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rfc:rfc6503

Internet Engineering Task Force (IETF) M. Barnes Request for Comments: 6503 Polycom Category: Standards Track C. Boulton ISSN: 2070-1721 NS-Technologies

                                                             S. Romano
                                                  University of Napoli
                                                        H. Schulzrinne
                                                   Columbia University
                                                            March 2012
           Centralized Conferencing Manipulation Protocol

Abstract

 The Centralized Conferencing Manipulation Protocol (CCMP) allows a
 Centralized Conferencing (XCON) system client to create, retrieve,
 change, and delete objects that describe a centralized conference.
 CCMP is a means to control basic and advanced conference features
 such as conference state and capabilities, participants, relative
 roles, and details.  CCMP is a stateless, XML-based, client server
 protocol that carries, in its request and response messages,
 conference information in the form of XML documents and fragments
 conforming to the centralized conferencing data model schema.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc6503.

Barnes, et al. Standards Track [Page 1] RFC 6503 CCMP March 2012

Copyright Notice

 Copyright (c) 2012 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
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Table of Contents

 1. Introduction ....................................................4
 2. Conventions and Terminology .....................................5
 3. XCON Conference Control System Architecture .....................5
    3.1. Conference Objects .........................................7
    3.2. Conference Users ...........................................7
 4. Protocol Overview ...............................................8
    4.1. Protocol Operations ........................................9
    4.2. Data Management ...........................................10
    4.3. Data Model Compliance .....................................11
    4.4. Implementation Approach ...................................12
 5. CCMP Messages ..................................................13
    5.1. CCMP Request Message Type .................................13
    5.2. CCMP Response Message Type ................................15
    5.3. Detailed Messages .........................................17
         5.3.1. blueprintsRequest and blueprintsResponse ...........20
         5.3.2. confsRequest and confsResponse .....................22
         5.3.3. blueprintRequest and blueprintResponse .............24
         5.3.4. confRequest and confResponse .......................26
         5.3.5. usersRequest and usersResponse .....................30
         5.3.6. userRequest and userResponse .......................32
         5.3.7. sidebarsByValRequest and sidebarsByValResponse .....37
         5.3.8. sidebarByValRequest and sidebarByValResponse .......39
         5.3.9. sidebarsByRefRequest and sidebarsByRefResponse .....42
         5.3.10. sidebarByRefRequest and sidebarByRefResponse ......44
         5.3.11. extendedRequest and extendedResponse ..............47
         5.3.12. optionsRequest and optionsResponse ................49
    5.4. CCMP Response Codes .......................................53
 6. A Complete Example of CCMP in Action ...........................57
    6.1. Alice Retrieves the Available Blueprints ..................58
    6.2. Alice Gets Detailed Information about a Specific
         Blueprint .................................................60

Barnes, et al. Standards Track [Page 2] RFC 6503 CCMP March 2012

    6.3. Alice Creates a New Conference through a Cloning
         Operation .................................................62
    6.4. Alice Updates Conference Information ......................65
    6.5. Alice Inserts a List of Users into the Conference Object ..66
    6.6. Alice Joins the Conference ................................68
    6.7. Alice Adds a New User to the Conference ...................70
    6.8. Alice Asks for the CCMP Server Capabilities ...............72
    6.9. Alice Makes Use of a CCMP Server Extension ................75
 7. Locating a Conference Server ...................................78
 8. Managing Notifications .........................................79
 9. HTTP Transport .................................................80
 10. Security Considerations .......................................82
    10.1. Assuring That the Proper Conference Server Has
          Been Contacted ...........................................83
    10.2. User Authentication and Authorization ....................84
    10.3. Security and Privacy of Identity .........................85
    10.4. Mitigating DoS Attacks ...................................86
 11. XML Schema ....................................................87
 12. IANA Considerations ..........................................105
    12.1. URN Sub-Namespace Registration ..........................105
    12.2. XML Schema Registration .................................106
    12.3. MIME Media Type Registration for
          'application/ccmp+xml' ..................................106
    12.4. DNS Registrations .......................................107
         12.4.1. Registration of a Conference Server
                 Application Service Tag ..........................108
         12.4.2. Registration of a Conference Server
                 Application Protocol Tag for CCMP ................108
    12.5. CCMP Protocol Registry ..................................108
         12.5.1. CCMP Message Types ...............................109
         12.5.2. CCMP Response Codes ..............................111
 13. Acknowledgments ..............................................113
 14. References ...................................................113
    14.1. Normative References ....................................113
    14.2. Informative References ..................................114
 Appendix A.  Evaluation of Other Protocol Models and
              Transports Considered for CCMP ......................116
   A.1.  Using SOAP for CCMP ......................................117
   A.2.  A RESTful Approach for CCMP ..............................117

Barnes, et al. Standards Track [Page 3] RFC 6503 CCMP March 2012

1. Introduction

 "A Framework for Centralized Conferencing" [RFC5239] (XCON framework)
 defines a signaling-agnostic framework, naming conventions, and
 logical entities required for building advanced conferencing systems.
 The XCON framework introduces the conference object as a logical
 representation of a conference instance, representing the current
 state and capabilities of a conference.
 The Centralized Conferencing Manipulation Protocol (CCMP) defined in
 this document allows authenticated and authorized users to create,
 manipulate, and delete conference objects.  Operations on conferences
 include adding and removing participants, changing their roles, as
 well as adding and removing media streams and associated endpoints.
 CCMP implements the client-server model within the XCON framework,
 with the conferencing client and conference server acting as client
 and server, respectively.  CCMP uses HTTP [RFC2616] as the protocol
 to transfer requests and responses, which contain the domain-specific
 XML-encoded data objects defined in [RFC6501] "Conference Information
 Data Model for Centralized Conferencing (XCON)".
 Section 2 clarifies the conventions and terminology used in the
 document.  Section 3 provides an overview of the conference control
 functionality of the XCON framework, together with a description of
 the main targets CCMP deals with, namely conference objects and
 conference users.  A general description of the operations associated
 with protocol messages is given in Section 4 together with
 implementation details.  Section 5 delves into the details of
 specific CCMP messages.  A complete, non-normative, example of the
 operation of CCMP, describing a typical call flow associated with
 conference creation and manipulation, is provided in Section 6.  A
 survey of the methods that can be used to locate a conference server
 is provided in Section 7, and Section 8 discusses potential
 approaches to notifications management.  CCMP transport over HTTP is
 highlighted in Section 9.  Security considerations are presented in
 Section 10.  Finally, Section 11 provides the XML schema.

Barnes, et al. Standards Track [Page 4] RFC 6503 CCMP March 2012

2. Conventions and Terminology

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
 "OPTIONAL" in this document are to be interpreted as described in
 [RFC2119].
 In addition to the terms defined in "A Framework for Centralized
 Conferencing" [RFC5239], this document uses the following terms and
 acronyms:
 XCON-aware client:   An XCON conferencing system client that is able
    to issue CCMP requests.
 First-Party Request:   A request issued by the client to manipulate
    its own conferencing data.
 Third-Party Request:   A request issued by a client to manipulate the
    conference data of another client.

3. XCON Conference Control System Architecture

 CCMP supports the XCON framework.  Figure 1 depicts a subset of the
 "Conferencing System Logical Decomposition" architecture from the
 XCON framework document.  It illustrates the role that CCMP assumes
 within the overall centralized architecture.

Barnes, et al. Standards Track [Page 5] RFC 6503 CCMP March 2012

 ........................................................
 .  Conferencing System                                 .
 .                                                      .
 .        +---------------------------------------+     .
 .        |   C O N F E R E N C E   O B J E C T   |     .
 .      +-+-------------------------------------+ |     .
 .      |   C O N F E R E N C E   O B J E C T   | |     .
 .    +-+-------------------------------------+ | |     .
 .    |   C O N F E R E N C E   O B J E C T   | | |     .
 .    |                                       | |-+     .
 .    |                                       |-+       .
 .    +---------------------------------------+         .
 .                        ^                             .
 .                        |                             .
 .                        v                             .
 .               +-------------------+                  .
 .               | Conference Control|                  .
 .               | Server            |                  .
 .               +-------------------+                  .
 .                        ^                             .
 .........................|..............................
                          |
                          |Centralized
                          |Conferencing
                          |Manipulation
                          |Protocol
                          |
 .........................|..............................
 .                        V                             .
 .                +----------------+                    .
 .                | Conference     |                    .
 .                | Control        |                    .
 .                | Client         |                    .
 .                +----------------+                    .
 .                                                      .
 .  Conferencing Client                                 .
 ........................................................
               Figure 1: Conferencing Client Interaction
 The Centralized Conferencing Manipulation Protocol (CCMP) allows the
 conference control client (conferencing client) to interface with the
 conference object maintained by the conferencing system, as depicted
 in Figure 1.  Note that additional functionality of the conferencing
 client and conferencing system is discussed in the XCON framework and
 related documents.

Barnes, et al. Standards Track [Page 6] RFC 6503 CCMP March 2012

 This section provides details of the identifiers REQUIRED to address
 and manage the clients associated with a conferencing system using
 CCMP.

3.1. Conference Objects

 Conference objects feature a simple dynamic inheritance-and-override
 mechanism.  Conference objects are linked into a tree known as a
 "cloning tree" (see Section 7.1 of [RFC5239]).  Each cloning tree
 node inherits attributes from its parent node.  The roots of these
 inheritance trees are conference templates also known as
 "blueprints".  Nodes in the inheritance tree can be active
 conferences or simply descriptions that do not currently have any
 resources associated with them (i.e., conference reservations).  An
 object can mark certain of its properties as unalterable, so that
 they cannot be overridden.  Per the framework, a client may specify a
 parent object (a conference or blueprint) from which to inherit
 values when a conference is created using the conference control
 protocol.
 Conference objects are uniquely identified by the XCON-URI within the
 scope of the conferencing system.  The XCON-URI is introduced in the
 XCON framework and defined in the XCON common data model.
 Conference objects are comprehensively represented through XML
 documents compliant with the XML schema defined in the XCON data
 model [RFC6501].  The root element of such documents, called
 <conference-info>, is of type "conference-type".  It encompasses
 other XML elements describing different conference features and users
 as well.  Using CCMP, conferencing clients can use these XML
 structures to express their preferences in creating or updating a
 conference.  A conference server can convey conference information
 back to the clients using the XML elements.

3.2. Conference Users

 Each conference can have zero or more users.  All conference
 participants are users, but some users may have only administrative
 functions and do not contribute or receive media.  Users are added
 one user at a time to simplify error reporting.  When a conference is
 cloned from a parent object, users are inherited as well, so that it
 is easy to set up a conference that has the same set of participants
 or a common administrator.  The conference server creates individual
 users, assigning them a unique conference user identifier (XCON-
 USERID).  The XCON-USERID as identifier of each conferencing system
 client is introduced in the XCON framework and defined in the XCON

Barnes, et al. Standards Track [Page 7] RFC 6503 CCMP March 2012

 common data model.  Each CCMP request, with an exception pointed out
 in Section 5.3.6 representing the case of a user at his first
 entrance in the system as a conference participant, must carry the
 XCON-USERID of the requestor in the proper <confUserID> parameter.
 The XCON-USERID acts as a pointer to the user's profile as a
 conference actor, e.g., her signaling URI and other XCON protocol
 URIs in general, her role (moderator, participant, observer, etc.),
 her display text, her joining information, and so on.  A variety of
 elements defined in the common <conference-info> element as specified
 in the XCON data model are used to describe the users related to a
 conference including the <users> element, as well as each <user>
 element included within it.  For example, it is possible to determine
 how a specific user expects and is allowed to join a conference by
 looking at the <allowed-users-list> in <users>: each <target> element
 involved in such a list represents a user and shows a 'method'
 attribute defining how the user is expected to join the conference,
 i.e., "dial-in" for users that are allowed to dial, "dial-out" for
 users that the conference focus will be trying to reach (with
 "dial-in" being the default mode).  If the conference is currently
 active, dial-out users are contacted immediately; otherwise, they are
 contacted at the start of the conference.  CCMP, acting as the
 conference control protocol, provides a means to manipulate these and
 other kinds of user-related features.
 As a consequence of an explicit user registration to a specific XCON
 conferencing system, conferencing clients are usually provided
 (besides the XCON-USERID) with log-in credentials (i.e., username and
 password).  Such credentials can be used to authenticate the XCON-
 aware client issuing CCMP requests.  Thus, both username and password
 should be carried in a CCMP request as part of the "subject"
 parameter whenever a registered conferencing client wishes to contact
 a CCMP server.  CCMP does not maintain a user's subscriptions at the
 conference server; hence, it does not provide any specific mechanism
 allowing clients to register their conferencing accounts.  The
 "subject" parameter is just used for carrying authentication data
 associated with pre-registered clients, with the specific
 registration modality outside the scope of this document.

4. Protocol Overview

 CCMP is a client-server, XML-based protocol for user creation,
 retrieval, modification, and deletion of conference objects.  CCMP is
 a stateless protocol, such that implementations can safely handle
 transactions independently from each other.  CCMP messages are XML
 documents or XML document fragments compliant with the XCON data
 model representation [RFC6501].

Barnes, et al. Standards Track [Page 8] RFC 6503 CCMP March 2012

 Section 4.1 specifies the basic operations that can create, retrieve,
 modify, and delete conference-related information in a centralized
 conference.  The core set of objects manipulated by CCMP includes
 conference blueprints, the conference object, users, and sidebars.
 Each operation in the protocol model, as summarized in Section 4.1,
 is atomic and either succeeds or fails as a whole.  The conference
 server MUST ensure that the operations are atomic in that the
 operation invoked by a specific conferencing client completes prior
 to another client's operation on the same conference object.  While
 the details for this data locking functionality are out of scope for
 the CCMP specification and are implementation specific for a
 conference server, some core functionality for ensuring the integrity
 of the data is provided by CCMP as described in Section 4.2.
 While the XML documents that are carried in CCMP need to comply with
 the XCON data model, there are situations in which the values for
 mandatory elements are unknown by the client.  The mechanism for
 ensuring compliance with the data model in these cases is described
 in Section 4.3.
 CCMP is completely independent from underlying protocols, which means
 that there can be different ways to carry CCMP messages from a
 conferencing client to a conference server.  The specification
 describes the use of HTTP as a transport solution, including CCMP
 requests in HTTP POST messages and CCMP responses in HTTP 200 OK
 replies.  This implementation approach is further described in
 Section 4.4.

4.1. Protocol Operations

 The main operations provided by CCMP belong in four general
 categories:
 create:  for the creation of a conference object, a conference user,
    a sidebar, or a blueprint.
 retrieve:  to get information about the current state of either a
    conference object (be it an actual conference, a blueprint, or a
    sidebar) or a conference user.  A retrieve operation can also be
    used to obtain the XCON-URIs of the current conferences (active or
    registered) handled by the conferencing server and/or the
    available blueprints.
 update:  to modify the current features of a specified conference or
    conference user.

Barnes, et al. Standards Track [Page 9] RFC 6503 CCMP March 2012

 delete:  to remove from the system a conference object or a
    conference user.
 Thus, the main targets of CCMP operations are as follows:
 o  conference objects associated with either active or registered
    conferences,
 o  conference objects associated with blueprints,
 o  conference objects associated with sidebars, both embedded in the
    main conference (i.e., <entry> elements in <sidebars-by-value>)
    and external to it (i.e., whose XCON-URIs are included in the
    <entry> elements of <sidebars-by-ref>),
 o  <user> elements associated with conference users, and
 o  the list of XCON-URIs related to conferences and blueprints
    available at the server, for which only retrieval operations are
    allowed.

4.2. Data Management

 The XCON framework defines a model whereby the conference server
 centralizes and maintains the conference information.  Since multiple
 clients can modify the same conference objects, a conferencing client
 might not have the latest version of a specific conference object
 when it initiates operations.  To determine whether the client has
 the most up-to-date conference information, CCMP defines a versioning
 approach.  Each conference object is associated with a version
 number.  All CCMP response messages containing a conference document
 (or a fragment thereof) MUST contain a <version> parameter.  When a
 client sends an update message to the server, which includes
 modifications to a conference object, if the modifications are all
 successfully applied, the server MUST return a response, with a
 <response-code> of "200", containing the version number of the
 modified object.  With this approach, a client working on version "X"
 of a conference object that receives a response, with a <response-
 code> of "200", with a version number that is "X+1" can be certain
 that the version it manipulated was the most up to date.  However, if
 the response contains a version that is at least "X+2", the client
 knows that the object modified by the server was more up to date than
 the object the client was manipulating.  In order to ensure that the
 client always has the latest version of the modified object, the
 client can send a request to the conference server to retrieve the
 conference object.  The client can then update the relevant data
 elements in the conference object prior to invoking a specific
 operation.  Note that a client subscribed to the XCON event package

Barnes, et al. Standards Track [Page 10] RFC 6503 CCMP March 2012

 [RFC6502] notifications about conference object modifications, will
 receive the most up-to-date version of that object upon receipt of a
 notification.
 The "version" parameter is OPTIONAL for requests, since it is not
 needed by the server: as long as the required modifications can be
 applied to the target conference object without conflicts, the server
 does not care whether the client has stored an up-to-date view of the
 information.  In addition, to ensure the integrity of the data, the
 conference server first checks all the parameters, before making any
 changes to the internal representation of the conference object.  For
 example, it would be undesirable to change the <subject> of the
 conference, but then detect an invalid URI in one of the <service-
 uris> and abort the remaining updates.

4.3. Data Model Compliance

 The XCON data model [RFC6501] identifies some elements and attributes
 as mandatory.  Since the XML documents carried in the body of the
 CCMP requests and responses need to be compliant with the XCON data
 model, there can be a problem in cases of client-initiated
 operations, such as the initial creation of conference objects and
 cases whereby a client updates a conference object adding new
 elements, such as a new user.  In such cases, not all of the
 mandatory data can be known in advance by the client issuing a CCMP
 request.  As an example, a client cannot know, at the time it issues
 a conference creation request, the XCON-URI that the server will
 assign to the yet-to-be-created conference; hence, it is not able to
 populate the mandatory 'entity' attribute of the conference document
 contained in the request with the correct value.  To solve this
 issue, the CCMP client fills all mandatory data model fields, for
 which no value is available at the time the request is constructed,
 with placeholder values in the form of a wildcard string,
 AUTO_GENERATE_X (all uppercase), with X being a unique numeric index
 for each data model field for which the value is unknown.  This form
 of wildcard string is chosen, rather than the use of random unique
 strings (e.g., FOO_BAR_LA) or non-numeric values for X, to simplify
 processing at the server.  The values of AUTO_GENERATE_X are only
 unique within the context of the specific request.  The placeholder
 AUTO_GENERATE_X values MUST be within the value part of an attribute
 or element (e.g., <userinfo
 entity="xcon-userid:AUTO_GENERATE_1@example.com">).

Barnes, et al. Standards Track [Page 11] RFC 6503 CCMP March 2012

 When the server receives requests containing values in the form of
 AUTO_GENERATE_X, the server does the following:
 (a)  Generates the proper identifier for each instance of
      AUTO_GENERATE_X in the document.  If an instance of
      AUTO_GENERATE_X is not within the value part of the attribute/
      element, the server MUST send a <response-code> of "400 Bad
      Request".  In cases where AUTO_GENERATE_X appears only in the
      user part of a URI (i.e., in the case of XCON-USERIDs or XCON-
      URIs), the server needs to ensure that the domain name is one
      that is within the server's domain of responsibility.  If the
      domain name is not within the server's domain of responsibility,
      then the server MUST send a <response-code> of "427 Invalid
      Domain Name".  The server MUST replace each instance of a
      specific wildcard field (e.g., AUTO_GENERATE_1) with the same
      identifier.  The identifiers MUST be unique for each instance of
      AUTO_GENERATE_X within the same XML document received in the
      request; for example, the value that replaces AUTO_GENERATE_1
      MUST NOT be the same as the value that replaces AUTO_GENERATE_2.
      Note that the values that replace the instances of
      AUTO_GENERATE_X are not the same across all conference objects;
      for example, different values can be used to replace
      AUTO_GENERATE_1 in two different documents.
 (b)  Sends a response in which all values of AUTO_GENERATE_X received
      in the request have been replaced by the newly created one(s).
 With this approach, compatibility with the data model requirements is
 maintained, while allowing for client-initiated manipulation of
 conference objects at the server's side.  Note that the use of this
 mechanism could be avoided in come cases by using multiple
 operations, such as creating a new user and then adding the new user
 to an existing conference.  However, the AUTO_GENERATE_X mechanism
 allows a single operation to be used to effect the same change on the
 conference object.

4.4. Implementation Approach

 CCMP is implemented using HTTP, placing the CCMP request messages
 into the body of an HTTP POST operation and placing the CCMP
 responses into the body of the HTTP response messages.  A non-
 exhaustive summary of the other approaches that were considered and
 the perceived advantages of the HTTP solution described in this
 document are provided in Appendix A.
 Most CCMP commands can pend indefinitely, thus increasing the
 potential that pending requests can continue to increase when a
 server is receiving more requests than it can process within a

Barnes, et al. Standards Track [Page 12] RFC 6503 CCMP March 2012

 specific time period.  In this case, a server SHOULD return a
 <response-code> of "510" to the pending requests.  In addition, to
 mitigate the situation, clients MUST NOT wait indefinitely for a
 response and MUST implement a timer such that when it expires, the
 client MUST close the connection.  Thirty seconds is RECOMMENDED as
 the default value for this timer.  Sixty seconds is considered a
 reasonable upper range.  Note that there may be cases where a
 response message is lost and a request has been successful (e.g.,
 user added to a conference); yet, the client will be unaware and
 close the connection.  However, as described in Section 4.2, there is
 a versioning mechanism for the conference objects; thus, there is a
 mechanism for the conference object stored by the client to be
 brought up to date.
 CCMP messages have a MIME-type of "application/ccmp+xml", which
 appears inside the Content-Type and Accept header fields of HTTP
 requests and responses.  The XML documents in the CCMP messages MUST
 be encoded in UTF-8.  This specification follows the recommendations
 and conventions described in [RFC3023], including the naming
 convention of the type ('+xml' suffix) and the usage of the 'charset'
 parameter.  The 'charset' parameter MUST be included with the XML
 document.  Section 9 provides the complete requirements for an HTTP
 implementation to support CCMP.

5. CCMP Messages

 CCMP messages are either requests or responses.  The general CCMP
 request message is defined in Section 5.1.  The general CCMP response
 message is defined in Section 5.2.  The details of the specific
 message type that is carried in the CCMP request and response
 messages are described in Section 5.3.  CCMP response codes are
 listed in Section 5.4.

5.1. CCMP Request Message Type

 A CCMP request message is comprised of the following parameters:
 subject:  An OPTIONAL parameter containing the username and password
    of the client registered at the conferencing system.  Each user
    who subscribes to the conferencing system is assumed to be
    equipped with those credentials and SHOULD enclose them in each
    CCMP request she issues.  These fields can be used to control that
    the user sending the CCMP request has the authority to perform the
    requested operation.  The same fields can also be used for other
    authorization and authentication procedures.

Barnes, et al. Standards Track [Page 13] RFC 6503 CCMP March 2012

 confUserID:  An OPTIONAL parameter containing the XCON-USERID of the
    client.  The XCON-USERID is used to identify any conferencing
    client within the context of the conferencing system and it is
    assigned by the conference server for each conferencing client who
    interacts with it.  The <confUserID> parameter is REQUIRED in the
    CCMP request and response messages with the exception of the case
    of a user who has no XCON-USERID and who wants to enter, via CCMP,
    a conference whose identifier is known.  In such case, a side
    effect of the request is that the user is provided with an
    appropriate XCON-USERID.  An example of the aforementioned case
    will be provided in Section 5.3.6.
 confObjID:  An OPTIONAL parameter containing the XCON-URI of the
    target conference object.
 operation:  An OPTIONAL parameter refining the type of specialized
    request message.  The <operation> parameter is REQUIRED in all
    requests except for the blueprintsRequest and confsRequest
    specialized messages.
 conference-password:  The parameter is OPTIONAL except that it MUST
    be inserted in all requests whose target conference object is
    password-protected i.e., contains the <conference-password>
    element in [RFC6501]).  A CCMP <response-code> of "423" MUST be
    returned if a conference-password is not included in the request
    when required.
 specialized request message:  This is a specialization of the generic
    request message (e.g., blueprintsRequest), containing parameters
    that are dependent on the specific request sent to the server.  A
    specialized request message MUST be included in the CCMP request
    message.  The details for the specialized messages and associated
    parameters are provided in Section 5.3.

