Key Components

Microsoft® Exchange 2000 Conferencing Server enables remote, real-time collaboration between team members of large and small companies. Exchange Conferencing Server consists of three interrelated, key components: Conference Management Service, Data Conferencing Provider, and Video Conferencing Provider. Together, these components create an extensible environment for online collaboration.

Conference Management Service

Conference Management Service manages conference resources and supports conference technology providers. Conference Management Service provides access to online conferences through a Web site hosted by Microsoft Internet Information Services (IIS). You can configure Exchange Conferencing Server to require user authentication on these Web pages, thus limiting access to private conferences.

Conference resources are mailbox-enabled objects in the Active Directory™ directory service in Microsoft Windows® 2000. Conference Management Service publishes the availability of conference resources through Exchange 2000 Server free/busy data. Microsoft Outlook® uses this information to indicate the availability of conference resources at specific times.

When you schedule a conference, Conference Management Service creates a URL for the conference. Conference attendees then use this URL to access the conference through conference access pages. Conference Management Service stores all scheduled conferences in a specific mailbox, called the conference calendar mailbox. This information is used to create a persistent representation of the conference format, structure, and any additional information associated with the conference. Conference Management Service also makes it possible for e-mail clients that cannot reserve conference resources to invite conference resources.

Conference Management Service controls the lifetime of an online conference. This service works in cooperation with each conference technology provider to ensure that the conference starts and ends according to the schedule.

Using the conference resources it defines, Conference Management Service keeps a list of all scheduled conferences. Public conferences are included in a list of available meetings on the conference access pages, and any user with access to conference access pages can participate in a public conference. Private conferences are not listed; to join a private conference, participants must have the correct URL.

Conference Management Service allows the Exchange Conferencing Server administrator to analyze schedule and conference data available in audit log files. These formatted, comma-delimited files are created daily and are available on the conferencing server hosting the active instance of Conference Management Service.

Data Conferencing Provider

Data Conferencing Provider is a conference technology provider that enables conference participants to share applications, conduct whiteboard sessions, transfer documents, and chat. This data collaboration is accomplished using tools such as Microsoft NetMeeting® or other applications that support the T.120 network communications standard. Participants experience data conferencing in various ways, depending on their T.120 and Internet browser applications.

How Data Conferencing Provider Works

Data Conferencing Provider creates a resource scheme based on its maximum permissible number of simultaneous conference participant connections. This maximum participation count is the physical resource against which the conferencing resource makes reservations when you invite the resource to an online conference. Each conferencing resource has a size associated with it, and Conference Management Service considers this size as the cost of hosting the conference. Data Conferencing Provider subtracts the resource cost from the maximum participation count. If the remaining available maximum participation count is greater than the resource cost, the resource is reserved for the time period you request. If the available count is less than the size of the resource for any specific requested time, Data Conferencing Provider prompts Conference Management Service to publish a busy indication, and no additional reservations are accepted.

During a data conference, the computer of each participant is connected to a T.120 multipoint control unit (MCU). On the conferencing site, you can install the T.120 MCU on multiple servers running Microsoft Windows 2000. Exchange Conferencing Server groups these MCUs to provide fail-over and load balancing across the conferencing site. These groups of MCUs provide the platforms on which each scheduled data conference is hosted. When a participant joins a data conference, Data Conferencing Provider uses the following criteria to select the best MCU:

Using these criteria, Data Conferencing Provider connects a conference participant to a load-balanced MCU that is closest to his or her network location, minimizing the number of data copies that are sent between these locations. Because Data Conferencing Provider assigns an MCU when a participant joins a conference, the interconnection of MCUs in the conference is always dynamic and can optimize server availability..

If the client is running NetMeeting 3.01 or later, Data Conferencing Provider places the controls for NetMeeting within the conference window. Both Microsoft Internet Explorer 4.01 and NetMeeting 3.01 or later are required to join a private conference that uses a public certificate for authentication and encryption of the conference data.

You can install the T.120 MCU independently of other services. Each MCU automatically attempts to retrieve a machine certificate from Windows 2000 Certificate Services. The MCU hosts private conferences by authenticating the connection between the MCU and clients when building the conference topology. Without a valid certificate, the MCU cannot host a private data conference.

A data conference has the following features:

Application sharing   You can share a program running on one computer with other participants in the conference. Participants can review the same data and see the actions while the person sharing the application works on the program; for example, editing content or scrolling through data. Participants can share Windows-based applications without any special knowledge of the application. The person sharing the application can choose to collaborate with conference participants, allowing them to take turns editing or controlling the application. Only the person sharing the program must have the application installed on his or her computer.

Also, with NetMeeting 3.0, you can share your desktop, allowing another person to remotely control your computer.

Shared clipboard   You can share data with other participants by using cut, copy, and paste operations; for example, you can copy information from a local document and paste the contents into a shared application. The shared clipboard provides an easy way for participants to exchange data between shared and local applications.

File transfer   You can send a file in the background to one or more conference participants using a file transfer. Because the file transfer occurs in the background, participants can continue sharing an application or using other data conferencing features.

