Client/server latency optimizations

ICA Data Compression

The winstation driver can compress ICA data before sending it. Compression is enabled or disabled through the user interface, which directly modifies the .ICA file parameter shown in the following table.

By default, compression is enabled. If this setting is not modified, the Winstation driver receives data from the virtual channels and compresses it before sending the data to the encryption driver.

Disabling the Use data compression setting allows the ICA packet to move from the Winstation driver to the Encryption drier without compression. If resources on the client device are limited, disabling compression allows for better usage of the system resources because compression and decompression require additional processor resources on both client device and server.

In an environment where system and client resources are not a concern, data compression can be used to decrease the amount of data that must be sent across the network.

Bitmaps can be cached on the local hard disk to limit the amount of bandwidth that is required for an ICA session since some bitmaps may be available locally. The Use disk cache for bitmaps option allows graphical objects to be sorted in the local disk cache on the client device. When the server identifies a bitmap to be displayed, the server sends the bitmap to the client device and adds it to the list of cached bitmaps. The client sores the bitmap locally for future use.

The first launch of an application can yield high bandwidth because all graphical objects are being sent across the network for the client to cache locally. Not all ICA client devices support bitmap caching.

Use disk cache for bitmaps can be enabled or disabled through the user interface on the client, which directly modifies the following .ICA file parameters.

One additional parameter, Maximum compression, is automatically enabled when Use disk cache for bitmaps is enabled. This parameter controls the size of the buffer used by the data compression process. When the parameter is enabled, the buffer is maximized to allow more ICA data to be compressed by the Winstation driver. Compression decreases the amount of bandwidth required by decreasing the total number of ICA packets that are transferred.

Note: MaximumCompression cannot be explicitly set from the Program Neighborhood user interface. This setting is not the same as DataCompression, which is set from the Program Neighborhood user interface.

The ICA client processes mouse movements and keystrokes to gather the information that is sent to the MetaFrame XP server. Separate mouse and keyboard timers track the time, in milliseconds. At the end of the specified time period the mouse and keyboard data are sent to the serer. By default, these time intervals are:

• 100 milliseconds by default for mouse movements

• 50 milliseconds by default for keystrokes

The ICA client sends the following data:

• All keyboard events that occur during the specified time period

• Only the latest mouse movements, although all movements are processed

Use Queue mouse movements and keystrokes can be enabled or disabled through the user interface on the client device, which directly modifies the following .ICA file parameters.

Delays between entry and echo of mouse movements and keyboard input are one of the primary frustrations that client users can experience on a high-latency network connection. SpeedScreen features in MetaFrame XP and the ICA client software enable almost immediate echo of mouse movements and keystrokes at the ICA Client.

Use SpeedScreen Latency Reduction manager to customize SpeedScreen settings for a MetaFrame XP server, individual published applications, and input controls within applications. You can save a SpeedScreen configuration file and then deploy the file across your server farm.

To launch Speedscreen Latency Reduction Manager from the start menu, choose programs>Citrix>MetaframeXP>SpeedScreen Latency Reduction Manager.

Tip: You can launch SpeedScreen Latency Reduction Manager by clicking its button on the ICA Administrator Toolbar.

By default, instant mouse click feedback is enabled and local text echo is disabled for all applications.

You can enable local text echo on an application –by-application basis only. If you use this feature, the programs to which you apply it must use only standard Windows APIs for displaying text or the settings will not work correctly.

Important: Test all aspects of an application with local text echo in a no0n production environment before enabling text echo for your users.

With SpeedScreen Latency reduction manager, you can also configure local text echo settings for individual input fields within an application. See the application help for the SpeedScreen Latency Reduction Manager utility for more configuration information.

For general information about SpeedScreen options, see the online help in the SpeedScreen Latency Reduction Manager.

After you use Speed Screen Latency Reduction Manager to configure SpeedScreen settings for the server (and specific applications, if you choose), the manager saves the settings for each application in the directory C:\Winnt\system32\ss3config. To deploy the configuration settings throughout a server farm, copy the entire directory and its contents to each MetaFrame server in the server farm.

Tip: If you plan to copy SpeedScreen configuration settings across a server farm, apply the settings to “all instances of an app” on the server when you configure individual application settings, because, path names might differ on various destination servers.

Be aware that applications developed using MFC generate application window names dynamically. This is not standard behavior. The SpeedScreen Latency Reduction Manager uses window names to identify exception entries, and could apply saved settings erroneously on a destination server if you applied SpeedScreen settings to a specific instance of the application.