Barnes, et al. Standards Track [Page 14] RFC 6503 CCMP March 2012

 <!-- Definition of CCMP Request -->
 <xs:element name="ccmpRequest" type="ccmp-request-type" />
 <!-- Definition of ccmp-request-type-->
 <xs:complexType name="ccmp-request-type">
     <xs:sequence>
         <xs:element name="ccmpRequest"
                     type="ccmp-request-message-type" />
     </xs:sequence>
 </xs:complexType>
  <!--  Definition of ccmp-request-message-type -->
  <xs:complexType abstract="true"
                  name="ccmp-request-message-type">
      <xs:sequence>
          <xs:element name="subject" type="subject-type"
                      minOccurs="0" maxOccurs="1" />
          <xs:element name="confUserID" type="xs:string"
                      minOccurs="0" maxOccurs="1" />
          <xs:element name="confObjID" type="xs:string"
                      minOccurs="0" maxOccurs="1" />
          <xs:element name="operation" type="operationType"
                      minOccurs="0" maxOccurs="1" />
          <xs:element name="conference-password" type="xs:string"
                      minOccurs="0" maxOccurs="1" />
          <xs:any namespace="##other" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>
      <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
             Figure 2: Structure of CCMP Request Messages

5.2. CCMP Response Message Type

 A CCMP response message is comprised of the following parameters:
 confUserID:  A REQUIRED parameter in CCMP response messages
    containing the XCON-USERID of the conferencing client that issued
    the CCMP request message.
 confObjID:  An OPTIONAL parameter containing the XCON-URI of the
    target conference object.

Barnes, et al. Standards Track [Page 15] RFC 6503 CCMP March 2012

 operation:  An OPTIONAL parameter for CCMP response messages.  This
    parameter is REQUIRED in all responses except for the
    "blueprintsResponse" and "confsResponse" specialized messages.
 response-code:  A REQUIRED parameter containing the response code
    associated with the request.  The response code MUST be chosen
    from the codes listed in Section 5.4.
 response-string:  An OPTIONAL reason string associated with the
    response.  In case of an error, in particular, this string can be
    used to provide the client with detailed information about the
    error itself.
 version:  An OPTIONAL parameter reflecting the current version number
    of the conference object referred by the confObjID.  This number
    is contained in the 'version' attribute of the <conference-info>
    element related to that conference.  This parameter is REQUIRED in
    CCMP response messages and SHOULD NOT be included in CCMP request
    messages.
 specialized response message:  This is specialization of the generic
    response message, containing parameters that are dependent on the
    specific request sent to the server (e.g., "blueprintsResponse").
    A specialized response message SHOULD be included in the CCMP
    response message, except in an error situation where the CCMP
    request message did not contain a valid specialized message.  In
    this case, the conference server MUST return a <response-code> of
    "400".  The details for the specialized messages and associated
    parameters are provided in Section 5.3.

Barnes, et al. Standards Track [Page 16] RFC 6503 CCMP March 2012

 <!-- Definition of CCMP Response -->
 <xs:element name="ccmpResponse" type="ccmp-response-type" />
 <!-- Definition of ccmp-response-type -->
 <xs:complexType name="ccmp-response-type">
     <xs:sequence>
         <xs:element name="ccmpResponse"
                     type="ccmp-response-message-type" />
     </xs:sequence>
 </xs:complexType>
 <!--  Definition of ccmp-response-message-type -->
 <xs:complexType abstract="true"
                 name="ccmp-response-message-type">
     <xs:sequence>
         <xs:element name="confUserID" type="xs:string"
                     minOccurs="1" maxOccurs="1" />
         <xs:element name="confObjID" type="xs:string"
                     minOccurs="0" maxOccurs="1" />
         <xs:element name="operation" minOccurs="0"
                     maxOccurs="1" />
         <xs:element name="response-code"
                     type="response-codeType"
                     minOccurs="1" maxOccurs="1" />
         <xs:element name="response-string" type="xs:string"
                     minOccurs="0" maxOccurs="1" />
         <xs:element name="version" type="xs:positiveInteger"
                     minOccurs="0" maxOccurs="1" />
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
             Figure 3: Structure of CCMP Response Message

5.3. Detailed Messages

 Based on the request and response message structures described in
 Sections 5.1 and 5.2, the following summarizes the specialized CCMP
 request and response types described in this document:
 1.   blueprintsRequest/blueprintsResponse
 2.   confsRequest/confsResponse

Barnes, et al. Standards Track [Page 17] RFC 6503 CCMP March 2012

 3.   blueprintRequest/blueprintResponse
 4.   confRequest/confResponse
 5.   usersRequest/usersResponse
 6.   userRequest/userResponse
 7.   sidebarsByValRequest/sidebarsByValResponse
 8.   sidebarsByRefRequest/sidebarsByRefResponse
 9.   sidebarByValRequest/sidebarByValResponse
 10.  sidebarByRefRequest/sidebarByRefResponse
 11.  extendedRequest/extendedResponse
 12.  optionsRequest/optionsResponse
 These CCMP request/response pairs use the fundamental CCMP operations
 as defined in Section 4.1 to manipulate the conference data.  These
 request/response pairs are included in an IANA registry as defined in
 Section 12.5.  Table 1 summarizes the remaining CCMP operations and
 corresponding actions that are valid for a specific CCMP request
 type, noting that neither the blueprintsRequest/blueprintsResponse
 nor confsRequest/confsResponse require an <operation> parameter.  An
 entity MUST support the response message for each of the request
 messages that is supported.  The corresponding response message MUST
 contain the same <operation> parameter.  Note that some entries are
 labeled "N/A", indicating that the operation is invalid for that
 request type.  In the case of an "N/A*" label, the operation MAY be
 allowed for specific privileged users or system administrators but is
 not part of the functionality included in this document.

Barnes, et al. Standards Track [Page 18] RFC 6503 CCMP March 2012

 +---------------+------------+------------+------------+------------+
 | Operation     |  Retrieve  |   Create   |   Update   |   Delete   |
 | ------------- |            |            |            |            |
 | Request Type  |            |            |            |            |
 +---------------+------------+------------+------------+------------+
 | blueprints    |  Get list  |     N/A    |     N/A    |     N/A    |
 | Request       |     of     |            |            |            |
 |               | blueprints |            |            |            |
 | ------------- | ---------- | ---------- | ---------- | ---------- |
 | blueprint     |     Get    |    N/A*    |    N/A*    |    N/A*    |
 | Request       |  blueprint |            |            |            |
 | ------------- | ---------- | ---------- | ---------- | ---------- |
 | confsRequest  |  Get list  |     N/A    |     N/A    |     N/A    |
 |               |  of confs  |            |            |            |
 | ------------- | ---------- | ---------- | ---------- | ---------- |
 | confRequest   |     Get    |   Create   |   Change   |   Delete   |
 |               | conference | conference | conference | conference |
 |               |   object   |   object   |   object   |   object   |
 | ------------- | ---------- | ---------- | ---------- | ---------- |
 | usersRequest  |     Get    |   N/A(**)  |   Change   |   N/A(**)  |
 |               |   <users>  |            |   <users>  |            |
 | ------------- | ---------- | ---------- | ---------- | ---------- |
 | userRequest   |     Get    |    Add a   |   Change   |   Delete   |
 |               |  specified |  <user> to |  specified |  specified |
 |               |   <user>   |   a conf   |   <user>   |   <user>   |
 |               |            |    (***)   |            |            |
 | ------------- | ---------- | ---------- | ---------- | ---------- |
 | sidebarsByVal |     Get    |     N/A    |     N/A    |     N/A    |
 | Request       | <sidebars- |            |            |            |
 |               |   by-val>  |            |            |            |
 | ------------- | ---------- | ---------- | ---------- | ---------- |
 | sidebarsByRef |     Get    |     N/A    |     N/A    |     N/A    |
 | Request       | <sidebars- |            |            |            |
 |               |   by-ref>  |            |            |            |
 | ------------- | ---------- | ---------- | ---------- | ---------- |
 | sidebarByValR |     Get    |   Create   |   Change   |   Delete   |
 | equest        |  sidebar-  |  sidebar-  |  sidebar-  |  sidebar-  |
 |               |   by-val   |   by-val   |   by-val   |   by-val   |
 | ------------- | ---------- | ---------- | ---------- | ---------- |
 | sidebarByRefR |     Get    |   Create   |   Change   |   Delete   |
 | equest        |  sidebar-  |  sidebar-  |  sidebar-  |  sidebar-  |
 |               |   by-ref   |   by-ref   |   by-ref   |   by-ref   |
 +---------------+------------+------------+------------+------------+
          Table 1: Request Type Operation-Specific Processing

Barnes, et al. Standards Track [Page 19] RFC 6503 CCMP March 2012

 (**): These operations are not allowed for a usersRequest message,
 since the <users> section, which is the target element of such a
 request, is created and removed in conjunction with the creation and
 deletion, respectively, of the associated conference document.  Thus,
 "update" and "retrieve" are the only semantically correct operations
 for such message.
 (***): This operation can involve the creation of an XCON-USERID, if
 the sender does not add it in the <confUserID> parameter and/or if
 the entity field of the <userInfo> parameter is void.
 Additional parameters included in the specialized CCMP request and
 response messages are detailed in the subsequent sections.  If a
 required parameter is not included in a request, the conference
 server MUST return a <response-code> of "400" per Section 5.4.

5.3.1. blueprintsRequest and blueprintsResponse

 A blueprintsRequest (Figure 4) message is sent to request the list of
 XCON-URIs associated with the available blueprints from the
 conference server.  These XCON-URIs can be subsequently used by the
 client to access detailed information about a specified blueprint
 with a specific blueprintRequest message per Section 5.3.3.
 The <confUserID> parameter MUST be included in every
 blueprintsRequest/Response message and reflect the XCON-USERID of the
 conferencing client issuing the request.  Since a blueprintsRequest
 message is not targeted to a specific conference instance and is a
 "retrieve-only" request, the <confObjID> and <operation> parameters
 MUST NOT be included in the blueprintsRequest/Response messages.
 In order to obtain a specific subset of the available blueprints, a
 client may specify a selection filter providing an appropriate xpath
 query in the OPTIONAL "xpathFilter" parameter of the request.  The
 information in the blueprints typically represents general
 capabilities and characteristics.  For example, to select blueprints
 having both audio and video stream support, a possible xpathFilter
 value could be: "/conference-info[conference-description/
 available-media/entry/type='audio' and conference-description/
 available-media/entry/type='video']".  A conference server SHOULD NOT
 provide any sensitive information (e.g., passwords) in the
 blueprints.
 The associated blueprintsResponse message SHOULD contain, as shown in
 Figure 4, a "blueprintsInfo" parameter containing the above mentioned
 XCON-URI list.

Barnes, et al. Standards Track [Page 20] RFC 6503 CCMP March 2012

<!– blueprintsRequest –> <xs:complexType name="ccmp-blueprints-request-message-type">

   <xs:complexContent>
       <xs:extension base="tns:ccmp-request-message-type">
           <xs:sequence>
               <xs:element ref="blueprintsRequest" />
           </xs:sequence>
       </xs:extension>
   </xs:complexContent>

</xs:complexType>

<!– blueprintsRequestType –>

<xs:element name="blueprintsRequest" type="blueprintsRequestType"/>

<xs:complexType name="blueprintsRequestType">

   <xs:sequence>
       <xs:element name="xpathFilter" type="xs:string" minOccurs="0"/>
       <xs:any namespace="##other" processContents="lax"
               minOccurs="0" maxOccurs="unbounded"/>
   </xs:sequence>
   <xs:anyAttribute namespace="##any" processContents="lax"/>

</xs:complexType>

<!– blueprintsResponse –>

<xs:complexType name="ccmp-blueprints-response-message-type">

   <xs:complexContent>
       <xs:extension base="tns:ccmp-response-message-type">
           <xs:sequence>
               <xs:element ref="blueprintsResponse" />
           </xs:sequence>
       </xs:extension>
   </xs:complexContent>

</xs:complexType>

Barnes, et al. Standards Track [Page 21] RFC 6503 CCMP March 2012

<!– blueprintsResponseType –>

<xs:element name="blueprintsResponse" type="blueprintsResponseType"/>

<xs:complexType name="blueprintsResponseType">

   <xs:sequence>
       <xs:element name="blueprintsInfo"
                   type="info:uris-type" minOccurs="0"/>
       <xs:any namespace="##other" processContents="lax"
               minOccurs="0" maxOccurs="unbounded"/>
   </xs:sequence>
   <xs:anyAttribute namespace="##any" processContents="lax"/>

</xs:complexType>

           Figure 4: Structure of the blueprintsRequest and
                      blueprintsResponse Messages

5.3.2. confsRequest and confsResponse

 A confsRequest message is used to retrieve, from the server, the list
 of XCON-URIs associated with active and registered conferences
 currently handled by the conferencing system.  The <confUserID>
 parameter MUST be included in every confsRequest/Response message and
 reflect the XCON-USERID of the conferencing client issuing the
 request.  The <confObjID> parameter MUST NOT be included in the
 confsRequest message.  The confsRequest message is of a retrieve-only
 type, since the sole purpose is to collect information available at
 the conference server.  Thus, an <operation> parameter MUST NOT be
 included in a confsRequest message.  In order to retrieve a specific
 subset of the available conferences, a client may specify a selection
 filter providing an appropriate xpath query in the OPTIONAL
 "xpathFilter" parameter of the request.  For example, to select only
 the registered conferences, a possible xpathFilter value could be "/
 conference-info[conference-description/conference-state/
 active='false']".  The associated confsResponse message SHOULD
 contain the list of XCON-URIs in the "confsInfo" parameter.  A user,
 upon receipt of the response message, can interact with the available
 conference objects through further CCMP messages.

Barnes, et al. Standards Track [Page 22] RFC 6503 CCMP March 2012

<!– confsRequest –>

<xs:complexType name="ccmp-confs-request-message-type">

   <xs:complexContent>
       <xs:extension base="tns:ccmp-request-message-type">
           <xs:sequence>
               <xs:element ref="confsRequest" />
           </xs:sequence>
       </xs:extension>
   </xs:complexContent>

</xs:complexType>

<!– confsRequestType –>

<xs:element name="confsRequest" type="confsRequestType" />

<xs:complexType name="confsRequestType">

   <xs:sequence>
       <xs:element name="xpathFilter" type="xs:string" minOccurs="0"/>
       <xs:any namespace="##other" processContents="lax"
               minOccurs="0" maxOccurs="unbounded"/>
   </xs:sequence>
   <xs:anyAttribute namespace="##any" processContents="lax"/>

</xs:complexType>

<!– confsResponse –>

<xs:complexType name="ccmp-confs-response-message-type">

   <xs:complexContent>
       <xs:extension base="tns:ccmp-response-message-type">
           <xs:sequence>
               <xs:element ref="confsResponse" />
           </xs:sequence>
       </xs:extension>
   </xs:complexContent>

</xs:complexType>

Barnes, et al. Standards Track [Page 23] RFC 6503 CCMP March 2012

<!– confsResponseType –>

<xs:element name="confsResponse" type="confsResponseType"/>

<xs:complexType name="confsResponseType">

   <xs:sequence>
       <xs:element name="confsInfo" type="info:uris-type"
                   minOccurs="0"/>
       <xs:any namespace="##other" processContents="lax"
               minOccurs="0" maxOccurs="unbounded"/>
   </xs:sequence>
   <xs:anyAttribute namespace="##any" processContents="lax"/>

</xs:complexType>

  Figure 5: Structure of the confsRequest and confsResponse Messages

5.3.3. blueprintRequest and blueprintResponse

 Through a blueprintRequest, a client can manipulate the conference
 object associated with a specified blueprint.  Along with the
 <confUserID> parameter, the request MUST include the <confObjID> and
 the <operation> parameters.  Again, the <confUserID> parameter MUST
 be included in every blueprintRequest/Response message and reflect
 the XCON-USERID of the conferencing client issuing the request.  The
 <confObjID> parameter MUST contain the XCON-URI of the blueprint,
 which might have been previously retrieved through a
 blueprintsRequest message.
 The blueprintRequest message SHOULD NOT contain an <operation>
 parameter with a value other than "retrieve".  An <operation>
 parameter with a value of "create", "update", or "delete" SHOULD NOT
 be included in a blueprintRequest message except in the case of
 privileged users (e.g., the conference server administration staff),
 who might authenticate themselves by the mean of the "subject"
 request parameter.
 A blueprintRequest/retrieve carrying a <confObjID> parameter whose
 value is not associated with one of the available system's
 blueprints, will generate, on the server's side, a blueprintResponse
 message containing a <response-code> of "404".  This also holds for
 the case in which the mentioned <confObjID> parameter value is
 related to an existing conference document stored at the server, but
 associated with an actual conference (be it active or registered) or
 with a sidebar rather than a blueprint.

Barnes, et al. Standards Track [Page 24] RFC 6503 CCMP March 2012

 For a <response-code> of "200" in a "retrieve" operation, the
 <blueprintInfo> parameter MUST be included in the blueprintResponse
 message.  The <blueprintInfo> parameter contains the conference
 document associated with the blueprint as identified by the
 <confObjID> parameter specified in the blueprintRequest.
 <!--  blueprintRequest -->
 <xs:complexType name="ccmp-blueprint-request-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-request-message-type">
             <xs:sequence>
                 <xs:element ref="blueprintRequest" />
             </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>
 <!-- blueprintRequestType -->
 <xs:element name="blueprintRequest" type="blueprintRequestType" />
 <xs:complexType name="blueprintRequestType">
     <xs:sequence>
         <xs:element name="blueprintInfo"
                     type="info:conference-type" minOccurs="0"/>
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
 <!-- blueprintResponse -->
 <xs:complexType name="ccmp-blueprint-response-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-response-message-type">
             <xs:sequence>
                 <xs:element ref="blueprintResponse" />
             </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>

Barnes, et al. Standards Track [Page 25] RFC 6503 CCMP March 2012

 <!-- blueprintResponseType -->
 <xs:element name="blueprintResponse" type="blueprintResponseType"/>
 <xs:complexType name="blueprintResponseType">
     <xs:sequence>
         <xs:element name="blueprintInfo" type="info:conference-type"
                     minOccurs="0"/>
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded">
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
            Figure 6: Structure of the blueprintRequest and
                      blueprintResponse Messages

5.3.4. confRequest and confResponse

 With a confRequest message, CCMP clients can manipulate conference
 objects associated with either active or registered conferences.  The
 <confUserID> parameter MUST be included in every confRequest/Response
 message and reflect the XCON-USERID of the conferencing client
 issuing the request. confRequest and confResponse messages MUST also
 include an <operation> parameter.  ConfResponse messages MUST return
 to the requestor a <response-code> and MAY contain a <response-
 string> explaining it.  Depending upon the type of operation, a
 <confObjID> and <confInfo> parameter MAY be included in the
 confRequest and response.  For each type of operation, the text below
 describes whether the <confObjID> and <confInfo> parameters need to
 be included in the confRequest and confResponse messages.
 The creation case deserves care.  To create a new conference through
 a confRequest message, two approaches can be considered:
 1.  Creation through explicit cloning: the <confObjID> parameter MUST
     contain the XCON-URI of the blueprint or of the conference to be
     cloned, while the <confInfo> parameter MUST NOT be included in
     the confRequest.  Note that cloning of an active conference is
     only done in the case of a sidebar operation per the XCON
     framework and as described in Section 5.3.8.
 2.  Creation through implicit cloning (also known as "direct
     creation"): the <confObjID> parameter MUST NOT be included in the
     request and the CCMP client can describe the desired conference
     to be created using the <confInfo> parameter.  If no <confInfo>
     parameter is provided in the request, the new conference will be
     created as a clone of the system default blueprint.

Barnes, et al. Standards Track [Page 26] RFC 6503 CCMP March 2012

 In both creation cases, the confResponse, for a successful completion
 of a "create" operation, contains a <response-code> of "200" and MUST
 contain the XCON-URI of the newly created conference in the
 <confObjID> parameter, in order to allow the conferencing client to
 manipulate that conference through following CCMP requests.  In
 addition, the <confInfo> parameter containing the conference document
 created MAY be included, at the discretion of the conferencing system
 implementation, along with the REQUIRED <version> parameter
 initialized at "1", since, at creation time, the conference object is
 at its first version.
 In the case of a confRequest with an <operation> parameter of
 "retrieve", the <confObjID> parameter representing the XCON-URI of
 the target conference MUST be included and the <confInfo> parameter
 MUST NOT be included in the request.  The conference server MUST
 ignore any <confInfo> parameter that is received in a confRequest
 "retrieve" operation.  If the confResponse for the retrieve operation
 contains a <response-code> of "200", the <confInfo> parameter MUST be
 included in the response.  The <confInfo> parameter MUST contain the
 entire conference document describing the target conference object in
 its current state.  The current state of the retrieved conference
 object MUST also be reported in the proper "version" response
 parameter.
 In case of a confRequest with an <operation> parameter of "update",
 the <confInfo> and <confObjID> parameters MUST be included in the
 request.  The <confInfo> represents an object of type
 "conference-type" containing all the changes to be applied to the
 conference whose identifier has the same value as the <confObjID>
 parameter.  Note that, in such a case, though the <confInfo>
 parameter indeed has to follow the rules indicated in the XCON data
 model, it does not represent the entire updated version of the target
 conference, since it conveys just the modifications to apply to that
 conference.  For example, in order to change the conference title,
 the <confInfo> parameter will be of the form:
 <confInfo entity="xcon:8977777@example.com">
   <conference-description>
     <display-text> *** NEW CONFERENCE TITLE *** </display-text>
   </conference-description>
 </confInfo>
         Figure 7: Updating a Conference Object: Modifying the
                         Title of a Conference
 Similarly, to remove the title of an existing conference, a
 confRequest/update carrying the following <confInfo> parameter would
 do the job.

Barnes, et al. Standards Track [Page 27] RFC 6503 CCMP March 2012

 <confInfo entity="xcon:8977777@example.com">
   <conference-description>
     <display-text/>
   </conference-description>
 </confInfo>
                Figure 8: Updating a Conference Object:
                  Removing the Title of a Conference
 In the case of a confResponse/update with a <response-code> of "200",
 no additional information is REQUIRED in the response message, which
 means the return of a <confInfo> parameter is OPTIONAL.  A subsequent
 confRequest/retrieve transaction might provide the CCMP client with
 the current status of the conference after the modification, or the
 notification protocol might address that task as well.  A <response-
 code> of "200" indicates that the conference object has been changed
 according to the request by the conference server.  The <version>
 parameter MUST be enclosed in the confResponse/update message, in
 order to let the client understand what is the current conference-
 object version, upon the applied modifications.  A <response-code> of
 "409" indicates that the changes reflected in the <confInfo>
 parameter of the request are not feasible.  This could be due to
 policies, requestor roles, specific privileges, unacceptable values,
 etc., with the reason specific to a conferencing system and its
 configuration.  Together with a <response-code> of "409", the
 <version> parameter MUST be attached in the confResponse/update,
 allowing the client to later retrieve the current version of the
 target conference if the one she attempted to modify was not the most
 up to date.
 In the case of a confRequest with an <operation> parameter of
 "delete", the <confObjID> parameter representing the XCON-URI of the
 target conference MUST be included while the <confInfo> parameter
 MUST NOT be included in the request.  The conference server MUST
 ignore any <confInfo> parameter that is received within such a
 request.  The confResponse MUST contain the same value for the
 <confObjID> parameter that was included in the confRequest.  If the
 confResponse/delete operation contains a <response-code> of "200",
 the conference indicated in the <confObjID> parameter has been
 successfully deleted.  A confResponse/delete with a <response-code>
 of "200" MUST NOT contain the <confInfo> parameter.  The <version>
 parameter SHOULD NOT be returned in any confResponse/delete.  If the
 conference server cannot delete the conference referenced by the
 <confObjID> parameter received in the confRequest because it is the
 parent of another conference object that is in use, the conference
 server MUST return a <response-code> of "425".

