Citrix’s HDX technologies for delivering a high definition user experience have been a big factor in XenDesktop’s rise to first place in the desktop and application virtualization market. With today’s release of XenDesktop 5.5, including XenApp 6.5 and Citrix Receiver 3.0 for Windows, HDX is even better. We’ve worked hard to address more challenging network conditions such as limited bandwidth, high latency, jitter, congestion and packet loss. We’ve improved the responsiveness and fidelity of the Windows 7 desktop experience. And we’ve continued to find ways of better leveraging the capabilities of the user device when possible, which not only improves user experience but also reduces server costs.

We’ll publish a series of blog posts in the weeks ahead to give you more detail on these new HDX capabilities, but let’s start with an overview.

Bandwidth Efficiency

Remarkably, XenDesktop 5.5 dramatically reduces bandwidth consumption while delivering a higher fidelity desktop experience and optimizing server scalability. That’s a triple win that’s seldom seen in our industry, since improved bandwidth efficiency usually implies lossier compression or a processing penalty on the server. XenDesktop 5.5 (including XenApp 6.5) and Citrix Receiver 3.0 achieve this extraordinary feat through improved leverage of the user device for rendering of graphics commands commonly used in business applications.

We ran the Login VSI version 3 Medium Multimedia Workload, representative of a typical office worker using apps such as Word, PowerPoint and Outlook, scrolling through pdf files, and watching videos. We measured a whopping 30% reduction in bandwidth consumption! That’s great news for all of our customers with branch offices and bandwidth-constrained network connections.

Smoother Audio

Smooth audio is critical whether the use case is real-time “voice chat” (VoIP) or watching a video. We’ve done a lot in this release to ensure that audio stays smooth even under difficult network conditions or when the user has a lot of applications running at the same time. This is a big topic so I’ll save the details for another blog post. But I can tell you that the feedback from customers participating in our Early Release program has been ebullient.

Better Video Performance

This is another big topic, but here are a few highlights. First of all, for the VDI FlexCast model, XenDesktop 5.5 introduces Adaptive Display, the successor to Progressive Display. No more complex configuration of policies to tweak image quality for different network scenarios. Adaptive Display is self-tuning, optimizing video frame rate and compression level dynamically, while ensuring that other regions of the screen remain crisp and clear. Secondly, we’ve extended our unique Flash Redirection technology to WAN-connected users by abstracting the protocol between the Adobe Flash Player and Internet Explorer. That means the server scalability benefits of leveraging the user device for video rendering are now applicable in many more cases, further reducing TCO. And thirdly, we’ve improved Windows Media Redirection so that it can even address situations where the available bandwidth is less than the bitrate of the video.

Windows 7 Aero

XenDesktop 5.5, under the VDI FlexCast model, introduces two innovative solutions for delivering the full Windows 7 Aero experience, including Flip 3D, Aero Peek, glass effects and more. If the user is on a “rich client”, that is, a Windows device with a fast CPU and an Aero-capable graphics processor, Aero Redirection can leverage those capabilities for local rendering. This is accomplished by sending the DirectX graphics commands over ICA to the GPU or IGP on the user device. Alternatively, Aero can be rendered server-side using Microsoft’s RemoteFX technology for Hyper‑V and delivered even to relatively low-end thin clients.

3D Graphics

This is another huge topic. Even if rendering on the CPU is adequate for the applications you need to deliver, you’ll notice meaningful improvements in this release, especially with Adaptive Display.  And it gets even more interesting when you factor in the Multi-GPU Passthrough capabilities coming in XenServer 6. With multiple graphics cards in your XenDesktop (VDI) or XenApp server, the cost per user of delivering high-end 3D graphics is substantially reduced. And we’re seeing smoking performance!

Derek Thorslund
Citrix Product Strategist, HDX