifier, as illustrated in Figure 15. This
mechanism allows conferencing systems to manage and relate system
wide user identities in relation to specific conference objects and
helps in the enforcement of system wide policies.
The following example illustrates the representation and
relationships that might occur in a typical conference instance. The
table in Figure 16 lists a typical representation of user identifier
hierarchy and associations.
+----------------+----------------+---------------+----------------+
| Conf User ID | BFCP User ID | SIP User ID | H323 User ID |
+----------------+----------------+---------------+----------------+
| John | HK37ihdaj | 123674 | 928373 |
+----------------+----------------+---------------+----------------+
Figure 16: User Identitier Representation
The information from Figure 16 can then be applied to the
representation introduced in Figure 15. This results in Figure 17.
Barnes, et al. Expires April 4, 2006 [Page 48]
Internet-Draft XCON Framework Oct 2005
+--------------+
| Conference |
| User |
| Identifier |
+--------------+
| John |
+------+-------+
|
|
|
+---------------------+---------------------+
| | |
+-------+--------+ +-------+-------+ +--------+-------+
| BFCP User ID | | SIP User ID | | H323 User ID |
+----------------+ +---------------+ +----------------+
| HK37ihdaj | | 123674 | | 928373 |
+----------------+ +-------+-------+ +----------------+
Figure 17: User ID Tree Representation
Further elements can be added to the tree representation in Figure 14
to enable a complete representation of a conference instance within a
conferencing system.
16.1. Conference User Definition
[Editors Note: When the appendix is split from the Framework
document, full definition will be included.
17. References
17.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
17.2. Informative References
[2] Handley, M. and V. Jacobson, "SDP: Session Description
Protocol", RFC 2327, April 1998.
[3] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax", RFC 2396,
August 1998.
Barnes, et al. Expires April 4, 2006 [Page 49]
Internet-Draft XCON Framework Oct 2005
[4] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002.
[5] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
Session Description Protocol (SDP)", RFC 3264, June 2002.
[6] Roach, A., "Session Initiation Protocol (SIP)-Specific Event
Notification", RFC 3265, June 2002.
[7] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,
"RTP: A Transport Protocol for Real-Time Applications", STD 64,
RFC 3550, July 2003.
[8] Dawson, F. and Stenerson, D., "Internet Calendaring and
Scheduling Core Object Specification (iCalendar)", RFC 2445,
November 1998.
[9] Rosenberg, J., "A Framework for Conferencing with the Session
Initiation Protocol",
draft-ietf-sipping-conferencing-framework-05 (work in
progress), May 2005.
[10] Levin, O. and R. Even, "High Level Requirements for Tightly
Coupled SIP Conferencing",
draft-ietf-sipping-conferencing-requirements-01 (work in
progress), October 2004.
[11] Rosenberg, J., "A Session Initiation Protocol (SIP) Event
Package for Conference State",
draft-ietf-sipping-conference-package-12 (work in progress),
July 2005.
[12] Schulzrinne, H., "Requirements for Floor Control Protocol",
draft-ietf-xcon-floor-control-req-03 (work in progress),
October 2005.
[13] Koskelainen, P. and H. Khartabil, "Requirements for Conference
Policy Control Protocol", draft-ietf-xcon-cpcp-reqs-04 (work in
progress), August 2004.
[14] Even, R. and N. Ismail, "Conferencing Scenarios",
draft-ietf-xcon-conference-scenarios-05 (work in progress),
September 2005.
[15] Johnston, A. and O. Levin, "Session Initiation Protocol Call
Control - Conferencing for User Agents",
draft-ietf-sipping-cc-conferencing-07 (work in progress),
Barnes, et al. Expires April 4, 2006 [Page 50]
Internet-Draft XCON Framework Oct 2005
June 2005.
[16] Camarillo, G., "The Binary Floor Control Protocol (BFCP)",
draft-ietf-xcon-bfcp-05 (work in progress), July 2005.
[17] Khartabil, H., "The Conference Policy Control Protocol (CPCP)",
draft-ietf-xcon-cpcp-01 (work in progress), October 2004.
[18] Khartabil, H., "An Extensible Markup Language (XML)
Configuration Access Protocol (XCAP) Usages for Conference
Policy Manipulation and Conference Policy Privelges
Manipulation", draft-ietf-xcon-cpcp-xcap-03 (work in progress),
October 2004.
[19] Khartabil, H. and A. Niemi, "Privileges for Manipulating a
Conference Policy",
draft-ietf-xcon-conference-policy-privileges-01 (work in
progress), October 2004.
[20] Levin, O. and G. Kimchi, "Centralized Conference Data Model",
draft-levin-xcon-cccp-02 (work in progress), February 2005.
[21] Jennings, C. and B. Rosen, "Media Conference Server Control for
XCON", draft-jennings-xcon-media-control-03 (work in progress),
July 2005.
[22] Rosen, B., "SIP Conferencing: Sub-conferences and Sidebars",
draft-rosen-xcon-conf-sidebars-01 (work in progress),
July 2004.
[23] Levin, O. and G. Camarillo, "The SDP (Session Description
Protocol) Label Attribute",
draft-ietf-mmusic-sdp-media-label-01 (work in progress),
January 2005.
[24] Camarillo, G., "Session Description Protocol (SDP) Format for
Binary Floor Control Protocol (BFCP) Streams",
draft-camarillo-mmusic-sdp-bfcp-00 (work in progress),
October 2004.
[25] Campbell, B., "The Message Session Relay Protocol",
draft-ietf-simple-message-sessions-12 (work in progress),
October 2005.
[26] Jennings, C. and A. Roach, "Conference State Change Protocol
(CSCP)", draft-jennings-xcon-cscp-01 (work in progress),
July 2005.
Barnes, et al. Expires April 4, 2006 [Page 51]
Internet-Draft XCON Framework Oct 2005
[27] Enns, R., "NETCONF Configuration Protocol",
draft-ietf-netconf-prot-09 (work in progress), October 2005.
Barnes, et al. Expires April 4, 2006 [Page 52]
Internet-Draft XCON Framework Oct 2005
Authors' Addresses
Mary Barnes
Nortel
2201 Lakeside Blvd
Richardson, TX
Email: mary.barnes@nortel.com
Chris Boulton
Ubiquity Software Corporation
Building 3
Wern Fawr Lane
St Mellons
Cardiff, South Wales CF3 5EA
Email: cboulton@ubiquitysoftware.com
Orit Levin
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052
Email: oritl@microsoft.com
Barnes, et al. Expires April 4, 2006 [Page 53]
Internet-Draft XCON Framework Oct 2005
Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Disclaimer of Validity
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2005). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Barnes, et al. Expires April 4, 2006 [Page 54]
