The display offset protocols are not lacking. Most VDI users use Citrix ICA or HDX, Microsoft RDP or RemoteFX, or VMware's Blast Extreme, or even Teradici's PCoIP.

Microsoft RDP

Microsoft's RDP is ubiquitous for Windows servers and workstations. Over time, it has grown considerably in maturity and supports: 32-bit color management, 128-bit encryption, audio redirection, file system redirection, printer redirection - as well as USB ports, in particular - or adjustment bandwidth.

Microsoft Terminal Services Client is part of the core offering of the Windows client operating system. Therefore, deploying a minimal remote access service is easy, including from macOS stations. FreeRDP extends the perimeter to Linux.

One of the main limitations of RDP in terms of virtual office experience is connectivity. If RDP recognizes that there has been no activity for 10 seconds, it reduces its bandwidth consumption by 50%, per design. This delay can be far too short and affect the user's experience by introducing waiting phases for full recovery of the connection.

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For the rest, RDP is quite capable of providing quality service in most cases.

Microsoft RemoteFX

RemoteFX is actually an evolution of RDP based on the acquisition of Calista Technologies by Microsoft in 2008. This protocol appeared with Server 2008 R2 SP1.

RemoteFX can transfer a virtualized instance of a physical GPU to a virtualized version of Windows 7, 8.1, and 10 when run on Hyper-V.

It is particularly useful for deployments involving graphics-intensive applications such as CAD or real-time video. RemoteFX is only available in Hyper-V environments.

Citrix ICA

Like RDP, ICA offers virtual channels that enhance basic protocol capabilities, allowing local folder redirection, USB redirection, or the use of terminal graphics processing resources to improve rendering and experience.

ICA can also degrade the display to accommodate low bandwidth or high latency. ICA is not dependent on a specific hypervisor, but XenServer is needed to unload CPU graphics processing on the GPU.

Citrix HDX

HDX is similar to RemoteFX in that it is about improving the virtualized desktop experience with reduced bandwidth and higher latency. Three technical principles underlie HDX.

Intelligent Redirection monitors on-screen activity, application commands, pointing device, and network and server functionality to instantly determine how and where to render an application or desktop action.

Client redirection unloads the server from certain tasks to perform on the client. With device redirection, connections to webcams, printers, and scanners can be terminated locally to allow users to interact with these devices at native USB speeds.

Adaptive compression defines the codecs used based on network conditions and determines the intelligent use of CPU and GPU resources.

Deduplication of network traffic enables HDX to support multicasting of media streams to avoid overloading bandwidth by multiplying distribution streams with the same content. HDX caching deduplicates data access, including bitmap graphics, files, print jobs, and streaming media.

HDX also recalculates processing using x264 protocol enhancements that make it easier to use GPUs installed on servers. HDX processes graphics at the source and deduplicates or compresses them before sending them to the customer, providing a better end-user experience.

Like ICA, HDX can use almost any hypervisor, except when it comes to offloading GPU-based processing: there, XenServer is needed.

Teradici PCoIP

Horizon View has a long-term relationship with Teradici and its PCoIP protocol. The first difference between PCoIP and RDP and ICA is that the protocol uses the User Datagram Protocol (UDP) to transfer data packets. UDP makes PCoIP faster than other protocols because it does not have to wait for the endpoint to confirm that it has received a packet, as is the case for TCP.

In deployments with high bandwidth and low latency, PCoIP provides a near-native virtual desktop experience through UDP. But on networks where this is not the case, problems can arise.

Teradici is trying to solve this problem by allowing PCoIP to reduce the amount of traffic that traverses the network using adaptive encoders. These are intelligent enough to push the threshold of occurrence of phenomena related to congestion.

The VMware PCoIP stack is not the full version. It is not necessary to install a Teradici card on the terminal to take advantage of it, as the ability to decode the PCoIP stream is integrated with the Horizon View client. But, installing such a card will improve performance.

PCoIP only works with the ESXi hypervisor.

VMware Blast Extreme

If PCoIP is going to significantly alter the performance, the users will not fail to notice. VMware's answer to this problem is Blast Extreme.

Originally based on HTML Access and called Blast, this protocol was very limited in functionality and based on a JPG / PNG codec that did not support very well video or graphics-intensive applications.

Introduced with Horizon 7, Blast Extreme is in functional parity with PCoIP and uses the H.264 codec for highly graphical content. Like PCoIP, Blast Extreme requires the ESXi hypervisor.