Product Documentation

Improve performance over low-bandwidth connections

Jul 15, 2013

Citrix recommends that you use the latest version of XenApp or XenDesktop on the server and Receiver on the user device.

If you are using a low-bandwidth connection, you can make a number of changes to your Receiver configuration and the way you use Receiver to improve performance.

  • Configure your Receiver connection - Configuring your Receiver connections can reduce the bandwidth that ICA requires and improve performance
  • Change how Receiver is used - Changing the way Receiver is used can also reduce the bandwidth required for a high-performance connection
  • Enable UDP audio - This feature can maintain consistent latency on congested networks in Voice-over-IP (VoIP) connections
  • Use the latest versions of XenApp and Receiver for Linux - Citrix continually enhances and improves performance with each release, and many performance features require the latest Receiver and server software

Configure connections

On devices with limited processing power or where limited bandwidth is available, there is a trade-off between performance and functionality. Users and administrators can choose an acceptable mixture of rich functionality and interactive performance. Making one or more of these changes, often on the server not the user device, can reduce the bandwidth that a connection requires and can improve performance:
  • Enable SpeedScreen Latency Reduction - SpeedScreen Latency Reduction improves performance over high latency connections by providing instant feedback to the user in response to typed data or mouse clicks. Use SpeedScreen Latency Reduction Manager to enable this server-side feature.
  • Enable data compression - Data compression reduces the amount of data transferred across the connection. This requires additional processor resources to compress and decompress the data, but it can increase performance over low-bandwidth connections. Use Citrix Audio Quality and Image Compression policy settings to enable this feature.
  • Reduce the window size - Change the window size to the minimum that is comfortable. On the XenApp Services site set the Session Options.
  • Reduce the number of colors - Reduce the number of colors to 256. On the XenApp Services site set the Session Options.
  • Reduce sound quality - If audio mapping is enabled, reduce the sound quality to the minimum setting using the Citrix Audio quality policy setting.

Enable UDP audio

UDP audio can improve the quality of phone calls made over the Internet. It uses User Datagram Protocol (UDP) instead of Transmission Control Protocol (TCP).

Note the following:

  • UDP audio is not available in encrypted sessions (that is, those using SSL or ICA Encryption). In such sessions, audio transmission uses TCP.
  • The ICA channel priority can affect UDP audio.
  1. Set the following options in the ClientAudio section of module.ini:
    • Set EnableUDPAudio to True. By default, this is set to False, which disables UDP audio.
    • Specify the minimum and maximum port numbers for UDP audio traffic using UDPAudioPortLow and UDPAudioPortHigh respectively. By default, ports 16500 to 16509 are used.
  2. Set client and server audio settings as follows so that the resultant audio is of a medium quality (that is, not high or low).
       

    Audio quality on client

       

    High

    Medium

    Low

    Audio quality on server

    High

    High

    Medium

    Low

    Medium

    Medium

    Medium

    Low

    Low

    Low

    Low

    Low

    If UDP audio is enabled but the resultant quality is not medium, audio transmission will use TCP not UDP.

Change how Receiver is used

ICA technology is highly optimized and typically does not have high CPU and bandwidth requirements. However, if you are using a very low-bandwidth connection, consider the following to preserve performance:
  • Avoid accessing large files using client drive mapping. When you access a large file with client drive mapping, the file is transferred over the server connection. On slow connections, this may take a long time.
  • Avoid printing large documents on local printers. When you print a document on a local printer, the print file is transferred over the server connection. On slow connections, this may take a long time.
  • Avoid playing multimedia content. Playing multimedia content uses a lot of bandwidth and can cause reduced performance.