XCON Working Group C. Boulton
Internet-Draft NS-Technologies
Intended status: Standards Track M. Barnes
Expires: September 8, 2009 Nortel
March 7, 2009
Chatrooms within a Centralized Conferencing (XCON) System
draft-boulton-xcon-session-chat-03
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and 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 September 8, 2009.
Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents in effect on the date of
publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document.
Abstract
The document "A Framework for Centralized Conferencing" defines a
centralized conference as both signaling and protocol agnostic. The
Boulton & Barnes Expires September 8, 2009 [Page 1]
Internet-Draft XCON Chat March 2009
primary examples within this framework focus on audio and video as
the media types for the session. This document provides an overview
of the mechanisms defined in the centralized conferencing framework
that can be used to support chatrooms. In addition, the document
describes additional functionality and requirements necessary to
provide feature rich chatroom functionality.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 3
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Protocol Operations . . . . . . . . . . . . . . . . . . . 5
3.2. Chat Session and Conferencing Identifiers . . . . . . . . 5
4. Basic Operations . . . . . . . . . . . . . . . . . . . . . . . 7
5. Advanced Operations . . . . . . . . . . . . . . . . . . . . . 8
6. Additional Operations . . . . . . . . . . . . . . . . . . . . 8
6.1. Nicknames . . . . . . . . . . . . . . . . . . . . . . . . 8
6.2. Logging . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.3. History . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.4. Indicating Alternate Venue . . . . . . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
10.1. Normative References . . . . . . . . . . . . . . . . . . . 11
10.2. Informative References . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
Boulton & Barnes Expires September 8, 2009 [Page 2]
Internet-Draft XCON Chat March 2009
1. Introduction
A Centralized Conference as defined by the "A Framework for
Centralized Conferencing" [RFC5239] 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 provides
an overview of the mechanisms and associated framework elements
involved when text is the media for the conference. This
functionality is often referred to as a "chatroom" as it provides the
text equivalent of a voice conversation involving multiple parties.
Several existing protocols support this chatroom functionality, such
as Internet Relay Chat (IRC) [RFC1459] and Extensible Messaging and
Presence Protocol (XMPP) [RFC3920]. In addition,
[I-D.ietf-simple-chat] provides chatroom functionality for a purely
SIP signaling based solution option using Message Session Relay
Protocol (MSRP) [RFC4975].
The focus of this document is to describe the interface and provide
guidelines for the the support of existing chatroom functionality on
a conferencing system based on the XCON framework, independent of the
specific media type used by the chat client. The details of the use
of the XCON framework for chat are provided in the Conference Control
Manipulation Protocol (CCMP) call flow document
[I-D.barnes-xcon-examples]
The functionality described in this document is not intended to
replace any of the existing chat protocols, nor is it specifying a
new chat protocol. The motivation for this document is to allow
clients that use the conferencing framework model for other media
types (e.g. voice/video) to utilize the same conference control
mechanisms and conferencing system to establish, update and delete a
conference instance associated with a chatroom, independent of the
chat protocol. This approach also allows the conferencing system to
provide a natural interworking point for various chat 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 [I-D.ietf-xcon-ccmp].
The terms "chat" and "chatroom" are used as described in [RFC2664].
Group chat is used to refer to the conferencing system "chatroom"
functionality. A Chat Client is a Conferencing Client as defined in
[RFC5239] that participates in a "chatroom".
Boulton & Barnes Expires September 8, 2009 [Page 3]
Internet-Draft XCON Chat March 2009
3. Overview
Figure 1 provides a general illustration of chat clients having a
direct, 1:1 connection to the conferencing system. The conferencing
system receives messages sent from a client participating in a
conference instance and then distributes them to the other clients
associated with the conference instance.
+--------+
| Chat |
| Client |
| |
+--------+
|
|
|
|
|
|
v
+------------+
+--------+ | | +--------+
| Chat | | | | Chat |
| Client |-------------->|Conferencing|<--------------| Client |
| | | System | | |
+--------+ | | +--------+
+------------+
^
|
|
|
|
|
|
+--------+
| Chat |
| Client |
| |
+--------+
Figure 1: Client Connection
The approach in this document is to have no impact on the existing
Boulton & Barnes Expires September 8, 2009 [Page 4]
Internet-Draft XCON Chat March 2009
chat protocols, while taking full advantage of the functionality
provided by the centralized conferencing framework.
