One document matched: draft-boulton-xcon-msrp-conferencing-05.txt
Differences from draft-boulton-xcon-msrp-conferencing-04.txt
XCON Working Group C. Boulton
Internet-Draft Ubiquity Software Corporation
Expires: January 10, 2008 M. Barnes
Nortel
July 9, 2007
Instant Messaging Sessions within a Centralized Conferencing (XCON)
System
draft-boulton-xcon-msrp-conferencing-05
Status of this Memo
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Copyright (C) The IETF Trust (2007).
Abstract
The document "A Framework and Data Model for Centralized
Conferencing" defines a centralized conference as both signaling and
protocol agnostic. The primary examples within this framework focus
on audio and video as the media types for the session. This document
describes the mechanisms, in the context of this centralized
conferencing framework, when using instant messaging sessions as the
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media.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 3
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Protocol Operations . . . . . . . . . . . . . . . . . . . 5
3.2. IM and Conferencing Identifiers . . . . . . . . . . . . 5
4. Basic Operations . . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Creating a Chat Room . . . . . . . . . . . . . . . . . . . 8
4.2. Joining a Chat Room . . . . . . . . . . . . . . . . . . . 10
4.3. Deleteing a Chat Room . . . . . . . . . . . . . . . . . . 12
5. Advanced Operations . . . . . . . . . . . . . . . . . . . . . 13
5.1. Text Sidebar . . . . . . . . . . . . . . . . . . . . . . . 13
5.2. Private Message . . . . . . . . . . . . . . . . . . . . . 16
6. Security Considerations . . . . . . . . . . . . . . . . . . . 19
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20
8. Informative References . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
Intellectual Property and Copyright Statements . . . . . . . . . . 22
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1. Introduction
A Centralized Conference as defined by the "A Framework for
Centralized Conferencing" [1] is both signaling and protocol
agnostic. The primary examples within the framework focus on audio
and video as the media types for the session. This document
describes the mechanisms and associated framework elements involved
when instant messages are the media for the conference. This
functionality is often referred to as a "chat room" or simply "chat"
as it provides the text equivalent of a voice conversation involving
multiple parties.
Several existing protocols support this chat functionality, such as
Internet Relay Chat (IRC) [3] and Extensible Messaging and Presence
Protocol (XMPP) [4]. In addition, [8] provides IM chat functionality
for a purely SIP signaling based solution option using Message
Session Relay Protocol MSRP [6]. The focus of this document is to
describe the interface to a conferencing system based on the XCON
framework, independent of the specific IM media type used by the
client. The intent is not replace the existing IM protocols, but
rather to allow clients using the different protocols, that also use
the centralized conferencing framework model for voice and audio
conferences, to make use of the same conference control mechanisms
and conferencing system to establish, update and delete the chat
room. While this approach also allows the conferencing system to
provide a natural interworking point for various IM protocols, the
details of the interworking are outside the scope of this document.
2. Conventions and Terminology
This document reuses the terminology defined in "A Framework for
Centralized Conferencing" and the protocol operations defined in the
Centralized Conferencing Protocol document [ref:TBD].
3. Overview
Figure 1 provides a general illustration of IM clients having a
direct, 1:1 connection to the conferencing system. The conferencing
system receives any IMs sent by the clients and then distributes them
to the appropriate IM sessions.
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+--------+
| IM |
| Client |
| |
+--------+
|
|
|
|
|
|
v
+------------+
+--------+ | | +--------+
| IM | | | | IM |
| Client |-------------->|Conferencing|<--------------| Client |
| | | System | | |
+--------+ | | +--------+
+------------+
^
|
|
|
|
|
|
+--------+
| IM |
| Client |
| |
+--------+
Figure 1: Client Connection
The approach in this document is to have no impact on the existing IM
protocols, while taking full advantage of the functionality provided
by the centralized conferencing framework. The solution proposal in
this document meets the requirements identified in the requirements
section of the multiparty IM with MSRP document [8], with the
exception of the requirements (REQ-5, REQ-6 and REQ-7) related to the
concept of nicknames. A solution for nicknames is currently not
within the scope of the centralized conferencing framework or
associated protocol documents, although it is a useful and desireable
concept. [Editor's Note: Should the generic requirements from the
simple-chat draft be pulled into a separate document (as they had
been in the past) or is it okay for this doc to reference those
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requirements, which are for the most part quite generic?].
