RFC 5239
A Framework for Centralized Conferencing
7. Conferencing System Realization
Implementations based on this centralized conferencing framework can range from systems supporting ad hoc conferences, with default behavior only, to sophisticated systems with the ability to schedule recurring conferences, each with distinct characteristics, being integrated with external resource reservation tools, and providing snapshots of the conference information at any of the stages of the conference life-cycle. A conference object is the logical representation of a conference instance at a certain stage, such as capabilities description upon conference creation, reservation, activation, etc., which a conferencing system maintains in order to describe the system capabilities and to provide access to the available services provided by the conferencing system. Consequently, this centralized conferencing framework does not mandate the actual usage of the conference object, but rather defines the general cloning tree concept and the mechanisms required for its realization, as described in detail in Section 7.1. Ad hoc and advanced conferencing examples are provided in Section 7.2 and Section 7.3, with the latter providing additional description of the conference object in terms of the stages of a conference, to support scheduled and other advanced conference capabilities. The scheduling of a conference based on these concepts and mechanisms is then detailed in Section 7.4 As discussed in Section 5.2, the overall policy in terms of permissions and limitations is outside the scope of this framework document. The policies applicable to the conference object as a whole in terms of read/write access would require a conferencing system have access to basic policy information to make the decisions. In the examples in this section, the policies are shown logically associated with the conference objects to emphasize the general requirement for policy functionality necessary for the realization of this framework.7.1. Cloning Tree
The concept defined in this section is a logical representation only, as it is reflected through the centralized conferencing mechanisms: the URIs and the protocols. Of course, the actual system realization can differ from the presented model. The intent is to illustrate the role of the logical elements in providing an interface to the data, based on conferencing system and conferencing client actions, and describe the resultant protocol implications.
Any conference object in a conferencing system is created by either being explicitly cloned from an existing parent object or being implicitly cloned from a default system conference blueprint. A conference blueprint is a static conference object used to describe a typical conference setting supported by the system. Each system can maintain multiple blueprints, typically each describing a different conferencing type using the conference information format. This document uses the "cloning" metaphor instead of the "inheritance" metaphor because it more closely fits the idea of object replication, rather than a data type re-usage and extension concept. The cloning operation needs to specify whether or not the link between the parent and child needs to be maintained in the system. If no link between the parent and child exists, the objects become independent and the child is not impacted by any operations on the parent object nor subject to any limitations of the parent object. Once the new object is created, it can be addressed by a unique conference object URI assigned by the system, as described in Section 6.2.1. By default, the newly created object contains all the data existing in the parent object. The newly created object can expand the data it contains, within the schema types supported by the parent. It can also restrict the read/write access to its objects. However, unless the object is independent, it cannot modify the access restrictions imposed by the parent object. Any piece of data in the child object can be independently accessed and, by default, can be independently modified without affecting the parent data. Unless the object is independent, the parent object can enforce a different policy by marking certain data elements as "parent enforceable". The values of these data elements cannot be changed by directly accessing the child object, nor can they be expanded in the child object alone. Figure 4 illustrates an example of a conference (Parent B), which is created independent of its Parent (Parent A). Parent B creates two child objects, Child 1 and Child 2. Any of the data elements of Parent B can be modified (i.e., there are no "parent enforceable" data elements), and depending upon the element, the changes will be reflected in Child 1 and Child 2 , whereas changes to Parent A will not impact the data elements of Parent B. Any "parent enforceable" data elements, as defined by Parent B, cannot be modified in the child objects.
+---+-----------------------+ | p | | | o | P A R E N T A | | l | | | i | C O N F E R E N C E | | c | | | i | O B J E C T | | e | | +-s-+-----------------------+ | \| / \/ INDEPENDENT /\ /| \ V +---+-----------------------+ | p | | | o | P A R E N T B | | l | | | i | C O N F E R E N C E | | c | | | i | O B J E C T | | e | | +-s-+-----------------------+ | | | | | --------------------------- | | V V +---+-----------------------+ +---+-----------------------+ | p | | | p | | | o | C H I L D 1 | | o | C H I L D 2 | | l | | | l | | | i | C O N F E R E N C E | | i | C O N F E R E N C E | | c | | | c | | | i | O B J E C T | | i | O B J E C T | | e | | | e | | +-s-+-----------------------+ +-s-+-----------------------+ Figure 4: The Cloning Tree Using the defined cloning model and its tools, the following sections show examples of how different systems based on this framework can be realized.
