XCON Working Group O. Levin
Internet-Draft Microsoft Corporation
Expires: July 3, 2006 R. Even
Polycom
P. Hagendorf
RADVISION
December 30, 2005
Centralized Conference Control Protocol
draft-levin-xcon-cccp-04
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Abstract
This document defines a Centralized Conferencing Control Protocol
(CCCP) as a part of the XCON Working Group protocols suite. CCCP
uses a client-server model for creation, querying, and manipulation
of XCON entities, conference objects and sub-objects. An XCON
entity, which implements a CCCP server, provides a means for
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authorized CCCP clients (e.g. conference participants) to affect the
behavior of a conference in the XCON system.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Transport . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. The Protocol . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Transaction Model . . . . . . . . . . . . . . . . . . . . 4
4.2. Multiple Primitives in a Single Operation . . . . . . . . 6
4.3. Response Codes and Failures . . . . . . . . . . . . . . . 6
5. Using the Data Model . . . . . . . . . . . . . . . . . . . . . 6
6. Design Rationale . . . . . . . . . . . . . . . . . . . . . . . 7
6.1. Remote Procedure vs. Data Manipulation . . . . . . . . . . 7
6.2. CCCP Transactions vs. SOAP . . . . . . . . . . . . . . . . 8
7. Primitives . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. System Primitives . . . . . . . . . . . . . . . . . . . . 9
7.1.1. Cancel . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1.2. Ping . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1.3. getTemplates . . . . . . . . . . . . . . . . . . . . . 11
7.1.4. getActiveConferences . . . . . . . . . . . . . . . . . 11
7.2. Conference Primitives . . . . . . . . . . . . . . . . . . 11
7.2.1. addConference . . . . . . . . . . . . . . . . . . . . 11
7.2.2. modifyConference . . . . . . . . . . . . . . . . . . . 13
7.2.3. deleteConference . . . . . . . . . . . . . . . . . . . 14
7.2.4. getConference . . . . . . . . . . . . . . . . . . . . 15
7.3. User Primitives . . . . . . . . . . . . . . . . . . . . . 16
7.3.1. addUser . . . . . . . . . . . . . . . . . . . . . . . 16
7.3.2. modifyUser . . . . . . . . . . . . . . . . . . . . . . 17
7.3.3. modifyUserRoles . . . . . . . . . . . . . . . . . . . 18
7.3.4. deleteUser . . . . . . . . . . . . . . . . . . . . . . 19
7.3.5. getUser . . . . . . . . . . . . . . . . . . . . . . . 20
7.4. Endpoint Primitives . . . . . . . . . . . . . . . . . . . 21
7.4.1. addEndpoint . . . . . . . . . . . . . . . . . . . . . 21
7.4.2. modifyEndpoint . . . . . . . . . . . . . . . . . . . . 22
7.4.3. deleteEndpoint . . . . . . . . . . . . . . . . . . . . 23
7.4.4. getEndpoint . . . . . . . . . . . . . . . . . . . . . 24
7.5. Endpoint Media Primitives . . . . . . . . . . . . . . . . 25
7.5.1. addEndpointMedia . . . . . . . . . . . . . . . . . . . 26
7.5.2. modifyEndpointMedia . . . . . . . . . . . . . . . . . 26
7.5.3. deleteEndpointMedia . . . . . . . . . . . . . . . . . 27
7.5.4. getEndpointMedia . . . . . . . . . . . . . . . . . . . 28
7.6. Sidebar Primitives . . . . . . . . . . . . . . . . . . . . 29
7.6.1. addSidebar . . . . . . . . . . . . . . . . . . . . . . 29
7.6.2. modifySidebar . . . . . . . . . . . . . . . . . . . . 30
7.6.3. deleteSidebar . . . . . . . . . . . . . . . . . . . . 30
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7.6.4. addUserToSidebar . . . . . . . . . . . . . . . . . . . 30
7.6.5. deleteUserFromSidebar . . . . . . . . . . . . . . . . 30
7.6.6. moveUserBetweenSidebars . . . . . . . . . . . . . . . 30
7.7. Stimulus Primitives . . . . . . . . . . . . . . . . . . . 30
8. The XML Schema . . . . . . . . . . . . . . . . . . . . . . . . 30
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 49
9.1. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:cccp . . . . . . . . . . . . . . . 49
9.2. XML Schema Registration . . . . . . . . . . . . . . . . . 50
10. Security Considerations . . . . . . . . . . . . . . . . . . . 50
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 50
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 51
12.1. Normative References . . . . . . . . . . . . . . . . . . . 51
12.2. Informative References . . . . . . . . . . . . . . . . . . 51
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 52
Intellectual Property and Copyright Statements . . . . . . . . . . 53
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1. Introduction
The SIPPING Conference Framework [6] describes a general centralized
conferencing architecture. The XCON Framework [7] defines how this
architecture can be realized by an XCON compliant system. This
document defines a Centralized Conferencing Control Protocol (CCCP)
as a conference control protocol in the XCON protocols suite
described in XCON Framework [7]
CCCP uses a client-server model for creation, querying, and
manipulation of XCON entities, conference objects and sub-objects.
