ICA protocol limitations in Citrix XenDesktop 3: What's there, what's still missing?

Citrix's ICA protocol (and related acceleration technologies, like SpeedScreen) have been around for over a decade. Even though not too many people focus on the value of ICA anymore, its value becomes immediately apparent to anyone who switches back to RDP after using ICA for awhile.

Citrix's ICA protocol (and related acceleration technologies, like SpeedScreen) have been around for over a decade. Even though not too many people focus on the value of ICA anymore, its value becomes immediately apparent to anyone who switches back to RDP after using ICA for awhile. So when Citrix announced their XenDesktop product last May, a lot of us were excited because we could use ICA for a VDI product.

Unfortunately, we quickly learned that the capabilities of the ICA protocol implementation in XenDesktop were not as fully-featured as the capabilities in Presentation Server / XenApp. (I called this "Partial ICA") It was ironic, because moving to XenDesktop is kind of an all-or-nothing thing, yet the experience was worse than using XenApp, which could be used for just certain applications as needed.

Citrix announced XenDesktop 3 yesterday, and one of the big parts of the announcements was some additional capabilities of the ICA protocol that will bring ICA on XenDesktop more in line with ICA on XenApp. I asked Citrix's Calvin Hsu to clarify exactly what was and was not included with ICA in XenDesktop 3.

The first clarification that Calvin wanted to make was that ICA on XenDesktop 2 wasn't "limited" per se, it's just that Citrix didn't have time to implement all of the features that are in XenApp. In other words, ICA is ICA... it's all the same "version." But XenDesktop 2 didn't have all of the host side code written yet to do as much as XenApp 5.

That said, let's take a look at the specific limitations capabilities of ICA that were not included in the XenDesktop 2 product. (This list is pasted directly from Citrix's official XenDesktop 2 Technical FAQ.)

  • Kerberos SSPI or SmartCard Virtual Channels
  • SpeedScreen multimedia acceleration & zero latency
  • PDA sync, TWAIN, shadowing and SmartAuditor
  • Audio on Vista
  • ICA perfmon counters (SMC) and end-user experience metrics

Let's break this down into two lists, to look at what's there and what's not.

New capabilities of ICA in XenDesktop 3

  • SpeedScreen multimedia acceleration (which is now called HDX MediaStream)
  • Smartcard virtual channels
  • PDA sync and TWAIN (both covered by the new, broad support for USB devices called HDX Plug-n-Play, which actually supports more than devices than on XenApp now)
  • ICA perfmon counters (SMC) and end-user experience metrics. Perfmon counters can be consumed by any software running on the Virtual Desktop Agent.

ICA limitations / missing features in XenDesktop 3

  • Kerberos SSPI
  • SpeedScreen local text echo. (Instant mouse click feedback is a client side feature and has always been available.)
  • Shadowing
  • SmartAuditor
  • Audio on Vista (this is coming soon)
  • EdgeSight agent to consume the Citrix-specific metrics, like SMC and end user experience. (Although EdgeSight can now track the other usual historical metrics for pooled / non-persistent desktops.

Thanks to Calvin for taking the time to make these clarifications!

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I just want to add that I hope it's clear we are prioritizing these feature developments to deliver on our "high definition user experience" strategy (www.citrix.com/hdx for more details on our HDX announcement - it's much broader set of technologies than what technically makes up the protocol itself).


Do you think Citrix leaves shadowing out intentionally?  As I understand it, if you want shadowing you need to go to XenDesktop Platinum to get the GoToMyPC and use that feature as a shadowing solution.

I don't think we'll ever see shadowing in XenDesktop as long as Citrix can squeeze a couple extra bucks out of its customers for it....


I am pretty sure at some point you will see shadowing. Citrix is trying to get features out as quickly as possible to meet the market need. I am sure its on the list.

You also should keep in mind that while yes, Citrix is supporting these desktops with GotoAssist, you can put whatever VNC client you wanted to on these desktops instead. They arent locking you into using GoToAssist, rather offering this as value add in the platinum packaging.

I would not be surprised at all if Citrix just came up with a simple VNC client that they build into the XD receiver software, or just license someone elses VNC for this functionality.


XenDesktop include GoToAssist in some edition that could remove the need for the Shadowing features....


Have they changed the requirements for the gotoassist account?

With 2.x I believe it was only available for > 250 licenses of platinum.

Currently I am recommending VNC for my client deployments.  It's free.  Can be pre-setup in the image.  And in most cases something they are using already.


a) There's nothing sinister about the gotoassist and shadowing situation - I know most here don't trust us marketing types, but I offer that for what it's worth.

b) I think there's a lot of confusion about GoToAssist and how it's licensed and what it offers... and in particular, why we offer it with your active subscription advantage of >200 XD platinums. I've attempted to explain it here:



It appears the marketing department is busy at Citrix.

Lots of fluff, no real value add for the customer in terms of products that make a difference in everyday life of the user!



No real value?  I do not agree.

Firstly the assumptions being made here are that it is simple to port ICA over to XP/Vista from a Server environment.  Features such as shadowing, MultiMedia etc has to be somewhat re-engineered to work on XP and seeing as Citrix have bought these out in XD 3 is very good.  I remember working on XD 2 Beta which was in March/April last year from memory I was hoping these features would come out.  Within a year they are here so I think that is a big plus.  Furthermore they have not just ported over the abilities XenApp bought with it but have improved it in the process.

And Edgesight for endpoints, this is huge and required allot of work to get the client on XD with PVS to work, and they are still working on it.  Edgesight is a very valuable product.

In relation to GoToAssist, it comes as part of a license, not separately.  It is just an option for people, that is all.

That is my 2 cents anyway :)


An item that I find useful is ease of access to information relating to the endpoint device.  The ability in XenApp to collect endpoint clientname and clientIP information is valuable from a services/security context.  There is not ability within XenApp to collect clientname or clientIP.

Within the IIS logs of the WI you can collect the client IP, but with regard to session services management within the environment, running Query on any console environment associated with the XD environment offers you info on the admin console session, and that's it.

Endpoint identity!  May we please get some endpoint identity available without applying that PowerFuse script that is being passed around, or leveraging the arcane .exes also being passed?  Thanks.