Barnes, et al. Standards Track [Page 28] RFC 6503 CCMP March 2012

 A confRequest with an <operation> parameter of "retrieve", "update",
 or "delete" carrying a <confObjID> parameter which is not associated
 with one of the conferences (active or registered) that the system is
 holding will generate, on the server's side, a confResponse message
 containing a <response-code> of "404".  This also holds for the case
 in which the mentioned <confObjID> parameter is related to an
 existing conference object stored at the server, but associated with
 a blueprint or with a sidebar rather than an actual conference.
 The schema for the confRequest/confResponse pair is shown in
 Figure 9.
 <!-- confRequest -->
 <xs:complexType name="ccmp-conf-request-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-request-message-type">
             <xs:sequence>
                 <xs:element ref="confRequest" />
             </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>
 <!-- confRequestType -->
 <xs:element name="confRequest" type="confRequestType" />
 <xs:complexType name="confRequestType">
     <xs:sequence>
         <xs:element name="confInfo" type="info:conference-type"
                     minOccurs="0"/>
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>

Barnes, et al. Standards Track [Page 29] RFC 6503 CCMP March 2012

 <!-- confResponse -->
 <xs:complexType name="ccmp-conf-response-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-response-message-type">
             <xs:sequence>
                 <xs:element ref="confResponse" />
             </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>
 <!-- confResponseType -->
 <xs:element name="confResponse" type="confResponseType" />
 <xs:complexType name="confResponseType">
     <xs:sequence>
         <xs:element name="confInfo" type="info:conference-type"
                     minOccurs="0"/>
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
   Figure 9: Structure of the confRequest and confResponse Messages

5.3.5. usersRequest and usersResponse

 The usersRequest message allows a client to manipulate the <users>
 element of the conference object represented by the <confObjID>
 parameter.  The <users> element contains the list of <user> elements
 associated with conference participants, the list of the users to
 which access to the conference is allowed/denied, conference
 participation policies, etc.  The <confObjID> parameter MUST be
 included in a usersRequest message.
 A <usersInfo> parameter MAY be included in a usersRequest message
 depending upon the operation.  If the <usersInfo> parameter is
 included in the usersRequest message, the parameter MUST be compliant
 with the <users> field of the XCON data model.
 Two operations are allowed for a usersRequest message:
 1.  "retrieve": In this case the request MUST NOT include a
     <usersInfo> parameter, while the successful response MUST contain
     the desired <users> element in the <usersInfo> parameter.  The

Barnes, et al. Standards Track [Page 30] RFC 6503 CCMP March 2012

     conference server MUST ignore a <usersInfo> parameter if it is
     received in a request with an <operation> parameter of
     "retrieve".
 2.  "update": In this case, the <usersInfo> parameter MUST contain
     the modifications to be applied to the <users> element indicated.
     If the <response-code> is "200", then the <usersInfo> parameter
     SHOULD NOT be returned.  Any <usersInfo> parameter that is
     returned SHOULD be ignored.  A <response-code> of "426" indicates
     that the conferencing client is not allowed to make the changes
     reflected in the <usersInfo> contained in the usersRequest
     message.  This could be due to policies, roles, specific
     privileges, etc., with the reason being specific to a
     conferencing system and its configuration.
 Operations of "create" and "delete" are not applicable to a
 usersRequest message and MUST NOT be considered by the server, which
 means that a <response-code> of "403" MUST be included in the
 usersResponse message.
 <!-- usersRequest -->
 <xs:complexType name="ccmp-users-request-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-request-message-type">
             <xs:sequence>
                 <xs:element ref="usersRequest" />
             </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>
 <!-- usersRequestType -->
 <xs:element name="usersRequest" type="usersRequestType" />
 <xs:complexType name="usersRequestType">
     <xs:sequence>
         <xs:element name="usersInfo"
                     type="info:users-type" minOccurs="0" />
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>

Barnes, et al. Standards Track [Page 31] RFC 6503 CCMP March 2012

 <!-- usersResponse -->
 <xs:complexType name="ccmp-users-response-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-response-message-type">
             <xs:sequence>
                 <xs:element ref="usersResponse" />
             </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>
 <!-- usersResponseType -->
 <xs:element name="usersResponse" type="usersResponseType" />
 <xs:complexType name="usersResponseType">
     <xs:sequence>
         <xs:element name="usersInfo" type="info:users-type"
                     minOccurs="0"/>
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
  Figure 10: Structure of the usersRequest and usersResponse Messages

5.3.6. userRequest and userResponse

 A userRequest message is used to manipulate <user> elements inside a
 conference document associated with a conference identified by the
 <confObjID> parameter.  Besides retrieving information about a
 specific conference user, the message is used to request that the
 conference server either create, modify, or delete information about
 a user.  A userRequest message MUST include the <confObjID> and the
 <operation> parameters, and it MAY include a <userInfo> parameter
 containing the detailed user's information depending upon the
 operation and whether the <userInfo> has already been populated for a
 specific user.  Note that a user may not necessarily be a
 conferencing control client (i.e., some participants in a conference
 are not "XCON aware").
 An XCON-USERID SHOULD be assigned to each and every user subscribed
 to the system.  In such a way, a user who is not a conference
 participant can make requests (provided she has successfully passed
 authorization and authentication checks), like creating a conference
 or retrieving conference information.

Barnes, et al. Standards Track [Page 32] RFC 6503 CCMP March 2012

 Conference users can be created in a number of different ways.  In
 each of these cases, the <operation> parameter MUST be set to
 "create" in the userRequest message.  Each of the userResponse
 messages for these cases MUST include the <confObjID>, <confUserID>,
 <operation>, and <response-code> parameters.  In the case of a
 <response-code> of "200", the userResponse message MAY include the
 <userInfo> parameter depending upon the manner in which the user was
 created:
 o  A conferencing client with an XCON-USERID adds itself to the
    conference: In this case, the <userInfo> parameter MAY be included
    in the userRequest.  The <userInfo> parameter MUST contain a
    <user> element (compliant with the XCON data model) and the
    'entity' attribute MUST be set to a value that represents the
    XCON-USERID of the user initiating the request.  No additional
    parameters beyond those previously described are required in the
    userResponse message, in the case of a <response-code> of "200".
 o  A conferencing client acts on behalf of another user whose XCON-
    USERID is known: In this case, the <userInfo> parameter MUST be
    included in the userRequest.  The <userInfo> parameter MUST
    contain a <user> element and the 'entity' attribute value MUST be
    set to the XCON-USERID of the other user in question.  No
    additional parameters beyond those previously described are
    required in the userResponse message, in the case of a <response-
    code> of "200".
 o  A conferencing client who has no XCON-USERID and who wants to
    enter, via CCMP, a conference whose identifier is known: In this
    case, a side effect of the request is that the user is provided
    with a new XCON-USERID (created by the server) carried inside the
    <confUserID> parameter of the response.  This is the only case in
    which a CCMP request can be valid though carrying a void
    <confUserID> parameter.  A <userInfo> parameter MUST be enclosed
    in the request, providing at least a contact URI of the joining
    client, in order to let the focus initiate the signaling phase
    needed to add her to the conference.  The mandatory 'entity'
    attribute of the <userInfo> parameter in the request MUST be
    filled with a placeholder value with the user part of the XCON-
    USERID containing a value of AUTO_GENERATE_X as described in
    Section 4.3, to conform to the rules contained in the XCON data
    model XML schema.  The messages (userRequest and userResponse) in
    this case should look like the following:

Barnes, et al. Standards Track [Page 33] RFC 6503 CCMP March 2012

 Request fields:
 confUserID=null;
 confObjID=confXYZ;
 operation=create;
 userInfo=
 <userInfo entity="xcon-userid:AUTO_GENERATE_1@example.com">
         <endpoint entity="sip:GHIL345@example.com">
         ...
 Response fields (in case of success):
 confUserID=user345;
 confObjID=confXYZ;
 operation=create;
 response-code=200;
 userInfo=null; //or the entire userInfo object
              Figure 11: userRequest and userResponse in the
                        Absence of an xcon-userid
 o  A conferencing client is unaware of the XCON-USERID of a third
    user: In this case, the XCON-USERID in the request, <confUserID>,
    is the sender's and the 'entity' attribute of the attached
    <userInfo> parameter is filled with the placeholder value
    "xcon-userid:AUTO_GENERATE_1@example.com".  The XCON-USERID for
    the third user MUST be returned to the client issuing the request
    in the 'entity' attribute of the response <userInfo> parameter, if
    the <response-code> is "200".  This scenario is intended to
    support both the case where a brand new conferencing system user
    is added to a conference by a third party (i.e., a user who has
    not yet been provided with an XCON-USERID) and the case where the
    CCMP client issuing the request does not know the to-be-added
    user's XCON-USERID (which means such an identifier could already
    exist on the server's side for that user).  In this last case, the
    conference server is in charge of avoiding XCON-URI duplicates for
    the same conferencing client, looking at key fields in the
    request-provided <userInfo> parameter, such as the signaling URI.
    If the joining user is brand new, then the generation of a new
    XCON-USERID is needed; otherwise, if that user exists already, the
    server must recover the corresponding XCON-USERID.
 In the case of a userRequest with an <operation> parameter of
 "retrieve", the <confObjID> parameter representing the XCON-URI of
 the target conference MUST be included.  The <confUserID>, containing
 the CCMP client's XCON-USERID, MUST also be included in the

Barnes, et al. Standards Track [Page 34] RFC 6503 CCMP March 2012

 userRequest message.  If the client wants to retrieve information
 about her profile in the specified conference, no <userInfo>
 parameter is needed in the retrieve request.  On the other hand, if
 the client wants to obtain someone else's info within the given
 conference, she MUST include in the userRequest/retrieve a <userInfo>
 parameter whose 'entity' attribute conveys the desired user's XCON-
 USERID.  If the userResponse for the retrieve operation contains a
 <response-code> of "200", the <userInfo> parameter MUST be included
 in the response.
 In case of a userRequest with an <operation> parameter of "update",
 the <confObjID>, <confUserID>, and <userInfo> parameters MUST be
 included in the request.  The <userInfo> parameter is of type "user-
 type" and contains all the changes to be applied to a specific <user>
 element in the conference object identified by the <confObjID>
 parameter in the userRequest message.  The user to be modified is
 identified through the 'entity' attribute of the <userInfo> parameter
 included in the request.  In the case of a userResponse with a
 <response-code> of "200", no additional information is required in
 the userResponse message.  A <response-code> of "200" indicates that
 the referenced <user> element has been updated by the conference
 server.  A <response-code> of "426" indicates that the conferencing
 client is not allowed to make the changes reflected in the <userInfo>
 in the initial request.  This could be due to policies, roles,
 specific privileges, etc., with the reason specific to a conferencing
 system and its configuration.
 In the case of a userRequest with an <operation> parameter of
 "delete", the <confObjID> representing the XCON-URI of the target
 conference MUST be included.  The <confUserID> parameter, containing
 the CCMP client's XCON-USERID, MUST be included in the userRequest
 message.  If the client wants to exit the specified conference, no
 <userInfo> parameter is needed in the delete request.  On the other
 hand, if the client wants to remove another participant from the
 given conference, she MUST include in the userRequest/delete a
 <userInfo> parameter whose 'entity' attribute conveys the XCON-USERID
 of that participant.  The userResponse MUST contain the same value
 for the <confObjID> parameter that was included in the <confObjID>
 parameter in the userRequest.  The userResponse MUST contain a
 <response-code> of "200" if the target <user> element has been
 successfully deleted.  If the userResponse for the delete operation
 contains a <response-code> of "200", the userResponse MUST NOT
 contain the <userInfo> parameter.

Barnes, et al. Standards Track [Page 35] RFC 6503 CCMP March 2012

 <!-- userRequest -->
 <xs:complexType name="ccmp-user-request-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-request-message-type">
             <xs:sequence>
                 <xs:element ref="userRequest" />
             </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>
 <!-- userRequestType -->
 <xs:element name="userRequest" type="userRequestType" />
 <xs:complexType name="userRequestType">
     <xs:sequence>
         <xs:element name="userInfo"
                     type="info:user-type" minOccurs="0" />
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
 <!-- userResponse -->
 <xs:complexType name="ccmp-user-response-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-response-message-type">
             <xs:sequence>
                 <xs:element ref="userResponse" />
             </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>

Barnes, et al. Standards Track [Page 36] RFC 6503 CCMP March 2012

 <!-- userResponseType -->
 <xs:element name="userResponse" type="userResponseType" />
 <xs:complexType name="userResponseType">
     <xs:sequence>
         <xs:element name="userInfo" type="info:user-type"
                     minOccurs="0"/>
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
   Figure 12: Structure of the userRequest and userResponse Messages

5.3.7. sidebarsByValRequest and sidebarsByValResponse

 A sidebarsByValRequest message is used to execute a retrieve-only
 operation on the <sidebars-by-val> field of the conference object
 represented by the <confObjID>.  The sidebarsByValRequest message is
 of a retrieve-only type, so an <operation> parameter MUST NOT be
 included in a sidebarsByValRequest message.  As with blueprints and
 conferences, CCMP allows for the use of xpath filters whenever a
 selected subset of the sidebars available at the server's side has to
 be retrieved by the client.  This applies both to sidebars by
 reference and sidebars by value.  A sidebarsByValResponse message
 with a <response-code> of "200" MUST contain a <sidebarsByValInfo>
 parameter containing the desired <sidebars-by-val> element.  A
 sidebarsByValResponse message MUST return to the client a <version>
 element related to the current version of the main conference object
 (i.e., the one whose identifier is contained in the <confObjID> field
 of the request) with which the sidebars in question are associated.
 The <sidebarsByValInfo> parameter contains the list of the conference
 objects associated with the sidebars by value derived from the main
 conference.  The retrieved sidebars can then be updated or deleted
 using the sidebarByValRequest message, which is described in
 Section 5.3.8.

Barnes, et al. Standards Track [Page 37] RFC 6503 CCMP March 2012

<!– sidebarsByValRequest –>

<xs:complexType name="ccmp-sidebarsByVal-request-message-type">

   <xs:complexContent>
       <xs:extension base="tns:ccmp-request-message-type">
           <xs:sequence>
               <xs:element ref="sidebarsByValRequest"/>
           </xs:sequence>
       </xs:extension>
  </xs:complexContent>

</xs:complexType>

<!– sidebarsByValRequestType –>

<xs:element name="sidebarsByValRequest"

           type="sidebarsByValRequestType" />

<xs:complexType name="sidebarsByValRequestType">

   <xs:sequence>
       <xs:element name="xpathFilter" type="xs:string" minOccurs="0"/>
       <xs:any namespace="##other" processContents="lax"
               minOccurs="0" maxOccurs="unbounded"/>
 </xs:sequence>
 <xs:anyAttribute namespace="##any" processContents="lax"/>

</xs:complexType>

<!– sidebarsByValResponse –>

<xs:complexType name="ccmp-sidebarsByVal-response-message-type">

       <xs:complexContent>
        <xs:extension base="tns:ccmp-response-message-type">
               <xs:sequence>
          <xs:element ref="sidebarsByValResponse"/>
         </xs:sequence>
        </xs:extension>
       </xs:complexContent>

</xs:complexType>

Barnes, et al. Standards Track [Page 38] RFC 6503 CCMP March 2012

<!– sidebarsByValResponseType –>

<xs:element name="sidebarsByValResponse"

           type="sidebarsByValResponseType" />

<xs:complexType name="sidebarsByValResponseType">

   <xs:sequence>
       <xs:element name="sidebarsByValInfo"
                   type="info:sidebars-by-val-type" minOccurs="0"/>
       <xs:any namespace="##other" processContents="lax"
               minOccurs="0" maxOccurs="unbounded"/>
  </xs:sequence>
  <xs:anyAttribute namespace="##any" processContents="lax"/>

</xs:complexType>

         Figure 13: Structure of the sidebarsByValRequest and
                    sidebarsByValResponse Messages

5.3.8. sidebarByValRequest and sidebarByValResponse

 A sidebarByValRequest message MUST contain the <operation> parameter,
 which distinguishes among retrieval, creation, modification, and
 deletion of a specific sidebar.  The other required parameters depend
 upon the type of operation.
 In the case of a "create" operation, the <confObjID> parameter MUST
 be included in the sidebyValRequest message.  In this case, the
 <confObjID> parameter contains the XCON-URI of the main conference in
 which the sidebar has to be created.  If no "sidebarByValInfo"
 parameter is included, the sidebar is created by cloning the main
 conference, as envisioned in the XCON framework [RFC5239] following
 the implementation specific cloning rules.  Otherwise, similar to the
 case of direct creation, the sidebar conference object is built on
 the basis of the "sidebarByValInfo" parameter provided by the
 requestor.  As a consequence of a sidebar-by-val creation, the
 conference server MUST update the main conference object reflected by
 the <confObjID> parameter in the sidebarbyValRequest/create message
 introducing the new sidebar object as a new <entry> in the proper
 section <sidebars-by-val>.  The newly created sidebar conference
 object MAY be included in the sidebarByValResponse in the
 <sidebarByValInfo> parameter, if the <response-code> is "200".  The
 XCON-URI of the newly created sidebar MUST appear in the <confObjID>
 parameter of the response.  The conference server can notify any
 conferencing clients that have subscribed to the conference event
 package and that are authorized to receive the notification of the
 addition of the sidebar to the conference.

Barnes, et al. Standards Track [Page 39] RFC 6503 CCMP March 2012

 In the case of a sidebarByValRequest message with an <operation>
 parameter of "retrieve", the URI for the conference object created
 for the sidebar (received in response to a create operation or in a
 sidebarsByValResponse message) MUST be included in the <confObjID>
 parameter in the request.  This retrieve operation is handled by the
 conference server in the same manner as in the case of an <operation>
 parameter of "retrieve" included in a confRequest message, as
 described in Section 5.3.4.
 In the case of a sidebarByValRequest message with an <operation>
 parameter of "update", the <sidebarByValInfo> MUST also be included
 in the request.  The <confObjID> parameter contained in the request
 message identifies the specific sidebar instance to be updated.  An
 update operation on the specific sidebar instance contained in the
 <sidebarByValInfo> parameter is handled by the conference server in
 the same manner as an update operation on the conference instance as
 reflected by the <confInfo> parameter included in a confRequest
 message as detailed in Section 5.3.4.  A sidebarByValResponse message
 MUST return to the client a <version> element related to the current
 version of the sidebar whose identifier is contained in the
 <confObjID> field of the request.
 If an <operation> parameter of "delete" is included in the
 sidebarByVal request, the <sidebarByValInfo> parameter MUST NOT be
 included in the request.  Any <sidebarByValInfo> included in the
 request MUST be ignored by the conference server.  The URI for the
 conference object associated with the sidebar MUST be included in the
 <confObjID> parameter in the request.  If the specific conferencing
 user, as reflected by the <confUserID> parameter, in the request is
 authorized to delete the conference, the conference server deletes
 the conference object reflected by the <confObjID> parameter and
 updates the data in the conference object from which the sidebar was
 cloned.  The conference server can notify any conferencing clients
 that have subscribed to the conference event package and that are
 authorized to receive the notification of the deletion of the sidebar
 from the conference.
 If a sidebarByValRequest with an <operation> parameter of "retrieve",
 "update", or "delete" carries a <confObjID> parameter which is not
 associated with any existing sidebar-by-val, a confResponse message
 containing a <response-code> of "404" will be generated on the
 server's side.  This also holds for the case in which the mentioned
 <confObjID> parameter is related to an existing conference object
 stored at the server, but associated with a blueprint or with an
 actual conference or with a sidebar-by-ref rather than a sidebar-by-
 val.

Barnes, et al. Standards Track [Page 40] RFC 6503 CCMP March 2012

 <!-- sidebarByValRequest -->
 <xs:complexType name="ccmp-sidebarByVal-request-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-request-message-type">
             <xs:sequence>
                 <xs:element ref="sidebarByValRequest"/>
             </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>
 <!-- sidebarByValRequestType -->
 <xs:element name="sidebarByValRequest"
             type="sidebarByValRequestType" />
 <xs:complexType name="sidebarByValRequestType">
     <xs:sequence>
         <xs:element name="sidebarByValInfo"
                     type="info:conference-type" minOccurs="0"/>
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
 <!-- sidebarByValResponse -->
 <xs:complexType name="ccmp-sidebarByVal-response-message-type">
  <xs:complexContent>
         <xs:extension base="tns:ccmp-response-message-type">
          <xs:sequence>
                 <xs:element ref="sidebarByValResponse"/>
          </xs:sequence>
   </xs:extension>
  </xs:complexContent>
 </xs:complexType>

Barnes, et al. Standards Track [Page 41] RFC 6503 CCMP March 2012

 <!-- sidebarByValResponseType -->
 <xs:element name="sidebarByValResponse"
             type="sidebarByValResponseType" />
 <xs:complexType name="sidebarByValResponseType">
   <xs:sequence>
      <xs:element name="sidebarByValInfo"
                  type="info:conference-type" minOccurs="0"/>
      <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
   </xs:sequence>
   <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
          Figure 14: Structure of the sidebarByValRequest and
                     sidebarByValResponse Messages

5.3.9. sidebarsByRefRequest and sidebarsByRefResponse

 Similar to the sidebarsByValRequest, a sidebarsByRefRequest can be
 invoked to retrieve the <sidebars-by-ref> element of the conference
 object identified by the <confObjID> parameter.  The
 sidebarsByRefRequest message is of a retrieve-only type, so an
 <operation> parameter MUST NOT be included in a sidebarsByRefRequest
 message.  In the case of a <response-code> of "200", the
 <sidebarsByRefInfo> parameter, containing the <sidebars-by-ref>
 element of the conference object, MUST be included in the response.
 The <sidebars-by-ref> element represents the set of URIs of the
 sidebars associated with the main conference, whose description (in
 the form of a standard XCON conference document) is external to the
 main conference itself.  Through the retrieved URIs, it is then
 possible to access single sidebars using the sidebarByRefRequest
 message, described in Section 5.3.10.  A sidebarsByRefResponse
 message MUST carry back to the client a <version> element related to
 the current version of the main conference object (i.e., the one
 whose identifier is contained in the <confObjId> field of the
 request) with which the sidebars in question are associated.

