Perhaps this should be in General, but I figured someone who knows the answer to this question might actually frequent this particular forum.

From what I understand from reading all of Citrix's documentation:

HDx 3Dpro is a high speed protocol for virtual desktop & app delivery. It sets up a mirror driver on the Windows host, just as Real VNC Server (though not eg tightVNC) does. You can run that host as a VM under XenServer (or some other Linux), or of course it can be a physical machine. You can then get compressed OpenGL and DirectX using the newer Citrix Receiver on the client, which of course can also be Linux. Sort of like an better version of VNC. Apparently Microsoft's RemoteFX is similar, though that's a Windows Server only deal.

But the question is, apparently you also need a Windows Server running XenDesktop (XenDesktop apparently only runs on Windows Server, not XenServer) acting as a Delivery Controller on a third machine: What, exactly, is the Delivery Controller on that third machine doing? Seems like a shame to have Windows desktop delivery with Linux serving and Linux receiving but still need a separate Windows Server to.. bless the transaction? Plus, I'd think that involving another machine would slow the whole transaction down.

We'll skip over the part where you also need an Active Directory server on the network.

What am I missing here? Does anyone know how exactly these Xen-things are working together? Better yet, is there any Linux only equivalent to Hdx 3Dpro and Remotefx?