About ICA
Independent Computing Architecture or ICA is a proprietary protocol developed by Citrix. The purpose of the technology is to have a way to consume computing resources from any device or platform independent of the user's platform or transport protocol.
How ICA Works
The ICA protocol operates at the presentation layer (layer 6) of the OSI model, where data is prepared to be presented at the application layer (layer 7).
It delivers inputs from the client to the server and provides output such as video and audio from the server back to the user. Traffic flows over port 1494 (ICA) and 2598 (session reliability) by creating dynamically allocated TCP ports for client/server communication. The protocol's virtual channels are used for functions such as printing, typing, video, audio, and USB among others.
About HDX
HDX has become the modern acronym given to the delivery protocol for XenDesktop and XenApp. It is a set of capabilities designed to enhance the user experience for sessions delivered over ICA by bringing a more native feel and user experience to ICA.
How HDX Works
The three main capabilities that comprise the underpinnings for HDX per Citrix are: intelligent redirection, adaptive compression, and data de-duplication. Working together to enhance the quality of user experience while reducing session bandwidth demands.
These capabilities were purpose built and introduced to allow for graphic and processer-intense computing to be performed from a virtual computing environment. While HDX technologies accomplish that goal, the foundation remains ICA.
Metrics
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ICA RTT: Is the detected time from when the user hits a key until the response is displayed back at the end point, as calculated by the session experience monitoring service. This metric should be observed in conjunction with the ICA Latency and Network Latency.
If the ICA Latency is the cause of the high ICA RTT, it should be further analyzed using Network Latency. If not, then the cause is the application layer and requires troubleshooting of the application and OS performance.
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ICA Latency: Time from when a user executes a keystroke or mouse click to when it is processed on the session host. A high ICA Latency should be compared first to the Network Latency to determine what is causing the delay.
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Network Latency: Is a measure of time delay from one networked point to another. In the context of ICA/HDX, this must be measured through the channel itself and not through standard network tools.
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Connection Speed: Defined as the amount of connection speed available to the Citrix Receiver as a subset of the overall connection speed for the endpoint.
If a user is on a laptop or workstation, there may be other activities at the OS layer between other applications, updates, and downloads that Citrix must contend with to secure connection speed for the user’s Citrix Session.
The impact of ICA RTT, ICA Latency, Network Latency, and Connection Speed on user's experience issues generally fall into the category of blurry screens (pixelation), session speed, highly latent or poor connection speeds, and general user activity.
Thresholds
ICA/HDX metrics are categorized from poor (red) to excellent (green) based on the following thresholds:
| Metric | Scores | |||
|---|---|---|---|---|
| Poor (40 points) | Fair (60 points) | Good (80 points) | Excellent (100 points) | |
| ICA RTT | From 450 ms | 350 to 449 ms | 200 to 349 ms | 0 to 199 ms |
| ICA Latency | From 400 ms | 200 to 399 ms | 100 to 199 ms | 0 to 99 ms |
| Network Latency | From 250 ms | 150 to 249 ms | 100 to 149 ms | 0 to 99 ms |
| Connection Speed | 0 to 1 Mbps | 1.1 to 2.4 Mbps | 2.5 to 4.9 Mbps | From 5 Mbps |
Dashboard
View information related to the ICA/HDX performance and use the top filters to narrow down the data. Divided in three tabs for improved analysis: Overall Score, Worst Experience Scorecard, and Trellis Chart.
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Overall Score
Get a general performance overview. Identify issues by analyzing the main ICA/HDX metrics.
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Worst Experience Scorecard
Sorted by worst experience first, it helps to identify which users are having issues. Can be grouped by Farm Name, Hostname, Custom Location, Country, Regions, Department, Division, Username, and Machine Name for deeper analysis.
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Trellis Chart
Graphic information regarding the ICA/HDX perfomance. Can be grouped by different dimensions and specific metrics.