“What gets measured, gets improved” — Peter Drucker

What ultimately determines the success of a digital workspace initiative? Unquestionably, user acceptance. Virtualizing apps and desktops offers compelling benefits in security, management and compliance, but success ultimately depends on users embracing the technology because it makes work easier.

Being able to work anytime, from anywhere, and on any device is hugely attractive, provided the quality of experience is high. Many elements, such as fidelity, fluidity, responsiveness, and linearity, contribute to user experience (UX). Citrix’ HDX technologies are known for delivering a great experience, even in challenging network conditions. And yet, the network connection remains one of the biggest factors in determining whether the experience feels “like local.”

Consistency of cadence, for example, has a big impact on user productivity. The user’s ability to work at a steady pace can be negatively affected when network conditions deviate from the norm. Intermittent packet loss, variations in latency, and network congestion degrade linearity. When network characteristics fluctuate out of the average, users may encounter issues such as:

  1. Slow file transfers
  2. Choppy interactivity
  3. Degraded image quality
  4. Sluggish mouse movements and keystrokes

NetScaler SD-WAN technology can overcome many network issues and deliver a more consistent cadence to the user, but how do you know if you even have a problem? Historically, there have been many cases where IT personnel didn’t have any way of knowing when users were experiencing poor network connectivity. This lack of information resulted in long resolution times and wasted effort spent trying to reproduce the conditions that caused the issue.

This is where the Citrix NetScaler SD-WAN Center Quality of Experience (QoE) score comes in. The QoE score numerically defines the quality of an HDX session. Essentially, it’s a measure of HDX session quality based on network conditions, calculated taking key factors such as latency, packet loss and jitter into consideration. A QoE score of 90-100 indicates a great user experience. A score of 50-60 suggests that some action needs to be taken to improve the situation.

Let’s look at how QoE scores help IT to identify problems and how NetScaler SD-WAN can improve the end user experience.

The QoE dashboard provides quality scores across all sites with HDX traffic. It lists the five sites with the lowest QoE score, so that a network admin can immediately begin to look for ways to positively impact performance using NetScaler SD-WAN.

Figure 1.1 QoE scores

Since the network resources in any enterprise are limited, user experience tends to get affected as more and more users share the network. The number-of-users widget in the QoE dashboard highlights the number of concurrent users on a network connection. This metric can be used to derive a correlation with session quality. Based on the available data, decisions may be taken to augment network resources or to apply QoS policies.

Figure 1.2 Number of users for a site

Since a user can have multiple HDX sessions running, driving a correlation based only on the number of users wouldn’t be entirely accurate. Hence, the dashboard provides for listing the number of sessions, both Multi-Session ICA (MSI) and Single Session ICA (SSI), in order to provide deeper visibility, since the behavior of SSI and MSI sessions can be different even under the same network conditions.

Figure 1.3 Number of SSI/MSI sessions

Once we’ve figured out the probable cause for a less-than-optimal user experience, we can further drill down to see the status of the underlying constituent links to check if the network conditions are optimal for HDX workloads. Typically, the quality of an HDX session deteriorates when packet loss or latency is high, as may be the case on wireless or long-haul Internet connections. While HDX Adaptive Transport handles these adverse conditions surprisingly well, NetScaler SD-WAN can further boost the UX. In the first screen shot above (Figure 1.1) we see that the QoE score for MCN-SITE is 60 and when we drill down further we find that there is packet loss of around 10% on the constituent links, likely contributing to a suboptimal user experience.

Figure 1.4

Based on the inputs received from the HDX QoE reports, further tweaks could be made to NetScaler SD-WAN configuration to improve end user experience in the following ways:

  1. NetScaler SD-WAN can retransmit lost packets when the links are lossy. In addition to this, since the wait time before requesting the retransmission of an incoming packet can be configured, HDX session deterioration can be minimized without exceeding the maximum tolerable packet latency.
  2. In the case of applications which are sensitive to both latency and loss, such as VoIP traffic (Skype for Business and Jabber, for instance), packet duplication can be enabled on NetScaler SD-WAN. This improves call quality by reducing latency and dropped packets. Each packet traverses the absolute lowest latency path; the first packet to arrive at the destination is accepted while the duplicated packet is dropped. As an example, the screenshot below shows that the QoE score has improved after enabling packet duplication. Before enabling packet duplication, the score was 60, but after enabling packet duplication the effects of excessive packet loss have been reduced to a great extent as can be seen in the new QoE score of 98. Now our users are super happy!
Figure 1.5

Moreover, when it comes to delivering superior VoIP/HDX performance over links that are lossy and have limited bandwidth, this configuration can be further enhanced to only allow packet duplication after waiting for a configurable time value.

So, here we’ve seen how the QoE score helps in highlighting problem areas in the network when HDX connections seem to be behaving worse than usual, and how NetScaler SD-WAN can be utilized to mitigate those issues. The HDX user experience is a huge differentiator for XenApp and XenDesktop, and Citrix is the only app and desktop virtualization vendor to also provide integrated networking solutions that strengthen the end-to-end digital workspace solution.

Special thanks to Jaskirat Chauhan, Mayank Singh and Donna Johnson for their help in creating this blog post. We hope you found it useful, and look forward to your comments.

Ready to get started? Please refer to: https://www.citrix.co.in/products/netscaler-sd-wan/get-started.html.

To learn more about the NetScaler SD-WAN dashboard and the QoE metric, please refer to: http://docs.citrix.com/en-us/netscaler-sd-wan-center/9-3/dashboard.html