Product Documentation

HDX Policy Templates for XenApp and XenDesktop 7.6 to the Current Version

Sep 12, 2016

XenApp and XenDesktop 7.6 Feature Pack 3 (FP3) include new and redesigned HDX policy templates that simplify how you can deploy the many enhancements and innovations in this release. Such a significant improvement of the policy templates is a major task, and has been long overdue. This document lists the design considerations when using these templates to create policies, and discuss the planning guidance to determine the right settings for a given use case. It does not replace comprehensive product documentation on the XenApp and XenDesktop polices available on the Citrix Product Documentation site. The intended audience for this document is an advanced Citrix administrator who is familiar with HDX concepts, policy templates, and previous versions of the product.

FP3 supports both built-in templates that ship with the product and custom templates that are made available periodically on the Citrix support site to help with additional use-cases. This document focuses on the built-in templates.

Here is the list of the built-in Citrix templates in FP3:

  • High Server Scalability. Apply this template to economize on server resources.
    This template balances user experience and server scalability. It offers a good user experience while increasing the number of users you can host on a single server. Among other settings, this template enables Thinwire Compatibility mode (does not use video codec), and prevents server side video rendering.
  • High Server Scalability-Legacy OS. This High Server Scalability template applies only to VDAs running Server 2008 R2 or Windows 7 and earlier. This template relies on the Legacy graphics mode which is more efficient for those operating systems.
  • Optimized for WAN. This template is intended for task workers in branch offices using a shared WAN connection or remote locations with low bandwidth connections accessing applications with graphically simple user interfaces with little video content (suitable for Thinwire Compatibility mode). This template trades off video playback experience and some server scalability for optimized bandwidth efficiency.
  • Optimized for WAN-Legacy OS. This Optimized for WAN template applies only to VDAs running Windows Server 2008 R2 or Windows 7 and earlier. This template relies on the Legacy graphics mode which is more efficient for those operating systems.
  • Very High Definition User Experience. This template enforces default settings which maximize the user experience. Use this template in scenarios where multiple policies are processed in order of precedence.
  • Security and Control. Will not be examined in this document.

A side-by-side list of the policy settings used in these templates is included in this document.

High Server Scalability

You can use this template to provide maximum user density per server. This design is for VDAs running modern operating systems like Windows 8, Windows 10, and Windows Server 2012 R2. Citrix also provides a separate template with the suffix ‘- Legacy OS’ for Windows 7 and Windows Server 2008 R2.

What this template does: Disables the use of video codec for compression of graphics. This change alone improves the user density per server while trading off on server render graphics. Most user applications will not be impacted by this change while reducing server rendered multimedia playback experience. Also, and to further increase density, settings in this template preventing server rendered multimedia playback on the default Windows applications while allowing the redirection technologies provided by Citrix to operate whenever possible.

How to use this template: Best practice is to apply a policy created from this template to all users in a server. You can set exceptions (like different printing settings or even advanced graphics modes like Framehawk or DCR)  by applying a higher priority policy filtered to the desired users.

Considerations when using this template:

