Users expect a real-time response from the apps they are working with, both when they connect from reliable corporate networks (LANs) and when coming in over challenging wide area networks (WANs), such as 3G/4G/LTE mobile networks and satellite links that are typically low-bandwidth, high-latency and/or high packet-loss. HDX technologies, included with XenApp and XenDesktop, address these scenarios to ensure the best possible user experience at all times.
Over the past 25 years, the Independent Computing Architecture (ICA) standard developed by Citrix has become the de-facto protocol for highly-efficient delivery of app and desktop workloads across a wide variety of conditions and connection scenarios. HDX technologies extend the ICA protocol to satisfy modern demands for rich media apps, and leverage innovations in endpoint computing power to deliver a “high-definition” experience. This whitepaper provides an overview of HDX capabilities and their benefits for both end-users and IT administrators.
HDX technologies offer a set of capabilities that deliver a “high-definition” experience to users of centralized applications and desktops, on any device and over any network. HDX technologies are built on top of the ICA remoting protocol, proven in large enterprise environments and accessed by millions of users globally.
Simply put, HDX is designed around three technical principles – intelligent redirection, adaptive compression, and data de-duplication – which are applied in different combinations to meet one or more of these business goals:
Intelligent redirection determines which component in the chain, whether server, endpoint, network, or something else, could render application activity to meet the three design principles. HDX examines screen activity, application commands, network conditions, and capabilities of endpoint device and server to decide the optimal redirection.
Adaptive compression is a core intellectual property of the ICA protocol which allows rich multimedia display to be delivered on thin network connections. HDX chooses the most optimal compression codec and the best proportion of CPU and/or GPU utilization, after evaluating a number of variables such as the type of display (text, video, voice, multimedia), the type of input, the type of device (smartphone, tablet, desktop), network conditions, and so on. This is intelligently adapted per user, or even per-session, as necessary.
De-duplication of network traffic reduces the aggregate data sent between client and server by taking advantage of repeated patterns in commonly accessed data such as bitmap graphics, documents, print jobs and streamed media. Caching these patterns allows only changes to be transmitted across the network, eliminating duplicate traffic. HDX also supports multicasting of multimedia streams, where a single transmission from the source is viewed by multiple “subscribers” at one location, rather than one-to-one connections for each user.
Figure 1: HDX is far more than just a protocol
Users expect app and desktop delivery solutions to have “real time” audio and multimedia characteristics similar to what they receive from local app and desktop implementations. HDX technologies deliver bandwidth-efficient, crystal-clear voice, multimedia and video and are refined through the use of policies and templates.
Ever-increasing use-cases in verticals such as medical, manufacturing and finance require high-resolution displays and/or setups with more than one monitor. XenApp and XenDesktop have extensive support for these scenarios by leveraging underlying graphics hardware capabilities along with HDX technologies for crisp, detailed images, smooth video and clear text.
HDX 3D Pro is a specialized technology that pioneered the use of graphics processors (GPUs) in virtual apps and desktops. Today, there are virtualization-aware GPU cards available, which provide hardware acceleration to multiple virtual machines (VMs) using a single physical GPU. Originally designed for high-end 3D professional graphics, the technology is now available to optimize the performance of business graphics apps that leverage GPU acceleration, such as web browsers and Office apps.
HDX supports business graphics acceleration through the use of a software rasterizer to render Microsoft DirectX using a CPU or GPU if available. On Microsoft endpoints, DirectX graphics command redirection offloads Windows desktop composition from the server for greater scalability and enhanced user experience.
Modern business apps, whether Microsoft Office apps or Web browsers, are often designed to leverage graphics processors. HDX technologies support multiple GPU vendors to deliver cost-effective graphics performance using GPU sharing on different platforms, such as Citrix XenServer, VMware vSphere, or bare metal. Depending on the workload, up to 150-200 users may benefit from accelerated business graphics delivered from a single server.
Citrix developed the first virtualization solution to support hardware-based GPU sharing of OpenGL and DirectX-based 3D professional graphics apps. This led to hardware acceleration of graphics commands for achieving smooth graphics performance, and breakthrough deep compression technologies for maximizing traffic throughput over low-bandwidth networks. The parameters can be tuned all the way up to lossless compression that enables delivery of pixel-perfect images for applications such as medical imaging.
Some 3D professional graphics apps that benefit from HDX 3D Pro:
HDX 3D Pro allows you to provision a GPU to users in a flexible manner. To support designers and engineers who require dedicated graphics performance, provision one virtual GPU per user or VM using XenDesktop, on either XenServer or VMware vSphere. For more cost-effective deployments, provision many users to share a GPU to view and edit 3D models – as many as 64 users per VM per server – depending on the workflows and demands. In all cases, the latest drivers and codec versions supported by GPU vendors are available to the user.