7.2. Ad Hoc Example
Figure 5 illustrates how an ad hoc conference can be created and managed in a conferencing system. A client can create a conference by establishing a call signaling channel with a conference factory, as specified in Section 6.1. The conference factory can internally select one of the system supported conference blueprints based on the requesting client privileges and the media lines included in the Session Description Protocol (SDP) body. The selected blueprint with its default values is copied by the server into a newly created conference object, referred to as an 'Active Conference'. At this point, the conference object becomes independent from its blueprint. A new conference object identifier, a new conference identifier, and a new focus are allocated by the server. During the conference lifetime, an authorized client can manipulate the conference object, by performing operations such as adding participants, using the conference control protocol. +---+-----------------------+ | p | | | o | System Default | | l | | | i | Conference | | c | | | i | Blueprint | | e | | +-s-+-----------------------+ | \| / \/ /\ /| \ V +---+-----------------------+ | p | | | o | Active | | l | | | i | Conference | | c | | | i | | | e | | +-s-+-----------------------+ Figure 5: Conference Ad-hoc Creation and Lifetime
7.3. Advanced Example
Figure 6 illustrates how a recurring conference can be specified according to system capabilities, scheduled, reserved, and managed in a conferencing system. A client would first query a conferencing system for its capabilities. This can be done by requesting a list of the conference blueprints the system supports. Each blueprint contains a specific combination of capabilities and limitations of the conference server in terms of supported media types (e.g., audio, video, text, or combinations of these), participant roles, maximum number of participants of each role, availability of floor control, controls available for participants, availability and type of sidebars, the definitions and names of media streams, etc. The selected blueprint with its default values is cloned by the client into a newly created conference object, referred to as a conference reservation, that specifies the resources needed from the system for this conference instance. At this point, the conference reservation becomes independent from its blueprint. The client can also change the default values, within the system ranges, and add additional information, such as the list of participants and the conference 'start' time, to the conference reservation. At this point, the client can ask the conference server to create new conference reservations by attaching the conference reservation to the request. As a result, the server can allocate the needed resources, create the additional conference objects for the child conference reservations, and allocate the conference object identifiers for all -- the original conference reservation and for each child conference reservation. From this point on, any authorized client is able to access and modify each of the conference objects independently. By default, changes to an individual child conference reservation will affect neither the parent conference reservation, from which it was created, nor its siblings. On the other hand, some of the conference sub-objects, such as the maximum number of participants and the participants list, can be defined by the system as parent enforceable. As a result, these objects can be modified by accessing the parent conference reservation only. The changes to these objects can be applied automatically to each of the child reservations, subject to local policy.
+---+-----------------------+ | p | | | o | Selected | | l | | | i | Conference | | c | | | i | Blueprint | | e | | +-s-+-----------------------+ | \| / \/ /\ /| \ V +---+-----------------------+ | p | | | o | Conference | | l | | | i | Reservation | | c | | | i | | | e | | +-s-+-----------------------+ | | | | | | | | | | | | +---|--|--V-----------------+ +-+---|--V------------------+ | +-+-+---V-------------------+ | | | p | | | | | o | Child Conference | | | | l | | | | | i | Reservation | | | | c | | | | | i | | |-+ | e | |-+ +-s-+-----------------------+ Figure 6: Advanced Conference Definition, Creation, and Lifetime When the time comes to schedule the conference reservation, either via the system determination that the 'start' time has been reached or via client invocation, an active conference is cloned based on the conference reservation. As in the ad hoc example, the active conference is independent from the parent, and changes to the conference reservation will not impact the active conference. Any
desired changes must be targeted towards the active conference. An example of this interaction is shown in Section 9.1.7.4. Scheduling a Conference
The capability to schedule conferences forms an important part of the conferencing system solution. An individual conference reservation typically has a specified 'start' and 'end' time, with the times being specified relative to a single specified 'fixed' time (e.g., 'start' = 09.00 GMT, 'end'= 'start'+2), subject to system considerations. In most advanced conferencing solutions, it is possible to not only schedule an individual occurrence of a conference reservation, but also schedule a series of related conferences (e.g., a weekly meeting that starts on Thursday at 09.00 GMT). To be able to achieve such functionality, a conferencing system needs to be able to appropriately schedule and maintain conference reservations that form part of a recurring conference. The mechanism proposed in this document makes use of the "Internet Calendaring and Scheduling Core Object" specification defined in [RFC2445] in union with the concepts introduced in Section 5 for the purpose of achieving advanced conference scheduling capability. Figure 7 illustrates a simplified view of a client interacting with a conferencing system. The client is using the conference control protocol to add a new conference reservation to the conferencing system by interfacing with the conference control server. A CCP request contains a valid conference reservation and reference by value to an "iCal" object that contains scheduling information about the conference (e.g., 'start' time, 'end' time).
