Compare Citrix, VMware and Microsoft remote display protocol options

Citrix ICA and HDX protocols

Citrix started the whole remote display protocol industry with its independent computing architecture, or ICA protocol. Citrix more recently put a vast amount of development effort into transforming ICA into the HDX protocol -- which is a group of several remote display technologies that work together -- used in XenDesktop and XenApp since 2009.

The wild card is the recent rise of clientless HTML5 access to corporate resources.

In the early days, the only way to get good USB redirection, Windows multi-monitor support or video playback was by using third-party software. But over the years, Citrix has continuously made improvements to ICA/HDX to turn it into a modern remote display protocol. There are no significant features missing from HDX.

Additionally, Citrix HDX includes technologies that focus on specific aspects of remote desktop and application delivery. For example, HDX 3D Pro helps IT deliver a quality user experience for employees using remote 3D or other resource-intensive applications. Another HDX subgroup, HDX Mobile, improves the user experience when accessing Windows apps and virtual desktops on mobile devices.

VMware Blast protocol and PCoIP

VMware signed a license agreement with Teradici in 2008 to use the PC-over-IP (PCoIP) protocol in its Horizon end-user computing suite. Teradici has a long engineering history in remote graphics delivery, which is why PCoIP has always supported USB redirection, video playback and multi-monitor well. PCoIP was originally designed for hardware clients, so it did not originally support client printers or disk drives on the client. However, over the past eight years VMware and Teradici have co-developed a lot of enhancements to PCoIP to keep pace with Citrix HDX and Microsoft RemoteFX. Not all of these features are available to other PCoIP licensees. For example, the AWS WorkSpaces DaaS offering only includes basic PCoIP protocol.

The VMware-PCoIP alliance might not last forever, though. VMware introduced its own protocol, Blast Extreme, in Horizon 7. VMware designed Blast protocol to support virtual desktops and applications on mobile devices, basing it off its preexisting HTML Access protocol and H.264 compression, which nearly all smartphones and tablets support. IT can now choose between using the VMware Blast protocol or PCoIP, but VMware says there are no feature gaps between the two.

Microsoft RDP and RemoteFX

Microsoft originally developed Remote Desktop Protocol (RDP) to coincide with the release of Terminal Services -- now named Remote Desktop Services -- back in 1996 with Windows NT 4.0 Server, Terminal Server Edition. Since then, Microsoft has enhanced RDP in every major Windows release.

However, a lot of the recent enhancements in RDP are considered part of Microsoft RemoteFX, which the company released in the Windows Server 2008 R2 Service Pack 1 in 2009. Similar to how Citrix HDX works with ICA, Microsoft RemoteFX is a group of technologies that enhance the performance of RDP. That includes features such as support for multi-touch, hardware-based graphics acceleration using GPUs and better USB redirection support. Although RDP is an older remote display protocol, the features RemoteFX add to it make RDP a perfectly acceptable protocol that generally matches the performance of the Citrix and VMware competition.

There are a number of other remote display protocols out there, but the vast majority of VDI and DaaS shops use these ones. The wild card is the recent rise of clientless HTML5 access to corporate resources. Now every VDI or DaaS vendor is working to support the same client -- an HTML5 browser -- and must reengineer their feature sets for a universal client. Clientless HTML5 access is a trend that bears watching, but when choosing between Citrix, VMware and Microsoft's remote display protocols, it's hard to go wrong with any of them.