A basic solution for MSRP based IM chat sessions is documented in
[I-D.ietf-simple-chat]. 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
[I-D.ietf-simple-chat] 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. The MSRP based IM chat solution 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 to take advantage of
the centralized conferencing framework model for advanced features,
such as sidebars and private conferences, and manipulation of the
conference data.
[Editor's Note: Add detail as to how this relates to XMPP, as well.]
3.1. Protocol Operations
A chat 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 a message is specific to the chat protocol (e.g.,
MSRP SEND). Upon issuing a request to send a message, the message
will be replicated and forwarded by the conferencing system to all
other chat clients that are participants of the Group Chat conference
instance.
A chat client wishing to delete a chat room uses standardized
mechanisms for deleting a conference instance. Non-signaling
specific mechanisms are defined in the Centralized Conferencing
Framework [RFC5239] and related protocol document
[I-D.ietf-xcon-ccmp]. Protocol specific mechanisms are defined in
other documents such as for SIP in the SIPPING Conference Framework
[RFC4353].
3.2. Chat Session and Conferencing Identifiers
As highlighted in the overview section, a chat client connecting to a
conferencing system has a 1:1 relationship with the chat signaling
entity, each having a unique protocol specific Chat Session
identifier (ID). When referring to Chat Session IDs the document is
making reference to the locally (at conferencing system) generated
Boulton & Barnes Expires September 8, 2009 [Page 5]
Internet-Draft XCON Chat March 2009
Chat Session ID used for session signaling identification. In the
case of MSRP, this Chat Session ID is inserted into the local path
SDP attribute. An important concept in this proposal is the creation
and management of Group Chats. It is important that each chat
session created, as identified by a unique chat session ID, is
explicitly tied to an associated conference, represented by the
conference identifier (as defined in the Centralized Conferencing
Framework [RFC5239]). This provides the relevant association between
a chat session and a centralized conference. A generic example
representation is illustrated by the rows contained in Figure 2.
+-----------------------------------------+
| Conference Identifier |
+-----------------------------------------+
| Chat Session ID=8asjdhk |
| Chat Session ID=38iuhds |
| Chat Session ID=djiowid |
| Chat Session ID=389hewu |
+-----------------------------------------+
Figure 2: Simple Session Association
The Centralized Conferencing Framework[RFC5239] introduces the
concept of a conference user identifier defined in
[I-D.ietf-xcon-common-data-model]. 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 a chat 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 |
+--------------------------------+-----------------------------+
| Chat Session ID=8asjdhk | Conf User ID=839ULjj |
| Chat Session ID=38iuhds | Conf User ID=0283hHu |
| Chat Session ID=djiowid | Conf User ID=ncH37H |
| Chat Session ID=389hewu | Conf User ID=pakdjjH |
+--------------------------------+-----------------------------+
Boulton & Barnes Expires September 8, 2009 [Page 6]
Internet-Draft XCON Chat March 2009
Figure 3: Advanced Session Association
A more complex session association is necessary due to potential for
a user to have multiple group chats 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.
This process becomes complex in the case that multiple SDP MSRP media
sessions (m=) are defined in a single payload. This internal
representation needs expanding to enable a conferencing system to
explicitly associate a media session (m=). This involves including
the media label, as defined in [RFC4574], to maintain the internal
conference association. An example is illustrated in Figure 4.
+-----------------------------------------------------------------+
| Conference Identifier |
+-----------------------------------------------------------------+
| Chat Session ID=8asjdhk | Conf User ID=839ULjj | Label=iede3 |
| Chat Session ID=38iuhds | Conf User ID=0283hHu | Label=8heus |
| Chat Session ID=838unaH | Conf User ID=0283hHu | Label=3cnu7 |
| Chat Session ID=djiowid | Conf User ID=ncH37Hs | Label=jd38J |
| Chat Session ID=389hewu | Conf User ID=pakdj7H | Label=U83hd |
| Chat Session ID=Ko03jdk | Conf User ID=pakdj7H | Label=ehy3h |
+-----------------------------------------------------------------+
Figure 4: Advanced Session Association + Media Label
In Figure 4, conference user identifiers '0283hHu' and 'pakdj7H'
appear twice. The combination of multiple conference user
identifiers and a unique Group Chat session ID enables the conference
system to clearly identify a specific Group Chat instance. 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
The basic operations for creating, joining, and deleting a chat based
conference are all supported by the XCON framework using CCMP. The
discovery of chat rooms available on a specific conferencing system
is inherent in the blueprint capability provided by the conferencing
Boulton & Barnes Expires September 8, 2009 [Page 7]
Internet-Draft XCON Chat March 2009
system. The protocol details for these basic operations are provided
in [I-D.barnes-xcon-examples].