+--------------+ +-------Conferencing System-----------------+ | Generic ICAL | | | | Resource | | ..Conference Instance.... | +--------------+ | . . +-----------+| ^ ^ | . +-------------------+ . | Conference|| | | | . |Conference Objects |<--| Control || | ----------------->. +-------------------+ . | Server || | | . . +-----------+| | | ......................... ^ | | | ^ | | +-----|--------------+ | | | | v | | | | +--------------+ | | | | | Resource |<------------------+ | | | | Scheduler | | | | +--------------+ | | | | | +---------------------------------------------------------|------+ | | +-Request-+ | | +----+ | |ICAL| | +----+----+ | | | Conference Control| Protocol | | +-------------+ | Conferencing| | Client | +-------------+ Figure 7: Resource Scheduling A CCP request to create a new conference reservation is validated, including the associated iCal object, and the resultant conference reservation is created. The conference reservation is uniquely represented within the conferencing system by a conference object identifier (e.g., xcon:hd87928374), as introduced in Section 6.2.1 and defined in [XCON-COMMON]. This unique URI is returned to the client and can be used to reference the conference reservation, if any future manipulations are required (e.g., alter 'start' time), using a CCP request.
The previous example explains how a client creates a basic conference reservation using an iCal reference in association with a conference control protocol. Figure 7 can also be applied when explaining how a series of conferences are scheduled in the system. The description is almost identical with the exception that the iCal definition that is included in a CCP request represents a series of recurring conference instances (e.g., conference 'start' time, 'end' time, occur weekly). The conferencing system will treat this request the same as the first example. The CCP request will be validated, along with the associated iCal object, and the conference reservation is created. The conference reservation and its conference object ID, created for this example, represent the entire series of recurring conference instances rather than a single Conference. If the client uses the conference object ID provided and a CCP request to adjust the conference reservation, every conference instance in the series will be altered. This includes all future occurrences, such as a conference scheduled as an infinite series, subject to the limitations of the available calendaring interface. A conferencing system that supports the scheduling of a series of conference instances should also be able to support manipulation within a specific range of the series. A good example is a conference reservation that has been scheduled to occur every Monday at 09.00 GMT. For the next three weeks only, the meeting has been altered to occur at 10.00 GMT in an alternative venue. With Figure 7 in mind, the client will construct a CCP request whose purpose is to modify the existing conference reservation for the recurring conference instance. The client will include the conference object ID provided by the conferencing system to explicitly reference the conference reservation within the conferencing system. A CCP request will contain all the required changes to the conference reservation (e.g., change of venue). The conferencing system matches the incoming CCP request to the existing conference reservation but identifies that the associated iCal object only refers to a range of the existing series. The conferencing system creates a child, by cloning the original conference reservation, to represent the altered conference instances within the series. The cloned child object is not independent of the original parent object, thus preventing any potential conflicts in scheduling (e.g., a change to the whole series ''start' time'). The cloned conference reservation, representing the altered series of conference instances, has its own associated conference object ID that is returned to the client using a CCP response. This conference object ID is then used by the client to make any future alterations on the newly defined sub-series. This process can be repeated any number of times as the newly returned conference object ID representing an altered (cloned) series of conference instances, can
itself be manipulated using a CCP request for the newly created conference object ID . This provides a flexible approach to the scheduling of recurring conference instances.8. Conferencing Mechanisms
8.1. Call Signaling
The focus is the central component of the conference. Participants interface with the focus using an appropriate call signaling protocol (CSP). Participants request to establish or join a conference using the CSP. After checking the applicable policies, a focus then either accepts the request, sends a progress indication related to the status of the request (e.g., for a parked call while awaiting moderator approval to join), or rejects that request using the call signaling interface. During an active conference, a conference control protocol can be used to affect the conference state. For example, CCP requests to add and delete participants are communicated to the focus and checked against the conference policies. If approved, the participants are added or deleted using the call signaling to/from the focus.8.2. Notifications
