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Microsoft Office Communications Server 2007 R2 includes a new feature, desktop sharing, which allows others to view a user’s entire desktop remotely and, with the user’s permission, to take control of the user’s mouse and keyboard. The inclusion of this feature may seem puzzling to those familiar with the history of the product, because the on-premises Live Meeting feature introduced in Office Communications Server 2007 already includes this capability and much more, and this functionality remains available with Office Communications Server 2007 R2.

There are several reasons for adding a new separate desktop sharing feature:

• Microsoft already has a very mature and efficient technology in which it continues to invest and develop, the Remote Desktop Protocol (RDP), already at the core of the Remote Assistance, Remote Desktop, and Terminal Services features of the Microsoft Windows operating system. However, the Live Meeting technology used in Office Communications Server uses a legacy application sharing protocol rather than RDP. In Office Communications Server 2007 R2, Microsoft has begun a transition toward adopting RDP as the universal protocol for application sharing (of which desktop sharing is a subset) for Office Communications Server.
  
  
• To use the Live Meeting application sharing feature, users had to install the full Live Meeting client. Even though it is available from Microsoft as a free download, in many cases—particularly for external participants who were not employees of the organization—installing this client by end users could be problematic and time consuming, and without prior familiarity it sometimes confused users. Furthermore, since the Live Meeting client ran only on Windows, Apple Macintosh and Linux users were unable to participate in these meetings.
  
  
• If the Live Meeting session was between only two participants, application sharing traffic was still relayed by a Web Conferencing Server (formerly known as a multipoint control unit or MCU). Additionally, if both users were connecting from the Internet, each packet of desktop sharing data had to traverse the Web Conferencing Edge Server twice. This architecture imposed unnecessary workloads on these servers when the viewing/sharing traffic need only communicate directly between the two endpoints.
  
  
• Users often want to add desktop sharing to an existing Office Communicator-based voice call or multiparty meeting, but because the Share Information Using Live Meetingmenu option in Office Communicator launched a new client, it often created confusion as to which of the two clients was controlling the audio/video.
  
  

The approach taken in Office Communications Server 2007 R2 was to leave the on-premises Live Meeting capability as it was in the 2007 release but to add a new entirely separate desktop sharing feature that gives users an easier and more efficient way to share their entire desktop remotely with others. Office Communications Server 2007 R2 also adds Web browser–based desktop sharing support for users who do not have any Office Communications Server client, even anonymous (unauthenticated) users connecting from the Internet.

This section of the Office Communications Server 2007 R2 Technical Reference explores in detail the architecture and protocol flows of the desktop sharing feature. The following information can be useful in troubleshooting and correcting problems:

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