14.2.16 Remote Desktop Protocol: Multiparty Virtual Channel Extension
The Remote Desktop Protocol: Basic Connectivity and Graphics Remoting [MS-RDPBCGR] enables the remote display of desktop and application content. To effectively implement an application-sharing or collaborative solution, additional information must be conveyed to keep the participants apprised of who else is involved, in addition to which applications or windows are being shared. The Remote Desktop Protocol: Multiparty Virtual Channel Extension (as specified in [MS-RDPEMC]) defines a set of messages that are used to communicate the information between the participants and to signal the occurrence of significant events.
The Remote Desktop Protocol: Multiparty Virtual Channel Extension provides the following message types:
Application and Window Filtering - A host may choose to share all application windows on a desktop or, instead, limit the sharing to a subset. The process of limiting the sharing to a subset is known as filtering. Application filtering is used when the host wants to share the current windows for a specific application in addition to any others subsequently created while the application is being shared. Although the term "application" is operating system specific, it generally denotes all windows created by a certain process as well as all windows related to the original windows by window hierarchy. Window filtering is purely explicit. A window is selected for sharing, and any subsequent windows created by an application must be manually added to the sharing list. The precise mode of operation depends on a combination of user preference and the features of a sharing manager.
Participant Management - Participant Management facilities allow the sharing manager to send notifications to all participants when an individual participant connects or disconnects from the sharing session or when a participant's control level changes.
Graphics Stream Control - The host may choose to momentarily suspend or resume desktop sharing. This capability is useful when an event, such as the input of a plain-text password, would reveal sensitive information to all participants. Participants should be notified when sharing is suspended, so they know why they are no longer receiving information.