A conferencing system is responsible for implementing a conference notification service. The conference notification service provides updates about the conference instance state to authorized parties, including participants. A model for notifications using SIP is defined in [RFC3265] with the specifics to support conferencing defined in [RFC4575]. The conference user identifier and associated role are used by the conferencing system to filter the notifications such that they contain only information that is allowed to be sent to that user.8.3. Conference Control Protocol
The conference control protocol provides for data manipulation and state retrieval for the centralized conferencing data, represented by the conference object. The details of the conference control protocol are provided in separate documents.8.4. Floor Control
A floor control protocol allows an authorized client to manage access to a specific floor and to grant, deny or revoke access of other conference users to that floor. Floor control is not a mandatory
mechanism for a conferencing system implementation, but it provides advanced media input control features for conference users. A mechanism for floor control within a conferencing system is defined in the "Binary Floor Control Protocol (BFCP)" specification [RFC4582]. Within this framework, a client supporting floor control needs to obtain information for connecting to a floor control server to enable it to issue floor requests. This connection information can be retrieved using information provided by mechanisms such as negotiation using the SDP [RFC4566] offer/answer [RFC3264] exchange on the signaling interface with the focus. Section 11.3 provides a discussion of client authentication of a floor control server. As well as the client to the floor control server connection information, a client wishing to interact with a floor control server requires access to additional information. This information associates floor control interactions with the appropriate floor instance. Once a connection has been established and authenticated (see [RFC4582] for authentication details), a specific floor control message requires detailed information to uniquely identify a conference, a user, and a floor. The conference is uniquely identified by the conference object ID per Section 6.2.1. This conference object ID must be included in all floor control messages. When the SDP model is used as described in [RFC4583], this identifier maps to the 'confid' SDP attribute. Each authorized user associated with a conference object is uniquely represented by a conference user ID per Section 6.3. This conference user ID must be included in all floor control messages. When using SDP offer/answer exchange to negotiate a floor control connection with the focus using the call signaling protocol, the unique conference user identifier is contained in the 'userid' SDP attribute, as defined in [RFC4583]. A media session within a conferencing system can have any number of floors (0 or more) that are represented by the conference identifier. When using SDP offer/answer exchange to negotiate a floor control connection with the focus using the call signaling interface, the unique conference identifier is contained in the 'floorid' SDP attribute, as defined in [RFC4583], e.g., a=floorid:1 m-stream:10 . Each 'floorid' attribute, representing a unique floor, has an 'm-stream' tag containing one or more identifiers. The identifiers represent individual SDP media sessions (as defined using 'm=' from SDP) using the SDP 'Label' attribute, as defined in [RFC4574].
9. Conferencing Scenario Realizations
This section addresses how advanced conferencing scenarios, many of which have been described in [RFC4597], are realized using this centralized conferencing framework. The objective of this section is to further illustrate the model, mechanisms, and protocols presented in the previous sections and also serves to validate that the model, mechanisms, and protocols are sufficient to support advanced conferencing scenarios. The scenarios provide a high level primitive view of the necessary operations and general logic flow. The details shown in the scenarios are for illustrative purposes only and don't necessarily reflect the actual structure of the conference control protocol messages nor the detailed data, including states, which are defined in separate documents. It should be noted that not all entities impacted by the request are shown in the diagram (e.g., focus), but rather the emphasis is on the new entities introduced by this centralized conferencing framework.9.1. Conference Creation
There are different ways to create a conference. A participant can create a conference using call signaling means only, such as SIP detailed in [RFC4579]. For a conferencing client to have more flexibility in defining the characteristics and capabilities of a conference, a conferencing client would implement a conference control protocol client. By using a conference control protocol, the client can determine the capabilities of a conferencing system and its various resources. Figure 8 provides an example of one client "Alice" determining the conference blueprints available for a particular conferencing system and creating a conference based on the desired blueprint.