By implementing a CCCP server, an XCON entity provides a means for
authorized CCCP clients (e.g. conference participants) to affect the
behavior of a conference in the XCON system. CCCP is a semantic-
oriented protocol, which uses the XML types defined in the SIPPING
Conference Package [2] for the representation of the conference
object and its sub-objects . In future, the CCCP can be extended to
include manipulations on additional conferencing objects being
represented by XML schemas such as policies and templates.
2. Terminology
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. Transport
The protocol design assumes that CCCP runs on a reliable transport
protocol.
CCCP is agnostic to the details of the transport protocol being used
beneath and does not rely on any information being conveyed on the
transport level. This model allows for using different transport
protocols based on the system requirements and also for multiplexing
otherwise independent CCCP communications over a common transport
channel.
4. The Protocol
4.1. Transaction Model
CCCP is a client-server protocol. The protocol defines two
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operations: request and response.
A client issues requests to a server. The server MUST reply with a
single final response. Two final responses are defined: "failure"
and "success".
Before issuing the final response, the server MAY reply with multiple
provisional responses. Currently a single provisional response
"pending" is defined.
Editor's Note: Timeouts TBD.
A CCCP request carries the following attributes:
+------------+------------------------------------------------------+
| Attribute | Description |
+------------+------------------------------------------------------+
| requestId | A unique string generated by the CCCP client across |
| | all its requests. |
| from | A transport URI which identifies the CCCP client. |
| to | A transport URI which identifies the CCCP server. |
| originator | A trusted ID of the originator of the request. |
+------------+------------------------------------------------------+
Table 1
The combination of the 'requestId', 'to', and 'from' attributes in
the request constitutes the CCCP transaction ID.
A CCCP response carries the following attributes:
+------------+------------------------------------------------------+
| Attribute | Description |
+------------+------------------------------------------------------+
| requestId | The original request ID generated by the client and |
| | echoed as is by the server. |
| from | A transport URI which identifies the CCCP server. |
| to | A transport URI which identifies the CCCP client. |
| code | The general response code: success, pending, or |
| | failure. |
| reason | The general CCCP failure reason. |
| timeout | The updated timeout used with pending responses |
| | (details TBD). |
| retryAfter | The suggested delay used with serverBusy responses. |
+------------+------------------------------------------------------+
Table 2
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4.2. Multiple Primitives in a Single Operation
A CCCP operation (i.e. a request and a corresponding response) MAY
contain multiple primitives. The CCCP MUST process the received
primitives one-by-one in the order they appear in the request body.
If the request contains multiple primitives, the corresponding
response operation MUST contain the response primitive for each and
in the same order as in the request.
Multiple primitives within the same request MUST be executed as an
atomic operation. This means that if one primitive fails, the state
of the object MUST be rolled back to its state before processing the
request.
If a CCCP server is not willing to process a multi-primitive request,
it MUST fail the transaction with the response code "notSupported".
4.3. Response Codes and Failures
CCCP defines the following reasons for failure of a request operation
+------------------+------------------------------------------------+
| Failure | Description |
+------------------+------------------------------------------------+
| serverBusy | Optional retryAfter can be included in the |
| | response. |
| timeout | Operation took too long and was aborted by the |
| | server |
| unauthorized | Client is not authorized to perform the |
| | operation. |
| requestMalformed | The XML document in the request is either not |
| | well-formed or not compliant with the schema. |
| requestTooLarge | Result of the request operation length check. |
| requestCancelled | The pending request was canceled by CCCP. |
| notSupported | One of the primitives or their combination is |
| | not supported by the server. |
| otherFailure | Result of any other server fault condition. |
+------------------+------------------------------------------------+
Table 3
Most CCCP primitives define their own optional response codes. This
allows communicating the detailed primitive result in addition to the
CCCP general response code.
5. Using the Data Model
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The CCCP operations are applied to the data objects expressed in
terms of SIPPING Conference Package [2] XML types whenever possible.
The considerations listed below MUST be taken into account when using
the schema with CCCP.
The information included in the request expresses the desired data
object state to be achieved after the operation is successfully
completed. By definition, the CCCP primitives allow for inclusion of
any information that can be expressed in terms of the conference-type
and its sub-types.