A basic solution for IM chat sessions, also meeting the Multiparty IM
using MSRP requirements, is documented in [8]. It uses the concept
of an "MSRP switch" as the centralized component, whose role is very
similar to the MSRP Conferencing Server in this document. The
solution in [8] doesn't explicitly take advantage of the centralized
conferencing framework model, as it primarily intends to make use of
the basic SIP conferencing framework to provide the basic chat
functionality. However, that solution approach is compatible with
the solution components described in this document, with no impact on
that basic solution proposal. One of the advantages of applying the
two solutions in concert would be a reuse of the centralized
conferencing framework model for advanced features, such as sidebars
and private conferences, and manipulation of the conference data.
3.1. Protocol Operations
An IM client wishing to join a conference uses standardized
centralized conferencing mechanisms for creating and joining a
conference, as identified in the centralized conferencing framework
and related protocol documents.
The request to send an IM to an IM media session is specific to the
IM protocol (e.g., MSRP SEND). On issuing an request to send an IM
to an IM media session that is a member of a conference instance, the
IM will be replicated and forwarded, in the relevant context, to all
other IM media sessions that are participants of the conference
instance.
An IM client wishing to delete a chat room uses standardized
mechanisms for deleteing a conference. Non-signaling specific
mechanisms are defined in the Centralized Conferencing Framework [1]
and related protocol document [TBD], with protocol specific
mechanisms defined in other documents such as for SIP in the SIPPING
Conference Framework [5].
3.2. IM and Conferencing Identifiers
As mentioned in the overview, an IM client connecting to a
conferencing system has a 1:1 relationship with the IM signaling
entity, each having a unique protocol specific session ID. When
referring to IM session ID's the document is making reference to the
locally (at conferencing system) generated session ID used for IM
session signaling identification. In the case of MSRP, this session
ID is inserted into the local path SDP attribute. An important
concept in this proposal is the creation and management of IM
sessions. It is important that each IM session created, as
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identified by a unique IM session ID, is explicitly tied to an
associated conference, represented by the conference identifier (as
defined in the Centralized Conferencing Framework [1]). This
provides the relevant association between IM session and an XCON
Conference. A generic example representation is illustrated by the
rows contained in Figure 2.
-------------------------------------------
| Conference Identifier |
-------------------------------------------
| IM Session ID=8asjdhk |
| IM Session ID=38iuhds |
| IM Session ID=djiowid |
| IM Session ID=389hewu |
-------------------------------------------
Figure 2: Simple Session Association
The Centralized Conferencing Framework[1] introduces the concept of a
conference user identifier defined in [2]. When a user joins a
conference instance through the signaling protocol, it is allocated
an appropriate conference user identifer either through
authentication or system allocation. The conference user identifer
MUST be used in conjunction with an IM session identifier to
internally represent a participant in a conference instance.
Figure 2 is then expanded to look like Figure 3. Again a row in the
table representing a single entry.
----------------------------------------------------------------
| Conference Identifier |
----------------------------------------------------------------
| IM Session ID=8asjdhk | Conf User ID=839ULjj |
| IM Session ID=38iuhds | Conf User ID=0283hHu |
| IM Session ID=djiowid | Conf User ID=ncH37H |
| IM Session ID=389hewu | Conf User ID=pakdjjH |
----------------------------------------------------------------
Figure 3: Advanced Session Association
A more complex session association is necessary due to potential for
a user to have multiple IM sessions in a single conference instance,
such as multi-lingual conference support. In an example with SIP and
MSRP, the conference representation in Figure 3 allows for such
functionality when separate SIP dialogs represent MSRP sessions.
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This process becomes complex when multiple SDP MSRP media sessions
(m=) are defined in a single payload. This internal representation
now needs expanding to enable a conferencing system to explicitly
associate a media session (m=). This involves including the media
label, as defined in [9], to maintain the internal conference
association. An example is illustrated in Figure 4.
----------------------------------------------------------------------------
| Conference Identifier |
----------------------------------------------------------------------------
| MSRP Session ID=8asjdhk | Conf User ID=839ULjj | Label=iede3 |
| MSRP Session ID=38iuhds | Conf User ID=0283hHu | Label=8heus |
| MSRP Session ID=838unaH | Conf User ID=0283hHu | Label=3cnu7 |
| MSRP Session ID=djiowid | Conf User ID=ncH37Hs | Label=jd38J |
| MSRP Session ID=389hewu | Conf User ID=pakdj7H | Label=U83hd |
| MSRP Session ID=Ko03jdk | Conf User ID=pakdj7H | Label=ehy3h |
----------------------------------------------------------------------------
Figure 4: Advanced Session Association + Media Label
In Figure 4 conference user uidentifiers '0283hHu' and 'pakdj7H'
appear twice. The combination of multiple conference user
identifiers and a unique MSRP session ID enables the conference
system to clearly identify a specific MSRP instance. The
representation also includes the media label, as defined in [9],for
identification purposes. This added property, which is extracted
from the SDP media line, enables clear identification when multi SDP
media (m=) lines appear in the same SDP payload.