HDX Mobile improves the experience of Citrix Receiver users working in supported Windows applications and server-based desktops on mobile devices. HDX includes a native interface control channel allowing Windows apps to be re-factored for a touch experience while leveraging device features such as multi- touch gestures, native menu controls, camera and GPS device functions. Many touch features are available natively in XenApp and XenDesktop and do not require any application source code changes to activate. Native touch features include:
Additional capabilities can be implemented using the HDX Windows Mobile Application SDK. It enables enterprise developers to update Windows applications just once for mobile devices using familiar Windows programming languages. The SDK includes more than 50 APIs. Following are examples of programmable mobility enhancements:
Citrix provides an SDK to system-on-chip (SoC) vendors that enables compute-intensive HDX algorithms to execute outboard from the CPU, allowing inexpensive processor-based devices to deliver a high-definition user experience. Device manufacturers using these SoCs have now brought to market a broad portfolio of low-cost HDX Ready thin clients, zero clients and other products. Unlike competing solutions that burn the remoting protocol into silicon, which can result in device obsolescence within months, the Citrix approach supports ongoing innovation without hardware replacement. Get the latest information on HDX SoC thin clients available from HP, Dell/Wyse, NComputing and others.
Citrix supports both local and network printing. Local printing entails redirecting and terminating the printer locally to allow the user to interact with it at native speeds. Network-based printing is supported using Citrix Universal Print Server and Universal Print Driver technologies.
Citrix developed these print driver and print server technologies from the ground up for network printing. They provide many of the features needed for daily printing while taking into consideration the amount of bandwidth a print job requires. Using a single driver to manage hundreds or thousands of printers also simplifies management of print drivers in the XenApp/XenDesktop environment. With the Universal Print Server, the print engine is moved to a Windows print server which prevents the need to install device-specific drivers in the machine image. Firewall-friendly printing protocols provide greater bandwidth efficiency than native Windows protocols and extend printing to non-Windows devices. The latest Universal Print Server also provides improved scalability, greater OS-support and performance monitoring. Additionally, it integrates with Citrix’s Customer Experience Improvement Program (CEIP) to continually help make the product better.
NetScaler SD-WAN branch caching analyzes commonly used data such as file header and footer content and company logos, and caches the content locally on the print server for retrieval by users without resending the data for each print job.
Although scanners can be supported through basic USB direction, the Citrix implementation permits additional intelligence between the endpoint and the host. Local scanner termination allows the user to interact with the peripheral at native USB speeds. Once the scan is completed, ICA compresses the scanned image and sends it to the host server; thus, the only content that travels over the network is a compressed image.
HDX provides seamless plug-and-play connectivity for a broad range of devices such as webcams, music players, audio recorders and specialty peripherals. USB redirection to cloud makes these peripherals available within sessions hosted hundreds of miles away from the point of use. HDX technologies optimize USB traffic over common wide area network conditions to ensure real-time feedback and full-feature support. Support for digital pens, electronic signature pads, and drawing tablets in cloud-hosted apps is an important requirement in retail, finance, design, CAD and other such markets.
HDX technologies ensure the highest quality of service and reliability through a combination of ICA traffic prioritization, branch office caching and ICA protocol optimizations.
Virtual app and desktop traffic competes with everything else on a network. To meet stringent service level agreements (SLAs), network administrators need tools that help prioritize and optimize application and desktop traffic to deliver a great user experience every day. HDX traffic prioritization capabilities include:
WAN optimized branch caching is accomplished by NetScaler SD-WAN with integrated HDX caching technology to provide groundbreaking multi- user optimization for virtual desktops and applications. Organizations can get more from their existing network infrastructure while providing a high-definition experience to branch office workers.
HDX caching technology adaptively orchestrates with XenApp and XenDesktop to disable the native ICA compression used for optimizing single-user sessions. It then optimizes XenApp and XenDesktop delivery across multiple user sessions by locally caching and de-duplicating transmission of commonly accessed data, including bitmap graphics, files, print jobs and streamed media. Branch caching for hosted apps and desktops occurs transparently, requiring no additional configuration or tuning on the NetScaler SD-WAN appliance or the XenApp/XenDesktop server.
ICA protocol optimizations include TCP flow control, traffic compression and protocol acceleration.
Improved overall diagnostics with new telemetry functionality is available on virtual desktops to assist with troubleshooting. This capability also leverages the Citrix Insight Services platform for centralized management of environmental health along with tight integration to Citrix Technical Support.
Pre-defined HDX policy templates make it easy to ensure that users receive the best possible experience for their connection scenario while also meeting IT objectives. Templates for high server scalability, bandwidth-constrained WAN users, security and control, and a high-definition experience are included.
HDX technologies are the foundation of the Citrix apps and desktop delivery platform, which provides a superior virtual app and desktop solution accessible from any device, over any network and gives end users an application and desktop experience that rivals that of a local PC—even when people are using multimedia, real-time collaboration, USB peripherals and 3D graphics apps over low-bandwidth, high-latency networks. With XenApp and XenDesktop and HDX technologies, IT can successfully extend delivery of virtual apps and desktops beyond the corporate HQ to remote, mobile and branch office users.