Whiteboard   You can load or sketch diagrams and organizational charts, or display other graphic information in this multipage, multiuser drawing application. Whiteboard is object-oriented (versus pixel-oriented), allowing you to move and manipulate the contents using a click-and-drag operation. In addition, you can use a remote pointer or highlighting tool to point out specific content or sections of shared pages.

Chat   You can type text messages to share common ideas or topics with conference participants, or you can use text messages to record conference notes and action items. You can also use chat to communicate if audio is not available. The NetMeeting whisper feature allows you to have a separate, private conversation with one of the conference participants during a group chat session.

NetMeeting 3.01 or later is the recommended client software for Data Conferencing Provider. It provides the features mentioned previously; it can run as an embedded control on the Web page; and it facilitates private, secure conferences.

Multipoint Control Unit

Multipoint control units (MCUs) are required for data conferences. MCUs interconnect multiple conference participants, and synchronize and distribute conference data between participants.

The NetMeeting client includes an MCU. Each client connection to an MCU requires a separate copy of the conference data. This means that in a peer-to-peer conference, a NetMeeting application with ten participants sends ten copies of the information. If the participant is on a modem or at the other end of a slow WAN link, the response can be slow.

To prevent clients from sending multiple copies of the conference data, move the MCU to a central server and enable each participant to connect to it. If you deploy this MCU server so that it bridges multiple networks, a conference can take place between participants on your intranet and participants on the Internet. Also, when the conference is hosted on a server, the organizer is not required to remain in the conference until it ends. In peer-to-peer conferencing, the organizer’s computer acts as an MCU and must stay in the conference for its duration.

This single server deployment does not address the issue of multiple participants on the remote end of a WAN link, because the deployment still requires multiple copies of the conference data to be transmitted across the link. In this scenario, you should place an MCU at both ends of the WAN link and instruct participants to connect to the MCU closest to their physical locations on the network. Although this increases the complexity of participation in a conference, you can build a conference topology in this manner using peer-to-peer logic only. But if you stretch the conference over multiple WAN links, and if multiple participants often travel, changing which MCU is closest, this manual solution becomes impossible to manage. Data Conferencing Provider offers a solution to these problems by creating an automatic topology that sends single instances of data across the WAN link. A persistent location for the conference allows participants to come and go. Data Conferencing Provider automatically directs a client to the closest server, and in addition, provides a high level of security.

Video Conferencing Provider

Video conferencing is a technology that allows two or more people in remote locations to exchange voice and video images in real time. NetMeeting offers limited video conferencing capabilities; for example, with NetMeeting 3.01, you can establish a peer-to-peer video conference using the International Telecommunications Union–Telecommunication Standardization Sector (ITU-T) H.323 unicast standard.

Video Conferencing Provider allows users to organize and participate in multiparty video and audio conferences. Video Conferencing Provider technology is based on the Internet Engineering Task Force (IETF) IP multicast standards. In addition, Video Conferencing Provider conferences are available for clients with H.323 capabilities, such as NetMeeting, over an IP multicast/H.323 unicast bridge — which is part of Exchange Conferencing Server and can be deployed on a separate MCU server. Video Conferencing Provider combines greater efficiency on multicast-enabled networks with wider accessibility and low-bandwidth support over non-multicast networks, such as the Internet.

How Video Conferencing Provider Works

When a conference with a Video Conferencing Provider resource is scheduled, a special multicast IP address is requested from a Multicast Address Dynamic Client Allocation Protocol (MADCAP) server and reserved for the conference. MADCAP, which is part of the Windows 2000 Dynamic Host Configuration Protocol (DHCP) service, assigns a multicast group IP address to each Exchange video conference. This multicast IP address cannot be used in subsequent reservations until the initial reservation expires. The expiration time is

defined as the scheduled conference end time plus the maximum video conference extension time. You configure the maximum video conference extension time from the Video Conferencing Provider in Conferencing Manager. The maximum video conference extension time is the maximum amount of time, in minutes, that the conference organizer can extend a conference in progress.

When you join a Video Conferencing Provider conference as a multicast client, your multicast client ActiveX® control receives the multicast IP address that the Video Conferencing Provider reserved for the conference. The control then subscribes to the multicast conference and retrieves and sends video and audio data to and from that multicast address.

In a pure multicast video conference, no servers participate in the actual transfer of video and audio traffic. If routers are in the way of the multicast packets, they serve as replicators or multiplexers, which forward packets to the network segments on which the clients participating in the conference are located.


Servers running Multicast Address Dynamic Client Allocation Protocol (MADCAP) in Windows 2000 must exist on the network and routers must be multicast-aware for a multicast video conference to work. Servers running Dynamic Host Configuration Protocol (DHCP) in Windows 2000 can assign multicast and unicast addresses. You configure multicast scopes and corresponding multicast IP ranges with Windows 2000 Administrative Tools. This is required before users can successfully schedule and conduct video conferences. Once you set and activate these scopes, the DHCP service in Windows 2000 can provide multicast addresses in the same way it normally provides unicast IP addresses.

If a participant cannot connect directly to the multicast streams and Data Conferencing Provider is installed on the site, Video Conferencing Provider requests that Data Conferencing Provider supply a bridge between the multicast streams and the participant.