Monday, April 15, 2024

What’s new with HDX in the 2402 LTSR

I’ve said this before, and I’ll say it again – if you are on the Citrix Long Term Service Release (LTSR) track, you’ve most likely been missing out on a lot of great features. But I get it; there are many valid reasons for choosing this path, including extended support. The good news is that Citrix Virtual Apps and Desktops 2402 LTSR is now available, and you can now take advantage of all the great features and enhancements made available over the last couple of years.

This post is focused exclusively on our high-definition experience (HDX) capabilities. More specifically, the key HDX features and enhancements that we’ve introduced since the last LTSR (2203) was released. If you are still using Citrix Virtual Apps and Desktops 1912 LTSR, you should also take a look at my other post that talks about key features released between Citrix Virtual Apps and Desktops 1912 LTSR and Citrix Virtual Apps and Desktops 2203 LTSR.

Without further ado, let’s jump right in!


Security is always top of mind, so let’s start with updates around security-related features:

  • TLS 1.3 support: if the operating system on the client device and the session host supports it, you can now use TLS 1.3 to secure your HDX traffic using one of the following cipher suites: TLS_AES_256_GCM_SHA384 or TLS_AES_128_GCM_SHA256

Similarly, Universal Print Server also supports TLS 1.3 to help you secure your print data in transit. For more details, check out the Transport Layer Security section in our documentation.

  • Virtual Channel Allow List enhancements: if you use custom virtual channels in your environment, you’ll be happy to know that there have been a few enhancements to simplify the configuration and ongoing management of this feature:
  • Support for wildcards: you can now use wildcards when defining the trusted processes.
  • Support for system environment variables: you can now use system environment variables when defining the trusted processes.
  • Logging settings: you can configure the level of logging as well as the throttling period for virtual channel allow list events.

For additional information, take a look at the Virtual Channel Allow List and Virtual channel allow list policy settings documentation. 

Transport and Networking

There have been a few updates in the area of core networking capabilities:

  • Enhanced EDT congestion control: EDT, our default out-of-box transport protocol, has a new and improved congestion control algorithm that provides a much better user experience and interactivity by improving in-session responsiveness, higher throughput, and higher frame rate, as well as up to 5X improvement in bulk data transfer. If you want to see an example of how those metrics compare with the old and the new EDT, check out this blog post.
  • Loss tolerant mode: in addition to the new congestion control, we also made significant enhancements to EDT Lossy, the unreliable, loss-tolerant version of EDT, in order to improve real-time traffic in highly challenging networks. You can leverage these improvements through these features:
  • Loss tolerant mode for audio: this feature allows the delivery of audio traffic using loss-tolerant EDT to maintain a high-quality audio experience in varying network conditions. For more information, check out the Audio documentation.
  • Loss tolerant mode for graphics: this feature enables the delivery of the session’s graphics using loss-tolerant EDT to maintain interactivity when network conditions degrade beyond the defined latency and loss thresholds. Take a look at the Graphics documentation for more information.

  • Enhanced compression: part of the benefits of using HDX to deliver your virtual apps and desktops is to be able to provide a superior experience to a wider range of users without having to worry too much about the connection speed that is available to them. To help you with this, we enhanced our protocol compression algorithm to allow you to reduce the bandwidth required to deliver HDX sessions by up to 15 percent! To learn more, take a look at this blog post.
  • New platforms for virtual loopback: for those of you who need to support applications that make use of loopback calls on multi-user session hosts, you can now use virtual loopback on Windows Server 2019 and Windows Server 2022.
  • Rendezvous version: if you don’t use our cloud control plane or the Citrix Gateway Service, feel free to move on to the next one. But if you use Rendezvous to optimize your HDX sessions’ connection path, note that version 2 of the Rendezvous protocol is the new default. Take a look at the documentation to review the requirements and ensure everything is in place before you upgrade.


We also added major improvements to our graphics capabilities:

  • AV1 codec support: AV1 has superior compression and image quality compared to H.264 and H.265. So, if you’re looking for the best image quality without maxing out your bandwidth, this one is for you. All the details on how to take advantage of this feature are available in the documentation.


  • Automatic video codec selection: adding support for new codecs is great as it gives you the flexibility to support various platforms and the best possible user experience for your end users. On the other hand, the configuration to accommodate different codecs in your environment could be anything but straightforward. So we decided to simplify this for you and allow HDX to select the appropriate codec for the session automatically! So, in essence, you could consider this as ‘the easy’ button. Because we turn it on automatically, and you benefit from the added value that the new video codecs bring to the table without having to do anything. More details available in the documentation.
  • Adaptive refresh rate: image quality is important for a good user experience, but efficient resource utilization and scalability are critical for the long-term success of the solution. With this feature, HDX automatically adapts the session’s refresh rate to the optimal rate for that session to ensure resources are being used optimally. Take a look a the documentation for details.
  • Enhanced build-to-lossless: additional enhancements were made to our B2L functionality to ensure your 3D graphics use cases can get the pixel-perfect images they need. For more information, review the documentation.
  • Virtual display layout per monitor: virtual display layout has allowed many to make the most effective use of large screens by allowing them to divide the display into multiple virtual monitors. To provide even more flexibility, you can now customize the display layout of every monitor independently to obtain the custom layout that best works for you. Take a look at the virtual display layout documentation for details on how to use this feature.
  • Citrix Indirect Display Driver: Some of the most demanding use cases leverage the Citrix Indirect Display Driver (CitrixIDD) to ensure the best quality and response time in highly time-sensitive situations. To provide everyone with the greatest flexibility, compatibility, and graphics quality possible, CitrixIDD is now the default display driver used by HDX. Take a look at this blog post for a case study.

Endpoint Synchronization

Here are a few enhancements to help provide a local-like experience:

  • Audio volume synchronization: it is now a lot easier for users to set the volume to the desired level as the volume is synchronized between the client device and the VDA (in both directions), so they no longer have to manage volume levels in two different places.
  • Support for multiple audio devices: if your users are like me, they probably have at least two different audio devices available at any given time. They can now choose which one to use in their session if they want to use something other than the client’s default device. They can even use different devices with different applications inside the session!

Multimedia and Collaboration

Part of that local-like experience is the ability to use communication solutions, so we also worked on a few enhancements in this area:

  • Multiple webcam resolutions: all webcam resolutions are now supported when using your webcam inside the session! Take a look at High-definition webcam streaming for details.
  • Teams app sharing for custom apps: if you use Microsoft Teams as your unified communications solution and also use home-grown applications, such as Java-based applications, you can now share them in your Teams meetings when using optimized Teams. Check out App sharing for details.

Try it today!

As you can see, there is a lot waiting for you in the new Citrix Virtual Apps and Desktops 2402 LTSR. But keep in mind that this only covers the top HDX features and enhancements. I suggest you take a look at our documentation and review the “What’s New” section for all releases between your current LTSR version and Citrix Virtual Apps and Desktops 2402 LTSR for a comprehensive list of new features and enhancements across all areas.

If you have any questions or feedback, please feel free to drop us a line.

Disclaimer: This publication may include references to the planned testing, release and/or availability of Cloud Software Group, Inc. products and services. The information provided in this publication is for informational purposes only, its contents are subject to change without notice, and it should not be relied on in making a purchasing decision. The information is not a commitment, promise or legal obligation to deliver any material, code, or functionality. The development, release, and timing of any features or functionality described for products remains at the sole discretion of Cloud Software Group, Inc.

from Citrix Blogs

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