I read in Wikipedia that XenApp is based on GDI commands sent over the network instead of based on images sent over the network like VNC does; does XenApp use less network traffic then Terminal Server?

I ask because when our users use the VPN to connect via RDP to our Terminal Server, they get kicked off a lot, but when they use Citrix, I hear no such complaints.

  • I am confused about how Citrix relates to your VPN. What VPN are you using, and why would that have anything to do with XenApp? You then mention 'terminal server', that is not a protocol, that is a generic name for a particular technology, are you talking about RDP? – Zoredache Jan 3 '13 at 1:14
  • Yes, clients use the RDP to connect to Terminal server don't they? – leeand00 Jan 3 '13 at 14:37
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    I think this question should be re-opened. Citrix and RDP are very similar, but there are definitely differences, especially when it comes to latency and unstable connections, which Citrix (ICA) is able to handle better, as well as many options on how to handle those types of connections. – KJ-SRS Jan 3 '13 at 16:14
  • @KJ-RSR Thank you, and please click the reopen button. – leeand00 Jan 3 '13 at 17:09
  • Please clean up body of the question some more. "Citrix" is the name of a company, not a piece of software. Did you mean Citrix Xenapp? Link to the Wikipedia article you mentioned. – Stefan Lasiewski Jan 3 '13 at 20:05

Simple answer is "Yes." The ICA protocol was developed when dial-up was a very common internet connection : if you tuned it properly, you could fit a single ICA connection into about 8-10 kbps. You can add, remove, and rate-limit all the channels for things like file transfers, sound mapping, removable devices, etc.

RDP is a lot like ICA but not quite as configurable.

VNC is a remote framebuffer - in its original iteration, it was a think-tank project for an ATM LAN, when 155 Mbps was insanely good. Nowadays, many flavors of VNC have lots of different compression options, so it's better than it was.

  • To add to this: Only with Server 2012 RemoteFx is Microsoft acknowledging "WAN Scenarios" for rich RDP sessions (with lot of animations). Before that it is "hit the bandwidth". – TomTom Jan 4 '13 at 22:19

XenApp should use roughly the same bandwidth as Terminal Server and less bandwidth than VNC. XenApp and Terminal Server use the concept of a "remote HDC" which as you say, sends GDI drawing commands. VNC is a remote bitmap display so the traffic is pixels.

From the Citrix XenApp Wikipedia article:

XenApp is built on top of the Windows Terminal Server platform which was originally developed by Citrix in the early-mid 90s

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