5. Advanced Operations
Advanced chat features, such as sidebars and private messages can
also be suppported within the context of the centralized conferencing
framework using CCMP. The protocol details for these advanced
features are provided in [I-D.barnes-xcon-examples].
6. Additional Operations
This section discusses additional operations or features required to
provide chat room functionality. Most of the operations are not
explicitly defined in the centralized conferencing framework.
However, some of the features and operations are achievable using
data maintained by a conferencing system based on the framework.
6.1. Nicknames
Nicknames allow a user to define a text string that uniquely
identifies the user within a particular chatroom without necessarily
reflecting any protocol specific identity (e.g., SIP URI, Conference
User Indentifier, etc.). It is also important to note that the
functionality to provide nicknames is not limited to users involved
in chatrooms, thus it should be a general feature of the conferencing
system.
Within a conferencing system, all nicknames should map to a
conference user identifier. The nicknames are unique only to the
specific conferencing system. There may be multiple nicknames
associated with a single conference user identifier (e.g., a user
that has different nicknames for different chat rooms and/or voice/
video conferences). In order to support nicknames, an attribute is
defined to the createUser CCMP request message to specify that a user
wants a nickname. The conferencing client may include a preferred
nickname in the createUser CCMP request.
The conferencing system allocates a conference user identifer and a
nickname using system specific mechanisms, which may also include
authentication. The conferencing system associates the assigned
nickname with the specific conference user identifier that has been
allocated.
As described Section 3.2, the conference user identifer MUST be used
in conjunction with a chat session identifier to internally represent
Boulton & Barnes Expires September 8, 2009 [Page 8]
Internet-Draft XCON Chat March 2009
a participant in a conference instance. This association is created
when a conferencing client requests to create or join a specific
chatroom. The nickname allocated for the specific conferencing user
identifier MUST also be associated with the chat session ID.
Figure 5 provides an example of the association between the chat
session identifier, the conference user identifier and conference
nickname for a specific Group Chat represented by the conference
identfier.
+-----------------------------------------------------------------+
| Conference Identifier |
+-----------------------------------------------------------------+
| Chat Session ID=8asjdhk | Conf User ID=839ULjj | Nick=Alice |
| Chat Session ID=38iuhds | Conf User ID=0283hHu | Nick=Bob |
| Chat Session ID=838unaH | Conf User ID=0283hHu | Nick=Cliff |
| Chat Session ID=djiowid | Conf User ID=ncH37Hs | Nick=Dude |
| Chat Session ID=389hewu | Conf User ID=pakdj7H | Nick=Elliott |
| Chat Session ID=Ko03jdk | Conf User ID=pakdj7H | Nick=Fluffy |
+-----------------------------------------------------------------+
Figure 5: Nickname Associations for a Group Chat
Depending upon the conferencing system, the conference system may
allocate the preferred nickname for that user or return a different
nickname in the createUser CCMP response message.
In the future, if a more generic nickname mechanism is available,
rather than provide nicknames that are specific to the conferencing
system, a conferencing system may interface with a nickname registry,
for example, in order to allocate a new nickname for a specific
conferencing client. This change in how a conferencing system
allocates nicknames should not impact the CCMP protocol interface to
support nicknames.
6.2. Logging
A common chat feature involves logging the history of a chat room.
This provides a record of a chat room that can be used when a user
first joins a chat room as discussed in Section 6.3. It can also be
used to provide a complete capture of a specific chat room session.
The centralized conferencing framework does not fully describe the
role of recording or logging of active conferences. However, this
functionality can be realized with the manipulation of the
appropriate elements in the data model using the general conference
Boulton & Barnes Expires September 8, 2009 [Page 9]
Internet-Draft XCON Chat March 2009
control protocol operations. One approach for implementing this
function would be to have it be based on specific manipulation of the
conference by a user with the appropriate permissions (e.g., CHANGE
operation to start and stop recording). Another mechanism for
implementing this function would be to have a specific user as part
of the conference to perform this function, by defining a specific
role such as "observer" and having the media proxied to a logging
device.
