Citrix XenApp 6.0 and Slow WAN Performance

Wait! Why even bother with slow performance issues in XenApp 6.0? XA 6.0 was released ages ago in like 2010, and XA 6.5 in 2011… Dog years and tech years are almost about the same, haha! So just update and deal with whatever issues you have in the latest version… Sound familiar? Yeah, but in the end, in large companies and corporations it’s not that easy with upgrades because dev/test phases take time, securing dependencies etc. as well as rolling out the upgrades and new solutions.

I’ve held of this post for over a year, almost two, but now I am on vacation and had some time over! Working on my vacation *grin*. Well, some time over and that I realize that even though there are things like EOM, EOL, ( and the, to me at least, very funny EOES – End of Extended Support, there are still a lot of Citrix customers stuck on XenApp 6.0. (I think it’s funny because I am just waiting for the acronym EOPES – End of Prolonged Extended Support).

Enough rambling! Citrix, and namely Dan Allen, said “Don’t forget to turn on Progressive Display . So Progressive Display is turned off by default?! To worsen the issue that this blog post is all about, “Slow WAN Performance”, the other really great Citrix ICA graphical compression technique/algorithm called Lossy Compression is often turned off as well! In most cases (my field experience) it’s turned off, not always, but because during XenApp proof of concepts and pilot tests some LAN users complained about the graphical experience and that it looks blurry here and there, it’s been disabled. (Blurriness is more visible due to Desktop Experience usually enabled and Win7 look and feel themes activated with gradients and animations instead of the actual Windows Server 2008 R2 default theme which looks more like the good old Windows Server 2003 desktop and doesn’t reveal these graphical compression as much).

What happens is the good Citrix technician turns off Lossy Compression, i.e. sets it to “None”. The test/pilot users are happy with “pixel perfect” Citrix user sessions and most importantly the PoC or Pilot is approved and the XA 6.0 solution is rolled out! Well, was rolled out somewhere around 2010/2011 at least. But the consequences are huge for the global Citrix XenApp farm once in production state. The WAN links are congested and Citrix is to blame. If the customer ran Metaframe/Presentation Server, they will see a huge increase in bandwidth utilization going to XenApp 6.0 with this kind of setup.

At my latest customer, I flagged about this when I started. But they were still – in late 2012 – running Internet Explorer 8 due to Intranet sites, fat client standards and compatibility issues etc. So, Citrix said in the aforementioned blog post, turn on Progressive Compression. But in the production environments heeding this advice, people started to get a lot of flickering in IE8. Oops! Turn it off quickly and never re-evaluate that setting again. Well, it’s possible to disable Off Screen Surfaces (since limited hotfixes and the latest Hotfix Rollup Pack 2 – no. 53 Fixes from Previously…) to get rid of that messy flickering issue in IE8, but this latest customer of ours updated to IE9 that doesn’t have this flickering issue.

Even so, it took me some months after that IE upgrade to argument with the customer (because they had tested themselves, bandwidth savings weren’t that great, marketing bs etc. plus they experienced the flickering issue as well.) but once we took the time to test the end user experience with a WAN simulator and capped bandwidth of 1 Mbit, they realized that by simply setting Lossy Compression to Low and Progressive Compression to Medium, the end user experience went to quite responsive and usable from, well frankly, laggy and slow as hell… (because most sites for this customer doesn’t have this amount of bandwidth for the whole site yet alone a single user). Enough testing, that would be the baseline for all users;


Whilst optimizing for the low bandwidth situation was an easy “win”, another benefit that the customer would get that we would show with hard facts was the bigger sites with much more bandwidth but also much more graphic intensive so called “knowledge worker”. These sites have 1/2/10/20/45 Mbit, you name it, and a handful of (Citrix) users could congest these links… Yikes!

Optimizations in place! The result speaks for itself;


Mondays and Tuesdays are the worst, but you can probably guess from where in time the “Lossy Compression: Low” and “Progressive Compression: Medium” settings were activated as a default setting for all users globally. This graph only represent one of the many bigger sites in this global company.

For those that upgraded to XenApp 6.5 instead of troubleshooting 6.0, this is more often not an issue, as “Adaptive Display” default settings actually have Progressive Display activated. But it’s still possible to mess it up. Leave it as it works fine, although for LAN users you might want to disable it to enable better/higher quality graphics. Should Adaptive Display be fine tuned? It depends. By the way, XenApp 6.5 Feature Pack 2 did not include Super Codec, but XenDesktop 7 does. Even more graphical stuff to look into, possibly mess up. And if you know the exact conditions for your LAN and WAN users you can obviously fine tune better than Citrix can. Maybe we’ll dig into this in another blog post!

Written by Fredrik Kämpe. Connect with me at

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