+--------------------------------+ | Conferencing System | "Alice" | +------------+| +--------+ | | || | |CCP Request <blueprints> | +-----------+ | || | Client |-------------------------->|Conference | |Conference || | |<--------------------------|Control |~~~>|Blueprint(s)|| +--------+CCP Response<blueprintA, | |Server | | || ... | +-----------+ +------------+| blueprintZ, | | confUserID> | | "Alice" | +--------+ | | | |CCP Request <reserve, | +------------+| | | blueprintAConfObjID,| +-----------+ | || | Client |-------------------------->|Conference | |Conference || | | confUserID> | |Control |~~~>|BlueprintA || | |<--------------------------|Server | | || | |CCP Response | | | +------------+| +--------+ <reservationConfObjID, | | | \|/ | confID> | | | /|\ | | | | V | | | | +------------+| | | |~~~>|Conference || | | | |Reservation || | +-----------+ +------------+| "Alice" | | | +--------+ | | | | |CCP Request <add, | V | | |reservationConfObjID, | +-----------+ +------------+| | Client |-------------------------->|Conference | |Active || | | confID,confUserID> | |Control |~~~>|Conference || | |<--------------------------|Server | | || | |CCP Response | | | +------------+| +--------+ <activeConfObjID, | | | | confID> | +-----------+ | +--------------------------------+ Figure 8: Client Creation of Conference Using Blueprints Upon receipt of the conference control protocol request for blueprints, the conferencing system would first authenticate "Alice" (and allocate a conference user identifier, if necessary) and then ensure that "Alice" has the appropriate authority based on system policies to receive any blueprints supported by that system. Any blueprints that "Alice" is authorized to use are returned in a response, along with the conference user ID.
Upon receipt of the conference control protocol response containing the blueprints, "Alice" determines which blueprint to use for the conference to be created. "Alice" creates a conference object based on the blueprint (i.e., clones) and modifies applicable fields, such as membership list and 'start' time. "Alice" then sends a request to the conferencing system to create a conference reservation based upon the updated blueprint. Upon receipt of the conference control protocol request to "reserve" a conference based upon the blueprint in the request, the conferencing system ensures that the blueprint received is a valid blueprint (i.e., the values of the various field are within range). The conferencing system determines the appropriate read/write access of any users to be added to a conference based on this blueprint (using membership, roles, etc.). The conferencing system uses the received blueprint to clone a conference reservation. The conferencing system also reserves or allocates a conference ID to be used for any subsequent protocol requests from any of the members of the conference. The conferencing system maintains the mapping between this conference ID and the conference object ID associated with the reservation through the conference instance. Upon receipt of the conference control protocol response to reserve the conference, "Alice" can now create an active conference using that reservation or create additional reservations based upon the existing reservations. In this example, "Alice" has reserved a meetme conference bridge. Thus, "Alice" provides the conference information, including the necessary conference ID, to desired participants. When the first participant, including "Alice", requests to be added to the conference, an active conference and focus are created. The focus is associated with the conference ID received in the request. Any participants that have the authority to manipulate the conference would receive the conference object identifier of the active conference object in the response.9.2. Participant Manipulations
There are different ways to affect a participant state in a conference. A participant can join and leave the conference using call signaling means only, such as SIP. This kind of operation is called "1st party signaling" and does not affect the state of other participants in the conference.
Limited operations for controlling other conference participants (a so called "3rd party control") through the focus, using call signaling only, may also be available for some signaling protocols. For example, "Conferencing for SIP User Agents" [RFC4579] shows how SIP with REFER can be used to achieve this functionality. In order to perform richer conference control, a user client needs to implement a conference control protocol client. By using a conference control protocol, the client can affect its own state, the state of other participants, and the state of various resources (such as media mixers) that may indirectly affect the state of any of the conference participants. Figure 9 provides an example of one client "Alice" impacting the state of another client "Bob". This example assumes an established conference. In this example, "Alice" wants to add "Bob" to the conference. +--------------------------------+ | Conferencing System | "Alice" | +---------+--+| +--------+ | |policies | || | |CCP Request < | +-----------+ +---------+ || | Client |-------------------------->|Conference | | Active || | | Conference Object ID, | |Control |~~~>|Conference || +--------+ Add, "Bob" > | |Server | | || | +-----------+ +-------+ || | |"Alice"| || "Carol" | ' ' '| +--------+ NOTIFY <"Bob"="added"> |+------------+ ' ' '| | |<-------------------------|Notification|<~~~| || | Client |. . ||Service | +-------+ || +--------+--+ . || | |"Bob" | || | |<----------------------| | +-------+----+| | Client |NOTIFY <"Bob"="added">|+------------+ | +--------+ +--------------------------------+ "Bob" Figure 9: Client Manipulation of Conference - Add a Party Upon receipt of the conference control protocol request to "add" a party ("Bob") in the specific conference as identified by the conference object ID, the conferencing system ensures that "Alice" has the appropriate authority based on the policies associated with that specific conference object to perform the operation. The conferencing system must also determine whether "Bob" is already a user of this conferencing system or whether he is a new user.
