Essa sinopse da equipe de virtualização de desktops da Microsoft deve ajudar:
Remote Desktop Protocol was extended to support Desktop Composition remoting (or, composed mode RDP). This is achieved by transmitting composition commands from DWM on the server to the RDC client. The client interprets these commands and renders the desktop. The composition commands lead to increased bandwidth consumption. Desktop Composition remoting is only available from Windows Vista to Windows Vista.
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