Barnes, et al. Standards Track [Page 42] RFC 6503 CCMP March 2012

 <!-- sidebarsByRefRequest -->
 <xs:complexType name="ccmp-sidebarsByRef-request-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-request-message-type">
             <xs:sequence>
                 <xs:element ref="sidebarsByRefRequest"/>
             </xs:sequence>
         </xs:extension>
    </xs:complexContent>
 </xs:complexType>
 <!-- sidebarsByRefRequestType -->
 <xs:element name="sidebarsByRefRequest"
             type="sidebarsByRefRequestType" />
 <xs:complexType name="sidebarsByRefRequestType">
     <xs:sequence>
         <xs:element name="xpathFilter"
                     type="xs:string" minOccurs="0"/>
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
 <!-- sidebarsByRefResponse -->
 <xs:complexType name="ccmp-sidebarsByref-response-message-type">
         <xs:complexContent>
          <xs:extension base="tns:ccmp-response-message-type">
                  <xs:sequence>
                         <xs:element ref="sidebarsByRefResponse"/>
                  </xs:sequence>
          </xs:extension>
   </xs:complexContent>
 </xs:complexType>

Barnes, et al. Standards Track [Page 43] RFC 6503 CCMP March 2012

 <!-- sidebarsByRefResponseType -->
 <xs:element name="sidebarsByRefResponse"
             type="sidebarsByRefResponseType" />
 <xs:complexType name="sidebarsByRefResponseType">
     <xs:sequence>
        <xs:element name="sidebarsByRefInfo"
                    type="info:uris-type" minOccurs="0"/>
        <xs:any namespace="##other" processContents="lax"
                minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
           Figure 15: Structure of the sidebarsByRefRequest
                  and sidebarsByRefResponse Messages

5.3.10. sidebarByRefRequest and sidebarByRefResponse

 A sidebarByValResponse message MUST return to the client a <version>
 element related to the current version of the sidebar whose
 identifier is contained in the <confObjID> field of the request.
 In the case of a create operation, the <confObjID> parameter MUST be
 included in the sidebyRefRequest message.  In this case, the
 <confObjID> parameter contains the XCON-URI of the main conference in
 which the sidebar has to be created.  If no <sidebarByRefInfo>
 parameter is included, following the XCON framework [RFC5239], the
 sidebar is created by cloning the main conference, observing the
 implementation-specific cloning rules.  Otherwise, similar to the
 case of direct creation, the sidebar conference object is built on
 the basis of the <sidebarByRefInfo> parameter provided by the
 requestor.  If the creation of the sidebar is successful, the
 conference server MUST update the <sidebars-by-ref> element in the
 conference object from which the sidebar was created (i.e., as
 identified by the <confObjID> in the original sidebarByRefRequest),
 with the URI of the newly created sidebar.  The newly created
 conference object MAY be included in the response in the
 <sidebarByRefInfo> parameter with a <response-code> of "200".  The
 URI for the conference object associated with the newly created
 sidebar object MUST appear in the <confObjID> parameter of the
 response.  The conference server can notify any conferencing clients
 that have subscribed to the conference event package and that are
 authorized to receive the notification of the addition of the sidebar
 to the conference.

Barnes, et al. Standards Track [Page 44] RFC 6503 CCMP March 2012

 In the case of a sidebarByRefRequest message with an <operation>
 parameter of "retrieve", the URI for the conference object created
 for the sidebar MUST be included in the <confObjID> parameter in the
 request.  A retrieve operation on the <sidebarByRefInfo> is handled
 by the conference server in the same manner as a retrieve operation
 on the confInfo included in a confRequest message as detailed in
 Section 5.3.4.
 In the case of a sidebarByRefRequest message with an <operation>
 parameter of "update", the URI for the conference object created for
 the sidebar MUST be included in the <confObjID> parameter in the
 request.  The <sidebarByRefInfo> MUST also be included in the request
 in the case of an "update" operation.  An update operation on the
 <sidebarByRefInfo> is handled by the conference server in the same
 manner as an update operation on the <confInfo> included in a
 confRequest message as detailed in Section 5.3.4.  A
 sidebarByRefResponse message MUST carry back to the client a
 <version> element related to the current version of the sidebar whose
 identifier is contained in the <confObjID> field of the request.
 If an <operation> parameter of "delete" is included in the
 sidebarByRefRequest, the <sidebarByRefInfo> parameter MUST NOT be
 included in the request.  Any <sidebarByRefInfo> included in the
 request MUST be ignored by the conference server.  The URI for the
 conference object for the sidebar MUST be included in the <confObjID>
 parameter in the request.  If the specific conferencing user as
 reflected by the <confUserID> parameter in the request is authorized
 to delete the conference, the conference server SHOULD delete the
 conference object reflected by the <confObjID> parameter and SHOULD
 update the <sidebars-by-ref> element in the conference object from
 which the sidebar was originally cloned.  The conference server can
 notify any conferencing clients that have subscribed to the
 conference event package and that are authorized to receive the
 notification of the deletion of the sidebar.
 If a sidebarByRefRequest with an <operation> parameter of "retrieve",
 "update", or "delete" carries a <confObjID> parameter that is not
 associated with any existing sidebar-by-ref, a confResponse message
 containing a <response-code> of "404" will be generated on the
 server's side.  This also holds for the case in which the value of
 the mentioned <confObjID> parameter is related to an existing
 conference object stored at the server, but associated with a
 blueprint or with an actual conference or with a sidebar-by-val
 rather than a sidebar-by-ref.

Barnes, et al. Standards Track [Page 45] RFC 6503 CCMP March 2012

 <!-- sidebarByRefRequest -->
 <xs:complexType name="ccmp-sidebarByRef-request-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-request-message-type">
             <xs:sequence>
                 <xs:element ref="sidebarByRefRequest"/>
              </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>
 <!-- sidebarByRefRequestType -->
 <xs:element name="sidebarByRefRequest"
             type="sidebarByRefRequestType" />
 <xs:complexType name="sidebarByRefRequestType">
     <xs:sequence>
         <xs:element name="sidebarByRefInfo"
                     type="info:conference-type" minOccurs="0"/>
         <xs:any namespace="##other" processContents="lax"
                minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>
      <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
 <!-- sidebarByRefResponse -->
 <xs:complexType name="ccmp-sidebarByRef-response-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-response-message-type">
             <xs:sequence>
                 <xs:element ref="sidebarByRefResponse"/>
             </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>

Barnes, et al. Standards Track [Page 46] RFC 6503 CCMP March 2012

 <!-- sidebarByRefResponseType -->
 <xs:element name="sidebarByRefResponse"
             type="sidebarByRefResponseType" />
 <xs:complexType name="sidebarByRefResponseType">
     <xs:sequence>
         <xs:element name="sidebarByRefInfo"
                     type="info:conference-type" minOccurs="0"/>
         <xs:any namespace="##other" processContents="lax"
                minOccurs="0" maxOccurs="unbounded"/>
   </xs:sequence>
   <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
            Figure 16: Structure of the sidebarByRefRequest
                   and sidebarByRefResponse Messages

5.3.11. extendedRequest and extendedResponse

 In order to allow specifying new request and response pairs for
 conference control, CCMP defines the extendedRequest and
 extendedResponse messages.  Such messages constitute a CCMP skeleton
 in which implementers can transport the information needed to realize
 conference control mechanisms not explicitly envisioned in the CCMP
 specification; these mechanisms are called, in this context,
 "extensions".  Each extension is assumed to be characterized by an
 appropriate name that MUST be carried in the extendedRequest/
 extendedResponse pair in the provided <extensionName> field.
 Extension-specific information can be transported in the form of
 schema-defined XML elements inside the <any> element present in both
 extendedRequest and extendedResponse.
 The conferencing client SHOULD be able to determine the extensions
 supported by a CCMP server and to recover the XML schema defining the
 related specific elements by means of an optionsRequest/
 optionsResponse CCMP transaction (see Section 5.3.12).
 The meaning of the common CCMP parameters inherited by the
 extendedRequest and extendedResponse from the basic CCMP request and
 response messages SHOULD be preserved and exploited appropriately
 while defining an extension.

Barnes, et al. Standards Track [Page 47] RFC 6503 CCMP March 2012

 <!-- extendedRequest -->
 <xs:complexType name="ccmp-extended-request-message-type">
    <xs:complexContent>
        <xs:extension base="tns:ccmp-request-message-type">
           <xs:sequence>
                          <xs:element ref="extendedRequest"/>
           </xs:sequence>
        </xs:extension>
    </xs:complexContent>
 </xs:complexType>
 <!-- extendedRequestType -->
 <xs:element name="extendedRequest" type="extendedRequestType"/>
 <xs:complexType name="extendedRequestType">
   <xs:sequence>
         <xs:element name="extensionName"
                     type="xs:string" minOccurs="1"/>
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0"
             maxOccurs="unbounded" />
  </xs:sequence>
 </xs:complexType>
 <!-- extendedResponse -->
 <xs:complexType name="ccmp-extended-response-message-type">
    <xs:complexContent>
        <xs:extension base="tns:ccmp-response-message-type">
            <xs:sequence>
                          <xs:element ref="extendedResponse"/>
            </xs:sequence>
        </xs:extension>
     </xs:complexContent>
 </xs:complexType>

Barnes, et al. Standards Track [Page 48] RFC 6503 CCMP March 2012

 <!-- extendedResponseType -->
 <xs:element name="extendedResponse" type="extendedResponseType"/>
 <xs:complexType name="extendedResponseType">
         <xs:sequence>
                 <xs:element name="extensionName"
                             type="xs:string"
                             minOccurs="1"/>
                 <xs:any namespace="##other"
                         processContents="lax"
                         minOccurs="0" maxOccurs="unbounded" />
         </xs:sequence>
 </xs:complexType>
            Figure 17: Structure of the extendedRequest and
                       extendedResponse Messages

5.3.12. optionsRequest and optionsResponse

 The optionsRequest message (Figure 18) retrieves general information
 about conference server capabilities.  These capabilities include the
 standard CCMP messages (request/response pairs) and potential
 extension messages supported by the conference server.  As such, it
 is a basic CCMP message, rather than a specialization of the general
 CCMP request.
 The optionsResponse returns, in the appropriate <options> field, a
 list of the supported CCMP message pairs as defined in this
 specification.  These messages are in the form of a list: <standard-
 message-list> including each of the supported messages as reflected
 by <standard-message> elements.  The optionsResponse message also
 allows for an <extended-message-list>, which is a list of additional
 message types in the form of <extended-message-list> elements that
 are currently undefined, to allow for future extensibility.  The
 following information is provided for both types of messages:
 o  <name> (REQUIRED): in case of standard messages, it can be one of
    the 10 standard message names defined in this document (i.e.,
    "blueprintsRequest", "confsRequest", etc.).  In case of
    extensions, this element MUST carry the same value of the
    <extension-name> inserted in the corresponding extendedRequest/
    extendedResponse message pair.
 o  <operations> (OPTIONAL): this field is a list of <operation>
    entries, each representing the Create, Read, Update, Delete (CRUD)
    operation supported by the server for the message.  If this
    element is absent, the client SHOULD assume the server is able to

Barnes, et al. Standards Track [Page 49] RFC 6503 CCMP March 2012

    handle the entire set of CRUD operations or, in case of standard
    messages, all the operations envisioned for that message in this
    document.
 o  <schema-ref> (OPTIONAL): since all CCMP messages can potentially
    contain XML elements not envisioned in the CCMP schema (due to the
    presence of <any> elements and attributes), a reference to a
    proper schema definition specifying such new elements/attributes
    can also be sent back to the clients by means of such field.  If
    this element is absent, no new elements are introduced in the
    messages other than those explicitly defined in the CCMP
    specification.
 o  <description> (OPTIONAL): human-readable information about the
    related message.
 The only parameter needed in the optionsRequest is the sender
 confUserID, which is mirrored in the same parameter of the
 corresponding optionsResponse.
 The CCMP server MUST include the <standard-message-list> containing
 at least one <operation> element in the optionsResponse, since a CCMP
 server is REQUIRED to be able to handle both the request and response
 messages for at least one of the operations.
 <!-- optionsRequest -->
 <xs:complexType name="ccmp-options-request-message-type">
         <xs:complexContent>
                 <xs:extension base="tns:ccmp-request-message-type"/>
         </xs:complexContent>
 </xs:complexType>
 <!-- optionsResponse -->
 <xs:complexType name="ccmp-options-response-message-type">
    <xs:complexContent>
       <xs:extension base="tns:ccmp-response-message-type">
         <xs:sequence>
           <xs:element ref="optionsResponse"/>
         </xs:sequence>
       </xs:extension>
   </xs:complexContent>
 </xs:complexType>

Barnes, et al. Standards Track [Page 50] RFC 6503 CCMP March 2012

 <!-- optionsResponseType -->
 <xs:element name="optionsResponse"
                type="optionsResponseType" />
 <xs:complexType name="optionsResponseType">
   <xs:sequence>
    <xs:element name="options"
             type="options-type" minOccurs="0"/>
    <xs:any namespace="##other" processContents="lax"
              minOccurs="0" maxOccurs="unbounded"/>
  </xs:sequence>
  <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
 <!-- options-type -->
 <xs:complexType name="options-type">
    <xs:sequence>
         <xs:element name="standard-message-list"
                 type="standard-message-list-type"
                 minOccurs="1"/>
     <xs:element name="extended-message-list"
                 type="extended-message-list-type"
                 minOccurs="0"/>
     <xs:any namespace="##other" processContents="lax"
             minOccurs="0" maxOccurs="unbounded"/>
    </xs:sequence>
    <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
 <!-- standard-message-list-type -->
 <xs:complexType name="standard-message-list-type">
   <xs:sequence>
         <xs:element name="standard-message"
                     type="standard-message-type"
                     minOccurs="1" maxOccurs="10"/>
     <xs:any namespace="##other" processContents="lax"
             minOccurs="0" maxOccurs="unbounded"/>
   </xs:sequence>
   <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>

Barnes, et al. Standards Track [Page 51] RFC 6503 CCMP March 2012

 <!-- standard-message-type -->
 <xs:complexType name="standard-message-type">
    <xs:sequence>
         <xs:element name="name"
                     type="standard-message-name-type"
                     minOccurs="1"/>
         <xs:element name="operations"
                     type="operations-type"
                     minOccurs="0"/>
         <xs:element name="schema-def"
                     type="xs:string" minOccurs="0"/>
         <xs:element name="description"
                     type="xs:string" minOccurs="0"/>
     <xs:any namespace="##other" processContents="lax"
             minOccurs="0" maxOccurs="unbounded"/>
    </xs:sequence>
    <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
 <!-- standard-message-name-type -->
 <xs:simpleType name="standard-message-name-type">
    <xs:restriction base="xs:token">
     <xs:enumeration value="confsRequest"/>
     <xs:enumeration value="confRequest"/>
     <xs:enumeration value="blueprintsRequest"/>
     <xs:enumeration value="blueprintRequest"/>
     <xs:enumeration value="usersRequest"/>
     <xs:enumeration value="userRequest"/>
     <xs:enumeration value="sidebarsByValRequest"/>
     <xs:enumeration value="sidebarByValRequest"/>
     <xs:enumeration value="sidebarsByRefRequest"/>
     <xs:enumeration value="sidebarByRefRequest"/>
    </xs:restriction>
 </xs:simpleType>

Barnes, et al. Standards Track [Page 52] RFC 6503 CCMP March 2012

 <!-- operations-type -->
 <xs:complexType name="operations-type">
   <xs:sequence>
      <xs:element name="operation" type="operationType"
                  minOccurs="1" maxOccurs="4"/>
   </xs:sequence>
   <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
            Figure 18: Structure of the optionsRequest and
                       optionsResponse Messages

5.4. CCMP Response Codes

 All CCMP response messages MUST include a <response-code>.  This
 document defines an IANA registry for the CCMP response codes, as
 described in Section 12.5.2.  The following summarizes the CCMP
 response codes:
 200 Success:
    Successful completion of the requested operation.
 400 Bad Request:
    Syntactically malformed request.
 401 Unauthorized:
    User not allowed to perform the required operation.
 403 Forbidden:
    Operation not allowed (e.g., cancellation of a blueprint).
 404 Object Not Found:
    The target conference object does not exist at the server (The
    object in the error message refers to the <confObjID> parameter in
    the generic request message).
 409 Conflict:
    A generic error associated with all those situations in which a
    requested client operation cannot be successfully completed by the
    server.  An example of such a situation is when the modification
    of an object cannot be applied due to conflicts arising at the

Barnes, et al. Standards Track [Page 53] RFC 6503 CCMP March 2012

    server's side, e.g., because the client version of the object is
    an obsolete one and the requested modifications collide with the
    up-to-date state of the object stored at the server.  Such code
    would also be used if a client attempts to create an object
    (conference or user) with an entity that already exists.
 420 User Not Found:
    Target user missing at the server (it is related to the XCON-
    USERID in the 'entity' attribute of the <userInfo> parameter when
    it is included in userRequests).
 421 Invalid confUserID:
    User does not exist at the server (This code is returned for
    requests where the <confUserID> parameter is invalid).
 422 Invalid Conference Password:
    The password for the target conference object contained in the
    request is wrong.
 423 Conference Password Required:
    "conference-password" missing in a request to access a password-
    protected conference object.
 424 Authentication Required:
    User's authentication information is missing or invalid.
 425 Forbidden Delete Parent:
    Cancel operation failed since the target object is a parent of
    child objects that depend on it, or because it affects, based on
    the "parent-enforceable" mechanism, the corresponding element in a
    child object.
 426 Forbidden Change Protected:
    Update refused by the server because the target element cannot be
    modified due to its implicit dependence on the value of a parent
    object ("parent-enforceable" mechanism).
 427 Invalid Domain Name:
    The domain name in an AUTO_GENERATE_X instance in the conference
    object is not within the CCMP server's domain of responsibility.

Barnes, et al. Standards Track [Page 54] RFC 6503 CCMP March 2012

 500 Server Internal Error:
    The server cannot complete the required service due to a system
    internal error.
 501 Not Implemented:
    Operation defined by the protocol, but not implemented by this
    server.
 510 Request Timeout:
    The time required to serve the request has exceeded the configured
    service threshold.
 511 Resources Not Available:
    This code is used when the CCMP server cannot execute a command
    because of resource issues, e.g., it cannot create a sub-
    conference because the system has reached its limits on the number
    of sub-conferences, or if a request for adding a new user fails
    because the max number of users has been reached for the
    conference or the max number of users has been reached for the
    conferencing system.
 The handling of a <response-code> of "404", "409", "420", "421",
 "425", "426", or "427" is only applicable to specific operations for
 specialized message responses and the details are provided in
 Section 5.3.  The following table summarizes these response codes and
 the specialized message and operation to which they are applicable:

Barnes, et al. Standards Track [Page 55] RFC 6503 CCMP March 2012

 +----------+-------------+--------------+-------------+-------------+
 | Response | Create      | Retrieve     | Update      | Delete      |
 | code     |             |              |             |             |
 +----------+-------------+--------------+-------------+-------------+
 | 404      | userRequest | All retrieve | All update  | All delete  |
 |          | sidebarBy   | requests     | requests    | requests    |
 |          | ValRequest, | EXCEPT:      |             |             |
 |          | sidebarsBy  | blueprints   |             |             |
 |          | RefRequest  | Request,     |             |             |
 |          |             | confsRequest |             |             |
 | -------- | ----------- | ------------ | ----------- | ----------- |
 | 409      | N/A         | N/A          | All update  | N/A         |
 |          |             |              | requests    |             |
 | -------- | ----------- | -----------  | ----------- | ----------- |
 | 420      | userRequest | userRequest  | userRequest | userRequest |
 |          | (third-     |              |             |             |
 |          | party       |              |             |             |
 |          | invite with |              |             |             |
 |          | third-user  |              |             |             |
 |          | entity) (*) |              |             |             |
 | -------- | ----------- | -----------  | ----------- | ----------- |
 | 421      | All create  | All retrieve | All update  | All delete  |
 |          | requests    | requests     | requests    | requests    |
 |          | EXCEPT:     |              |             |             |
 |          | userRequest |              |             |             |
 |          | with no     |              |             |             |
 |          | confUserID  |              |             |             |
 |          | (**)        |              |             |             |
 | -------- | ----------- | -----------  | ----------- | ----------- |
 | 425      | N/A         | N/A          | N/A         | All delete  |
 |          |             |              |             | request     |
 | -------- | ----------- | -----------  | ----------- | ----------- |
 | 426      | N/A         | N/A          | All update  | N/A         |
 |          |             |              | requests    |             |
 | -------- | ----------- | -----------  | ----------- | ----------- |
 | 427      | ConfRequest | N/A          | All update  | N/A         |
 |          | UserRequest |              | requests    |             |
 +----------+-------------+--------------+-------------+-------------+
           Table 2: Response Codes and Associated Operations
 (*) "420" in answer to a "userRequest/create" operation: In the case
 of a third-party invite, this code can be returned if the
 <confUserID> (contained in the 'entity' attribute of the <userInfo>
 parameter) of the user to be added is unknown.  In the case above, if
 instead it is the <confUserID> parameter of the sender of the request
 that is invalid, a <response-code> of "421" is returned to the
 client.

Barnes, et al. Standards Track [Page 56] RFC 6503 CCMP March 2012

 (**) "421" is not sent in answer to userRequest/create messages
 having a "null" confUserID, since this case is associated with a user
 who is unaware of his own XCON-USERID, but wants to enter a known
 conference.
 In the case of a <response-code> of "510", a conferencing client MAY
 re-attempt the request within a period of time that would be specific
 to a conferencing client or conference server.
 A <response-code> of "400" indicates that the conferencing client
 sent a malformed request, which is indicative of an error in the
 conferencing client or in the conference server.  The handling is
 specific to the conferencing client implementation (e.g., generate a
 log, display an error message, etc.).  It is NOT RECOMMENDED that the
 client re-attempt the request in this case.
 A <response-code> of "401" or "403" indicates the client does not
 have the appropriate permissions, or there is an error in the
 permissions: re-attempting the request would likely not succeed and
 thus it is NOT RECOMMENDED.
 Any unexpected or unknown <response-code> SHOULD be treated by the
 client in the same manner as a <response-code> of "500", the handling
 of which is specific to the conferencing client implementation.

6. A Complete Example of CCMP in Action

 In this section a typical, non-normative, scenario in which CCMP
 comes into play is described, by showing the actual composition of
 the various CCMP messages.  In the call flows of the example, the
 conferencing client is a CCMP-enabled client, and the conference
 server is a CCMP-enabled server.  The XCON-USERID of the client,
 Alice, is "xcon-userid:alice@example.com" and it appears in the
 <confUserID> parameter in all requests.  The sequence of operations
 is as follows:
 1.  Alice retrieves the list of available blueprints from the server
     (Section 6.1);
 2.  Alice asks for detailed information about a specific blueprint
     (Section 6.2);
 3.  Alice decides to create a new conference by cloning the retrieved
     blueprint (Section 6.3);
 4.  Alice modifies information (e.g., XCON-URI, name, and
     description) associated with the newly created blueprint
     (Section 6.4);

Barnes, et al. Standards Track [Page 57] RFC 6503 CCMP March 2012

 5.  Alice specifies a list of users to be contacted when the
     conference is activated (Section 6.5);
 6.  Alice joins the conference (Section 6.6);
 7.  Alice lets a new user, Ciccio, (whose XCON-USERID is
     "xcon-userid:Ciccio@example.com") join the conference
     (Section 6.7).
 8.  Alice asks for the CCMP server capabilities (Section 6.8);
 9.  Alice exploits an extension of the CCMP server (Section 6.9).
 Note that the examples do not include any details beyond the basic
 operation.
 In the following sections, we deal with each of the aforementioned
 actions separately.

6.1. Alice Retrieves the Available Blueprints

 This section illustrates the transaction associated with retrieval of
 the blueprints, together with a dump of the two messages exchanged
 (blueprintsRequest and blueprintsResponse).  As shown in the figure,
 the blueprintsResponse message contains, in the <blueprintsInfo>
 parameter, information about the available blueprints, in the form of
 the standard XCON-URI of the blueprint, plus additional (and
 optional) information, like its display-text and purpose.
 Alice retrieves from the server the list of available blueprints:
  CCMP Client                                             CCMP Server
       |                                                       |
       | CCMP blueprintsRequest message                        |
       |   - confUserID: Alice                                 |
       |   - confObjID: (null)                                 |
       |------------------------------------------------------>|
       |                                                       |
       |                     CCMP blueprintsResponse message   |
       |                      - confUserID: Alice              |
       |                      - confObjID: (null)              |
       |                      - response-code: 200             |
       |                      - blueprintsInfo: bp123,bp124,.. |
       |<------------------------------------------------------|
       |                                                       |
       .                                                       .
       .                                                       .

