Internet DRAFT - draft-boulton-dispatch-conference-control-package
draft-boulton-dispatch-conference-control-package
DISPATCH Working Group C. Boulton
Internet-Draft NS-Technologies
Intended status: Standards Track M. Barnes
Expires: January 16, 2014 Polycom
July 15, 2013
An XCON Client Conference Control Package for the Media Control Channel
Framework
draft-boulton-dispatch-conference-control-package-01
Abstract
The Centralized Conferencing (XCON) framework defines a model whereby
client initiated interactions are required for creation, deletion,
manipulation and querying the state of a of conference. This
document defines a Media Control Channel Package for XCON
conferencing client initiated Conference Control. The Package is
based on the Media Control Channel Framework, which is also used for
media server control, thus optimizing the implementation for some
entities participating in an XCON system.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on January 16, 2014.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Control Package Detail . . . . . . . . . . . . . . . . . . . . 6
5.1. Control Package Name . . . . . . . . . . . . . . . . . . . 6
5.2. Framework Message Usage . . . . . . . . . . . . . . . . . 6
5.3. Common XML Support . . . . . . . . . . . . . . . . . . . . 6
5.4. Control Message Bodies . . . . . . . . . . . . . . . . . . 6
5.5. REPORT Message Bodies . . . . . . . . . . . . . . . . . . 7
5.6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6.1. Control Package Registration . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
9. Change History . . . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
The Conference Control Manipulation Protocol (CCMP) [RFC6503]
provides a standards based mechanism to enable third party conference
clients participating to interoperate with conference servers and
manipulate conference parameters using HTTP as a transport. A Data
Model [RFC6501] provides the data associated with a conference
instance that is the target for the CCMP protocol operations.
A Control Channel Framework [RFC6230] has been created based on the
Session Initiation protocol (SIP). It uses SIP to setup, maintain
and terminate a reliable control channel for the purpose of
exchanging control based interactions. While the control of media
was the original problem domain for which this framework was
developed, the Control Framework provides an extension template for
creating extensions that specify the semantic detail associated with
the control channel operations. The extension documents are known as
Control Packages and an example is the 'Basic Mixer Control Package'
[RFC6505].
This document will specify a Control Package for XCON conference
control using the SIP Control Framework. The target for these
operations is the same data, associated with conference instances per
the data model, as CCMP. It should be noted that this mechanism is a
complementary approach to CCMP [RFC6503]. In fact this specification
simply provides a different transport mechanism. While the use of
HTTP as a transport for CCMP is ideal for certain network deployments
(for example Service Orientated Architectures), it is important to
offer an alternative access method for clients with non SOA based
technologies.
The Media Control Channel Framework provides the ideal mechanism for
reliably exchanging control messages between a conferencing client
and conference server. It provides inherent properties such as:
o Reliable delivery of control messages.
o Lightweight Protocol Data Units (PDU).
o Linked asynchronous transactional mechanism.
o Asynchronous event mechanism.
The SIP Control Framework uses SIP as its overlying rendezvous
mechanism. This provides all the inherent benefits like:
o SIP Service Location - Use SIP Proxies or Back-to-Back User Agents
for discovering Control Servers.
o SIP Security Mechanisms - Leverage established security mechanisms
such as Transport Layer Security (TLS) and Client Authentication.
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o Connection Maintenance - The ability to re-negotiate a connection,
ensure it is active, audit parameters, and so forth.
o Agnostic - Allows for ease of extension.
Not only is the Media Control Channel Framework an ideal mechanism
for controlling conference instances by participating clients, it
also provides the property of re-use by conferencing systems of
functionality implemented for controlling Media Servers etc. This
includes re-using the SIP stack for control channel setup as well as
the Control Channel Framework stack for receiving/sending the PDUs
for multiple control packages in a conference system.
2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Terminology
This document reuses the terminology defined and used in the
framework and data model for centralized conferencing [RFC5239],
[RFC6501] and [RFC6503] .
4. Overview
The use of the Media Control Channel Framework offers an ideal
mechanism for creating, deleting and manipulating XCON conference
instances by participating clients. As the Control Channel Framework
is a generic mechanism, this section provides non-normative detail
showing how the Control Channel Framework can be applied to this
particular use-case.
In [RFC6230], two distinct roles are defined - A Control Client and a
Control Server. Such roles are interchangeable between entities
within a session depending on package requirements. A simple diagram
is illustrated in Figure 1
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+--------------SIP Traffic--------------+
| |
v v
+-----+ +--+--+
| SIP | | SIP |
|Stack| |Stack|
+---+-----+---+ +---+-----+---+
| Control | | Control |
| Client |<----Control Channel---->| Server |
+-------------+ +-------------+
Figure 1: Basic Architecture
The XCON Conference Control package will cast a participating
compliant XCON conferencing client that wishes to control a
conference instance as a Control Client as defined in the SIP Control
Framework. The conferencing client will have permission to generate
and issue commands in CONTROL messages as defined in Section 5.2 of
this document. It will also have the ability to receive responses to
Conference Package CONTROL requests that are contained in either
appropriate responses or subsequent REPORT messages, also specified
in Section 5.2. The previous diagram can be updated as illustrated
in Figure 2.