  • There is no client-side prerequisites for simple-graphics task work (office suite, etc.) use with a policy created from this template is used.
  • To accommodate with multimedia playback redirection with minimum user impact use Windows or Linux client devices with the latest receiver which provides the best multimedia redirection support. IOS and Macs will get limited multimedia playback options. Also, ensure the users have Internet Explorer and Windows Media Player as the default applications.
  • To accommodate with multimedia playback redirection with minimum user impact use Windows or Linux client devices with the latest receiver which provide the best multimedia redirection support. IOS and Macs will get limited multimedia playback options. Also, ensure the users have Internet Explorer and Windows Media Player as the default applications.
  • As already mentioned, server rendered multimedia playback may be suboptimal or prevented at all depending on the applications and media type used.
  • The template will disable some personalization and graphics effects like Desktop Wallpaper and Menu animations. While there are additional optimizations possible in the operating system, these could cause undesired scalability effects and should be applied only after testing and comparing with the settings from this template. Among these is ‘Show contents while dragging’, traditionally disabled in remote access scenarios but enabled on the template. Disabling this does not benefit the overall performance of the template because of the behavior of Thinwire Compatibility mode, used in this template.
  • Product additions such as the Lync Optimization Pack and Citrix Universal Printer Server enhances the user experience and potentially improves the user density.
  • Additional to the increase in User density per server, usage of this template may also reduce required bandwidth per session for simple graphical user interfaces (like Microsoft Office).
  • Printing is configured to map the default client printer only (preventing automatic mapping of multiple client printers per session) and use the Citrix Universal Printer driver. Implementing both settings can reduce processing during session establishment and disconnection.
  • In some scenarios, using Desktop Composition Redirection (DCR) can help improve user density per server. This graphic mode is not being recommended in this template as it is only compatible with Windows 7, 8 and 8.1 VDA and Windows or Mac Receivers.

CPU savings when using High Server Scalability template1

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VDA: Single session 1920x1080, Windows 10 32bit, 2GB RAM 2vCPU@3.2GHz

Disclaimer: This is a sample comparison. Actual savings will depend on the specific user workflow.

1 After the description and considerations for each of the templates, an indicative comparison is provided to visualize the savings in resource consumption using the templates. These are not intended as a performance benchmark, as they are based on simple tests conducted using single session of the LoginVSI 4.1 “Power user” workload. Please test using workloads typical in your organization to determine system scalability relevant to that environment.

High Server Scalability – Legacy OS

This template is provided for maximum user density per server on VDAs with Windows 7 and Windows Server 2008 R2 operating systems. It leverages the Legacy Thinwire graphics mode, optimized for these operating systems, and will provide results similar to those from XenApp 6.5 and XenDesktop 5.6.

How to use it: The legacy graphics mode is a machine policy and should be applied to all sessions on a server. Exceptions to settings other than graphics (like different printing settings) can be achieved by applying a higher priority policy filtered to the desired users.

What this template does: All other settings with the exception of "Legacy graphics mode" and "Show contents while dragging" are the same as the High Server Scalability template. All of the same considerations apply unless it specifed from the following considerations. 

See the Citrix Product Documenation site for in-depth description of Thinwire Legacy mode.

Considerations when using this template:

CPU savings when using High Server Scalability – Legacy OS template1

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VDA: Single session 1920x1080, Windows 7 32bit, 2GB RAM 2vCPU@3.2GHz

Disclaimer: The graph is a sample comparison. Actual savings will depend on the specific user workflow.

Optimized for WAN

This template works to improve the user experience when connecting with low bandwidth connections accessing applications with graphically simple user interfaces. The template design is for VDAs running modern operating systems like Windows 10 and Windows Server 2012 R2, a separate template with '- Legacy OS' suffix is provided for Windows 7 and Windows Server 2008 R2.

What this template does: This template disables the use of video codec for compression of graphics. This change is highly effective in reducing the bandwidth requirements for Office applications and alike but it may reduce the server rendered video quality and could reduce interactivity if the interfaces are highly graphical, such as CAD applications.

The template allows all (enabled by default) Citrix multimedia redirections for Windows Media Layer and Flash and on the fly optimization of windows media if required for the WAN link in use.

DO NOT use this template if users continuously view multimedia. In that case, use the default settings or customize this template by enabling the compression by using the video-codec.

How to use this template: You can apply the created policies from this template to Delivery Groups serving users across the described WAN links or on a per-user basis (with high policy priority).  The user connection determines the policies and uses the available User setting policy filters such as the client IP address, NetScaler Gateway access condition, and so forth.

