Feature Description

• This feature was designed to control how published applications are treated when launched from a published desktop session (double-hop scenario)
• When a user attempts to launch a published app from a published desktop session, a Receiver for Windows policy controls whether the app will launch the locally installed version of the app on the VDA instead. In addition, a new PowerShell cmdlet property controls, on an app-by-app basis, whether the published app will launch or the VDA installed equivalent.
• Code changes to Receiver for Windows, StoreFront, and the Delivery Controller have been introduced to support this feature

Purpose/Benefit

Double-hop published application launch control has historically required the use of the KEYWORDS:Prefer tag along with some complex workarounds by customers to achieve certain use cases. The VPrefer feature simplifies local app launches in published desktop sessions and provides precise control through a combination of Receiver policy and PowerShell.

Component Changes

Receiver for Windows

A new Receiver for Windows 4.11 policy setting controls the overall behavior:

Policy: Enable VPrefer

• Policy options:
  • Not Configured
  • Enabled
  • Disabled
• AllowApps Options (only configurable when VPrefer policy is set to Enabled):
  • AllowAllApps: The app will launch locally instead of the equivalent published app. This includes local Win32 apps (e.g. Calculator, Notepad)
  • AllowInstalledApps: Only additionally installed local apps (i.e. excluding local Win32 apps) will launch locally instead of the equivalent published app
  • AllowNetworkApps: The published app will always launch

1. When the Enable VPrefer policy is set to “Not Configured”, the default behavior is:
   • Enabled = > AllowInstalledApps
2. The behavior configured using Receiver for Windows VPrefer policy operates in conjunction with a new PowerShell cmdlet property (described later in this article)

StoreFront

The new StoreFront 3.14 version released with XenApp and XenDesktop 7.17 includes support for the VPrefer setting:

• The XML data in the app launch request incorporates the VPrefer tags and data:

  

Delivery Controller (PowerShell)

The Delivery Controller 7.17 Broker includes PowerShell support for the new VPrefer feature:

•  A new LocalLaunchDisabled property has been added to the Set-BrokerApplication and New-BrokerApplication cmdlets
• By default, the LocalLaunchDisabled property is set to $false, which means that by default, the Receiver for Windows VPrefer policy can successfully allow local installs of an app to launch instead of the published app equivalent
• If the LocalLaunchDisabled property is set to $true, the published app will always launch, no matter what the Receiver for Windows VPrefer policy is configured to
• Admins can check the current LocalLaunchDisabled property value for each published app by using the Get-BrokerApplication cmdlet

Limitations of the VPrefer feature

When configuring an application launch behavior with the LocalLaunchDisabled property, using the Set-BrokerApplication or New-BrokerApplication cmdlets:

• The application's ApplicationType value must be HostedOnDesktop
• This option is available only through PowerShell. It is not currently available in the Citrix Studio graphical interface

Other important limitations:

• The VPrefer feature requires a minimum of StoreFront 3.14, Citrix Receiver for Windows 4.11, and Delivery Controller 7.17
• The VPrefer feature works only with native Receiver launches of published apps – it cannot be used to launch an app locally if the published app is launched through the StoreFront site in a web browser. 

Considerations when using the VPrefer feature

• Administrators are still able to control published app launch behavior using the existing KEYWORDS:Prefer=“application” tag in Citrix Studio. The VPrefer feature and KEYWORDS:Prefer feature can essentially be configured to create the same resultant behavior; that is, to have a local app will launch instead of the published app equivalent. Customers have a choice as to which method to employ. If both methods have been configured, the VPrefer method will take precedence. If VPrefer fails to launch the selected application, then it would fall back to the KEYWORDS:Prefer option (if also configured for the app).
• The Receiver VPrefer GPO setting controls the behavior of published app launches on both single-hop scenarios (published app launched from Receiver for Windows installed on the client endpoint) and double-hop scenarios (published app launched from Receiver for Windows installed on the VDA).
• The LocalLaunchDisabled property controls the launch behavior for single-hop app and double-hop app scenarios.
• Since the default VDA vPrefer setting is Enabled (with AllowInstalledApp as the default option), and the default LocalLaunchDisabled property value is $false, it means that the default behavior is for the locally installed apps (except for Win32 apps) to launch in place of the published app equivalent. This differs from the KEYWORDS:Prefer method, which needs to be explicitly configured to achieve the same behavior.