Barnes, et al. Standards Track [Page 58] RFC 6503 CCMP March 2012

1. blueprintsRequest message:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ccmp:ccmpRequest
      xmlns:info="urn:ietf:params:xml:ns:conference-info"
      xmlns:ccmp="urn:ietf:params:xml:ns:xcon-ccmp"
      xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info">
    <ccmpRequest xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:type="ccmp:ccmp-blueprints-request-message-type">
        <confUserID>xcon-userid:alice@example.com</confUserID>
        <ccmp:blueprintsRequest/>
    </ccmpRequest>
</ccmp:ccmpRequest>
2. blueprintsResponse message from the server:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ccmp:ccmpResponse
 xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info"
 xmlns:info="urn:ietf:params:xml:ns:conference-info"
 xmlns:ccmp="urn:ietf:params:xml:ns:xcon-ccmp">
<ccmpResponse
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:type="ccmp:ccmp-blueprints-response-message-type">
   <confUserID>xcon-userid:alice@example.com</confUserID>
   <response-code>200</response-code>
     <ccmp:blueprintsResponse>
      <blueprintsInfo>
       <info:entry>
        <info:uri>xcon:AudioRoom@example.com</info:uri>
        <info:display-text>AudioRoom</info:display-text>
        <info:purpose>Simple Room:
           conference room with public access,
           where only audio is available, more users
           can talk at the same time
           and the requests for the AudioFloor
           are automatically accepted.
        </info:purpose>
       </info:entry>
       <info:entry>
        <info:uri>xcon:VideoRoom@example.com</info:uri>
        <info:display-text>VideoRoom</info:display-text>
        <info:purpose>Video Room:
            conference room with public access,
            where both audio and video are available,
            8 users can talk and be seen at the same time,
            and the floor requests are automatically accepted.
        </info:purpose>

Barnes, et al. Standards Track [Page 59] RFC 6503 CCMP March 2012

       </info:entry>
       <info:entry>
        <info:uri>xcon:AudioConference1@example.com</info:uri>
        <info:display-text>AudioConference1</info:display-text>
        <info:purpose>Public Audio Conference:
             conference with public access,
             where only audio is available,
             only one user can talk at the same time,
             and the requests for the AudioFloor MUST
             be accepted by a Chair.
        </info:purpose>
       </info:entry>
       <info:entry>
        <info:uri>xcon:VideoConference1@example.com</info:uri>
        <info:display-text>VideoConference1</info:display-text>
          <info:purpose>Public Video Conference: conference
              where both audio and video are available,
              only one user can talk.
          </info:purpose>
        </info:entry>
        <info:entry>
         <info:uri>xcon:AudioConference2@example.com</info:uri>
         <info:display-text>AudioConference2</info:display-text>
         <info:purpose>Basic Audio Conference:
              conference with private access,
              where only audio is available,
              only one user can talk at the same time,
              and the requests for the AudioFloor MUST
              be accepted by a Chair.
         </info:purpose>
        </info:entry>
     </blueprintsInfo>
   </ccmp:blueprintsResponse>
  </ccmpResponse>
</ccmp:ccmpResponse>
             Figure 19: Getting Blueprints from the Server

6.2. Alice Gets Detailed Information about a Specific Blueprint

 This section illustrates the second transaction in the overall flow.
 In this case, Alice, who now knows the XCON-URIs of the blueprints
 available at the server, makes a drill-down query, in the form of a
 CCMP blueprintRequest message, to get detailed information about one
 of them (the one called with XCON-URI "xcon:AudioRoom@example.com").
 The picture shows such a transaction.  Notice that the response
 contains, in the <blueprintInfo> parameter, a document compliant with
 the standard XCON data model.

Barnes, et al. Standards Track [Page 60] RFC 6503 CCMP March 2012

 Alice retrieves detailed information about a specified blueprint:
 CCMP Client                                             CCMP Server
      |                                                       |
      | CCMP blueprintRequest message                         |
      |   - confUserID: Alice                                 |
      |   - confObjID: bp123                                  |
      |   - operation: retrieve                               |
      |   - blueprintInfo: (null)                             |
      |------------------------------------------------------>|
      |                                                       |
      |                        CCMP blueprintResponse message |
      |                          - confUserID: Alice          |
      |                          - confObjID: bp123           |
      |                          - operation: retrieve        |
      |                          - response-code: 200         |
      |                          - blueprintInfo: bp123Info   |
      |<------------------------------------------------------|
      |                                                       |
      .                                                       .
      .                                                       .

1. blueprintRequest message:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <ccmp:ccmpRequest

     xmlns:info="urn:ietf:params:xml:ns:conference-info"
     xmlns:ccmp="urn:ietf:params:xml:ns:xcon-ccmp"
     xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info">
 <ccmpRequest xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                xsi:type="ccmp:ccmp-blueprint-request-message-type">
       <confUserID>xcon-userid:alice@example.com</confUserID>
       <confObjID>xcon:AudioRoom@example.com</confObjID>
       <operation>retrieve</operation>
       <ccmp:blueprintRequest/>
 </ccmpRequest>

</ccmp:ccmpRequest>

2. blueprintResponse message from the server:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <ccmp:ccmpResponse

     xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info"
     xmlns:info="urn:ietf:params:xml:ns:conference-info"
     xmlns:ccmp="urn:ietf:params:xml:ns:xcon-ccmp">
<ccmpResponse xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:type="ccmp:ccmp-blueprint-response-message-type">
<confUserID>xcon-userid:alice@example.com</confUserID>

Barnes, et al. Standards Track [Page 61] RFC 6503 CCMP March 2012

<confObjID>xcon:AudioRoom@example.com</confObjID>
<operation>retrieve</operation>
<response-code>200</response-code>
<response-string>Success</response-string>
<ccmp:blueprintResponse>
  <blueprintInfo entity="xcon:AudioRoom@example.com">
   <info:conference-description>
      <info:display-text>AudioRoom</info:display-text>
      <info:available-media>
         <info:entry label="audioLabel">
            <info:display-text>audio stream</info:display-text>
            <info:type>audio</info:type>
         </info:entry>
      </info:available-media>
   </info:conference-description>
   <info:users>
     <xcon:join-handling>allow</xcon:join-handling>
    </info:users>
   <xcon:floor-information>
    <xcon:floor-request-handling>confirm</xcon:floor-request-handling>
     <xcon:conference-floor-policy>
         <xcon:floor id="audioFloor">
             <xcon:media-label>audioLabel</xcon:media-label>
         </xcon:floor>
     </xcon:conference-floor-policy>
   </xcon:floor-information>
  </blueprintInfo>
 </ccmp:blueprintResponse>
</ccmpResponse>

</ccmp:ccmpResponse>

       Figure 20: Getting Information about a Specific Blueprint

6.3. Alice Creates a New Conference through a Cloning Operation

 This section illustrates the third transaction in the overall flow.
 Alice decides to create a new conference by cloning the blueprint
 having XCON-URI "xcon:AudioRoom@example.com", for which she just
 retrieved detailed information through the blueprintRequest message.
 This is achieved by sending a confRequest/create message having the
 blueprint's URI in the <confObjID> parameter.  The picture shows such
 a transaction.  Notice that the response contains, in the <confInfo>
 parameter, the document associated with the newly created conference,
 which is compliant with the standard XCON data model.  The
 <confObjID> parameter in the response is set to the XCON-URI of the
 new conference (in this case, "xcon:8977794@example.com").  We also

Barnes, et al. Standards Track [Page 62] RFC 6503 CCMP March 2012

 notice that this value is equal to the value of the 'entity'
 attribute of the <conference-info> element of the document
 representing the newly created conference object.
 Alice creates a new conference by cloning the
 "xcon:AudioRoom@example.com" blueprint:

CCMP Client CCMP Server

     |                                                       |
     | CCMP confRequest message                              |
     |   - confUserID: Alice                                 |
     |   - confObjID: AudioRoom                              |
     |   - operation: create                                 |
     |   - confInfo: (null)                                  |
     |------------------------------------------------------>|
     |                                                       |
     |                            CCMP confResponse message  |
     |                              - confUserID: Alice      |
     |                              - confObjID: newConfId   |
     |                              - operation: create      |
     |                              - response-code: 200     |
     |                              - version: 1             |
     |                              - confInfo: newConfInfo  |
     |<------------------------------------------------------|
     |                                                       |
     .                                                       .
     .                                                       .

1. confRequest message:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <ccmp:ccmpRequest

    xmlns:info="urn:ietf:params:xml:ns:conference-info"
    xmlns:ccmp="urn:ietf:params:xml:ns:xcon-ccmp"
    xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info">
 <ccmpRequest
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:type="ccmp:ccmp-conf-request-message-type">
    <confUserID>xcon-userid:alice@example.com</confUserID>
    <confObjID>xcon:AudioRoom@example.com</confObjID>
    <operation>create</operation>
    <ccmp:confRequest/>
 </ccmpRequest>

</ccmp:ccmpRequest>

Barnes, et al. Standards Track [Page 63] RFC 6503 CCMP March 2012

2. confResponse message from the server:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <ccmp:ccmpResponse

    xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info"
    xmlns:info="urn:ietf:params:xml:ns:conference-info"
    xmlns:ccmp="urn:ietf:params:xml:ns:xcon-ccmp">

<ccmpResponse xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

   xsi:type="ccmp:ccmp-conf-response-message-type">

<confUserID>xcon-userid:alice@example.com</confUserID> <confObjID>xcon:8977794@example.com</confObjID> <operation>create</operation> <response-code>200</response-code> <response-string>Success</response-string> <version>1</version> <ccmp:confResponse>

 <confInfo entity="xcon:8977794@example.com">
   <info:conference-description>
     <info:display-text>
            New conference by Alice cloned from AudioRoom
     </info:display-text>
     <info:available-media>
             <info:entry label="333">
               <info:display-text>audio stream</info:display-text>
               <info:type>audio</info:type>
             </info:entry>
      </info:available-media>
    </info:conference-description>
    <info:users>
         <xcon:join-handling>allow</xcon:join-handling>
    </info:users>
    <xcon:floor-information>
    <xcon:floor-request-handling>confirm</xcon:floor-request-handling>
     <xcon:conference-floor-policy>
        <xcon:floor id="11">
           <xcon:media-label>333</xcon:media-label>
        </xcon:floor>
     </xcon:conference-floor-policy>
    </xcon:floor-information>
   </confInfo>
  </ccmp:confResponse>
</ccmpResponse>

</ccmp:ccmpResponse>

      Figure 21: Creating a New Conference by Cloning a Blueprint

Barnes, et al. Standards Track [Page 64] RFC 6503 CCMP March 2012

6.4. Alice Updates Conference Information

 This section illustrates the fourth transaction in the overall flow.
 Alice decides to modify some of the details associated with the
 conference she just created.  More precisely, she changes the
 <display-text> element under the <conference-description> element of
 the document representing the conference.  This is achieved through a
 confRequest/update message carrying the fragment of the conference
 document to which the required changes have to be applied.  As shown
 in the picture, the response contains a code of "200", which
 acknowledges the modifications requested by the client, while also
 updating the conference version number from 1 to 2, as reflected in
 the "version" parameter.
 Alice updates information about the conference she just created:
 CCMP Client                                             CCMP Server
      |                                                       |
      | CCMP confRequest message                              |
      |   - confUserID: Alice                                 |
      |   - confObjID: 8977794                                |
      |   - operation: update                                 |
      |   - confInfo: confUpdates                             |
      |------------------------------------------------------>|
      |                                                       |
      |                            CCMP confResponse message  |
      |                              - confUserID: Alice      |
      |                              - confObjID: 8977794     |
      |                              - operation: update      |
      |                              - response-code: 200     |
      |                              - version: 2             |
      |                              - confInfo: (null)       |
      |<------------------------------------------------------|
      |                                                       |
      .                                                       .
      .                                                       .

1. confRequest message:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <ccmp:ccmpRequest

    xmlns:info="urn:ietf:params:xml:ns:conference-info"
          xmlns:ccmp="urn:ietf:params:xml:ns:xcon-ccmp"
    xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info">
 <ccmpRequest
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:type="ccmp:ccmp-conf-request-message-type">
   <confUserID>xcon-userid:alice@example.com</confUserID>

Barnes, et al. Standards Track [Page 65] RFC 6503 CCMP March 2012

   <confObjID>xcon:8977794@example.com</confObjID>
   <operation>update</operation>
   <ccmp:confRequest>
        <confInfo entity="xcon:8977794@example.com">
           <info:conference-description>
             <info:display-text>
                Alice's conference
             </info:display-text>
           </info:conference-description>
        </confInfo>
     </ccmp:confRequest>
 </ccmpRequest>

</ccmp:ccmpRequest>

2. confResponse message from the server:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <ccmp:ccmpResponse

    xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info"
    xmlns:info="urn:ietf:params:xml:ns:conference-info"
    xmlns:ccmp="urn:ietf:params:xml:ns:xcon-ccmp">
   <ccmpResponse xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:type="ccmp:ccmp-conf-response-message-type">
       <confUserID>xcon-userid:alice@example.com</confUserID>
       <confObjID>xcon:8977794@example.com</confObjID>
       <operation>update</operation>
       <response-code>200</response-code>
       <response-string>Success</response-string>
       <version>2</version>
       <ccmp:confResponse/>
   </ccmpResponse>

</ccmp:ccmpResponse>

              Figure 22: Updating Conference Information

6.5. Alice Inserts a List of Users into the Conference Object

 This section illustrates the fifth transaction in the overall flow.
 Alice modifies the <allowed-users-list> under the <users> element in
 the document associated with the conference she created.  To achieve
 this, she makes use of the usersRequest message provided by CCMP.
 Alice updates information about the list of users to whom access to
 the conference is permitted:

Barnes, et al. Standards Track [Page 66] RFC 6503 CCMP March 2012

 CCMP Client                                             CCMP Server
      |                                                       |
      | CCMP usersRequest message                             |
      |   - confUserID: Alice                                 |
      |   - confObjID: 8977794                                |
      |   - operation: update                                 |
      |   - usersInfo: usersUpdates                           |
      |------------------------------------------------------>|
      |                                                       |
      |                           CCMP usersResponse message  |
      |                             - confUserID: Alice       |
      |                             - confObjID: 8977794      |
      |                             - operation: update       |
      |                             - response-code: 200      |
      |                             - version: 3              |
      |                             - usersInfo: (null)       |
      |<------------------------------------------------------|
      |                                                       |
      .                                                       .
      .                                                       .

1. usersRequest message:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <ccmp:ccmpRequest

    xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info"
        xmlns:info="urn:ietf:params:xml:ns:conference-info"
        xmlns:ccmp="urn:ietf:params:xml:ns:xcon-ccmp">
   <ccmpRequest xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                xsi:type="ccmp:ccmp-users-request-message-type">
       <confUserID>xcon-userid:alice@example.com</confUserID>
       <confObjID>xcon:8977794@example.com</confObjID>
       <operation>update</operation>
       <ccmp:usersRequest>
           <usersInfo>
               <xcon:allowed-users-list>
                   <xcon:target method="dial out"
                                uri="xmpp:cicciolo@pippozzo.com"/>
                   <xcon:target method="refer"
                                uri="tel:+1-972-555-1234"/>
                   <xcon:target method="refer"
                                uri="sip:Carol@example.com"/>
               </xcon:allowed-users-list>
           </usersInfo>
       </ccmp:usersRequest>
   </ccmpRequest>

</ccmp:ccmpRequest>

Barnes, et al. Standards Track [Page 67] RFC 6503 CCMP March 2012

2. usersResponse message from the server:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <ccmp:ccmpResponse

     xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info"
     xmlns:info="urn:ietf:params:xml:ns:conference-info"
     xmlns:ccmp="urn:ietf:params:xml:ns:xcon-ccmp">
   <ccmpResponse xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:type="ccmp:ccmp-users-response-message-type">
       <confUserID>xcon-userid:alice@example.com</confUserID>
       <confObjID>xcon:8977794@example.com</confObjID>
       <operation>retrieve</operation>
       <response-code>200</response-code>
       <response-string>Success</response-string>
       <version>3</version>
       <ccmp:usersResponse/>
   </ccmpResponse>

</ccmp:ccmpResponse>

         Figure 23: Updating the List of Allowed Users for the
                 Conference 'xcon:8977794@example.com'

6.6. Alice Joins the Conference

 This section illustrates the sixth transaction in the overall flow.
 Alice uses CCMP to add herself to the newly created conference.  This
 is achieved through a userRequest/create message containing, in the
 <userInfo> parameter, a <user> element compliant with the XCON data
 model representation.  Notice that such an element includes
 information about the user's Addresses of Record, as well as her
 current endpoint.  The picture below shows the transaction.  Notice
 how the <confUserID> parameter is equal to the 'entity' attribute of
 the <userInfo> element, which indicates that the request issued by
 the client is a first-party one.
 Alice joins the conference by issuing a userRequest/create message
 with her own ID to the server:

Barnes, et al. Standards Track [Page 68] RFC 6503 CCMP March 2012

 CCMP Client                                             CCMP Server
      |                                                       |
      | CCMP userRequest message                              |
      |   - confUserID: Alice                                 |
      |   - confObjID: 8977794                                |
      |   - operation: create                                 |
      |   - userInfo: AliceUserInfo                           |
      |------------------------------------------------------>|
      |                                                       |
      |                            CCMP userResponse message  |
      |                              - confUserID: Alice      |
      |                              - confObjID: 8977794     |
      |                              - operation: create      |
      |                              - response-code: 200     |
      |                              - version: 4             |
      |                              - userInfo: (null)       |
      |<------------------------------------------------------|
      |                                                       |
      .                                                       .
      .                                                       .

1. userRequest message:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <ccmp:ccmpRequest

      xmlns:info="urn:ietf:params:xml:ns:conference-info"
          xmlns:ccmp="urn:ietf:params:xml:ns:xcon-ccmp"
          xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info">
   <ccmpRequest xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:type="ccmp:ccmp-user-request-message-type">
       <confUserID>xcon-userid:alice@example.com</confUserID>
       <confObjID>xcon:8977794@example.com</confObjID>
               <operation>create</operation>
       <ccmp:userRequest>
           <userInfo entity="xcon-userid:alice@example.com">
               <info:associated-aors>
                   <info:entry>
                       <info:uri>
                          mailto:Alice83@example.com
                       </info:uri>
                       <info:display-text>email</info:display-text>
                   </info:entry>
               </info:associated-aors>
               <info:endpoint entity="sip:alice_789@example.com"/>
           </userInfo>
       </ccmp:userRequest>
   </ccmpRequest>

</ccmp:ccmpRequest>

Barnes, et al. Standards Track [Page 69] RFC 6503 CCMP March 2012

2. userResponse message from the server:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <ccmp:ccmpResponse

     xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info"
     xmlns:info="urn:ietf:params:xml:ns:conference-info"
     xmlns:ccmp="urn:ietf:params:xml:ns:xcon-ccmp">
   <ccmpResponse xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:type="ccmp:ccmp-user-response-message-type">
       <confUserID>xcon-userid:alice@example.com</confUserID>
       <confObjID>xcon:8977794@example.com</confObjID>
       <operation>create</operation>
       <response-code>200</response-code>
       <response-string>Success</response-string>
       <version>4</version>
       <ccmp:userResponse/>
   </ccmpResponse>

</ccmp:ccmpResponse>

          Figure 24: Alice Joins the Conference through CCMP

6.7. Alice Adds a New User to the Conference

 This section illustrates the seventh and last transaction in the
 overall flow.  Alice uses CCMP to add a new conferencing system user,
 Ciccio, to the conference.  This "third-party" request is realized
 through a userRequest/create message containing, in the <userInfo>
 parameter, a <user> element compliant with the XCON data model
 representation.  Notice that such an element includes information
 about Ciccio's Addresses of Record, as well as his current endpoint,
 but has a placeholder 'entity' attribute,
 "AUTO_GENERATE_1@example.com" as discussed in Section 4.3, since the
 XCON-USERID is initially unknown to Alice.  Thus, the conference
 server is in charge of generating a new XCON-USERID for the user
 Alice indicates (i.e., Ciccio), and returning it in the 'entity'
 attribute of the <userInfo> parameter carried in the response, as
 well as adding the user to the conference.  The picture below shows
 the transaction.
 Alice adds user "Ciccio" to the conference by issuing a third-party
 userRequest/create message to the server:

Barnes, et al. Standards Track [Page 70] RFC 6503 CCMP March 2012

CCMP Client                                             CCMP Server
     |                                                       |
     | CCMP userRequest message                              |
     |   - confUserID: Alice                                 |
     |   - confObjID: 8977794                                |
     |   - operation: create                                 |
     |   - userInfo: dummyUserID, CiccioUserInfo             |
     |------------------------------------------------------>|
     |                                                       |
     |                       CCMP optionsResponse message    |
     |                            - confUserID: Alice        |
     |                            - confObjID: 8977794       |
     |                            - operation: create        |
     |                            - response-code: 200       |
     |                            - version: 5               |
     |                            - userInfo: userIDCiccio,  |
     |                                        CiccioUserInfo |
     |                                                       |
     |<------------------------------------------------------|
     |                                                       |
     .                                                       .
     .                                                       .

1. "third-party" userRequest message from Alice:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <ccmp:ccmpRequest

     xmlns:info="urn:ietf:params:xml:ns:conference-info"
     xmlns:ccmp="urn:ietf:params:xml:ns:xcon-ccmp"
     xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info">
  <ccmpRequest xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
               xsi:type="ccmp:ccmp-user-request-message-type">
      <confUserID>xcon-userid:alice@example.com</confUserID>
      <confObjID>xcon:8977794@example.com</confObjID>
      <operation>create</operation>
      <ccmp:userRequest>
          <userInfo entity="xcon-userid:AUTO_GENERATE_1@example.com">
              <info:associated-aors>
                  <info:entry>
                      <info:uri>
                          mailto:Ciccio@example.com
                      </info:uri>
                      <info:display-text>email</info:display-text>
                  </info:entry>
              </info:associated-aors>
              <info:endpoint entity="sip:Ciccio@example.com"/>
          </userInfo>

Barnes, et al. Standards Track [Page 71] RFC 6503 CCMP March 2012

      </ccmp:userRequest>
  </ccmpRequest>

</ccmp:ccmpRequest>

2. "third-party" userResponse message from the server:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <ccmp:ccmpResponse

      xmlns:info="urn:ietf:params:xml:ns:conference-info"
      xmlns:ccmp="urn:ietf:params:xml:ns:xcon-ccmp"
      xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info">
   <ccmpResponse xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                 xsi:type="ccmp:ccmp-user-response-message-type">
       <confUserID>xcon-userid:alice@example.com</confUserID>
       <confObjID>xcon:8977794@example.com</confObjID>
       <operation>create</operation>
       <response-code>200</response-code>
       <version>5</version>
       <ccmp:userResponse>
               <userInfo entity="xcon-userid:Ciccio@example.com">
               <info:associated-aors>
                   <info:entry>
                       <info:uri>
                           mailto:Ciccio@example.com
                       </info:uri>
                       <info:display-text>email</info:display-text>
                   </info:entry>
               </info:associated-aors>
               <info:endpoint entity="sip:Ciccio@example.com"/>
           </userInfo>
       </ccmp:userResponse>
   </ccmpResponse>

</ccmp:ccmpResponse>

    Figure 25: Alice Adds a New User to the Conference through CCMP

6.8. Alice Asks for the CCMP Server Capabilities

 This section illustrates how Alice can discover which standard CCMP
 messages and what extensions are supported by the CCMP server with
 which she interacts through an optionsRequest/optionsResponse
 transaction.
 To prepare the optionsRequest, Alice just puts her XCON-USERID in the
 <confUserID> parameter.  Looking at the <options> element in the
 received optionsResponse, Alice infers the following server
 capabilities as regards standard CCMP messages:

Barnes, et al. Standards Track [Page 72] RFC 6503 CCMP March 2012

 o  the server doesn't support sidebarsByValRequest nor the
    sidebarByValRequest messages, since they do not appear in the
    <standard-message-list>;
 o  the only implemented operation for the blueprintRequest message is
    "retrieve", since no other <operation> entries are included in the
    related <operations> field.
 By analyzing the <extended-message-list>, Alice discovers the server
 implements a bluePrint extension, referred to as "confSummaryRequest"
 in this example.  This extension allows Alice to recover via CCMP a
 brief description of a specific conference; the XML elements involved
 in this extended conference control transaction are available at the
 URL indicated in the <schema-ref> element, and the only operation
 provided by this extension is "retrieve".  To better understand how
 Alice can exploit the "confSummaryRequest" extension via CCMP, see
 Section 6.9.
 The figure below shows the optionsRequest/optionsResponse message
 exchange between Alice and the CCMP server.
 CCMP Client                                             CCMP Server
      |                                                       |
      | CCMP optionsRequest message                           |
      |   - confUserID: Alice                                 |
      |------------------------------------------------------>|
      |                                                       |
      |                          CCMP userResponse message    |
      |                            - confUserID: Alice        |
      |                            - response-code: 200       |
      |                            - options (list of both    |
      |                              standard and extended    |
      |                              supported messages)      |
      |<------------------------------------------------------|
      |                                                       |
      .                                                       .
      .                                                       .