Considerations when using this template:

  • There are no client-side prerequisites for simple-graphics task work (office suite, etc.) use with a policy created from this template is used.
  • Adverse results when using this template could indicate users continuously view multimedia content. See recommendations above if this user behavior is accepted.
  • Server-rendered multimedia playback can be sub-optimal as the frame rate is limited to a target maximum of 16.
  • Complex graphics images with gradient colors (such as a skyline) will not change gradually but in steps as the template ‘color depth for simple graphics’ setting subsamples the colors in the display to 16 bits per pixel to reduce bandwidth requirements.
  • The template disables some personalization and graphics effects such as Desktop Wallpaper and Menu animations. While there are additional optimizations possible in the operating system, these could cause undesired scalability effects and should be applied only after testing and comparing with the settings from this template. Among these is 'Show contents while dragging', traditionally disabled in remote access scenarios but enabled on the template. Disabling this does not benefit the overall performance of the template because of the behavior of Thinwire Compatibility mode, used in this template.
  • Product additions like Lync Optimization Pack and Citrix Universal Printer Server enhance the user experience and potentially improve the user density.
  • Additional to Optimization for WAN, usage of this template might also increase user density per server if sessions mainly have simple graphical user interfaces (like Microsoft Office).
  • Printing is configured to map the default client printer only (preventing automatic mapping of multiple client printers per session) and use the Citrix Universal Printer driver. The template implements both settings to reduce the bandwidth required for printing.
  • The universal printer driver is enabled for all printers. It can guarantee low bandwidth requirements regardless of the printer. While some printer specific drivers and the use of a print server might yield better results than the generic printer driver, we cannot enable it for general use as they require additional configurations and or testing.
  • Direct Connection to print servers is disabled, and network printers attached to the client device will use the Citrix Generic Printer driver to transverse the WAN and spool the print job from the client. Performing these actions is done to manage the print bandwidth (optimized inside the ICA session) and because we cannot predict how printer specific drivers will behave over the WAN link.
  • Desktop Composition Redirection (DCR) is not recommended in constrained bandwidth links and is disabled in this template. 

Bandwidth savings when using Optimized for WAN template1

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VDA: Single session 1920x1080, Windows 10 32bit, 2GB RAM 2vCPU@3.2GHz

Disclaimer: This is a sample comparison. Actual savings will depend on the specific user workflow.

Optimized for WAN – Legacy OS

This template works to improve the user experience when connecting to legacy operating systems, such as Windows 7 or Windows Server 2008 R2, VDAs with low bandwidth connections accessing applications with graphically simple user interfaces. It leverages the Legacy Thinwire graphics mode which will provide results similar to those from XenApp 6.5 and XenDesktop 5.6.

How to use this template: The legacy graphics mode is a machine policy and applies to all sessions on a server. You can set exceptions to settings other than graphics (like different printing settings) by configuring a higher priority policy filtered to the desired users.

What this template does: All other settings with the exception of 'Legacy graphics mode,' 'Show contents while dragging,' and 'Extra Color Compression' are the same as the Optimized for WAN template. All considerations from that template unless specified below apply.

See Graphics policy settings on the Citrix Product Documentation site for an in-depth description of Thinwire Legacy mode.

Considerations when using this template:

  • Administrators can expect similar user experience and bandwidth efficiency as XenApp 6.5 and XenDesktop 5.6. 
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VDA: Single session 1920x1080, Windows 7 32bit, 2GB RAM 2vCPU@3.2GHz

Disclaimer: This is a sample comparison. Actual savings depend on the specific user workflow.

Very High Definition User Experience

The product ships configured to provide a high-definition user experience. A close look at this template shows it enforces default values except High visual quality and Best Quality printing, which set these values higher than the default.

When to use: Use this template to ensure maximum user experience by using the created policy, which takes precedence over other policies with specific filters (such as VIP users).

How to use this template: Create and apply a policy with a filter to select the desired users or scenarios and with a higher priority than other policies created from the templates. You can use this policy with the general user base, such as Server Scalability policies or WAN.