+--------------SIP Traffic--------------+
| |
v v
+-----+ +--+--+
| SIP | | SIP |
|Stack| |Stack|
+---+-----+---+ +---+-----+---+
| XCON | | XCON |
|Conferencing | | Conference |
| Client |<----Control Channel---->| Server |
+-------------+ +-------------+
Figure 2: Conference Control Architecture
The specific format of the conference control messages and responses
are defined in Section 5.4 and Section 5.5. They content of the
control messages and responses is in the format specified in CCMP
[RFC6503]. This allows a conferencing client to manage the same data
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and message format independent of whether CCMP or the Control
Framework messages are used to transport the information.
5. Control Package Detail
The Media Control Channel Framework defines rules that Control
Package extensions must provide mandatory information as described in
section 10 of [RFC6230]. This section fulfils the obligation.
5.1. Control Package Name
The SIP Control Framework requires a Control Package definition to
specify and register a unique package name. The name and version of
this Control Package is "xcon-conf-control/1.0".
5.2. Framework Message Usage
The Conference Control package uses the XML schema defined in CCMP
[RFC6503]. To maintain the consistency with the design of the XML
schema, the SIP Control Framework messages will be applied in a
similar manner. The CONTROL message will be used to contain requests
that enable conference manipulation - as specified in Section 5.4 and
can only be sent from the conferencing client to a conference server.
Responses, as specified in Section 5.5, can only be sent from the
conference server to the conferencing client that initiated the
request. Depending on the time it takes to process the request (as
specified in [RFC6230]), responses can either be contained in a
Control Framework 200 response or subsequent REPORT method.
5.3. Common XML Support
The Control Framework requires a Control Package definition to
specify if the attributes for media dialog or conference references
are required.
This package requires that the XML Schema in Section 16.1 of
[RFC6230] MUST NOT be supported for media dialogs and conferences.
But rather this package SHOULD use the XML schema as defined in
[RFC6503], which is the same schema used for CCMP.
5.4. Control Message Bodies
A valid CONTROL body message MUST conform to the XML schema defined
in [RFC6503] for the conference control. To be precise, the CONTROL
message body MUST comply only to the 'ccmp-request-type' complexType.
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5.5. REPORT Message Bodies
A valid CONTROL body message MUST conform to the XML schema defined
in [RFC6503]. To be precise, the REPORT message body MUST comply
only to the 'ccmp-response-type' complexType.
5.6. Examples
TODO
6. IANA Considerations
6.1. Control Package Registration
This section registers a new Media Control Channel Framework package,
per the instructions in Section 12.1 of [RFC6230].
To: ietf-sip-control@iana.org Subject: Registration of new Media
Control Channel Framework package Package Name: xcon-conf-control/1.0
[NOTE TO IANA/RFC-EDITOR: Please replace XXXX with the RFC number for
this specification.] Published Specification(s): RFCXXXX Person &
email address to contact for further information: IETF, DISPATCH
working group, (dispatch@ietf.org), Mary Barnes
(mary.ietf.barnes@gmail.com).
7. Security Considerations
As this Control Package processes XML markup, implementations MUST
address the security considerations of [RFC3203].
As a Control Package of the Media Control Channel Framework,
security, confidentiality, and integrity of messages transported over
the Control Channel MUST be addressed as described in Section 12 of
the Media Control Channel Framework [RFC6230], including transport-
level protection, Control Channel policy management, and session
establishment.
The Framework for Centralized Conferencing [RFC5239] specifies that
the protocols used for manipulation and retrieval of confidential
information MUST support a confidentiality and integrity mechanism.
The XCON Data model [RFC6501] describes the requirements for ensuring
the conference data is secured by the conference server (section 8).
To support the confidentiality and integrity requirements, all
conference control information included in the package defined in
this document MUST have transport level protection; see [RFC6230],
section 12.2 for further details on this topic. Adequate transport
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protection and authentication are critical, especially when the
implementation is deployed in open networks. If the implementation
fails to correctly address these issues, it risks exposure to
malicious attacks, including (but not limited to):
Denial of Service: An attacker could insert a request message into
the transport stream causing specific conferences on the
conference server to be deleted. For example, a confRequest
message with an operation of "delete" with a "<confObjID>" of
"xcon:XXXX@example.com", where the value of "XXXX" could be
guessed or discovered by registering for the 'conference'
[RFC4575]. Likewise, an attacker could impersonate the conference
server and insert error responses into the transport stream
thereby denying the conferencing client access to package
capabilities.
