Generic RedirectionOur customers enjoy the Generic USB Redirection feature in Citrix XenDesktop

This is best utilized for simplifying their USB peripheral related use cases.

Generic USB redirection provides a valuable solution for specialty devices for which there is no optimized virtual channel. Following the 7.6 release, we are introducing Generic USB redirection on Citrix XenApp (RDSH platform).

With existing Windows Receiver versions (those available as of the date of this article) the feature will work for published desktop sessions hosted on RDS hosts in single-hop scenarios. To leverage the feature fully for published applications, a new version of Windows Receiver is required.

The Next New Receiver 4.2 for Windows

Will change the USB devices support options to be available for applications as well as desktops (Supporting published apps and double-hop scenarios). Citrix Receiver 4.2 is planned to be released in coming weeks. Currently the Linux Receiver doesn’t have this limitation but its applicability is not fully tested with apps and desktops and support should be considered experimental only (see notes below on experimental support).

One of the benefits of the unified XenDesktop and XenApp architecture

Is the ability for us to offer a broader continuum of options where users can realize the cost and licensing of benefits of XenApp and retain a workstation-like experience with specialty USB devices for designers like the 3D Space Mouse. Also, with Generic USB redirection, there is no need to install the device driver on the user device.

While this feature opens up greater opportunities for simplifying USB peripherals, there are historically multiple challenges exposed by RDSH (aka Terminal Server) platforms. With Generic USB redirection, the USB client drivers are installed on the host so these drivers must be compatible with RDSH for Windows 2012 R2 platforms. In our lab results we have found that most devices work with XenApp7.6 Generic USB Redirection but certain kinds of devices pose challenges when redirected to a XenApp session. There are certain devices that we have prohibited for performance reasons. The device types which don’t work out-of-the-box in XenApp 7.6 include:

  • USB storage devices
  • Audio devices
  •  Smartcard readers
  • Other device models which are not fully virtualized
    ( i.e. a device being managed by a dedicated service running in session 0)

Some indicators to look for when verifying the applicability of Generic USB redirection to a device in XenApp 7.6:

  1. Is the device a storage device? We have optimized channel for such devices.
  2. Does the device model use a dedicated service running in session 0 which is not virtualized? Like Smartcard Service.
  3. Does the device driver have the capability to handle multiple instances of the same device presented from different XenApp sessions? One such example could be if the device driver uses global structures to reference device specific information and is written with one device on a workstation use case.
  4. Does USB have Audio functions? Some composite devices (e.g. USB phones) have Audio functions and buttons, and audio USB devices being prohibited would make the device not usable inside a XenApp session.  We explicitly block USB audio device redirection in XenApp 7.6 however blocking can be turned off for experimental purposes allowing Audio composite devices to be used in XenApp 7.6 sessions.

With Citrix Receiver 4.2 for Windows,

Users will be presented with a simplified and rich experience for USB devices. Receiver 4.2 will not present USB Audio and USB Storage devices for Generic USB Redirection in XenApp 7.6. Current Receiver versions will not block USB storage or USB audio devices but if redirected through Generic USB Redirection, such devices will not be available for applications.

Supported platforms:

Generic USB Redirection in XenApp 7.6 is fully Citrix supported on the Windows Server 2012 R2 platform. Win 2008 R2 is not supported for Generic USB redirection.

Our lab didn’t perform formal validation on Win 2012 [“R1”] but Generic USB redirection on Win 2012 could well work without issue. As such, Win 2012 support is only experimental and should not be used in production environments. However, users with test labs are encouraged to try it and provide feedback on the behavior and any need they have for support (see notes on experimental features below).

The Generic USB redirection feature on XenDesktop and XenApp is controlled by the same policy rules. Further information on enabling Generic USB redirection can be found here: http://support.citrix.com/article/CTX137939 and http://support.citrix.com/article/CTX119722

If you are a device manufacturer and would like to have your device be compatible with XenApp 7.6, please reach out to the Citrix Ready partner program and we would love to share more details on testing and virtualizing your device on XenApp platforms. 

[Update] Generic USB redirection for storage devices,

Refer Generic USB Redirection for storage devices for support in latest release.

Experimental features mentioned in this blog article are current not supported by Citrix.  Use of this configuration should only be used in a lab or test environment and not with production deployments.  The author is actively seeking feedback on the potential of implementing support for this configuration, but the form any level of support takes has yet to be determined.

Note: Generic USB Redirection is a method for redirecting USB devices at low level USB interfaces but XenApp historically offers optimized virtual channel technology for redirecting a wide array of devices. Optimized redirection method always works at functional level and is the recommended method for redirection. Use Generic USB Redirection for devices which cannot be virtualized by one of the optimized virtual channel.