Considerations when using this template:

  • Requires updated client hardware and Citrix Receivers. For example,  CPUs faster than 2.0GHz with h.264 support and Receiver for Windows 4.x/Mac 11.8/Linux 13.0. If the user device does not meet the requirements, a policy created with this template might have adverse effects.
  • As mentioned in the built-in policy description, applying this template may consume more bandwidth and reduce user density per server.
  • Consider a VDA GPU solution. High-end user applications, graphical or with extreme processing needs, can leverage the processing power of a GPU allowing for better performance and in some instances better server scalability. For more info see HDX 3D Pro in the Citrix Production Documentation.
  • As with the default configuration, this template will allow the use of a video codec (h.264) for compression of screen graphics if the Receiver supports it and has it enabled. Visual quality is automatically adjusted by the video-codec as required and the ‘Visual Quality’ setting is not necessary.
  • High visual quality setting applies when using this template without the video codec (h.264) from compression (to increase User Density per server) only, which results in the graphics mode called Thinwire Compatibility mode. Administrators can achieve this by placing a higher priority policy with the Video codec from compression ‘Not used or if the client does not have or has disabled the video codec support (see client compatibility matrix). Under these circumstances, very high definition user experience will only be obtainable if the VDA and client device connects through an unrestricted high bandwidth LAN network.
  • This template also uses the Target frame rate setting of 30 fps which is suitable for most use cases requiring an HD experience; the default 30 fps should be considered to be an initial baseline which can be adjusted to meet the end-users HD eXperience (YouTube streams at 24 to 30 fps by default). Users with high-end graphical and GPU enabled applications may request higher values up to 60 fps). 
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  • This template allows Windows Media Player and Flash multimedia redirection to Citrix Receiver for Windows and Linux and Windows Media Player only to IOS devices. Use the latest Citrix Receiver in the client to take advantage of recent improvements.
  • The template configures printing for the best user experience including best print output quality and all configuration options available. If users install a large number of printers on their devices and manufacturer printer drivers are not optimized for remote printing, this could lead to very high bandwidth usage, reduction in user density per server and possible interoperability problems at the VDA.

Appendix

The following are the detailed policy settings in the templates.

Template

Very High Definition User Experience

High Server Scalability

High Server Scalability — Legacy OS

Optimized for WAN

Optimized for WAN—

Legacy OS

Bandwidth

Overall session bandwidth limit

 

 

0 Note: simply to expose the setting

 

Graphics

Legacy graphics mode

Disabled

 

Enabled

 

Enabled

Desktop Composition Redirection

 

 

 

Disabled

Disabled

Use video codec for compression

Use when available

Do not use

n/a

Do not use

n/a

Target frame rate

30

16

12

16

16

Target minimum frame rate

10

8

8

8

8

Visual quality

High

Medium

n/a

Low

n/a

Preferred color depth for simple graphics

24bpp

 

n/a

16bpp

n/a

Lossy compression level

n/a

n/a

 

n/a

High

Maximum allowed color depth

n/a

n/a

 

n/a

16bpp

Extra color compression

Disabled

Disabled

Disabled

Disabled

Enabled

Desktop UI

Desktop wallpaper

Allowed

Prohibited

Prohibited

View window contents while dragging

Allowed

Allowed

Prohibited

Allowed

Prohibited

Dynamic windows preview

Enabled

 

Disabled

Menu animations

Allowed

Prohibited

Prohibited

Multimedia

 

 

 

Optimization for Windows Media multimedia redirection over WAN

 

Prohibited

Allowed

Limit video quality

 

 

Maximum 480p

Windows media fallback prevention

Not configured

Play all content only on client

 

Flash video fallback prevention

Not configured

Only small content

 

Flash video fallback prevention error *.swf

 

Apply default sample (see policy)

 

Multimedia conferencing

Allowed

Prohibited

 

