Setting Windows Server 2008 Terminal Services Display Data Prioritization

Windows Server 2008 holds some major key benefits in Terminal Services technology. Some of these are discussed in various articles on my site (see Related Articles section below). One of these features is Display Data Prioritization.

Display Data Prioritization in Windows Server 2008 Terminal Services allows for automatic control over the virtual channel traffic that is passed between the client (RDP 6.0) and the server (running Windows Server 2008). This enables better performance and user experience because display, keyboard typing, and mouse movement data is given a higher priority over other virtual channel traffic, such as printing, clipboard operations or file transfers. This prioritization is designed to ensure that your screen performance (user experience) is not affected by bandwidth intensive actions, such as large print jobs.
In Windows Server 2008 Terminal Services, the default bandwidth ratio is 70:30. This means that display and input data will be allocated 70% of the bandwidth and all other traffic, such as print jobs , clipboard or file transfers will be allocated 30% of the bandwidth.

Changing the Display Data Prioritization

Warning! This document contains instructions for editing the registry. If you make any error while editing the registry, you can potentially cause Windows to fail or be unable to boot, requiring you to reinstall Windows. Edit the registry at your own risk. Always back up the registry before making any changes. If you do not feel comfortable editing the registry, do not attempt these instructions. Instead, seek the help of a trained computer specialist.
Display Data Prioritization can be changed by making changes to the Registry of the server.

  1. Click Start, and then click Run.
  2. In the Open box, type Regedit, and then click OK.
  3. In the left pane, locate and then click the following registry key:

The parameters you might want to change are:

  • FlowControlDisable – If display data prioritization is disabled, all requests are handled on a first-in-first-out basis. The default value is 0. You can disable display data prioritization by setting the value to 1.
  • FlowControlDisplayBandwidth – Controls the relative bandwidth priority for display (and input data). The default value is 70 and the maximum value allowed is 255.
  • FlowControlChannelBandwidth – Controls the relative bandwidth priority for other virtual channels (such as clipboard, file transfers, or print jobs). The default value is 30 and the maximum value allowed is 255.
  • FlowControlChargePostCompression – Determines if flow control will calculate the bandwidth allocation based on pre-compression or post-compression bytes. The default value is 0, which means that the calculation will be made on pre-compression bytes.

Note: If these entries do not appear, you can add them. To do this, right-click TermDD, point to New, and then click DWORD (32-bit) Value.
The bandwidth ratio for display data prioritization is based on the values of FlowControlDisplayBandwidth and FlowControlChannelBandwidth compared to each other. For example, if FlowControlDisplayBandwidth is set to 200 and FlowControlChannelBandwidth is set to 50, the ratio is 200:50.
Note: Changes to these registry values require you to restart the “Terminal Services” service before for the changes to take effect.

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