A client MUST include the media label attribute defined in [9] when
including multiple MSRP sessions in the same SDP payload. Even in
the simplest conferencing system, where users are allowed to enter
anonymously, the internal representation described in this section
should be observed. In this case, the conferencing system would
still internally create a conference user identifier for participant
reference purposes.
4. Basic Operations
This section provides details of the realization of the Multi-party
IM (chat) within the context of the centralized conferencing
framework. A brief discussion and diagrams are provided for
creating, joining and deleting a chat based conference. The
objective of this section is to further illustrate the model,
mechanisms and protocols presented in the previous sections and also
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serves to validate that the model, mechanisms and protocols are
sufficient to support IM chat.
The scenarios provide a high level primitive view of the necessary
operations and general logic flow. The details shown in the
scenarios are for illustrative purposes only and don't necessarily
reflect the actual structure of the conference control protocol
messages nor the detailed data, including states, which are defined
in separate documents. 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. [Editor's Note: Ideally, this
section will be updated with details once the protocol is agreed.]
4.1. Creating a Chat Room
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 [10]. For a conferencing client to have more flexibility
in defining the charaterisitics and capabilities of a chat based
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 5 provides an example of one client "Alice" determining the
conference blueprints available to support various types of chat
rooms for a particular conferencing system and creating a chat based
conference using the desired blueprint.
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+--------------------------------+
| Conferencing System |
"Alice" | +------------+|
+--------+ | | ||
| |CCP Request <blueprints> | +-----------+ | ||
| Client |-------------------------->|Conference | |Conference ||
| |<--------------------------|Control |~~~>|Blueprint(s)||
+--------+CCP Response<blueprintA, | |Server | | ||
... | +-----------+ +------------+|
blueprintZ, | |
confUserID> | |
"Alice" |
+--------+ | |
| |CCP Request <create, | +------------+|
| | chatBlueprintAConfObjID,| +-----------+ | ||
| Client |-------------------------->|Conference | |Conference ||
| | confUserID> | |Control |~~~>|Chat ||
| |<--------------------------|Server | |BlueprintA ||
| |CCP Response | | | +------------+|
+--------+ <chatResvConfObjID | | | \|/ |
confID> | | | /|\ |
| | | V |
| | | +------------+|
| | |~~~>|Conference ||
| | | |Chat ||
| | | |Reservation ||
| +-----------+ +------------+|
"Alice" | | |
+--------+ | | |
| |CCP Request <create, | V |
| | chatResvConfObjID, | +-----------+ +------------+|
| Client |-------------------------->|Conference | |Active ||
| | confID,confUserID> | |Control |~~~>|Chat ||
| |<--------------------------|Server | |Conference ||
| |CCP Response | | | +------------+|
+--------+ <chatActiveConfObjID, | | | |
confID> | +-----------+ |
+--------------------------------+
Figure 5: Client Creation of Chat room
Upon receipt of the Conference Control Protocol request for
blueprints associated with chat rooms, the conferencing system would
first authenticate "Alice" (and allocate a conference user
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identifier, if necessary) and then ensure that "Alice" has the
appropriate authority based on system policies to receive any chat
room based 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, topic details, 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 "create" a
conference based upon the blueprint in the request, the conferencing
system ensures that the 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" now creates an active chat room using that
reservation. "Alice" provides the conference information, including
the necessary conference ID, to desired participants to allow them to
join the chat room. "Alice" may also add other users to the chat
room. 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.
4.2. Joining a Chat Room
A participant can join and leave the conference using call signaling
means only, such as SIP. However, in order to perform richer
conference control a user client can implement a conference control
protocol client. By using a conference control protocol, the client
can affect its own state and the state of other participants,
depending upon policies, which may indirectly affect the state of any
of the conference participants.
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In the example in section Section 4.1, "Alice" has reserved a chat
room . "Alice" has also already joined the conference and made the
chat room active. "Alice" can either add additional participants to
the chat room or provide the conference information, including the
necessary conference ID, to desired participants and allow them to
request to join themselves. Any participants that have the authority
to manipulate the conference would receive the conference object
identifier of the active conference object in the response to their
request to join.