If "Bob" is a new user for this conferencing system, a Conference User Identifier is created for Bob. Based upon the addressing information provided for "Bob" by "Alice", the call signaling to add "Bob" to the conference is instigated through the focus. Once the call signaling indicates that "Bob" has been successfully added to the specific conference, per updates to the state, and depending upon the policies, other participants (including "Bob") may be notified of the addition of "Bob" to the conference via the conference notification service.9.3. Media Manipulations
There are different ways to manipulate the media in a conference. A participant can change its own media streams by, for example, sending re-INVITE with new SDP content using SIP only. This kind of operation is called "1st party signaling" and they do not affect the state of other participants in the conference. In order to perform richer conference control, a user client needs to implement a conference control protocol client. By using a conference control protocol, the client can manipulate the state of various resources, such as media mixers, which may indirectly affect the state of any of the conference participants. Figure 10 provides an example of one client "Alice" impacting the media state of another client "Bob". This example assumes an established conference. In this example, the client, "Alice" whose Role is "moderator" of the conference, wants to mute "Bob" on a medium-size multi-party conference, as his device is not muted (and he's obviously not listening to the call) and background noise in his office environment is disruptive to the conference.
+--------------------------------+ | Conferencing System | "Alice" | +---------+--+| +--------+ | |policies | || | |CCP Request < | +-----------+ +---------+ || | Client |-------------------------->|Conference | |Active || | | Conference Object ID, | |Control |~~~>|Conference || +--------+ Mute, "Bob" > | |Server | | || | +-----------+ +-------+ || | |"Alice"| || "Carol" | ' ' '| +--------+ NOTIFY <"Bob"=mute"> |+------------+ ' ' '| | |<-------------------------|Notification|<~~~| || | Client |. . ||Service | +-------+ || +--------+--+ . || | |"Bob" | || | |<----------------------| | +-------+----+| | Client | NOTIFY <"Bob"=mute">|+------------+ | +--------+ +--------------------------------+ "Bob" Figure 10: Client Manipulation of Conference - Mute a Party Upon receipt of the conference control protocol request to "mute" a party ("Bob") in the specific conference as identified by the conference object ID, the conference server ensures that "Alice" has the appropriate authority based on the policies associated with that specific conference object to perform the operation. "Bob's" status is marked as "recvonly" and the conference object is updated to reflect that "Bob's" media is not to be "mixed" with the conference media. Depending upon the policies, other participants (including "Bob") may be notified of this change via the conference notification service.9.4. Sidebar Manipulations
A sidebar can be viewed as a separate Conference instance that only exists within the context of a parent conference instance. Although viewed as an independent conference instance, it can not exist without a parent. A sidebar is created using the same mechanisms employed for a standard conference, as described in Section 7.1. A conference object representing a sidebar is created by cloning the parent associated with the existing conference and updating any information specific to the sidebar. A sidebar conference object is
implicitly linked to the parent conference object (i.e., it is not an independent object) and is associated with the parent conference object identifier, as shown in Figure 11. A conferencing system manages and enforces the parent and appropriate localized restrictions on the sidebar conference object (e.g., no members from outside the parent conference instance can join, sidebar conference cannot exist if parent conference is terminated, etc.). +--------------+ | Conference | | Object | | Identifier | +--------------+ | | | +---------------------+---------------------+ | | | +-------+-------+ +-------+-------+ +-------+-------+ | Sidebar | | Sidebar | | Sidebar | | Conference | | Conference | | Conference | | Object | | Object | | Object | | Identifier | | Identifier | | Identifier | +-------+-------+ +-------+-------+ +---------------+ Figure 11: Conference Object Mapping Figure 11 illustrates the relationship between a conference object and associated sidebar conference objects within a conferencing system. Each sidebar conference object has a unique conference object identifier, as described in Section 6.2.1. The main conference object identifier acts as a top level identifier for associated sidebars. A sidebar conference object identifier follows many of the concepts outlined in the cloning tree model described in Section 7.1. A sidebar conference object contains a subset of members from the original conference object. Properties of the sidebar conference object can be manipulated by a Conference Control Protocol using the unique conference object identifier for the sidebar. It is also possible for the top level conference object to enforce policy on the sidebar object (similar to parent enforceable, as discussed in Section 7.1).