Audio

Audio Quality

High – high definition audio

Medium-optimized for speech

Low – for low speed connections

Printing

Auto-create client printers

Auto-create all client printers

Auto-create the client's default printer only

Auto-create the client's default printer only

Direct connections print servers

Enabled

 

Disabled

Universal printer driver usage (UPD)

Use universal printing only if requested driver not available

Use universal printing only

Use universal printing only

Universal printing print quality limit

No limit

 

Medium resolution (600 DPI)

Universal printing optimization defaults

ImageCompression = BestQuality; Other settings = default

ImageCompression = StandardQuality; Other settings = default

ImageCompression = ReducedQuality;

Other Settings = default

File Redirection

Use asynchronous writes

Disabled

 

Enabled

Notes

  • Settings in bold are equal to the default values.
  • Settings assigned to default values are to ensure desired results when using stacked policies.
  • Crossed out boxes mark settings (in that row) that are not applicable to the graphics mode in the each template.
  • Empty boxes represent settings that don't have a specific recommendation for the template in that column.
  • The table does not list of all policy settings, only those used in the built-in templates. For the complete policy list, see the Citrix Product Documentation website.

 

Graphics Delivery Considerations

Thinwire use of video-codec for compression

In XenApp/XenDesktop version 7.6 FP3, HDX brings enhanced support for delivering simple graphics like basic Office applications. We are doing this to allow our customers to keep extending the life of already deployed network links, client devices, and locked-down receivers. To

achieve this, we now allow the administrator to control when to use a video codec for encoding the Thinwire graphics. 

By default, the product still ships with video-codec usage enabled (when available), suitable for most general use scenarios.

When High Server Scalability is paramount, and the Optimized for WAN (constrained bandwidth links are in) use, Citrix recommends disabling the use of Video Codec. When not using the video codec, the session can focus on optimizing the delivery of text and simple graphics (which are the basis of most business applications) with the minimum CPU and bandwidth requirements. Please note, server rendered video performance will not be optimal if bandwidth is limited. For more information, see Thinwire Compatibility Mode in the Citrix Product Documentation.

Legacy operating systems that allow for GDI use (Windows 7 & Windows Server 2008 R2)

Citrix recommends enabling the legacy graphics mode. The design of the legacy Thinwire mode is for the architecture of legacy Windows operating systems and it remains for many use cases the most optimized graphics modes for those operating systems.

Show window contents while dragging

Contrary to recommendations given for previous releases, Thinwire Compatibility mode performs best when Show window contents while dragging is allowed.

Disable the policy for legacy graphics mode and better scalability in scenarios were video codec (h.264) for compression is required but maximum user density is desired.

Target frame rate & Target minimum frame rate

For the High Server Scalability and Optimized for WAN (constrained bandwidth links) templates, targeted for simple graphics use, Citrix recommends reducing the target frame rate setting to 16 or 12 and lowering the target minimum to 8. These settings help in achieving the desired objective for those templates.

We selected the target frame rate of 16 as this is the absolute minimum for the human eye to detect motion.

The VDA and client continuously negotiate the appropriate frame rate to deliver in the session. In general, the frame rate is kept to the minimum required to display the changes on the screen. When high motion is detected, anything from video playback to window dragging to scrolling, the session will attempt to deliver every screen change up to the Target frame rate. In constrained bandwidth connections, it might not be possible to maintain the target frame rate and the VDA automatically balances increasing the screen graphics compression and lowering the frame rate until reaching the Target minimum frame rate, then increasing compression until a preset (non-configurable) value and lastly further reduce frame rate as needed. Think of this as an automatic adaptive display (a technique used in previous Citrix products).

Note: Setting visual quality to low does not affect high contrast text (for example black over white), and it is still delivered with high quality.

Color depth

Different than the legacy mode, the XenDesktop and XenApp 7.x Super-codec does not have control over the color depth and receives 24 bits per pixel. In FP3, as part of the enhancement of Thinwire without using video-codec for compression, we added the option to send the session graphics in 16 bits per pixel (controlled by the Preferred color depth for simple graphics setting). This option reduces the bandwidth required for simple graphics, and it is only noticeable when using color gradients. In this instance, devices might use slightly higher server CPU consumption.