1. optionsRequest (Alice asks for CCMP server capabilities)

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>

 <ccmp:ccmpRequest
       xmlns:info="urn:ietf:params:xml:ns:conference-info"
       xmlns:ccmp="urn:ietf:params:xml:ns:xcon-ccmp"
       xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info">
   <ccmpRequest xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:type="ccmp:ccmp-options-request-message-type">
       <confUserID>xcon-userid:alice@example.com</confUserID>

Barnes, et al. Standards Track [Page 73] RFC 6503 CCMP March 2012

   </ccmpRequest>
 </ccmp:ccmpRequest>

2. optionsResponse (the server returns the list of its conference

  control capabilities)

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>

 <ccmp:ccmpResponse
        xmlns:info="urn:ietf:params:xml:ns:conference-info"
        xmlns:ccmp="urn:ietf:params:xml:ns:xcon-ccmp"
        xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info">
   <ccmpResponse xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:type="ccmp:ccmp-options-response-message-type">
       <confUserID>xcon-userid:alice@example.com</confUserID>
       <response-code>200</response-code>
       <response-string>success</response-string>
       <ccmp:optionsResponse>
          <options>
             <standard-message-list>
                <standard-message>
                   <name>blueprintsRequest</name>
                </standard-message>
                <standard-message>
                  <name>blueprintRequest</name>
                  <operations>
                    <operation>retrieve</operation>
                  </operations>
                </standard-message>
                <standard-message>
                  <name>confsRequest</name>
                </standard-message>
                <standard-message>
                  <name>confRequest</name>
                </standard-message>
                <standard-message>
                   <name>usersRequest</name>
                </standard-message>
                <standard-message>
                   <name>userRequest</name>
                </standard-message>
                <standard-message>
                   <name>sidebarsByRefRequest</name>
                </standard-message>
                <standard-message>
                   <name>sidebarByRefRequest</name>
                </standard-message>
             </standard-message-list>
             <extended-message-list>

Barnes, et al. Standards Track [Page 74] RFC 6503 CCMP March 2012

                <extended-message>
                   <name>confSummaryRequest</name>
                   <operations>
                     <operation>retrieve</operation>
                   </operations>
                   <schema-def>
                        http://example.com/ccmp-extension-schema.xsd
                   </schema-def>
                   <description>
                        confSummaryRequest is intended
                        to allow the requestor to retrieve
                        a brief description
                        of the conference indicated in the
                        confObjID request parameter
                   </description>
                </extended-message>
             </extended-message-list>
          </options>
       </ccmp:optionsResponse>
   </ccmpResponse>
 </ccmp:ccmpResponse>
       Figure 26: Alice Asks for the Server Control Capabilities

6.9. Alice Makes Use of a CCMP Server Extension

 In this section, a very simple example of CCMP extension support is
 provided.  Alice can recover information about this and other server-
 supported extensions by issuing an optionsRequest (see Section 6.8).
 The extension in question is named "confSummaryRequest" and allows a
 CCMP client to obtain from the CCMP server synthetic information
 about a specific conference.  The conference summary is carried in
 the form of an XML element as follows:
   <?xml version="1.0" encoding="UTF-8"?>
     <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
               targetNamespace="http://example.com/ccmp-extension"
               xmlns="http://example.com/ccmp-extension">
     <xs:element name="confSummary" type="conf-summary-type"/>
     <xs:complexType name="conf-summary-type">
       <xs:sequence>
         <xs:element name="title" type="xs:string"/>
         <xs:element name="status" type="xs:string"/>
         <xs:element name="public" type="xs:boolean"/>
         <xs:element name="media" type="xs:string"/>

Barnes, et al. Standards Track [Page 75] RFC 6503 CCMP March 2012

       </xs:sequence>
     </xs:complexType>
   </xs:schema>
        Figure 27: Example of XML Schema defining an extension
                 parameter (ccmp-extension-schema.xsd)
 As can be inferred from the schema file, the <confSummary> element
 contains conference information related to the following:
 o  title
 o  status (active or registered)
 o  participation modality (if everyone is allowed to participate, the
    boolean <public> element is set to "true")
 o  involved media
 In order to retrieve a conference summary related to the conference
 she participates in, Alice sends to the CCMP server an
 extendedRequest with a "confSummaryRequest" <extensionName>,
 specifying the conference XCON-URI in the confObjID request
 parameter, as depicted in the figure below.
CCMP Client                                             CCMP Server
     |                                                       |
     | CCMP extendedRequest message                          |
     |   - confUserID: Alice                                 |
     |   - confObjID: 8977794                                |
     |   - operation: retrieve                               |
     |   - extensionName: confSummaryRequest                 |
     |------------------------------------------------------>|
     |                                                       |
     |                      CCMP extendedResponse message    |
     |                            - confUserID: Alice        |
     |                            - confObjID: 8977794       |
     |                            - operation: retrieve      |
     |                            - response-code: 200       |
     |                            - extensionName:           |
     |                              confSummaryRequest       |
     |                            - confSummary              |
     |<------------------------------------------------------|
     |                                                       |
     .                                                       .
     .                                                       .

Barnes, et al. Standards Track [Page 76] RFC 6503 CCMP March 2012

1. extendedRequest (Alice makes use of the "confSummaryRequest")

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>

<ccmp:ccmpRequest xmlns:info="urn:ietf:params:xml:ns:conference-info"
      xmlns:ccmp="urn:ietf:params:xml:ns:xcon-ccmp"
      xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info"
      xmlns:example="http://example.com/ccmp-extension">
  <ccmpRequest xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:type="ccmp:ccmp-extended-request-message-type">
      <confUserID>xcon-userid:alice@example.com</confUserID>
      <confObjID>xcon:8977794@example.com</confObjID>
      <operation>retrieve</operation>
      <ccmp:extendedRequest>
             <extensionName>confRequestSummary</extensionName>
      </ccmp:extendedRequest>
  </ccmpRequest>
</ccmp:ccmpRequest>

2. extendedResponse (the server provides Alice with a brief description

 of the desired conference)

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>

<ccmp:ccmpResponse xmlns:info="urn:ietf:params:xml:ns:conference-info"
        xmlns:ccmp="urn:ietf:params:xml:ns:xcon-ccmp"
        xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info"
        xmlns:example="http://example.com/ccmp-extension">
  <ccmpResponse xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:type="ccmp:ccmp-extended-response-message-type">
       <confUserID>xcon-userid:alice@example.com</confUserID>
       <confObjID>xcon:8977794@example.com</confObjID>
       <operation>retrieve</operation>
       <response-code>200</response-code>
       <response-string>success</response-string>
       <ccmp:extendedResponse>
         <extensionName>confSummaryRequest</extensionName>
         <example:confSummary>
             <title> Alice's conference </title>
             <status> active </status>
             <public> true </public>
             <media> audio </media>
         </example:confSummary>
       </ccmp:extendedResponse>
   </ccmpResponse>
</ccmp:ccmpResponse>
     Figure 28: Alice Exploits the 'confSummaryRequest' Extension

Barnes, et al. Standards Track [Page 77] RFC 6503 CCMP March 2012

7. Locating a Conference Server

 If a conferencing client is not pre-configured to use a specific
 conference server for the requests, the client MUST first discover
 the conference server before it can send any requests.  The result of
 the discovery process, is the address of the server supporting
 conferencing.  In this document, the result is an http: or https:
 URI, which identifies a conference server.
 DNS is RECOMMENDED to be used to locate a conference server in the
 case that the client is not pre-configured to use a specific
 conference server.  URI-Enabled NAPTR (U-NAPTR) resolution for
 conferencing takes a domain name as input and produces a URI that
 identifies the conference server.  This process also requires an
 Application Service tag and an Application Protocol tag, which
 differentiate conferencing-related NAPTR records from other records
 for that domain.
 Section 12.4.1 defines an Application Service tag of "XCON", which is
 used to identify the centralized conferencing (XCON) server for a
 particular domain.  The Application Protocol tag "CCMP", defined in
 Section 12.4.2, is used to identify an XCON server that understands
 CCMP.
 The NAPTR records in the following example (Figure 29) demonstrate
 the use of the Application Service and Application Protocol tags.
 Iterative NAPTR resolution is used to delegate responsibility for the
 conferencing service from "zonea.example.com." and
 "zoneb.example.com." to "outsource.example.com.".

Barnes, et al. Standards Track [Page 78] RFC 6503 CCMP March 2012

           zonea.example.com.
           ;;       order pref flags
           IN NAPTR 100   10   ""  "XCON-CCMP" (     ; service
           ""                                        ; regex
           outsource.example.com.                    ; replacement
           )
           zoneb.example.com.
           ;;       order pref flags
           IN NAPTR 100   10   ""  "XCON-CCMP" (     ; service
           ""                                        ; regex
           outsource.example.com.                    ; replacement
           )
           outsource.example.com.
           ;;       order pref flags
           IN NAPTR 100   10   "u"  "XCON-CCMP" (    ; service
           "!*.!https://confs.example.com/!"         ; regex
           .                                         ; replacement
           )
           Figure 29: Sample XCON-CCMP Service NAPTR Records
 Details for the "XCON" Application Service tag and the "CCMP"
 Application Protocol tag are included in Section 12.4.

8. Managing Notifications

 As per [RFC5239], CCMP is one of the following four protocols, which
 have been formally identified within the XCON framework:
 Conference Control Protocol:
    mediates between conference and media control client (conferencing
    client) and conference server.  This document describes such a
    protocol.
 Binary floor Control Protocol:
    operates between the floor control client and the floor control
    server.  An example of such a protocol is the Binary Floor Control
    Protocol (BFCP), specified in [RFC4582].
 Call Signaling Protocol:
    operates between the Call Signaling Client and the focus.
    Examples of call signaling protocols include SIP, H.323 and IAX.
    Such protocols are capable of negotiating a conferencing session.

Barnes, et al. Standards Track [Page 79] RFC 6503 CCMP March 2012

 Notification Protocol:
    operates between the Notification Client and the XCON Notification
    Service.  This specification does not define a new notification
    protocol.  For clients that use SIP as the call signaling
    protocol, the XCON event package [RFC6502] MUST be used by the
    client for notifications of changes in the conference data as
    described below.
 The protocol specified in this document is a proactive one and is
 used by a conferencing client to send requests to a conference server
 in order to retrieve information about the conference objects stored
 by the server and to possibly manipulate them.  However, a complete
 conferencing solution is not prohibited from providing clients with a
 means for receiving asynchronous updates about the status of the
 objects available at the server.  The notification protocol, while
 conceptually independent of all the mentioned companion protocols,
 can nonetheless be chosen in a way that is consistent with the
 overall protocol architecture characterizing a specific deployment,
 as discussed in the following.
 When the conferencing control client uses SIP [RFC3261] as the
 signaling protocol to participate in the conference, SIP event
 notification can be used.  In such a case, the conferencing control
 client MUST implement the conference event package for XCON
 [RFC6502].  This is the default mechanism for conferencing clients as
 is SIP for signaling per the XCON framework [RFC5239].
 In the case where the interface to the conference server is entirely
 web based, there is a common mechanism for web-based systems that
 could be used -- a "call back".  With this mechanism, the
 conferencing client provides the conference server with an HTTP URL
 that is invoked when a change occurs.  This is a common
 implementation mechanism for e-commerce.  This works well in the
 scenarios whereby the conferencing client is a web server that
 provides the graphical HTML user interface and uses CCMP as the back-
 end interface to the conference server.  This model can coexist with
 the SIP event notification model.  PC-based clients behind NATs could
 provide a SIP event URI, whereas web-based clients using CCMP in the
 back end would probably find the HTTP call back approach much easier.
 The details of this approach are out of scope for CCMP; thus, we
 expect a future specification will document this solution.

9. HTTP Transport

 This section describes the use of HTTP [RFC2616] and HTTP over TLS
 [RFC2818] as transport mechanisms for CCMP, which a conforming
 conference server and conferencing client MUST support.

Barnes, et al. Standards Track [Page 80] RFC 6503 CCMP March 2012

 Although CCMP uses HTTP as a transport, it uses a strict subset of
 HTTP features, and due to the restrictions of some features, a
 conferencing server might not be a fully compliant HTTP server.  It
 is intended that a conference server can easily be built using an
 HTTP server with extensibility mechanisms, and that a conferencing
 client can trivially use existing HTTP libraries.  This subset of
 requirements helps implementers avoid ambiguity with the many options
 the full HTTP protocol offers.
 Support of HTTP authentication [RFC2617] and cookies [RFC6265] is
 OPTIONAL for a conferencing client that conforms to this
 specification.  These mechanisms are unnecessary because CCMP
 requests carry their own authentication information (in the "subject"
 field; see Section 5.1).  A conferencing client SHOULD include
 support for HTTP proxy authentication.
 A CCMP request is carried in the body of an HTTP POST request.  The
 conferencing client MUST include a Host header in the request.
 The MIME type of CCMP request and response bodies is "application/
 ccmp+xml".  The conference server and conferencing client MUST
 provide this value in the HTTP Content-Type and Accept header fields.
 If the conference server does not receive the appropriate Content-
 Type and Accept header fields, the conference server SHOULD fail the
 request, returning a 406 (Not Acceptable) response.  CCMP responses
 SHOULD include a Content-Length header.
 Conferencing clients MUST NOT use the Expect header or the Range
 header in CCMP requests.  The conference server MAY return 501 (Not
 Implemented) errors if either of these HTTP features are used.  In
 the case that the conference server receives a request from the
 conferencing client containing an If-* (conditional) header, the
 conference server SHOULD return a 412 (precondition failed) response.
 The POST method is the only method REQUIRED for CCMP.  If a
 conference server chooses to support GET or HEAD, it SHOULD consider
 the kind of application doing the GET.  Since a conferencing client
 only uses a POST method, the GET or HEAD MUST be either a URL that
 was found outside its normal context (e.g., somebody found a URL in
 protocol traces or log files and fed it into their browser) or
 somebody is testing or debugging a system.  The conference server
 could provide information in the CCMP response indicating that the
 URL corresponds to a conference server and only responds to CCMP POST
 requests or the conference server could instead try to avoid any leak
 of information by returning a very generic HTTP error message such as
 405 (Method Not Allowed).

Barnes, et al. Standards Track [Page 81] RFC 6503 CCMP March 2012

 The conference server populates the HTTP headers of responses so that
 they are consistent with the contents of the message.  In particular,
 the CacheControl header SHOULD be set to disable caching of any
 conference information by HTTP intermediaries.  Otherwise, there is
 the risk of stale information and/or the unauthorized disclosure of
 the information.  The HTTP status code MUST indicate a 2xx series
 response for all CCMP Response and Error messages.
 The conference server MAY redirect a CCMP request.  A conference
 server MUST NOT include CCMP responses in a 3xx response.  A
 conferencing client MUST handle redirects by using the Location
 header provided by the server in a 3xx response.  When redirecting,
 the conferencing client MUST observe the delay indicated by the
 Retry-After header.  The conferencing client MUST authenticate the
 server that returns the redirect response before following the
 redirect.  A conferencing client SHOULD authenticate the conference
 server indicated in a redirect.
 The conference server SHOULD support persistent connections and
 request pipelining.  If pipelining is not supported, the conference
 server MUST NOT allow persistent connections.  The conference server
 MUST support termination of a response by the closing of a
 connection.
 Implementations of CCMP that implement HTTP transport MUST implement
 transport over TLS [RFC2818].  TLS provides message integrity and
 confidentiality between the conferencing client and the conference
 server.  The conferencing client MUST implement the server
 authentication method described in HTTPS [RFC2818].  The device uses
 the URI obtained during conference server discovery to authenticate
 the server.  The details of this authentication method are provided
 in Section 3.1 of HTTPS [RFC2818].  When TLS is used, the
 conferencing client SHOULD fail a request if server authentication
 fails.

10. Security Considerations

 As identified in the XCON framework [RFC5239], there are a wide
 variety of potential attacks related to conferencing, due to the
 natural involvement of multiple endpoints and the capability to
 manipulate the data on the conference server using CCMP.  Examples of
 attacks include the following: an endpoint attempting to listen to
 conferences in which it is not authorized to participate, an endpoint
 attempting to disconnect or mute other users, and an endpoint theft
 of service in attempting to create conferences it is not allowed to
 create.

Barnes, et al. Standards Track [Page 82] RFC 6503 CCMP March 2012

 The following summarizes the security considerations for CCMP:
 1.  The client MUST determine the proper conference server.  The
     conference server discovery is described in Section 7.
 2.  The client MUST connect to the proper conference server.  The
     mechanisms for addressing this security consideration are
     described in Section 10.1.
 3.  The protocol MUST support a confidentiality and integrity
     mechanism.  As described in Section 9, implementations of CCMP
     MUST implement the HTTP transport over TLS [RFC2818].
 4.  There are security issues associated with the authorization to
     perform actions on the conferencing system to invoke specific
     capabilities.  A conference server SHOULD ensure that only
     authorized entities can manipulate the conference data.  The
     mechanisms for addressing this security consideration are
     described in Section 10.2.
 5.  The privacy and security of the identity of a user in the
     conference MUST be assured.  The mechanisms to ensure the
     security and privacy of identity are discussed in Section 10.3.
 6.  A final issue is related to Denial-of-Service (DoS) attacks on
     the conference server itself.  The recommendations to minimize
     the potential and impact of DoS attacks are discussed in
     Section 10.4.
 Of the considerations listed above, items 1 and 3 are addressed
 within the referenced sections earlier in this document.  The
 remaining security considerations are addressed in detail in the
 following sections.

10.1. Assuring That the Proper Conference Server Has Been Contacted

 Section 7 describes a mechanism using DNS by which a conferencing
 client discovers a conference server.  A primary concern is spoofed
 DNS replies; thus, the use of DNS Security (DNSSEC) is RECOMMENDED to
 ensure that the client receives a valid response from the DNS server
 in cases where this is a concern.
 When the CCMP transaction is conducted using TLS [RFC5246], the
 conference server can authenticate its identity, either as a domain
 name or as an IP address, to the conferencing client by presenting a
 certificate containing that identifier as a subjectAltName (i.e., as
 an iPAddress or dNSName, respectively).  Any implementation of CCMP
 MUST be capable of being transacted over TLS so that the client can

Barnes, et al. Standards Track [Page 83] RFC 6503 CCMP March 2012

 request the above authentication.  Note that, in order for the
 presented certificate to be valid at the client, the client MUST be
 able to validate the certificate following the procedures in
 [RFC2818] in the case of HTTP as a transport.  In particular, the
 validation path of the certificate must end in one of the client's
 trust anchors, even if that trust anchor is the conference server
 certificate itself.  If the client has external information as to the
 expected identity or credentials of the proper conference server, the
 authentication checks described above MAY be omitted.

10.2. User Authentication and Authorization

 Many policy authorization decisions are based on the identity of the
 user or the role that a user may have.  The conference server MUST
 implement mechanisms for authentication of users to validate their
 identity.  There are several ways that a user might authenticate its
 identity to the system.  For users joining a conference using one of
 the call signaling protocols, the user authentication mechanisms for
 the specific protocol can be used.  For example, in the case of a
 user joining the conference using SIP signaling, the user
 authentication as defined in [RFC3261] MUST be used.  For the case of
 users joining the conference using CCMP, the CCMP Request messages
 provide a subject field that contains a username and password, which
 can be used for authentication.  Since the CCMP messages are
 RECOMMENDED to be carried over TLS, this information can be sent
 securely.
 The XCON framework [RFC5239] provides an overview of other
 authorization mechanisms.  In the cases where a user is authorized
 via multiple mechanisms, it is RECOMMENDED that the conference server
 associate the authorization of the CCMP interface with other
 authorization mechanisms; for example, Public Switched Telephone
 Network (PSTN) users that join with a PIN and control the conference
 using CCMP.  When a conference server presents the identity of
 authorized users, it MAY provide information about the way the
 identity was proven or verified by the system.  A conference server
 can also allow a completely unauthenticated user into the system --
 this information SHOULD also be communicated to interested parties.
 Once a user is authenticated and authorized through the various
 mechanisms available on the conference server, the conference server
 MUST allocate a conference user identifier (XCON-USERID) and SHOULD
 associate the XCON-USERID with any signaling specific user
 identifiers that were used for authentication and authorization.
 This XCON-USERID can be provided to a specific user through the
 conference notification interface and MUST be provided to users that
 interact with the conferencing system using CCMP (i.e., in the
 appropriate CCMP response messages).  The XCON-USERIDs for each user/

Barnes, et al. Standards Track [Page 84] RFC 6503 CCMP March 2012

 participant in the conference are contained in the 'entity' attribute
 in the <user> element in the conference object.  The XCON-USERID is
 REQUIRED for any subsequent operations by the user on the conference
 object and is carried in the confUserID parameter in the CCMP
 requests and responses.
 Note that the policy management of an XCON-compliant conferencing
 system is out of the scope of this document, as well as of the XCON
 working group (WG).  However, the specification of a policy
 management framework is realizable with the overall XCON
 architecture, in particular with regard to a Role-Based Access
 Control (RBAC) approach.  In RBAC, the following elements are
 identified: (i) Users; (ii) Roles; (iii) Objects; (iv) Operations;
 (v) Permissions.  For all of the above elements, a direct mapping
 exists onto the main XCON entities.  As an example, RBAC objects map
 onto XCON data model objects and RBAC operations map onto CCMP
 operations.
 Future documents can define an RBAC framework for XCON, by first
 focusing on the definition of roles and then specifying the needed
 permission policy sets and role policy sets (used to associate policy
 permission sets with specific roles).  With these policies in place,
 access to a conference object compliant with the XCON data model can
 be appropriately controlled.  As far as assigning users to roles, the
 Users in the RBAC model relate directly to the <users> element in the
 conference object.  The <users> element is comprised of <user>
 elements representing a specific user in the conferencing system.
 Each <user> element contains an 'entity' attribute with the XCON-
 USERID and a <role> element.  Thus, each authorized user (as
 represented by an XCON-USERID) can be associated with a <role>
 element.

10.3. Security and Privacy of Identity

 An overview of the required privacy and anonymity for users of a
 conferencing system are provided in the XCON framework [RFC5239].
 The security of the identity in the form of the XCON-USERID is
 provided in CCMP through the use of TLS.
 The conference server SHOULD support the mechanism to ensure the
 privacy of the XCON-USERID.  The conferencing client indicates the
 desired level of privacy by manipulation of the <provide-anonymity>
 element defined in the XCON data model [RFC6501].  The <provide-
 anonymity> element controls the degree to which a user reveals their
 identity.  The following summarizes the values for the <provide-
 anonymity> element that the client includes in their requests:

Barnes, et al. Standards Track [Page 85] RFC 6503 CCMP March 2012

    "hidden": Ensures that other participants are not aware that there
    is an additional participant (i.e., the user issuing the request)
    in the conference.  This could be used in cases of users that are
    authorized with a special role in a conference (e.g., a supervisor
    in a call center environment).
    "anonymous": Ensures that other participants are aware that there
    is another participant (i.e., the user issuing the request);
    however, the other participants are not provided information as to
    the identity of the user.
    "semi-private": Ensures that the user's identity is only to be
    revealed to other participants or users that have a higher-level
    authorization (e.g., a conferencing system can be configured such
    that a human administrator can see all users).
 If the client desires privacy, the conferencing client SHOULD include
 the <provide-anonymity> element in the <confInfo> parameter in a CCMP
 confRequest message with an <operation> parameter of "update" or
 "create" or in the <userInfo> parameter in a CCMP userRequest message
 with an <operation> parameter of "update" or "create".  If the
 <provide-anonymity> element is not included in the conference object,
 then other users can see the participant's identity.  Participants
 are made aware of other participants that are "anonymous" or "semi-
 private" when they perform subsequent operations on the conference
 object or retrieve the conference object or when they receive
 subsequent notifications.
 Note that independent of the level of anonymity requested by the
 user, the identity of the user is always known by the conferencing
 system as that is required to perform the necessary authorization as
 described in Section 10.2.  The degree to which human administrators
 can see the information can be controlled using policies (e.g., some
 information in the data model can be hidden from human
 administrators).