9.4.1. Internal Sidebar
Figure 12 provides an example of one client "Alice" involved in active conference with "Bob" and "Carol". "Alice" wants to create a sidebar to have a side discussion with "Bob" while still viewing the video associated with the main conference. Alternatively, the audio from the main conference could be maintained at a reduced volume. "Alice" initiates the sidebar by sending a request to the conferencing system to create a conference reservation based upon the active conference object. "Alice" and "Bob" would remain on the roster of the main conference, such that other participants could be aware of their participation in the main conference, while an internal-sidebar conference is occurring.
+--------------------------------+ | Conferencing System | | +---------+--+| | |policies | || | +---------+ || | |Active || | |Conference || "Alice" | +-------+ || +--------+ | |"Alice"| || | |CCP Req <createSidebar, | +-------+ || | | activeConfObjID, | +-----------+ |"Bob" | || | Client |-------------------------->|Conference | +-------+ || | | confUserID> | |Control |~~~>|"Carol"| || | |<--------------------------|Server | +-------+----+| | |CCP Response | | | | | +--------+ <sidebarResvConfObjID, | | | | | confID> | | | V | | | | +---------+--+| | | | |policies | || | | |~~~>+---------+ || | | | | || | +-----------+ | || "Alice" | | Sidebar || +--------+ | | Reservation|| | |CCP Request <update, | +-----------+ | || | | sidebarResvConfObjID,| | | | || | Client |-------------------------->| |~~~>| || | | confID,confUserID, | | | +------------+| | | video=parent, | | | | | | | audio=sidebar> | |Conference | | | | | | |Control | V | | | | |Server | +---------+--+| | |CCP Response | | | |policies | || | | <activeSideConfObjID,| | | +---------+ || | |<--------------------------| | |Active || +--------+ confID> | | | |Sidebar || | | | |Conference || | +-----------+ +-------+ || | |"Alice"| || "Bob" | | | || +--------+ NOTIFY <"Bob"=added> |+------------+ +-------+ || | |<-------------------------|Notification|<~~~| | || | Client | ||Service | |"Bob" | || +--------+ || | +-------+----+| |+------------+ | +--------------------------------+ Figure 12: Client Creation of a Sidebar Conference
Upon receipt of the conference control protocol request to "reserve" a new sidebar conference, based upon the active conference received in the request, the conferencing system uses the received active conference to clone a conference reservation for the sidebar. As discussed previously, the sidebar reservation is NOT independent of the active conference (i.e., parent). The conferencing system also reserves or allocates a conference ID to be used for any subsequent protocol requests from any of the members of the conference. The conferencing system maintains the mapping between this conference ID and the conference object ID associated with the sidebar reservation through the conference instance. Upon receipt of the conference control protocol response to reserve the conference, "Alice" can now create an active conference using that reservation or create additional reservations based upon the existing reservations. In this example, "Alice" wants only "Bob" to be involved in the sidebar, thus she manipulates the membership. "Alice" also only wants the video from the original conference and wants the audio to be restricted to the participants in the sidebar. Alternatively, "Alice" could manipulate the media values to receive the audio from the main conference at a reduced volume. "Alice" sends a conference control protocol request to update the information in the reservation and to create an active conference. Upon receipt of the conference control protocol request to update the reservation and to create an active conference for the sidebar, as identified by the conference object ID, the conferencing system ensures that "Alice" has the appropriate authority based on the policies associated with that specific conference object to perform the operation. The conferencing system must also validate the updated information in the reservation, ensuring that a member like "Bob" is already a user of this conferencing system. Depending upon the policies, the initiator of the request (i.e., "Alice") and the participants in the sidebar (i.e., "Bob") may be notified of his addition to the sidebar via the conference notification service.9.4.2. External Sidebar
Figure 13 provides an example of one client "Alice" involved in an active conference with "Bob", "Carol", "David", and "Ethel". "Alice" gets an important text message via a whisper from "Bob" that a critical customer needs to talk to "Alice", "Bob", and "Ethel". "Alice" creates a sidebar to have a side discussion with the customer "Fred" including the participants in the current conference with the
exception of "Carol" and "David", who remain in the active
conference. "Alice" initiates the sidebar by sending a request to
the conferencing system to create a conference reservation based upon
the active conference object. "Alice", "Bob", and "Ethel" would
remain on the roster of the main conference in a hold state. Whether
or not the hold state of these participants is visible to other
participants depends upon the individual and local policy.