Attributes 'state' and 'version' of the conference-type and its sub-
types are never used with CCCP. The information in the response is
provided as a feedback to the request only and typically does not
carry the full state of the object.
For each primitive request, the CCCP explicitly defines (see Section
6) what information (i.e. attributes and elements) MUST be provided
by the client and what information (when provided by the client) MUST
NOT be ignored by the server. The rest of the information included
by the client MAY be treated as optional by the server.
For each primitive response, the CCCP explicitly defines (see Section
6) what information (i.e. attributes and elements) if included by the
server MUST NOT be ignored by the client. The rest of the
information included by the client MAY be treated as optional by the
server. If neither mandatory information nor new data is generated,
the server MAY return minimum schema compliant construct, such as an
element with empty body and the attributes identifying the
corresponding request only. On the other hand, the CCCP server MAY
include any rich dynamically generated information to the client (for
example, to be displayed to a user or be logged in by the system) in
the response. The client MAY ignore any information received in the
response, unless stated otherwise in Section 6.
6. Design Rationale
6.1. Remote Procedure vs. Data Manipulation
The first step in the decision process was to compare between a data
manipulation approach and a remote procedure call approach.
The advantages of the data manipulation approach are:
o Mostly appropriate for simple lightweight clients using built on a
stimulus-response model
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o The data model is the protocol -- any existing generic data
manipulation protocol will work
o Adding functionality does not require changes to the protocol,
only to the data model. The server implementation needs to track
these changes of course and implement the corresponding new
functionality.
The advantages for the remote procedure call approach are:
o Mostly appropriate for conferencing-aware client applications that
are built to automate the experience and/or hide conferencing
complexity from the end user
o Makes compound operations and conference specific operations
explicit and thus much easier and faster for conferencing server
implementation
o Allows for inclusion of data manipulation primitives when desired,
e.g. for manipulating templates. In other words, a hybrid
approach is easily built where it makes sense.
We came to a conclusion that there is a place for both approaches to
co-exist in the industry. The decision of which to use in each case
will be based on the client side requirements.
We also came to a conclusion that it is not necessary to define a new
conference-specific protocol in order to meet the lightweight client
requirements for a stimulus-response approach. Instead one of the
existing standard data manipulation protocols can be used for this
purpose. This approach will require standardizing the user interface
in terms of a standard conferencing XML schema(s).
On the other hand, smart conference-aware conferencing clients cannot
operate using abstract stimulus-response approach only. In order to
achieve both efficient and flexible conference control, a truly
application-specific, i.e. a conferencing control protocol, is
needed. The CCCP is defined with this need in mind.
6.2. CCCP Transactions vs. SOAP
It is not difficult to map the CCCP primitives and functionality into
a SOAP compliant protocol as shown in [TBD]. Apart from the pure
syntax differences, the two protocols differ in the way they report
the final result of a requested operation.
According to the SOAP specification, each transaction is comprised of
a request and a single corresponding response (which are transported
over the underlying HTTP transaction). This definition means that an
application that uses SOAP needs to define its own conventions for
handling requests that can not be completed immediately. Typically
this is being achieved by introducing an additional notification
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channel in the direction opposite to the request. It is important to
note that this channel must not be mistaken with the conference state
notification channel defined in [conf package].
The conference control notification channel should be provided to the
client originating the request only and would not necessarily reflect
any changes in the conference state. For example, in case a request
transaction is completed with the "in progress" response and later a
server fails to execute the request, the notification sent to the
client will not convey any change in the conference state, but rather
needs to convey the request ID and the failure reason.
CCCP is different at that sense from the SOAP architecture. CCCP
does not use any dedicated notification channel. Instead CCCP has
the notion of possible multiple pending responses always followed by
the final (either success or failure) response. This approach
simplifies the conferencing application and also makes CCCP truly
independent from the underlying transport protocol.
It is important to note that a CCCP client is expected to support the
Conference State event package as the means for maintaining the most
current synchronized conference state. The client should not use the
CCCP responses for updating the local copy of the conference state
document.
7. Primitives
This section describes the defined CCCP primitives and includes valid
XML document examples for each. The corresponding CCCP XML schema is
provided in Section 7.
7.1. System Primitives
7.1.1. Cancel
Cancel a pending request.
This primitive can be issued by a client to cancel a pending
transaction. The primitive is an independent transaction on its own.
The body of the primitive MUST carry the requestId of one of the
pending requests.
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5
Note that a valid response can contain an empty body.
7.1.2. Ping
Ping a CCCP Server.
A successful response is shown below.