For Legacy graphics mode, in the Legacy OS templates for scalability and WAN, the setting Maximum allowed color depth is also limited to 16 or 12. Note that when using Legacy graphics mode, a lower Color depth can be requested or delivered based on other conditions.

A word on DCR

Desktop Composition Redirection (DCR) is a display Virtual Channel introduced by Citrix in XenDesktop 5.5. While this technology has many advantages, it is currently available for Windows 7, 8 and 8.1 VDAs, reduced Citrix Receiver support and mainly, customer adoption has been low. Additionally, DCR is not recommended for low-bandwidth WAN links. Because of these, as of FP3, this virtual channel is disabled by default and the Optimized for WAN templates actively disable it.

Further reading in HDX graphics modes

For information about how to check which graphics mode is in use, see How to Determine HDX Display Mode in the Citrix Support Knowledge Center.

Multimedia considerations

In all templates and by default on the product, redirection of multimedia playback is allowed. The following are the additional settings used in the templates:

Optimization for Windows Media multimedia redirection over WAN

Allowed by default, the just-in-time transcoding of media content for efficient delivery on a WAN is process intensive and thus prohibited in the High Server Scalability template. Please note that if a NVIDIA GPU is made available to the server and the setting: Use GPU for optimizing Windows Media multimedia redirection over WAN is enabled, you can offload the processing to the GPU.

Limit video quality

This settings applies only to optimization for Windows Media multimedia redirection. A value equivalent to a small embedded video player was selected as an initial recommendation in the 'Optimized for WAN' template where it is used. Otherwise this setting is not configured.

Multimedia conferencing

Redirection of a webcam from the client that is used in a unified communications or conferencing application running in the VDA will increase the required server resources. This feature is disabled in the High Server scalability template.

For more information on the multimedia and Flash redirection policy setting see the following topics in the Citrix Production Documentation site:

Audio considerations

The product ships with a default of high-quality audio (roughly 128Kbps). This value also applies to the Very High definition template in case a policy created from this template has a higher priority over other policies. 

The values listed in the following table are for audio direction (output and input) individually.

Template

Very High Definition experience and default setting

High server scalability

Optimized for WAN

Audio Quality setting

High

Medium

Low

Expected Bandwidth used

128Kbps

60Kbps

44Kbps

Printing considerations

XenApp and XenDesktop includes a universal printer driver that can operate with most client-attached printers. By default, the VDA uses this driver only if the VDA does not find the printer-specific driver. Also, by default all client attached printers are mapped into the session by default.

The new built-in templates use the following printing settings that differ from the defaults:

Auto-create the client’s default printer only

High Server scalability and Optimized for WAN – Creating one printer instead of the possibly many ensures for savings on both scenarios.

Users can change the default client printer while in session, and the mapped printer will update even in dual-hop scenarios.

Use Universal printer [driver] only

High server scalability – Prevents the VDA from having to search for printer drivers with each connection, saving disk I/O operations, and server load due to pre-printer model drivers.

Optimized for WAN – The universal printer driver can guarantee low bandwidth requirements regardless of the printer. While some printer specific drivers and the use of a print server (which requires additional setup) might yield better results than the generic printer driver, we cannot recommend it for general use as they require additional configurations and or testing.

Direct connections to print servers

Enabled by default, this setting allows a network printer configured in the client to be accessed directly from the session. Enabling this setting can potentially improve the options available to the user (depending on the printer) and save traffic on the client device.

For Optimized for WAN templates, this setting is disabled as it is likely that the network printer is collocated with the user (he has to retrieve the printout right?) and thus we can ensure the print job size will be small when printed using the Citrix Universal Printer driver. Additionally, the bandwidth used by the print job will adhere to the Session bandwidth limits.

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