10.4. Mitigating DoS Attacks

 [RFC4732] provides an overview of possible DoS attacks.  In order to
 minimize the potential for DoS attacks, it is RECOMMENDED that
 conferencing systems require user authentication and authorization
 for any client participating in a conference.  This can be
 accomplished through the use of the mechanisms described in
 Section 10.2, as well as by using the security mechanisms associated
 with the specific signaling (e.g., Session Initiation Protocol Secure
 (SIPS)) and media protocols (e.g., Secure Realtime Transport Protocol
 (SRTP)).  In addition, Section 4.4 describes the use of a timer
 mechanism to alleviate the situation whereby CCMP messages pend

Barnes, et al. Standards Track [Page 86] RFC 6503 CCMP March 2012

 indefinitely, thus increasing the potential that pending requests
 continue to increase when is a server is receiving more requests than
 it can process.

11. XML Schema

 This section gives the XML schema definition
 [W3C.REC-xmlschema-1-20041028] [W3C.REC-xmlschema-2-20041028] of the
 "application/ccmp+xml" format.  This is presented as a formal
 definition of the "application/ccmp+xml" format.  A new XML
 namespace, a new XML schema, and the MIME type for this schema are
 registered with IANA as described in Section 12.  Note that this XML
 Schema Definition is not intended to be used with on-the-fly
 validation of the presence XML document.  Whitespaces are included in
 the schema to conform to the line length restrictions of the RFC
 format without having a negative impact on the readability of the
 document.  Any conforming processor should remove leading and
 trailing white spaces.

<?xml version="1.0" encoding="utf-8"?>

 <xs:schema
    targetNamespace="urn:ietf:params:xml:ns:xcon-ccmp"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="urn:ietf:params:xml:ns:xcon-ccmp"
    xmlns:tns="urn:ietf:params:xml:ns:xcon-ccmp"
    xmlns:dm="urn:ietf:params:xml:ns:xcon-conference-info"
    xmlns:info="urn:ietf:params:xml:ns:conference-info"
    xmlns:xs="http://www.w3.org/2001/XMLSchema">
    <xs:import namespace="urn:ietf:params:xml:ns:xcon-conference-info"
               schemaLocation="DataModel.xsd"/>
    <xs:import namespace="urn:ietf:params:xml:ns:conference-info"
               schemaLocation="rfc4575.xsd"/>
    <xs:element name="ccmpRequest" type="ccmp-request-type" />
    <xs:element name="ccmpResponse" type="ccmp-response-type" />

<!– CCMP request definition –>

 <xs:complexType name="ccmp-request-type">
     <xs:sequence>
         <xs:element name="ccmpRequest"
                     type="ccmp-request-message-type" />
     </xs:sequence>
 </xs:complexType>

Barnes, et al. Standards Track [Page 87] RFC 6503 CCMP March 2012

 <!-- ccmp-request-message-type -->
 <xs:complexType abstract="true"
                 name="ccmp-request-message-type">
     <xs:sequence>
         <xs:element name="subject" type="subject-type"
                     minOccurs="0" maxOccurs="1" />
         <xs:element name="confUserID" type="xs:string"
                     minOccurs="0" maxOccurs="1" />
         <xs:element name="confObjID" type="xs:string"
                     minOccurs="0" maxOccurs="1" />
         <xs:element name="operation" type="operationType"
                     minOccurs="0" maxOccurs="1" />
         <xs:element name="conference-password" type="xs:string"
                     minOccurs="0" maxOccurs="1" />
        <xs:any namespace="##other" processContents="lax"
                minOccurs="0" maxOccurs="unbounded"/>
    </xs:sequence>
    <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>

<!– CCMP response definition –>

 <xs:complexType name="ccmp-response-type">
     <xs:sequence>
         <xs:element name="ccmpResponse"
                     type="ccmp-response-message-type" />
     </xs:sequence>
 </xs:complexType>
 <!-- ccmp-response-message-type -->
 <xs:complexType abstract="true" name="ccmp-response-message-type">
     <xs:sequence>
         <xs:element name="confUserID" type="xs:string"
                     minOccurs="1" maxOccurs="1" />
         <xs:element name="confObjID" type="xs:string"
                     minOccurs="0" maxOccurs="1" />
         <xs:element name="operation" type="operationType"
                     minOccurs="0"
                     maxOccurs="1" />
         <xs:element name="response-code"
                     type="response-codeType"
                     minOccurs="1" maxOccurs="1" />
         <xs:element name="response-string" type="xs:string"
                     minOccurs="0" maxOccurs="1" />
         <xs:element name="version" type="xs:positiveInteger"
                     minOccurs="0" maxOccurs="1" />

Barnes, et al. Standards Track [Page 88] RFC 6503 CCMP March 2012

         <xs:any namespace="##other" processContents="lax"
                     minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>

<!– CCMP REQUESTS –>

 <!-- blueprintsRequest -->
 <xs:complexType name="ccmp-blueprints-request-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-request-message-type">
             <xs:sequence>
                 <xs:element ref="blueprintsRequest" />
             </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>
 <!-- blueprintsRequestType -->
 <xs:element name="blueprintsRequest" type="blueprintsRequestType"/>
 <xs:complexType name="blueprintsRequestType">
     <xs:sequence>
         <xs:element name="xpathFilter" type="xs:string"
                     minOccurs="0"/>
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
 <!--  blueprintRequest -->
 <xs:complexType name="ccmp-blueprint-request-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-request-message-type">
             <xs:sequence>
                 <xs:element ref="blueprintRequest" />
             </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>

Barnes, et al. Standards Track [Page 89] RFC 6503 CCMP March 2012

 <!-- blueprintRequestType -->
 <xs:element name="blueprintRequest" type="blueprintRequestType" />
 <xs:complexType name="blueprintRequestType">
     <xs:sequence>
         <xs:element name="blueprintInfo"
                     type="info:conference-type" minOccurs="0"/>
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
 <!-- confsRequest -->
 <xs:complexType name="ccmp-confs-request-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-request-message-type">
             <xs:sequence>
                 <xs:element ref="confsRequest" />
             </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>
 <!-- confsRequestType -->
 <xs:element name="confsRequest" type="confsRequestType" />
 <xs:complexType name="confsRequestType">
     <xs:sequence>
         <xs:element name="xpathFilter" type="xs:string"
                     minOccurs="0"/>
         <xs:any namespace="##other" processContents="lax"
                minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
 <!-- confRequest -->
 <xs:complexType name="ccmp-conf-request-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-request-message-type">
             <xs:sequence>
                 <xs:element ref="confRequest" />
             </xs:sequence>
         </xs:extension>

Barnes, et al. Standards Track [Page 90] RFC 6503 CCMP March 2012

     </xs:complexContent>
  </xs:complexType>
 <!-- confRequestType -->
 <xs:element name="confRequest" type="confRequestType" />
 <xs:complexType name="confRequestType">
     <xs:sequence>
         <xs:element name="confInfo" type="info:conference-type"
                     minOccurs="0"/>
         <xs:any namespace="##other" processContents="lax"
                minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
 <!-- usersRequest -->
 <xs:complexType name="ccmp-users-request-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-request-message-type">
             <xs:sequence>
                 <xs:element ref="usersRequest" />
             </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>
 <!-- usersRequestType -->
 <xs:element name="usersRequest" type="usersRequestType" />
 <xs:complexType name="usersRequestType">
     <xs:sequence>
         <xs:element name="usersInfo" type="info:users-type"
                     minOccurs="0" />
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
  </xs:complexType>
 <!-- userRequest -->
 <xs:complexType name="ccmp-user-request-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-request-message-type">

Barnes, et al. Standards Track [Page 91] RFC 6503 CCMP March 2012

             <xs:sequence>
                 <xs:element ref="userRequest" />
             </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>
 <!-- userRequestType -->
 <xs:element name="userRequest" type="userRequestType" />
 <xs:complexType name="userRequestType">
     <xs:sequence>
         <xs:element name="userInfo" type="info:user-type"
                     minOccurs="0" />
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
 <!-- sidebarsByValRequest -->
 <xs:complexType name="ccmp-sidebarsByVal-request-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-request-message-type">
             <xs:sequence>
                 <xs:element ref="sidebarsByValRequest" />
              </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>
  <!-- sidebarsByValRequestType -->
  <xs:element name="sidebarsByValRequest"
              type="sidebarsByValRequestType" />
  <xs:complexType name="sidebarsByValRequestType">
      <xs:sequence>
          <xs:element name="xpathFilter"
                      type="xs:string" minOccurs="0"/>
          <xs:any namespace="##other" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>
          <xs:anyAttribute namespace="##any" processContents="lax"/>
  </xs:complexType>

Barnes, et al. Standards Track [Page 92] RFC 6503 CCMP March 2012

  <!-- sidebarsByRefRequest -->
  <xs:complexType name="ccmp-sidebarsByRef-request-message-type">
      <xs:complexContent>
          <xs:extension base="tns:ccmp-request-message-type">
              <xs:sequence>
                  <xs:element ref="sidebarsByRefRequest" />
              </xs:sequence>
          </xs:extension>
      </xs:complexContent>
  </xs:complexType>
 <!-- sidebarsByRefRequestType -->
 <xs:element name="sidebarsByRefRequest"
             type="sidebarsByRefRequestType" />
 <xs:complexType name="sidebarsByRefRequestType">
     <xs:sequence>
         <xs:element name="xpathFilter" type="xs:string"
                     minOccurs="0"/>
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
 <!-- sidebarByValRequest -->
 <xs:complexType name="ccmp-sidebarByVal-request-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-request-message-type">
             <xs:sequence>
                 <xs:element ref="sidebarByValRequest" />
             </xs:sequence>
          </xs:extension>
     </xs:complexContent>
 </xs:complexType>
 <!-- sidebarByValRequestType -->
 <xs:element name="sidebarByValRequest"
             type="sidebarByValRequestType"/>
 <xs:complexType name="sidebarByValRequestType">
     <xs:sequence>
         <xs:element name="sidebarByValInfo"
                     type="info:conference-type" minOccurs="0"/>

Barnes, et al. Standards Track [Page 93] RFC 6503 CCMP March 2012

         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
 <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
 <!-- sidebarByRefRequest -->
 <xs:complexType name="ccmp-sidebarByRef-request-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-request-message-type">
             <xs:sequence>
                 <xs:element ref="sidebarByRefRequest" />
             </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>
 <!-- sidebarByRefRequestType -->
 <xs:element name="sidebarByRefRequest"
             type="sidebarByRefRequestType" />
 <xs:complexType name="sidebarByRefRequestType">
     <xs:sequence>
         <xs:element name="sidebarByRefInfo"
                     type="info:conference-type" minOccurs="0"/>
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
 <!-- extendedRequest -->
 <xs:complexType name="ccmp-extended-request-message-type">
    <xs:complexContent>
        <xs:extension base="tns:ccmp-request-message-type">
           <xs:sequence>
                       <xs:element ref="extendedRequest"/>
           </xs:sequence>
        </xs:extension>
    </xs:complexContent>
 </xs:complexType>

Barnes, et al. Standards Track [Page 94] RFC 6503 CCMP March 2012

 <!-- extendedRequestType -->
 <xs:element name="extendedRequest" type="extendedRequestType"/>
 <xs:complexType name="extendedRequestType">
   <xs:sequence>
      <xs:element name="extensionName"
                  type="xs:string" minOccurs="1"/>
      <xs:any namespace="##other" processContents="lax" minOccurs="0"
                         maxOccurs="unbounded" />
  </xs:sequence>
 </xs:complexType>
 <!-- optionsRequest -->
      <xs:complexType name="ccmp-options-request-message-type">
      <xs:complexContent>
          <xs:extension base="tns:ccmp-request-message-type">
          </xs:extension>
      </xs:complexContent>
  </xs:complexType>

<!– CCMP RESPONSES –>

 <!-- blueprintsResponse -->
 <xs:complexType name="ccmp-blueprints-response-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-response-message-type">
             <xs:sequence>
                 <xs:element ref="blueprintsResponse" />
             </xs:sequence>
         </xs:extension>
     </xs:complexContent>
 </xs:complexType>
 <!-- blueprintsResponseType -->
 <xs:element name="blueprintsResponse" type="blueprintsResponseType"/>
 <xs:complexType name="blueprintsResponseType">
     <xs:sequence>
         <xs:element name="blueprintsInfo" type="info:uris-type"
                     minOccurs="0"/>
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>

Barnes, et al. Standards Track [Page 95] RFC 6503 CCMP March 2012

     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>
 <!-- blueprintResponse -->
 <xs:complexType name="ccmp-blueprint-response-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-response-message-type">
             <xs:sequence>
                 <xs:element ref="blueprintResponse" />
             </xs:sequence>
         </xs:extension>
     </xs:complexContent>
  </xs:complexType>
  <!-- blueprintResponseType -->
  <xs:element name="blueprintResponse" type="blueprintResponseType"/>
  <xs:complexType name="blueprintResponseType">
      <xs:sequence>
        <xs:element name="blueprintInfo" type="info:conference-type"
                      minOccurs="0"/>
        <xs:any namespace="##other" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>
      <xs:anyAttribute namespace="##any" processContents="lax"/>
  </xs:complexType>
  <!-- confsResponse -->
  <xs:complexType name="ccmp-confs-response-message-type">
      <xs:complexContent>
          <xs:extension base="tns:ccmp-response-message-type">
              <xs:sequence>
                  <xs:element ref="confsResponse" />
              </xs:sequence>
          </xs:extension>
      </xs:complexContent>
  </xs:complexType>
  <!-- confsResponseType -->
  <xs:element name="confsResponse" type="confsResponseType" />
  <xs:complexType name="confsResponseType">
      <xs:sequence>
          <xs:element name="confsInfo" type="info:uris-type"

Barnes, et al. Standards Track [Page 96] RFC 6503 CCMP March 2012

                      minOccurs="0"/>
          <xs:any namespace="##other" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>
      <xs:anyAttribute namespace="##any" processContents="lax"/>
  </xs:complexType>
  <!-- confResponse -->
  <xs:complexType name="ccmp-conf-response-message-type">
      <xs:complexContent>
          <xs:extension base="tns:ccmp-response-message-type">
              <xs:sequence>
                  <xs:element ref="confResponse"/>
              </xs:sequence>
          </xs:extension>
      </xs:complexContent>
  </xs:complexType>
  <!-- confResponseType -->
  <xs:element name="confResponse" type="confResponseType" />
  <xs:complexType name="confResponseType">
      <xs:sequence>
          <xs:element name="confInfo" type="info:conference-type"
                      minOccurs="0"/>
          <xs:any namespace="##other" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>
      <xs:anyAttribute namespace="##any" processContents="lax"/>
  </xs:complexType>
  <!-- usersResponse -->
  <xs:complexType name="ccmp-users-response-message-type">
      <xs:complexContent>
          <xs:extension base="tns:ccmp-response-message-type">
              <xs:sequence>
                  <xs:element ref="usersResponse" />
              </xs:sequence>
          </xs:extension>
       </xs:complexContent>
  </xs:complexType>

Barnes, et al. Standards Track [Page 97] RFC 6503 CCMP March 2012

  <!-- usersResponseType -->
  <xs:element name="usersResponse" type="usersResponseType" />
  <xs:complexType name="usersResponseType">
      <xs:sequence>
          <xs:element name="usersInfo" type="info:users-type"
                      minOccurs="0"/>
          <xs:any namespace="##other" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>
      <xs:anyAttribute namespace="##any" processContents="lax"/>
  </xs:complexType>
  <!-- userResponse -->
  <xs:complexType name="ccmp-user-response-message-type">
      <xs:complexContent>
          <xs:extension base="tns:ccmp-response-message-type">
              <xs:sequence>
                  <xs:element ref="userResponse" />
              </xs:sequence>
          </xs:extension>
      </xs:complexContent>
  </xs:complexType>
  <!-- userResponseType -->
  <xs:element name="userResponse" type="userResponseType" />
  <xs:complexType name="userResponseType">
      <xs:sequence>
          <xs:element name="userInfo" type="info:user-type"
                      minOccurs="0"/>
          <xs:any namespace="##other" processContents="lax"
                minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>
      <xs:anyAttribute namespace="##any" processContents="lax"/>
  </xs:complexType>
  <!-- sidebarsByValResponse -->
  <xs:complexType name="ccmp-sidebarsByVal-response-message-type">
      <xs:complexContent>
          <xs:extension base="tns:ccmp-response-message-type">
              <xs:sequence>
                  <xs:element ref="sidebarsByValResponse" />
              </xs:sequence>

Barnes, et al. Standards Track [Page 98] RFC 6503 CCMP March 2012

          </xs:extension>
      </xs:complexContent>
  </xs:complexType>
  <!-- sidebarsByValResponseType -->
  <xs:element name="sidebarsByValResponse"
              type="sidebarsByValResponseType" />
  <xs:complexType name="sidebarsByValResponseType">
      <xs:sequence>
          <xs:element name="sidebarsByValInfo"
                      type="info:sidebars-by-val-type" minOccurs="0"/>
          <xs:any namespace="##other" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>
      <xs:anyAttribute namespace="##any" processContents="lax"/>
  </xs:complexType>
  <!-- sidebarsByRefResponse -->
  <xs:complexType name="ccmp-sidebarsByRef-response-message-type">
      <xs:complexContent>
          <xs:extension base="tns:ccmp-response-message-type">
              <xs:sequence>
                  <xs:element ref="sidebarsByRefResponse" />
              </xs:sequence>
          </xs:extension>
     </xs:complexContent>
  </xs:complexType>
  <!-- sidebarsByRefResponseType -->
  <xs:element name="sidebarsByRefResponse"
              type="sidebarsByRefResponseType" />
  <xs:complexType name="sidebarsByRefResponseType">
      <xs:sequence>
          <xs:element name="sidebarsByRefInfo" type="info:uris-type"
                      minOccurs="0"/>
          <xs:any namespace="##other" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>
      <xs:anyAttribute namespace="##any" processContents="lax"/>
  </xs:complexType>

Barnes, et al. Standards Track [Page 99] RFC 6503 CCMP March 2012

  <!-- sidebarByValResponse -->
  <xs:complexType name="ccmp-sidebarByVal-response-message-type">
      <xs:complexContent>
          <xs:extension base="tns:ccmp-response-message-type">
              <xs:sequence>
                  <xs:element ref="sidebarByValResponse" />
              </xs:sequence>
          </xs:extension>
      </xs:complexContent>
  </xs:complexType>
  <!-- sidebarByValResponseType -->
  <xs:element name="sidebarByValResponse"
              type="sidebarByValResponseType" />
  <xs:complexType name="sidebarByValResponseType">
      <xs:sequence>
          <xs:element name="sidebarByValInfo"
                      type="info:conference-type" minOccurs="0"/>
          <xs:any namespace="##other" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
       </xs:sequence>
       <xs:anyAttribute namespace="##any" processContents="lax"/>
  </xs:complexType>
  <!-- sidebarByRefResponse -->
  <xs:complexType name="ccmp-sidebarByRef-response-message-type">
      <xs:complexContent>
          <xs:extension base="tns:ccmp-response-message-type">
              <xs:sequence>
                  <xs:element ref="sidebarByRefResponse" />
               </xs:sequence>
          </xs:extension>
      </xs:complexContent>
  </xs:complexType>
  <!-- sidebarByRefResponseType -->
  <xs:element name="sidebarByRefResponse"
              type="sidebarByRefResponseType" />
  <xs:complexType name="sidebarByRefResponseType">
      <xs:sequence>
          <xs:element name="sidebarByRefInfo"
                      type="info:conference-type" minOccurs="0"/>

Barnes, et al. Standards Track [Page 100] RFC 6503 CCMP March 2012

          <xs:any namespace="##other" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>
      <xs:anyAttribute namespace="##any" processContents="lax"/>
  </xs:complexType>
  <!-- extendedResponse -->
  <xs:complexType name="ccmp-extended-response-message-type">
     <xs:complexContent>
         <xs:extension base="tns:ccmp-response-message-type">
             <xs:sequence>
                               <xs:element ref="extendedResponse"/>
             </xs:sequence>
         </xs:extension>
      </xs:complexContent>
  </xs:complexType>
  <!-- extendedResponseType -->
  <xs:element name="extendedResponse" type="extendedResponseType"/>
  <xs:complexType name="extendedResponseType">
      <xs:sequence>
              <xs:element name="extensionName"
                          type="xs:string" minOccurs="1"/>
              <xs:any namespace="##other" processContents="lax"
                      minOccurs="0"
                  maxOccurs="unbounded" />
      </xs:sequence>
  </xs:complexType>
  <!-- optionsResponse -->
      <xs:complexType name="ccmp-options-response-message-type">
      <xs:complexContent>
          <xs:extension base="tns:ccmp-response-message-type">
              <xs:sequence>
                  <xs:element ref="optionsResponse"/>
               </xs:sequence>
          </xs:extension>
      </xs:complexContent>
  </xs:complexType>
  <!-- optionsResponseType -->
  <xs:element name="optionsResponse"
              type="optionsResponseType" />

Barnes, et al. Standards Track [Page 101] RFC 6503 CCMP March 2012

  <xs:complexType name="optionsResponseType">
      <xs:sequence>
          <xs:element name="options"
                      type="options-type" minOccurs="0"/>
          <xs:any namespace="##other" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>
      <xs:anyAttribute namespace="##any" processContents="lax"/>
  </xs:complexType>

<!– CCMP ELEMENT TYPES –>

  <!-- response-codeType-->
  <xs:simpleType name="response-codeType">
       <xs:restriction base="xs:positiveInteger">
               <xs:pattern value="[0-9][0-9][0-9]" />
       </xs:restriction>
  </xs:simpleType>
  <!-- operationType -->
  <xs:simpleType name="operationType">
    <xs:restriction base="xs:token">
      <xs:enumeration value="retrieve"/>
      <xs:enumeration value="create"/>
      <xs:enumeration value="update"/>
      <xs:enumeration value="delete"/>
    </xs:restriction>
  </xs:simpleType>
 <!-- subject-type -->
 <xs:complexType name="subject-type">
     <xs:sequence>
         <xs:element name="username" type="xs:string"
                     minOccurs="0" maxOccurs="1" />
         <xs:element name="password" type="xs:string"
                     minOccurs="0" maxOccurs="1" />
         <xs:any namespace="##other" processContents="lax"
                 minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>

Barnes, et al. Standards Track [Page 102] RFC 6503 CCMP March 2012

 <!-- options-type -->
  <xs:complexType name="options-type">
    <xs:sequence>
      <xs:element name="standard-message-list"
                  type="standard-message-list-type"
                  minOccurs="1"/>
      <xs:element name="extended-message-list"
                  type="extended-message-list-type"
                  minOccurs="0"/>
      <xs:any namespace="##other" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>
      <xs:anyAttribute namespace="##any" processContents="lax"/>
  </xs:complexType>
  <!-- standard-message-list-type -->
  <xs:complexType name="standard-message-list-type">
    <xs:sequence>
      <xs:element name="standard-message"
                  type="standard-message-type"
                  minOccurs="1" maxOccurs="10"/>
      <xs:any namespace="##other" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>
      <xs:anyAttribute namespace="##any" processContents="lax"/>
  </xs:complexType>
  <!-- standard-message-type -->
  <xs:complexType name="standard-message-type">
    <xs:sequence>
      <xs:element name="name"
                  type="standard-message-name-type"
                  minOccurs="1"/>
      <xs:element name="operations"
                  type="operations-type"
                  minOccurs="0"/>
      <xs:element name="schema-def" type="xs:string" minOccurs="0"/>
      <xs:element name="description" type="xs:string" minOccurs="0"/>
      <xs:any namespace="##other" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>
      <xs:anyAttribute namespace="##any" processContents="lax"/>
  </xs:complexType>

Barnes, et al. Standards Track [Page 103] RFC 6503 CCMP March 2012

  <!-- standard-message-name-type -->
  <xs:simpleType name="standard-message-name-type">
    <xs:restriction base="xs:token">
      <xs:enumeration value="confsRequest"/>
      <xs:enumeration value="confRequest"/>
      <xs:enumeration value="blueprintsRequest"/>
      <xs:enumeration value="blueprintRequest"/>
      <xs:enumeration value="usersRequest"/>
      <xs:enumeration value="userRequest"/>
      <xs:enumeration value="sidebarsByValRequest"/>
      <xs:enumeration value="sidebarByValRequest"/>
      <xs:enumeration value="sidebarsByRefRequest"/>
      <xs:enumeration value="sidebarByRefRequest"/>
    </xs:restriction>
  </xs:simpleType>
  <!-- operations-type -->
  <xs:complexType name="operations-type">
    <xs:sequence>
      <xs:element name="operation" type="operationType"
                  minOccurs="1" maxOccurs="4"/>
    </xs:sequence>
    <xs:anyAttribute namespace="##any" processContents="lax"/>
  </xs:complexType>
  <!-- extended-message-list-type -->
  <xs:complexType name="extended-message-list-type">
    <xs:sequence>
      <xs:element name="extended-message"
                  type="extended-message-type"
                  minOccurs="0"/>
      <xs:any namespace="##other" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>
      <xs:anyAttribute namespace="##any" processContents="lax"/>
  </xs:complexType>
  <!-- extended-message-type -->
  <xs:complexType name="extended-message-type">
    <xs:sequence>
      <xs:element name="name" type="xs:string" />
      <xs:element name="operations"
                  type="operations-type"
                  minOccurs="0"/>

Barnes, et al. Standards Track [Page 104] RFC 6503 CCMP March 2012

      <xs:element name="schema-def" type="xs:string" />
      <xs:element name="description"
                  type="xs:string"
                  minOccurs="0"/>
      <xs:any namespace="##other" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>
      <xs:anyAttribute namespace="##any" processContents="lax"/>
  </xs:complexType>

</xs:schema>

                      Figure 30: CCMP XML Schema

12. IANA Considerations

 This document registers a new XML namespace, a new XML schema, and
 the MIME type for the schema.  This document also registers the
 "XCON" Application Service tag and the "CCMP" Application Protocol
 tag and defines registries for the CCMP operation types and response
 codes.