Figure 6 provides an example of "Bob" joining the chat room using the
conference ID provided by "Alice" (e.g., in an IM).
+--------------------------------+
| Conferencing System |
"Bob" | +---------+--+|
+--------+ | |policies | ||
| |CCP Request < | +-----------+ +---------+ ||
| Client |-------------------------->|Conference | | Active ||
| | Conference Object ID, | |Control |~~~>| Chat ||
+--------+ Change, Member="Bob" > | |Server | |Conference ||
| +-----------+ +-------+ ||
| |"Alice"| ||
"Alice" | ' ' '|
+--------+ NOTIFY <"Bob"="added"> |+------------+ ' ' '|
| |<-------------------------|Notification|<~~~| ||
| Client |. . ||Service | +-------+ ||
+--------+--+ . || | |"Bob" | ||
| |<----------------------| | +-------+----+|
| Client |NOTIFY <"Bob"="added">|+------------+ |
+--------+ +--------------------------------+
"Bob"
Figure 6: Joining a chat room
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 must 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. The conferencing
system must also ensure that "Bob" has the appropriate authority
based on the policies associated with that specific conference object
to perform the operation.
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Once "Bob" has been successfully added to the chat room, 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.
4.3. Deleteing a Chat Room
Depending upon the conferencing system policies and policies specific
to the chat room, the creator of the chat would typically be the
participant authorized to delete the chat room.
In the example in section Section 4.1, "Alice" has created a chat
room and provided the conference information, including the necessary
conference ID, to desired participants and allow them to request to
join themselves. "Bob" and others are participants in the chat.
Figure 6 provides an example of "Alice" later deleting this same chat
room.
+--------------------------------+
| Conferencing System |
"Alice" | +---------+--+|
+--------+ | |policies | ||
| |CCP Request < | +-----------+ +---------+ ||
| Client |-------------------------->|Conference | | Active ||
| | Conference Object ID, | |Control |~~~>| Chat ||
+--------+ Delete > | |Server | |Conference ||
| +-----------+ +-------+ ||
| |"Alice"| ||
"Alice" | ' ' '|
+-------+ NOTIFY <confObjID, |+------------+ ' ' '|
| |<-------------------------||Notification|<~~~| ||
| Client| "deleted"> ||Service | +-------+ ||
+-------+--+ . || | |"Bob" | ||
| |<----------------------|| | +-------+----+|
|Client |NOTIFY<"Bob"="removed">|+------------+ |
+-------+ +--------------------------------+
"Bob"
Figure 7: Deleting a chat room
Upon receipt of the Conference Control Protocol request to "delete"
the specific chat room as identified by the conference object ID, the
conferencing system must determine whether "Alice" has the authority
to delete this conference. Since "Alice" is the creator of the
conference, the "delete" operation is performed, with the appropriate
signalling sent to the participants.
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One step in the deletion of the chat room may include notifitying the
participants (including "Bob") that they have been removed via the
Conference Notification Service.
5. Advanced Operations
This section provides details of the realization of advanced chat
features, such as sidebars and private messages, within the context
of the centralized conferencing framework. As with Section 4, 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 advance IM chat features.
5.1. Text Sidebar
The Multi-party IM using MSRP document [8] identifies the requirement
(REQ-GEN-12) to set up a sidebar conference with one or more
participants of the conference.
The concept of a 'sidebar' in an XCON compliant conference system is
fully described in the Sidebar section and related subsections within
the Conferencing Scenarios Realization section of the centralized
conferencing framework document [1]. The creation, manipulation and
deletion of sidebars for MSRP based sessions follows the same
principles.
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
implicitly linked to the parent conference object (i.e. it is not an
independent object) and is associated with the parent conference
object identifier. 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.).
Figure 8 provides an example of one client "Alice" involved in active
chat conference with "Bob" and "Carol". "Alice" wants to create a
sidebar to have a side discussion with "Bob" while still receiving
the session based messaging associated with the main chat conference.
Whether the text is interleaved with the main chat or whether a
separate window is created for the sidebar is implementation
specific. "Alice" initiates the sidebar by sending a request to the
conferencing system to create a conference chat reservation based
upon the active chat conference object. "Alice" and "Bob" would
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remain on the roster of the main conference, such that other
participants could be aware of their participation in the main
conference, while the text sidebar conference is occurring.