+--------------------------------+
| Conferencing System |
| +---------+--+|
| |policies | ||
| +---------+ ||
| |Active ||
| |Conference ||
"Alice" | +-------+ ||
+--------+ | |"Alice"| ||
| |CCP Req <createSidebar, | +-------+ ||
| | activeConfObjID, | +-----------+ |"Bob" | ||
| Client |-------------------------->|Conference | +-------+ ||
| | confUserID> | |Control |~~~>|"Carol"| ||
| |<--------------------------|Server | +-------+ ||
| |CCP Response | | | |"David"| ||
+--------+ <sidebarResvConfObjID, | | | +-------+ ||
confID> | | | |"Ethel"| ||
| | | +-------+----+|
| | | | |
| | | V |
| | | +---------+--+|
| | | |policies | ||
| | |~~~>+---------+ ||
| +-----------+ | ||
"Alice" | | Sidebar ||
+--------+ | | Reservation||
| |CCP Request <update, | +-----------+ | ||
| | sidebarResvConfObjID,| | | | ||
| Client |-------------------------->| |~~~>| ||
| | confID,confUserID, | | | +------------+|
| | video=sidebar, | | | | |
| | audio=sidebar> | |Conference | | |
| | | |Control | V |
| | | |Server | +---------+--+|
| |CCP Response | | | |policies | ||
| | <activeSideConfObjID,| | | +---------+ ||
| |<--------------------------| | |Active ||
+--------+ confID> | | | |Sidebar ||
| | | |Conference ||
| +-----------+ +-------+ ||
| |"Alice"| || "Bob" | +-------+ || +--------+ NOTIFY <"Bob"=added, |+------------+ |"Bob" | || | Client |<-------------------------|Notification|<~~~+-------+ || +--------+ "Ethel"=added, ||Service | |"Ethel"| || "Fred"=added,> || | +-------+ || "Ethel" +---| | |"Fred" | || +--------+ NOTIFY <"Bob"=added,| |+------------+ +-------+----+| | Client | <--------------------+ +--------------------------------+ +--------+ "Ethel"=added,"Fred"=added,> Figure 13: Client Creation of an External Sidebar Upon receipt of the conference control protocol request to "reserve" a new sidebar conference, based upon the active conference received in the request, the conferencing system uses the received active conference to clone a conference reservation for the sidebar. As discussed previously, the sidebar reservation is NOT independent of the active conference (i.e., parent). The conferencing system also reserves or allocates a conference ID to be used for any subsequent protocol requests from any of the members of the conference. The conferencing system maintains the mapping between this conference ID and the conference object ID associated with the sidebar reservation through the conference instance. Upon receipt of the conference control protocol response to reserve the conference, "Alice" can now create an active conference using that reservation or create additional reservations based upon the existing reservations. In this example, "Alice" wants only "Bob" and "Ethel", along with the new participant "Fred" to be involved in the sidebar; thus, she manipulates the membership. "Alice" sets the media such that the participants in the sidebar don't receive any media from the main conference. "Alice" sends a conference control protocol request to update the information in the reservation and to create an active conference. Upon receipt of the conference control protocol request to update the reservation and to create an active conference for the sidebar, as identified by the conference object ID, the conferencing system ensures that "Alice" has the appropriate authority based on the policies associated with that specific conference object to perform the operation. The conferencing system must also validate the updated information in the reservation, ensuring whether members like "Fred" are already a user of this conferencing system or whether he
is a new user. Since "Fred" is a new user for this conferencing system, a conference user identifier is created for "Fred". Based upon the addressing information provided for "Fred" by "Alice", the call signaling to add "Fred" to the conference is instigated through the focus. Depending upon the policies, the initiator of the request (i.e., "Alice") and the participants in the sidebar (i.e., "Bob" and "Ethel") may be notified of his addition to the sidebar via the conference notification service.
(page 40 continued on part 3)