Resource Exhaustion: An attacker could insert into the Control
Channel new request messages such as a confRequest message with an
operation of "create" causing large numbers of conference
resources to be allocated. At some point, this will exhaust the
number of conference resources that the conference server is able
to allocate.
The Media Control Channel Framework permits additional policy
management (beyond that specified for the Media Control Channel
Framework), including resource access and Control Channel usage, to
be specified at the Control Package level. (See Section 12.3 of
[RFC6230].)
Since creation of conference instances is associated with resources
on the conference server, the security policy for this Control
Package needs to address how such conference instances are securely
managed across more than one Control Channel. Such a security policy
is only useful for secure, confidential, and integrity-protected
channels. The identity of Control Channels is determined by the
channel identifier, i.e., the value of the 'cfw-id' attribute in the
SDP and Dialog-ID header in the channel protocol per [RFC6230].
Channels are the same if they have the same identifier; otherwise,
they are different. This Control Package imposes the following
additional security policies:
Responses: The conference server MUST only send a response to a
conference control request using the same Control Channel as the
one used to send the request.
Notifications: The conference server MUST only send notification
events for conference instances using the same Control Channel as
it received the request creating the conference instance.
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Rejection: The conference server SHOULD reject requests to
manipulate an existing conference on the conference server if the
channel is not the same as the one used when the mixer was
created. The conference server rejects a request by sending a
Control Framework 403 response (see Sections 7.4 and 12.3 of
[RFC6230]). For example, if a channel with identifier 'cfw1234'
has been used to send a request to create a particular conference
instance and the conference server receives on channel 'cfw98969'
a request to "delete" this particular conference instance, then
the conference server sends a Control Framework 403 response.
There can be valid reasons why an implementation does not reject an
manipulation request on a different channel from the one that created
the mixer. For example, a system administrator might require a
separate channel to delete conferences consuming excessive system
resources. However, the full implications need to be understood by
the implementation and carefully weighed before accepting these
reasons as valid. If the reasons are not valid in their particular
circumstances, the conference server rejects such requests.
There can also be valid reasons for 'channel handover' including high
availability support or when one conference server needs to take over
management of conference instances after the conference server that
created them has failed. This could be achieved by the Control
Channels using the same channel identifier, one after another. For
example, assume a channel is created with the identifier 'cfw1234',
and the channel is used to create conference instances on the
conference server. This channel (and associated SIP dialog) then
terminates due to a failure on the conference server. As permitted
by the Control Framework, the channel identifier 'cfw1234' could then
be reused so that another channel is created with the same identifier
'cfw1234', allowing it to 'take over' management of the conference
instances on the conference server. Again, the implementation needs
to understand the full implications and carefully weigh them before
accepting these reasons as valid. If the reasons are not valid for
their particular circumstances, the conference server uses the
appropriate SIP mechanisms to prevent session establishment when the
same channel identifier is used in setting up another Control Channel
(see Section 4 of [RFC6230]).
8. Acknowledgments
9. Change History
Note to RFC Editor: Please delete this section prior to publication.
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Changes between 00 and 01:
1. Updating terminology to be consistent with RFC 6503 - i.e.,
conferencing client and conference server.
2. Updates to security section to be consistent with requirements
for a control package per RFC6230.
3. Minor editorial changes.
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.
[RFC3203] T'Joens, Y., Hublet, C., and P. De Schrijver, "DHCP
reconfigure extension", RFC 3203, December 2001.
[RFC4575] Rosenberg, J., Schulzrinne, H., and O. Levin, "A Session
Initiation Protocol (SIP) Event Package for Conference
State", RFC 4575, August 2006.
[RFC6230] Boulton, C., Melanchuk, T., and S. McGlashan, "Media
Control Channel Framework", RFC 6230, May 2011.
[RFC6501] Novo, O., Camarillo, G., Morgan, D., and J. Urpalainen,
"Conference Information Data Model for Centralized
Conferencing (XCON)", RFC 6501, March 2012.
[RFC6505] McGlashan, S., Melanchuk, T., and C. Boulton, "A Mixer
Control Package for the Media Control Channel Framework",
RFC 6505, March 2012.
[RFC6503] Barnes, M., Boulton, C., Romano, S., and H. Schulzrinne,
"Centralized Conferencing Manipulation Protocol",
RFC 6503, March 2012.
10.2. Informative References
[RFC5239] Barnes, M., Boulton, C., and O. Levin, "A Framework for
Centralized Conferencing", RFC 5239, June 2008.
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Authors' Addresses
Chris Boulton
NS-Technologies
Email: chris@ns-technologies.com
Mary Barnes
Polycom
TX
Email: mary.ietf.barnes@gmail.com
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