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+--------------------------------+
| Conferencing System |
| +---------+--+|
| |policies | ||
| +---------+ ||
| |Active Chat ||
| |Conference ||
"Alice" | +-------+ ||
+--------+ | |"Alice"| ||
| |CCP Req <createSidebar, | +-------+ ||
| | activeChatConfObjID, | +-----------+ |"Bob" | ||
| Client |-------------------------->|Conference | +-------+ ||
| | confUserID> | |Control |~~~>|"Carol"| ||
| |<--------------------------|Server | +-------+----+|
| |CCP Response | | | | |
+--------+ <sidebarResvConfObjID, | | | | |
confID> | | | V |
| | | +---------+--+|
| | | |policies | ||
| | |~~~>+---------+ ||
| | | | ||
| +-----------+ | Sidebar ||
"Alice" | | Chat ||
+--------+ | | Reservation||
| |CCP Request <update, | +-----------+ | ||
| | sidebarResvConfObjID,| | | | ||
| Client |-------------------------->| |~~~>| ||
| | confID,confUserID, | | | +------------+|
| | video=parent, | | | | |
| | audio=sidebar> | |Conference | | |
| | | |Control | V |
| | | |Server | +---------+--+|
| |CCP Response | | | |policies | ||
| |<activeChatSideConfObjID,| | | +---------+ ||
| |<--------------------------| | |Active Chat ||
+--------+ confID> | | | |Sidebar ||
| | | |Conference ||
| +-----------+ +-------+ ||
| |"Alice"| ||
"Bob" | | | ||
+--------+ NOTIFY <"Bob"=added> |+------------+ +-------+ ||
| |<-------------------------|Notification|<~~~| | ||
| Client | ||Service | |"Bob" | ||
+--------+ || | +-------+----+|
|+------------+ |
+--------------------------------+
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Figure 8: Client Creation of a Sidebar Conference
Upon receipt of the Conference Control Protocol request to "reserve"
a new sidebar chat conference, based upon the active chat conference
received in the request, the conferencing system uses the received
active chat conference to clone a conference chat reservation for the
sidebar. As discussed previously, the sidebar reservation is NOT
independent of the active conference (i.e., parent). 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 sidebar reservation through the conference instance.
Upon receipt of the conference control protocol response to reserve
the conference, "Alice" can now create an active chat conference
using that reservation or create additional reservations based upon
the existing reservations. In this example, "Alice" wants only "Bob"
to be involved in the sidebar, thus she manipulates the membership.
"Alice" also only wants the text from the original conference, but
wants the text within the sidebar to be restricted to the
participants in the sidebar. "Alice" sends a conference control
protocol request to update the information in the reservation and to
create an active conference.
Upon receipt of the conference control protocol request to update the
reservation and to create an active chat conference for the sidebar,
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 validate the
updated information in the reservation, ensuring that a member like
"Bob" is already a user of this conferencing system.
Depending upon the policies, the initiator of the request (i.e.,
"Alice") and the participants in the sidebar (i.e., "Bob") may be
notified of his addition to the sidebar via the conference
notification service.
5.2. Private Message
The case of private messages can be handled as a sidebar with just
two participants, identical to the example in section Section 5.1.
The other context, referred to as whisper, in this document refers to
situations involving one time media targetted to specific user(s).
An example of a whisper would be a text message injected only to the
conference chair or to a new participant joining a conference.
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Figure 9 provides an example of one user "Alice" whose chairing a
fixed length conference with "Bob" and "Carol". The configuration is
such that only the chair is providing a warning when there is only 10
minutes left in the conference. At that time, "Alice" is moved into
a sidebar created by the conferencing system and only "Alice"
receives that text message announcing the 10 minute warning.
