The differences between Microsoft RemoteFX and Citrix HDX

Now that Windows 7 and Windows Server 2008 R2 Service Pack 1 are shipping, Microsoft's RemoteFX enhancements to RDP are available to everyone,

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giving Microsoft a protocol that seems to compete against partner Citrix's HDX. But in reality, the two protocols are distinctly different.

If you're not familiar with RemoteFX, check out this article on its capabilities and requirements. It's a significant enhancement to Remote Desktop Protocol (RDP), so people are starting to wonder how it will affect Citrix. After all, Microsoft and Citrix are great partners, right? What if RemoteFX competes with HDX? Let's dig into that a bit more.

First, it's important to know that RemoteFX is not a standalone protocol -- it's an enhancement to RDP. So asking how RemoteFX compares with HDX is not technically correct. Instead, we need to consider how RDP with the RemoteFX enhancement compares with Citrix HDX.

The biggest difference between RDP with RemoteFX and Citrix HDX is that Microsoft is supporting only RemoteFX connections from clients running Windows 7 SP1, Windows 7 or WES9 Embedded, or dedicated thin clients. So there will be no RemoteFX connects from Macs, Androids, iPhones, iPads, or Windows XP or Vista clients. But Citrix HDX works on all of these.

Also, RemoteFX is a LAN-only feature, so not only do you need a very specific client to use it, but you must also connect to a RemoteFX host that's on your same high-speed LAN. Citrix HDX, of course, works great on the WAN. (Microsoft RDP without RemoteFX can also work across the WAN, though not as well as HDX.)

All that said, remember that Citrix and Microsoft are partners, and Citrix will also get access to the RemoteFX code. In other words, Citrix will support RemoteFX for HDX connections. This makes sense. Since RemoteFX is just an add-on to RDP, Citrix can add it on to HDX just as easily.

And I've written for years that the value-add of Citrix is much more than just the protocol. Microsoft's addition of RemoteFX to RDP isn't going to start a mass exodus of users away from Citrix.

So the problem for Citrix is not that RDP is getting better than HDX, since HDX still has many, many advantages over RDP with RemoteFX. Actually, the problem for Citrix is that for virtual desktop infrastructure (VDI), RemoteFX works only when the virtual machine host is Hyper-V. This means that if you want to use RemoteFX for your Citrix XenDesktop environment, you can only do so if your desktops are running on Hyper-V.

So what? It's interesting because Citrix has its own hypervisor, XenServer, and has been working on its own hypervisor-based virtual desktop enhancement features that require XenServer. Citrix IntelliCache is one example of this. So now how does Citrix recommend a hypervisor? How do you pick? Can you mix and match?

The other noteworthy thing about Citrix and RemoteFX is that historically, Citrix has enabled additional client platforms to connect to Microsoft Terminal Server environments. (Microsoft provides RDP clients for Windows and Mac, and Citrix provides HDX clients for Windows, Mac, Linux, Blackberry, iOS, Android, Sun, DOS -- the list goes on.) So you'd assume that Citrix will extend RemoteFX to these other clients as well. Unfortunately, that's not the case, at least not initially. When asked about using RemoteFX on other Citrix clients, Citrix responded:

As noted in the press release announcing the RemoteFX collaboration with Microsoft, Citrix and Microsoft are working towards a longer term vision that will extend the capabilities of RemoteFX to a broader range of devices, locations and use cases. So although the initial focus will be on Windows 7 based devices, our goal is to support a wide range of devices in the future

OK, so what about Citrix XenApp? We know that Microsoft also supports a non-GPU-accelerated version of RemoteFX running on Remote Desktop Session Host (formerly known as “Terminal Services”), and that's what Citrix XenApp is based on. Will Citrix allow HDX connections enhanced with RemoteFX to XenApp servers? Again, the company's response:

Per a blog post from Harry Labana, we're focusing on XenDesktop VDI as our integration platform for RemoteFX. We're not making any statements about XenApp support for RemoteFX, one way or the other, at this time.

So I guess that's that? RemoteFX is a neat idea but not very usable in the real world yet. Ordinarily, we look to Citrix to add full usability to the marginal stuff that Microsoft releases, but in this case, no dice. (At least not yet.) So I guess we'll just have to wait and see what happens next.

Brian Madden is an independent industry analyst and blogger, known throughout the world as an opinionated, supertechnical desktop virtualization expert. He has written several books and more than 1,000 articles about desktop and application virtualization. Madden's blog,, receives millions of visitors per year and is a leading source for conversation, debate and discourse about the application and desktop virtualization industry. He is also the creator of BriForum, the premier independent application delivery technical conference.

This was first published in March 2011

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