How Citrix HDX technologies to solve the challenge of providing softphones and UC applications from ' a virtual desktop or hosted applications? As with multimedia playback, we use two complementary approaches.
Our technology "generic" HDX live are designed for any softphone or UC application without the need to modify or hook into in any way. Our "optimized" HDX architecture in real time, however, moves the application of media processing workloads hosted itself to a multimedia engine running on the user device, thereby maximizing server scalability this reduces bandwidth consumption of the network and ensure no degradation of the audio-video quality.
Let's take a look more closely at each of these approaches and how they work together.
Generic HDX RealTime
With our technologies in real-time generic HDX, the audio output of softphone or UC application is stopped, the tablet using the Optimized-for-Speech codec and sent via the ICA protocol on the device of the user. There, Citrix Receiver decodes and towards the headphones or speakers of the user. Video output is rendered by the application on the server and detected by Adaptive Display, which recognizes the video regions by the frequency with which the screen is updated. Adaptive Display adjusts dynamically to the network,
select the compression level and frame rate combination that will provide the best possible user experience on the available bandwidth in the policy. Le Citrix Receiver decodes trafficking and composites in office.
In the other direction, the Citrix Receiver uses the Optimized-for-Speech codec to compress the audio input from the user's microphone. Webcam video compression is used if the user participates in a video conference to reduce the bandwidth required upstream, usually up to 300-0 Kbps.
The HDX audio subsystem was designed to ensure the compatibility of wide application. It manages the particulars of softphones, which can open the first audio device for ringer, then again to set the path of the voice. Audio Plug-n-Play allows the user to connect or disconnect their headset or other audio device at any time; it should not be connected when the user logs on. And Audio Device Routing enables users ringtone directly to their speakers, but their audio headset, if they like to remove their helmet between calls.
jitter buffer smooths the audio when there are changes in the network latency so it does not speed up and slow down because of packets arriving at inconsistent rates. While buffering a small amount of delay, which is more than offset by latency reductions that our engineers have achieved by carefully controlling the HDX audio stack. A further reduction of the audio latency is performed on XenDesktop and VDI-in-a-Box by selecting the UDP / RTP transport in the ICA protocol, since UDP is no requirement for packages to be recognized, which could introduce delays if the network is lossy (as the case might be with a wireless connection) or congested.
Quality-of-server (QoS) routing on the network also minimizes latency in the audio path. The ICA protocol used by HDX supports multiple data streams. By default, the audio traffic is assigned the highest priority flow. virtual channel priorities within a data stream also help. And there is support for marking packet, both DSCP marking for RTP packets (Layer 3 tagging) and also WMM marking for WiFi.
echo cancellation is important when using speakers and a microphone instead of a helmet, for example when in a private office or in a meeting room. This technology was improved last year to be more tolerant of variations in distance between the speakers and the microphone.
Our HDX technologies in real-time generics are able to offer a very good audio and video quality. Some customers said they are getting better sound quality than before with HDX with physical telephones. This may be due to modern codec technologies that we use.
When designing a desktop virtualization system for real-time communications, it is important to consider the impact these applications can have on server scalability. With softphones and voice
chat capabilities, it is essential to minimize latency in the audio path. If too much load is put on the server, an unacceptable delay may be introduced which may interfere with normal conversation. Generally, the number of simultaneous audio conversations that can be supported on a server is about half the number of typical users of office applications. This is particularly important to consider in a call center environment where all users can use their softphone at the same time. Similarly, a user CPU impact engaged in a video chat session is several times greater than that of a user running only of typical office applications.
Optimized HDX RealTime
approach to both Citrix shutters to provide softphone and UC applications to optimize server scalability and reduce the cost of desktop virtualization. The idea behind the HDX optimized architecture in real time is to unload the server for the most common usage scenarios and demanding, leveraging the power of the user's device processing whenever possible. This is analogous to the way we handle media playback; in addition to a set of generic technologies for video and audio playback, we provide solutions for Adobe Flash and Windows Optimized numerous media formats.
If you think about the software layers that make up a softphone or UC application, you can imagine a user interface layer on top, a certain logic in the middle, and down to the bottom a 'media engine "that handles signaling, encoding and decoding. the trick to unload the server for maximum scalability is to move the entire media processing to the user device. This implies moving the media at the end of the motor. the inter-process communication between the business logic layer and the media engine and must occur on the network on a virtual channel.
When you move the user media engine device, there is no longer any need for audio and video traffic to go through the Citrix server. instead, the peer-to traffic flow -Peer, directly between the two
parties to the conversation or each user to a conference server in case of a multiparty call. This results in significant additional benefits outside server scalability; the consumption of network bandwidth is greatly reduced, no latency is added and there is no degradation in the quality of audio-video.
The implementation of this architecture can be done in two ways. Ideally, the application vendor alter their softphone so that the media engine can operate separately from other software layers; Citrix facilitates this by providing APIs for signaling on the CIA and to properly position the video made locally on the virtual desktop. Otherwise, the application provider may provide mechanisms to allow a third party to modify the way voice and video calls are initiated and controlled.
Cisco was the first major unified communications provider to implement an optimized architecture for XenDesktop. Cisco VXI solution for Unified Communications Manager supports a variety of devices, including customer VXC 6215 thin based on Linux, the VXC 2112 phone "backpack" (zero client) and the VXC 4000 software appliance Windows PC's. All these offers eliminate "hairpinning" and maximize scalability XenDesktop server by running the media engine on the endpoint.
Another very popular application used by Unified Communications Citrix customers today is Microsoft Lync. Citrix recently introduced an optimization pack for Microsoft Lync 2010 is currently available with XenDesktop 5.6 Feature Pack 1 and XenApp 6.5 Feature Pack 1. The optimization pack consists of two components. The HDX connector for Lync is installed alongside the Lync hosted customer to redirect the call initiation requests and other signals on an ICA virtual channel to the second component, the HDX RealTime Media Engine, a Citrix plug-in Receiver. Besides codecs Lync owners under license from Microsoft (ie, RT Audio and Video RT), the HDX RealTime Media Engine includes a variety of standard industry codecs such as H.264 and H.263 various flavors to facilitate interoperability with other products (for example, in parts of videoconferencing systems). The optimization pack for Lync does not require any modification of the existing Lync infrastructure such as Lync Server Front-End, Lync Audio / Video Conferencing Server and Lync Edge Server.
Avaya has long supported Citrix XenApp customers with unified communications and contact center solutions that allow the soft client to share control with an office phone. Communicator new VDI solution optimized for XenDesktop Avaya and thin clients ensures uncompromised voice quality
with treatment of local media and enables large scale deployments, while reducing capital expenses and total cost of ownership .
In short, the objective of Citrix is partnering with major UC vendors in the market to create optimization packs that will have the greatest benefit for our desktop virtualization customers. We regularly check with our customers to identify applications and devices are the most popular since the optimization of these will have the greatest positive impact on server scalability and user experience. We also continue to improve our technology in real-time generic HDX so users are never in a position where Citrix can not deliver the application they need right now. Generic and optimized technologies are designed to work together; for example, a user can at any time access Microsoft Lync from a device that supports the HDX optimized architecture, then get on a Cisco WebEx or Adobe Connect videoconferencing using our technologies in real-time generic HDX.
The net result is that HDX allows people to work from anywhere, on any device, using voice and video chat features they need for effective communications.
Derek Thorslund
Director of product management, HDX
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