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+--------------------------------+
| Conferencing System |
| +---------+--+|
| |policies | ||
| +---------+ ||
| |Active Chat ||
| |Conference ||
| +-------+ ||
| |"Alice"| ||
| +-------+ ||
| +-----------+ |"Bob" | ||
| |Conference | +-------+ ||
| |Control |~~~>|"Carol"| ||
| |Server | +-------+----+|
| | | | |
| | | | |
| | | V |
| | | +---------+--+|
| | | |policies | ||
| | |~~~>+---------+ ||
| | | | ||
| +-----------+ |Sidebar Chat||
"Alice" | |Conference ||
+--------+ NOTIFY <"Alice"=added, |+------------+ +-------+ ||
| |<-------------------------|Notification| | | ||
| Client | activeChatSideConfObjID,||Service |<~~~|"Alice"| ||
+--------+ confID > || | +-------+----+|
|+------------+ |
~~~Text message delivered to "Alice"~~~
| +-----------+ |
| |Conference | |
| |Control | |
| |Server | |
| | | |
| | | \---------+--/|
| | | |\ /||
| | |~~~>+ \ / ||
| | | | \ / ||
| +-----------+ |Sid\bar /hat||
"Alice" | |Conf\re/ce ||
+--------+ NOTIFY <"Alice"=removed,|+------------+ +-----\/+ ||
| |<-------------------------|Notification|<~~~| /\| ||
| Client | activeChatSideConfObjID,||Service | |"Ali/ce\ ||
+--------+ confID > || | +---/---+\---+|
|+------------+ / \ |
+--------------------------------+
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Figure 9: Whisper
When the conferencing system determines that there is only 10 minutes
left in the conference which "Alice" is chairing, rather than
creating a reservation as was done for the sidebar in Section 5.1,
the conferencing system directly creates an active chat sidebar
conference, based on the active chat conference associated with
"Alice". As discussed previously, the sidebar conference is NOT
independent of the active conference (i.e., parent). The
conferencing system also allocates a conference ID to be used for any
subsequent manipulations of the sidebar chat conference. The
conferencing system maintains the mapping between this conference ID
and the conference object ID associated with the active sidebar
conference through the conference instance.
Immediately upon creation of the active chat sidebar conference, the
text announcement is provided to "Alice". Depending upon the
policies, Alice may be notified of her addition to the sidebar via
the conference notification service. "Alice" continues to receive
the text messages from the main conference.
Upon delivery of the text announcement, "Alice" is removed from the
sidebar and the sidebar conference is deleted. Depending upon the
policies, "Alice" may be notified of her removal from the sidebar via
the conference notification service.
6. Security Considerations
As discussed in the XCON Framework, 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 in the context of MSRP conferencing would include the
following: an endpoint attempting to receive the messages for
conferences in which it is not authorized to participate, an endpoint
attempting to disconnect other users, and theft of service, by an
endpoint, in attempting to create conferences it is not allowed to
create.
Since this document describes the use of existing protocols (e.g.
MSRP, Conference Control Protocol, SIP, etc.), it also re-uses the
security solutions for those protocols and the associated
authorization mechanisms. Since this solution makes use of the XCON
framework, it makes use of the policy associated with the conference
object to ensure that only authorized entities are able to manipulate
the data to access the capabilities. This solution also makes use of
the privacy and security of the identity of a user in the conference,
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as discussed in the XCON Framework.
7. Acknowledgements
The authors appreciate the input and comments from Miguel Garcia-
Martin and Dave Morgan.
8. Informative References
[1] Barnes, M., "A Framework for Centralized Conferencing",
draft-ietf-xcon-framework-08 (work in progress), May 2007.
[2] Novo, O., "Conference Information Data Model for Centralized
Conferencing (XCON)", draft-ietf-xcon-common-data-model-05
(work in progress), April 2007.
[3] Kalt, C., "Internet Relay Chat: Architecture", RFC 2810,
April 2000.
[4] Saint-Andre, P., Ed., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 3920, October 2004.
[5] Rosenberg, J., "A Framework for Conferencing with the Session
Initiation Protocol (SIP)", RFC 4353, February 2006.
[6] Campbell, B., "The Message Session Relay Protocol",
draft-ietf-simple-message-sessions-19 (work in progress),
February 2007.
[7] Jennings, C., "Relay Extensions for the Message Sessions Relay
Protocol (MSRP)", draft-ietf-simple-msrp-relays-10 (work in
progress), December 2006.
[8] Niemi, A. and M. Garcia-Martin, "Multi-party Instant Message
(IM) Sessions Using the Message Session Relay Protocol
(MSRP)", draft-ietf-simple-chat-00 (work in progress),
June 2007.
[9] Levin, O. and G. Camarillo, "The Session Description Protocol
(SDP) Label Attribute", RFC 4574, August 2006.
[10] Johnston, A. and O. Levin, "Session Initiation Protocol (SIP)
Call Control - Conferencing for User Agents", BCP 119,
RFC 4579, August 2006.
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Authors' Addresses
Chris Boulton
Ubiquity Software Corporation
Building 3
Wern Fawr Lane
St Mellons
Cardiff, South Wales CF3 5EA
Email: cboulton@ubiquitysoftware.com
Mary Barnes
Nortel
2201 Lakeside Blvd
Richardson, TX
Email: mary.barnes@nortel.com
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