Too much compression can be a bad thing. For example, I've heard reports of problems when compressed RDP traffic sent from Remote Desktop Services (RDS) is passed over a network infrastructure based on Cisco Wide Area Application Services (WAAS) devices which themselves compress network traffic. In such a scenario you may want to disable RDP compression entirely on your RD Session Host servers. To do this, configure the following Group Policy setting:
Computer Configuration\Administrative Templates\Windows Components\Remote Desktop Services\Remote Desktop Session Host\Set compression algorithm for RDP data
Set this policy setting to "Do not use an RDP compression algorithm" to disable RDP compression entirely.