6.3. History
A common chat feature allows users to view the past history of chat
rooms. This operation is common when a user first joins a chat room
that is underway. A user is often offered the option to review a
specific number of past messages. Conferencing systems that maintain
the history associated with specific chat rooms through logging, as
described in Section 6.2, should provide a mechanism, using the
conference identifier, to access the specific information requested
by a user based on a specific timestamp. The user request for the
information and the rendering of the information is specific to the
user's session based messaging protocol and may not be supported by
all the messaging protocols.
6.4. Indicating Alternate Venue
Another chat room feature provides the details of an alternate chat
room venue for previously active chat rooms that have been closed,
with a related topic. While not detailed in the centralized
conferencing framework, this functionality can be accomplished by
creating the new chat room as a child or sibling of the previous chat
room and providing the Active chat conference object identifier to
any valid users that attempt to join a previous chat room. The
information about the new chat room can also be provided at the end
of a chat room that is being de-activated at the end of the session.
7. Security Considerations
As discussed in the Centralized Conferencing 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.
Boulton & Barnes Expires September 8, 2009 [Page 10]
Internet-Draft XCON Chat March 2009
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
Centralized Conferencing 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, as discussed in the Centralized
Conferencing Framework.
8. IANA Considerations
This document requires no IANA registrations.
9. Acknowledgements
The authors appreciate the input and comments from Miguel Garcia-
Martin, Dave Morgan and Salvatore Loreto.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5239] Barnes, M., Boulton, C., and O. Levin, "A Framework for
Centralized Conferencing", RFC 5239, June 2008.
[I-D.ietf-xcon-common-data-model]
Novo, O., Camarillo, G., Morgan, D., Even, R., and J.
Urpalainen, "Conference Information Data Model for
Centralized Conferencing (XCON)",
draft-ietf-xcon-common-data-model-12 (work in progress),
October 2008.
[I-D.ietf-xcon-ccmp]
Barnes, M., Boulton, C., Romano, S., and H. Schulzrinne,
"Centralized Conferencing Manipulation Protocol",
draft-ietf-xcon-ccmp-01 (work in progress), November 2008.
Boulton & Barnes Expires September 8, 2009 [Page 11]
Internet-Draft XCON Chat March 2009
10.2. Informative References
[I-D.roach-xcon-chatroom-analysis]
Roach, A., "An Analysis of Feature Parity Between XCON/
SIMPLE-Based Chatrooms and Other Chatrooms",
draft-roach-xcon-chatroom-analysis-00 (work in progress),
August 2007.
[I-D.barnes-xcon-examples]
Barnes, M., Boulton, C., Miniero, L., and S. Romano,
"Centralized Conferencing Manipulation Protocol (CCMP)
Call Flow Examples", draft-barnes-xcon-examples-00 (work
in progress), July 2008.
[RFC2664] Plzak, R., Wells, A., and E. Krol, "FYI on Questions and
Answers - Answers to Commonly Asked "New Internet User"
Questions", RFC 2664, August 1999.
[RFC1459] Oikarinen, J. and D. Reed, "Internet Relay Chat Protocol",
RFC 1459, May 1993.
[RFC2810] Kalt, C., "Internet Relay Chat: Architecture", RFC 2810,
April 2000.
[RFC3920] Saint-Andre, P., Ed., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 3920, October 2004.
[RFC4353] Rosenberg, J., "A Framework for Conferencing with the
Session Initiation Protocol (SIP)", RFC 4353,
February 2006.
[RFC4975] Campbell, B., Mahy, R., and C. Jennings, "The Message
Session Relay Protocol (MSRP)", RFC 4975, September 2007.
[I-D.ietf-simple-chat]
Niemi, A., Garcia-Martin, M., and G. Sandbakken, "Multi-
party Chat Using the Message Session Relay Protocol
(MSRP)", draft-ietf-simple-chat-03 (work in progress),
October 2008.
[RFC4574] Levin, O. and G. Camarillo, "The Session Description
Protocol (SDP) Label Attribute", RFC 4574, August 2006.
[RFC4579] Johnston, A. and O. Levin, "Session Initiation Protocol
(SIP) Call Control - Conferencing for User Agents",
BCP 119, RFC 4579, August 2006.
Boulton & Barnes Expires September 8, 2009 [Page 12]
Internet-Draft XCON Chat March 2009
Authors' Addresses
Chris Boulton
NS-Technologies
Email: chris@ns-technologies.com
Mary Barnes
Nortel
2201 Lakeside Blvd
Richardson, TX
Email: mary.barnes@nortel.com
Boulton & Barnes Expires September 8, 2009 [Page 13]