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7.1.3. getTemplates
Get the list of templates supported by the system. XML TBD.
7.1.4. getActiveConferences
Get the list of conference identifiers for active conference objects
in the system.
XML TBD.
7.2. Conference Primitives
7.2.1. addConference
Create a conference.
The 'conferenceEntity' value in the request is a client's suggestion
only. The CCCP server MAY replace the suggested value with a
different 'conferenceEntity' value in the corresponding response.
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Design Review
tel:+1-8666119036
FFD bridge
https://company.com/ConfServer
audio
The CCCP server MAY replace the suggested 'conferenceEntity' with a
different value in the corresponding response. In the case of a
successful response, the CCCP client MUST use the new value and
SHOULD use all the new parameters allocated by the server to the
conference.
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tel:+1-8666119036
FFD bridge
https://company.com/ConfServer
audio
7.2.2. modifyConference
Modify conference parameters.
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Spec Review
7.2.3. deleteConference
Remove conference from the system.
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7.2.4. getConference
Retrieve the conference information.
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Design Review
tel:+1-8666119036
FFD bridge
https://company.com/ConfServer
audio
7.3. User Primitives
7.3.1. addUser
The client MUST provide the 'userEntity' value in the request.
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Bob Hoskins
presenter
7.3.2. modifyUser
Modify the user information.
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Bob Hoskins III
tel:2562566
the description
optional tbd values
presenter
7.3.3. modifyUserRoles
This is a dedicated primitive to change user's roles. The same
effect can be achieved by using the modifyUser primitive. Note that
a CCCP server can choose to implement both approaches simultaneously
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to be invoked by different clients.
Editor's Note: The dedicated primitive is defined to demonstrate that
both approaches are possible with CCCP.
presenter
7.3.4. deleteUser
Remove the user from the conference roster.
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7.3.5. getUser
Retrieve the information about a conference participant.
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Bob Hoskins III
tel:2562566
the description
optional tbd values
presenter
7.4. Endpoint Primitives
7.4.1. addEndpoint
Bring the specified user into a conference by establishing a call
(signaling and media) with him/her/it.
The endpoint 'entity' value MAY be replaced or augmented by the CCCP
server. The 'media-id' value MAY be replaced or augmented by the
CCCP server. If the server returns this information in the response,
the client MUST use the values provided by the server.
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Bob's Laptop
dialed-out
main audio
audio
7.4.2. modifyEndpoint
Modify the call description or/and its behaivior.
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Bob's Laptop
7.4.3. deleteEndpoint
Disconnect the call.
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7.4.4. getEndpoint
Retrieve the information about the call.
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Bob's Laptop
dialed-out
main audio
audio
7.5. Endpoint Media Primitives
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7.5.1. addEndpointMedia
Add the specified media stream to the call.
The 'media-id' value MAY be replaced or augmented by the CCCP server.
The CCCP client MUST use the new value if returned by the server in
the response.
main audio
audio
7.5.2. modifyEndpointMedia
Modify the media behavior. This primitive can be used to mute and
un-mute the call.
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audio
recvonly
7.5.3. deleteEndpointMedia
Remove the specified media stream from the call.
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7.5.4. getEndpointMedia
Retrieve the information about the specified stream in the call.
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audio
recvonly
7.6. Sidebar Primitives
7.6.1. addSidebar
Create a sidebar in the conference.
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XML TBD.
7.6.2. modifySidebar
Modify the sidebar parameters in the conference.
XML TBD.
7.6.3. deleteSidebar
Remove the sidebar from the conference.
XML TBD.
7.6.4. addUserToSidebar
Add the specified conference participant to the sidebar.
XML TBD.
7.6.5. deleteUserFromSidebar
Remove the specified conference participant from the sidebar.
XML TBD.
7.6.6. moveUserBetweenSidebars
Move the the specified conference participant from sidebar A to
sidebar B.
XML TBD.
7.7. Stimulus Primitives
This operation is used to convey opaque to the CCCP logic requests
from a CCCP client to a CCCP server to be processed by applications
above CCCP.
XML TBD.
8. The XML Schema
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Figure 39
9. IANA Considerations
This document registers a new XML namespace and a new XML schema.
9.1. URN Sub-Namespace Registration for urn:ietf:params:xml:ns:cccp
This section registers a new XML namespace, as per the guidelines in
RFC 3688 [5].
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URI: The URI for this namespace is urn:ietf:params:xml:ns:cccp
Registrant Contact: IETF XCON Working Group , as
designated by the IESG
XML:
BEGIN
Centralized Conference Information Namespace
Namespace for Centralized Conference Control Protocol
urn:ietf:params:xml:ns:cccp
See RFCXXXX.