12.1. URN Sub-Namespace Registration

 This section registers a new XML namespace,
 "urn:ietf:params:xml:ns:xcon-ccmp".
    URI: urn:ietf:params:xml:ns:xcon-ccmp
    Registrant Contact: IETF XCON working group (xcon@ietf.org), Mary
    Barnes (mary.ietf.barnes@gmail.com).

Barnes, et al. Standards Track [Page 105] RFC 6503 CCMP March 2012

    XML:
 BEGIN
   <?xml version="1.0"?>
   <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
     "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
   <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
     <head>
       <title>CCMP Messages</title>
     </head>
     <body>
       <h1>Namespace for CCMP Messages</h1>
       <h2>urn:ietf:params:xml:ns:xcon-ccmp</h2>
       <p>See <a href="http://www.rfc-editor.org/rfc/rfc6503.txt">
          RFC 6503</a>.</p>
     </body>
   </html>
 END

12.2. XML Schema Registration

 This section registers an XML schema per the guidelines in [RFC3688].
 URI:  urn:ietf:params:xml:schema:xcon-ccmp
 Registrant Contact:  IETF XCON working group (xcon@ietf.org), Mary
    Barnes (mary.ietf.barnes@gmail.com).
 Schema:  The XML for this schema can be found as the entirety of
    Section 11 of this document.

12.3. MIME Media Type Registration for 'application/ccmp+xml'

 This section registers the "application/ccmp+xml" MIME type.
 To:  ietf-types@iana.org
 Subject:  Registration of MIME media type application/ccmp+xml
 MIME media type name:  application
 MIME subtype name:  ccmp+xml
 Required parameters:  (none)

Barnes, et al. Standards Track [Page 106] RFC 6503 CCMP March 2012

 Optional parameters:  charset
    Same as the charset parameter of "application/xml" as specified in
    [RFC3023], Section 3.2.
 Encoding considerations:  Same as the encoding considerations of
    "application/xml" as specified in [RFC3023], Section 3.2.
 Security considerations:  This content type is designed to carry
    protocol data related to conference control.  Some of the data
    could be considered private.  This media type does not provide any
    protection and thus other mechanisms such as those described in
    Section 10 are required to protect the data.  This media type does
    not contain executable content.
 Interoperability considerations:  None.
 Published specification:  RFC 6503.
 Applications that use this media type:  Centralized Conferencing
    control clients and servers.
 Additional Information:  Magic Number(s): (none)
    File extension(s): .ccmp
    Macintosh File Type Code(s): TEXT
 Person & email address to contact for further information:  Mary
    Barnes <mary.ietf.barnes@gmail.com>
 Intended usage:  LIMITED USE
 Author/Change controller:  The IETF
 Other information:  This media type is a specialization of
    application/xml [RFC3023], and many of the considerations
    described there also apply to application/ccmp+xml.

12.4. DNS Registrations

 Section 12.4.1 defines an Application Service tag of "XCON", which is
 used to identify the centralized conferencing (XCON) server for a
 particular domain.  The Application Protocol tag "CCMP", defined in
 Section 12.4.2, is used to identify an XCON server that understands
 CCMP.

Barnes, et al. Standards Track [Page 107] RFC 6503 CCMP March 2012

12.4.1. Registration of a Conference Server Application Service Tag

 This section registers a new S-NAPTR/U-NAPTR Application Service tag
 for XCON, as mandated by [RFC3958].
 Application Service Tag: XCON
 Intended usage: Identifies a server that supports centralized
 conferencing.
 Defining publication: RFC 6503
 Contact information: The authors of this document
 Author/Change controller: The IESG

12.4.2. Registration of a Conference Server Application Protocol Tag

       for CCMP
 This section registers a new S-NAPTR/U-NAPTR Application Protocol tag
 for CCMP, as mandated by [RFC3958].
 Application Service Tag: CCMP
 Intended Usage: Identifies the Centralized Conferencing (XCON)
 Manipulation Protocol.
 Applicable Service Tag(s): XCON
 Terminal NAPTR Record Type(s): U
 Defining Publication: RFC 6503
 Contact Information: The authors of this document
 Author/Change Controller: The IESG

12.5. CCMP Protocol Registry

 The IANA has created a new registry for CCMP:
 http://www.iana.org/assignments/ccmp-parameters.  The document
 creates initial sub-registries for CCMP operation types and response
 codes.

Barnes, et al. Standards Track [Page 108] RFC 6503 CCMP March 2012

12.5.1. CCMP Message Types

 The following summarizes the registry for CCMP messages:
 Related Registry:   CCMP Message Types Registry
 Defining RFC:  RFC 6503.
 Registration/Assignment Procedures:  Following the policies outlined
    in [RFC5226], the IANA policy for assigning new values for the
    CCMP message types for CCMP is Specification Required.
 Registrant Contact:  IETF XCON working group (xcon@ietf.org), Mary
    Barnes (mary.ietf.barnes@gmail.com).
 This specification establishes the Message sub-registry under
 http://www.iana.org/assignments/ccmp-messages.  The initial Message
 table is populated using the CCMP messages described in Section 4.1
 and defined in the XML schema in Section 11.
Message              Description                             Reference
-------              -----------                             ---------
optionsRequest       Used by a conferencing client           [RFC6503]
                     to query a conference server for
                     its capabilities, in terms of
                     supported messages.
optionsResponse      Returns a list of CCMP messages         [RFC6503]
                     supported by the specific
                     conference server.
blueprintsRequest    Used by a conferencing client           [RFC6503]
                     to query a conference server for
                     its capabilities, in terms of
                     available conference blueprints.
blueprintsResponse   Returns a list of blueprints supported  [RFC6503]
                     by the specific conference server.
blueprintRequest     Sent to retrieve the conference object  [RFC6503]
                     associated with a specific blueprint.
blueprintResponse    Returns the conference object           [RFC6503]
                     associated with a specific blueprint.
confsRequest         Used by a conferencing client           [RFC6503]
                     to query a conference server for
                     its scheduled/active conferences.

Barnes, et al. Standards Track [Page 109] RFC 6503 CCMP March 2012

confsResponse        Returns the list of the currently       [RFC6503]
                     activated/scheduled conferences
                     at the server.
confRequest          Used to create a conference object      [RFC6503]
                     and/or to request an operation on
                     the conference object as a whole.
confResponse         Indicates the result of the operation   [RFC6503]
                     on the conference object as a whole.
userRequest          Used to request an operation on the     [RFC6503]
                     <user> element in the conference object.
userResponse         Indicates the result of the requested   [RFC6503]
                     operation on the <user> element in
                     the conference object.
usersRequest         Used to manipulate the <users> element  [RFC6503]
                     in the conference object, including
                     parameters such as the <allowed-users-list>,
                     <join-handling>, etc.
usersResponse        Indicates the result of the request     [RFC6503]
                     to manipulate the <users> element in
                     the conference object.
sidebarsByValRequest Used to retrieve the <sidebars-by-val>  [RFC6503]
                     element of the target conference object.
sidebarsByValResponse Returns the list of the sidebar-by-val [RFC6503]
                      conferences within the target
                      conference object.
sidebarsByRefRequest  Used to retrieve the <sidebars-by-ref> [RFC6503]
                      element of the target conference
                      object.
sidebarsByRefResponse Returns the list of the sidebar-by-ref [RFC6503]
                      conferences associated with the target
                      conference object.
sidebarByValRequest  Used to request an operation on a       [RFC6503]
                     sidebar-by-val conference.
sidebarByValResponse Indicates the result of the request to  [RFC6503]
                     manipulate a sidebar-by-val conference.

Barnes, et al. Standards Track [Page 110] RFC 6503 CCMP March 2012

sidebarByRefRequest  Used to request an operation on a       [RFC6503]
                     sideber-by-ref conference.
sidebarByRefResponse Indicates the result of the request to  [RFC6503]
                     manipulate a sidebar-by-ref conference.

12.5.2. CCMP Response Codes

 The following summarizes the requested registry for CCMP response
 codes:
 Related Registry:   CCMP Response Code Registry
 Defining RFC:  RFC 6503.
 Registration/Assignment Procedures:  Following the policies outlined
    in [RFC5226], the IANA policy for assigning new values for the
    Response codes for CCMP shall be Specification Required.
 Registrant Contact:  IETF XCON working group (xcon@ietf.org), Mary
    Barnes (mary.ietf.barnes@gmail.com).
 This specification establishes the Response-code sub-registry under
 http://www.iana.org/assignments/ccmp-parameters.  The initial
 Response-code table is populated using the Response codes defined in
 Section 5.4 as follows:
       Default
       Response
Number String              Description                       Reference
------ -------------       ------------                      ---------
 200   Success             The request was successfully      [RFC6503]
                           processed.
 400   Bad Request         The request was badly formed in   [RFC6503]
                           some fashion.
 401   Unauthorized        The user was not authorized for   [RFC6503]
                           the specific operation on the
                           conference object.
 403   Forbidden           The specific operation is not     [RFC6503]
                           valid for the target conference
                           object.
 404   Object Not Found    The specific conference object    [RFC6503]
                           was not found.

Barnes, et al. Standards Track [Page 111] RFC 6503 CCMP March 2012

 409   Conflict            A requested operation cannot be   [RFC6503]
                           successfully completed by the
                           server. For example, the
                           modification of an object
                           cannot be applied because
                           the client version of the object
                           is obsolete and the requested
                           modifications collide with the
                           up-to-date state of the object
                           stored at the server.
 420   User Not Found      The user who is the target of the [RFC6503]
                           requested operation is unknown.
 421   Invalid confUserID  The <confUserID> parameter of the [RFC6503]
                           sender in the request is invalid.
 422   Invalid Conference  A request to access/manipulate    [RFC6503]
       Password            a password-protected conference
                           object contained an invalid
                           <conference-password> parameter.
 423   Conference Password A request to access/manipulate    [RFC6503]
       Required            a password-protected conference
                           object did not contain a
                           <conference-password> parameter.
 424   Authentication      The server wants to authenticate  [RFC6503]
       Required            the request through the <subject>
                           parameter but the parameter is
                           not provided in the request.
 425   Forbidden Delete    The conferencing system cannot    [RFC6503]
       Parent              delete the specific conference
                           object because it is a
                           parent for another conference object.
 426   Forbidden Change    The target conference object      [RFC6503]
       Protected           cannot be changed (e.g., due to
                           policies, roles or privileges).
 427   Invalid Domain Name The domain name in an             [RFC6503]
                           AUTO_GENERATE_X
                           instance in the conference object
                           is not within the conference
                           server's domain of responsibility.

Barnes, et al. Standards Track [Page 112] RFC 6503 CCMP March 2012

 500   Server Internal     The conference server experienced [RFC6503]
       Error               some sort of internal error.
 501   Not Implemented     The specific operation is not     [RFC6503]
                           implemented on the conferencing
                           system.
 510   Request Timeout     The request could not be          [RFC6503]
                           processed within a reasonable
                           time (as specified by the
                           conferencing system).
 511   Resources Not       The conference server cannot      [RFC6503]
       Available           execute a command because of
                           resource issues, e.g., it cannot
                           create a conference because
                           the system has reached its limits
                           on the number of conferences.

13. Acknowledgments

 The authors appreciate the feedback provided by Dave Morgan, Pierre
 Tane, Lorenzo Miniero, Tobia Castaldi, Theo Zourzouvillys, Sean
 Duddy, Oscar Novo, Richard Barnes, Simo Veikkolainen, Keith Drage,
 Peter Reissner, Tony Lindstrom, Stephen Kent (secdir review), Brian
 Carpenter (genart review), and Mykyta Yevstifeyev (IANA
 considerations).  Special thanks go to Roberta Presta for her
 invaluable contribution to this document.  Roberta has worked on the
 specification of CCMP at the University of Napoli for the preparation
 of her Master thesis.  She has also implemented the CCMP prototype
 used for the trials and from which the dumps provided in Section 6
 have been extracted.

14. References

14.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
            Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
            Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
 [RFC2617]  Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
            Leach, P., Luotonen, A., and L. Stewart, "HTTP
            Authentication: Basic and Digest Access Authentication",
            RFC 2617, June 1999.

Barnes, et al. Standards Track [Page 113] RFC 6503 CCMP March 2012

 [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
 [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
            January 2004.
 [RFC5239]  Barnes, M., Boulton, C., and O. Levin, "A Framework for
            Centralized Conferencing", RFC 5239, June 2008.
 [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
            (TLS) Protocol Version 1.2", RFC 5246, August 2008.
 [RFC6265]  Barth, A., "HTTP State Management Mechanism", RFC 6265,
            April 2011.
 [RFC6501]  Novo, O., Camarillo, G., Morgan, D., and J. Urpalainen,
            "Conference Information Data Model for Centralized
            Conferencing (XCON)", RFC 6501, March 2012.
 [W3C.REC-xmlschema-1-20041028]
            Beech, D., Thompson, H., Mendelsohn, N., and M. Maloney,
            "XML Schema Part 1: Structures Second Edition", World Wide
            Web Consortium Recommendation REC-xmlschema-1-20041028,
            October 2004,
            <http://www.w3.org/TR/2004/REC-xmlschema-1-20041028>.
 [W3C.REC-xmlschema-2-20041028]
            Biron, P. and A. Malhotra, "XML Schema Part 2: Datatypes
            Second Edition", World Wide Web Consortium
            Recommendation REC-xmlschema-2-20041028, October 2004,
            <http://www.w3.org/TR/2004/REC-xmlschema-2-20041028>.

14.2. Informative References

 [REST]     Fielding, "Architectural Styles and the Design of Network-
            based Software Architectures", 2000.
 [RFC3023]  Murata, M., St. Laurent, S., and D. Kohn, "XML Media
            Types", RFC 3023, January 2001.
 [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
            A., Peterson, J., Sparks, R., Handley, M., and E.
            Schooler, "SIP: Session Initiation Protocol", RFC 3261,
            June 2002.
 [RFC3958]  Daigle, L. and A. Newton, "Domain-Based Application
            Service Location Using SRV RRs and the Dynamic Delegation
            Discovery Service (DDDS)", RFC 3958, January 2005.

Barnes, et al. Standards Track [Page 114] RFC 6503 CCMP March 2012

 [RFC4582]  Camarillo, G., Ott, J., and K. Drage, "The Binary Floor
            Control Protocol (BFCP)", RFC 4582, November 2006.
 [RFC4732]  Handley, M., Rescorla, E., and IAB, "Internet Denial-of-
            Service Considerations", RFC 4732, December 2006.
 [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
            IANA Considerations Section in RFCs", BCP 26, RFC 5226,
            May 2008.
 [RFC6502]  Camarillo, G., Srinivasan, S., Even, R., and J.
            Urpalainen, "Conference Event Package Data Format
            Extension for Centralized Conferencing (XCON)", RFC 6502,
            March 2012.
 [W3C.REC-soap12-part1-20070427]
            Nielsen, H., Mendelsohn, N., Moreau, J., Gudgin, M.,
            Hadley, M., Lafon, Y., and A. Karmarkar, "SOAP Version 1.2
            Part 1: Messaging Framework (Second Edition)", World Wide
            Web Consortium Recommendation REC-soap12-part1-20070427,
            April 2007,
            <http://www.w3.org/TR/2007/REC-soap12-part1-20070427>.
 [W3C.REC-soap12-part2-20070427]
            Moreau, J., Gudgin, M., Karmarkar, A., Mendelsohn, N.,
            Hadley, M., Lafon, Y., and H. Nielsen, "SOAP Version 1.2
            Part 2: Adjuncts (Second Edition)", World Wide Web
            Consortium Recommendation REC-soap12-part2-20070427,
            April 2007,
            <http://www.w3.org/TR/2007/REC-soap12-part2-20070427>.

Barnes, et al. Standards Track [Page 115] RFC 6503 CCMP March 2012

Appendix A. Evaluation of Other Protocol Models and Transports

           Considered for CCMP
 This section provides some background as to the selection of HTTP as
 the transport for the CCMP requests/responses.  In addition to HTTP,
 the operations on the objects can be implemented in at least two
 different ways, namely as remote procedure calls -- using SOAP as
 described in Appendix A.1 and by defining resources following a
 RESTful architecture Appendix A.2.
 In both the SOAP and RESTFUL approaches, servers will have to
 recreate their internal state representation of the object with each
 update request, checking parameters and triggering function
 invocations.  In the SOAP approach, it would be possible to describe
 a separate operation for each atomic element, but that would greatly
 increase the complexity of the protocol.  A coarser-grained approach
 to CCMP does require that the server process XML elements in updates
 that have not changed and that there can be multiple changes in one
 update.  For CCMP, the resource (REST) model might appear more
 attractive, since the conference operations fit the CRUD approach.
 However, neither of these approaches were considered ideal.  SOAP was
 considered to bring additional overhead.  It is quite awkward to
 apply a RESTful approach since CCMP requires a more complex request/
 response protocol in order to maintain the data both in the server
 and at the client.  This doesn't map very elegantly to the basic
 request/response model, whereby a response typically indicates
 whether the request was successful or not, rather than providing
 additional data to maintain the synchronization between the client
 and server data.  In addition, the CCMP clients may also receive the
 data in notifications.  While the notification method or protocol
 used by some conferencing clients can be independent of CCMP, the
 same data in the server is used for both CCMP and notifications -
 this requires a server application above the transport layer (e.g.,
 HTTP) for maintaining the data, which in the CCMP model is
 transparent to the transport protocol.
 Thus, the solution for CCMP defined in this document is viewed as a
 good compromise amongst the most notable past candidates and is
 referred to as "HTTP single-verb transport plus CCMP body".  With
 this approach, CCMP is able to take advantage of existing HTTP
 functionality.  As with SOAP, CCMP uses a "single HTTP verb" for
 transport (i.e., a single transaction type for each request/response
 pair); this allows decoupling CCMP messages from HTTP messages.
 Similarly, as with any RESTful approach, CCMP messages are inserted
 directly in the body of HTTP messages, thus avoiding any unnecessary
 processing and communication burden associated with further
 intermediaries.  With this approach, no modification to the CCMP

Barnes, et al. Standards Track [Page 116] RFC 6503 CCMP March 2012

 messages/operations is required to use a different transport
 protocol.

A.1. Using SOAP for CCMP

 A remote procedure call (RPC) mechanism for CCMP could use SOAP
 (Simple Object Access Protocol [W3C.REC-soap12-part1-20070427]
 [W3C.REC-soap12-part2-20070427]), where conferences and the other
 objects are modeled as services with associated operations.
 Conferences and other objects are selected by their own local
 identifiers, such as email-like names for users.  This approach has
 the advantage that it can easily define atomic operations that have
 well-defined error conditions.
 All SOAP operations would use a single HTTP verb.  While the RESTful
 approach requires the use of a URI for each object, SOAP can use any
 token.

A.2. A RESTful Approach for CCMP

 Conference objects can also be modeled as resources identified by
 URIs, with the basic CRUD operations mapped to the HTTP methods POST/
 PUT for creating objects, GET for reading objects, PATCH/POST/PUT for
 changing objects, and DELETE for deleting them.  Many of the objects,
 such as conferences, already have natural URIs.
 CCMP can be mapped into the CRUD (Create, Read, Update, Delete)
 design pattern.  The basic CRUD operations are used to manipulate
 conference objects, which are XML documents containing the
 information characterizing a specified conference instance, be it an
 active conference or a conference blueprint used by the conference
 server to create new conference instances through a simple clone
 operation.
 Following the CRUD approach, CCMP could use a general-purpose
 protocol such as HTTP [RFC2616] to transfer domain-specific XML-
 encoded data objects defined in the "Conference Information Data
 Model for Centralized Conferencing" [RFC6501].
 Following on the CRUD approach, CCMP could follow the well-known REST
 (REpresentational State Transfer) architectural style [REST].  CCMP
 could map onto the REST philosophy, by specifying resource URIs,
 resource formats, methods supported at each URI and status codes that
 have to be returned when a certain method is invoked on a specific
 URI.  A REST-style approach must ensure sure that all operations can
 be mapped to HTTP operations.

Barnes, et al. Standards Track [Page 117] RFC 6503 CCMP March 2012

 The following summarizes the specific HTTP method that could be used
 for each of the CCMP Requests:
 Retrieve: HTTP GET could be used on XCON-URIs, so that clients can
 obtain data about conference objects in the form of XML data model
 documents.
 Create: HTTP PUT could be used to create a new object as identified
 by the XCON-URI or XCON-USERID.
 Change: Either HTTP PATCH or HTTP POST could be used to change the
 conference object identified by the XCON-URI.
 Delete: HTTP DELETE could be used to delete conference objects and
 parameters within conference objects identified by the XCON-URI.

Barnes, et al. Standards Track [Page 118] RFC 6503 CCMP March 2012

Authors' Addresses

 Mary Barnes
 Polycom
 TX
 USA
 EMail: mary.ietf.barnes@gmail.com
 Chris Boulton
 NS-Technologies
 EMail: chris@ns-technologies.com
 Simon Pietro Romano
 University of Napoli
 Via Claudio 21
 Napoli  80125
 Italy
 EMail: spromano@unina.it
 Henning Schulzrinne
 Columbia University
 Department of Computer Science
 450 Computer Science Building
 New York, NY  10027
 EMail: hgs+xcon@cs.columbia.edu

Barnes, et al. Standards Track [Page 119]

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