HDX Desktop Users Test

To ensure a high quality virtual desktop experience for a user, administrators must closely track that user’s desktop accesses, promptly detect probable access latencies, diagnose its root-cause, and take steps to avert it, well before that user notices and complains. To achieve this, administrators can use the HDX Desktop Users test. This test automatically discovers the users who are currently logged into the VDI infrastructure, and for each user, reports the latencies that user experienced when interacting with virtual desktops. This way, the test quickly and accurately points administrators to those users who are experiencing slowdowns, and also leads them to what is causing the slowness – the network? the NetScaler appliance? or the server hosting the desktops?

Target of the test : Citrix NetScaler HDX Insight

Agent deploying the test : A remote agent

Outputs of the test : One set of results for every user who is currently connected to the VDI infrastructure

Configurable parameters for the test
  1. Test period - How often should the test be executed. It is recommended that you set the test period to 5 minutes. This is because, the Nitro API using which the eG agent collects metrics from HDX Insight, is capable of capturing only the performance data related to the last 5 minutes.
  2. Host - The host for which the test is to be configured.
  3. insight username,insight password, and confirm password -  To connect to HDX Insight and collect the metrics it captures, the eG agent needs to be configured with the credentials of a user with read-only permissions to HDX Insight. Type the name of this user against insight username and the password of this user against insight password. Then, confirm the password by retyping it in the confirm password text box.
  4. ssl – By default, HDX Insight is not SSL-enabled. This is why, this flag is set to No by default. If it is SSL-enabled, then change this flag to Yes.
  5. DD FREQUENCY – Refers to the frequency with which detailed diagnosis measures are to be generated for this test. The default is 1:1. This indicates that, by default, detailed measures will be generated every time this test runs, and also every time the test detects a problem. You can modify this frequency, if you so desire. Also, if you intend to disable the detailed diagnosis capability for this test, you can do so by specifying none against DD FREQUENCY.
  6. To make diagnosis more efficient and accurate, the eG Enterprise suite embeds an optional detailed diagnostic capability. With this capability, the eG agents can be configured to run detailed, more elaborate tests as and when specific problems are detected. To enable the detailed diagnosis capability of this test for a particular server, choose the On option. To disable the capability, click on the Off option.

    The option to selectively enable/disable the detailed diagnosis capability will be available only if the following conditions are fulfilled:

    • The eG manager license should allow the detailed diagnosis capability
    • Both the normal and abnormal frequencies configured for the detailed diagnosis measures should not be 0.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

Desktop launches:

Indicates the number of desktop sessions currently launched by this user.

Number

Use the detailed diagnosis of this measure to know which desktops are currently accessed by the user.

Compare the value of this measure across users to know which user has launched the maximum desktop sessions, thus overloading the infrastructure.

Bandwidth:

Indicates the rate at which data is transferred over the ICA sessions of this user.

Kbps

Ideally, the value of this measure should be low.

A high value indicates excessive bandwidth usage by the user.

Compare the value of this measure across users to know which user is consuming bandwidth excessively

WAN latency:

Indicates the average latency experienced by this user due to problems with the client side network.

msecs

A high value for this measure indicates that the client side network is slow.

If the value of the Round trip time – RTT measure is abnormally high for any user, you can compare the value of this measure with that of the DC latency measure of that user to know what is causing the slowness – is it the client side network? or the server side network?

DC latency:

Indicates the average latency experienced by this user due to problems with the server side network.

msecs

A high value for this measure indicates that the server side network is slow.

If the value of the Round trip time – RTT measure is abnormally high for any user, you can compare the value of this measure with that of the WAN latency measure of that user to know what is causing the slowness – is it the client side network? or the server side network?

Round trip time - RTT:

Indicates the screen lag experienced by this user while interacting with desktops.

msecs

A high value for this measure is indicative of the poor quality of that user’s experience with virtual desktops.

To know the reason for this below-par UX, compare the value of the WAN latency and DC latency measures of that user.

Client smoothed round trip time - SRTT:

Indicates the RTT (round-trip time or screen lag time) of this user smoothed over the client side connection. 

 

msecs

TCP implementations attempt to predict future round-trip times by sampling the behavior of packets sent over a connection and averaging those samples into a ‘‘smoothed’’ round-trip time estimate, SRTT. When a packet is sent over a TCP connection, the sender times how long it takes for it to be acknowledged, producing a sequence, S, of round-trip time samples: s1, s2, s3.... With each new sample, si, the new SRTT is computed from the formula:

SRTTi+1 = (α x SRTTi) + (1 − α ) x si

Here, SRTTi is the current estimate of the round-trip time, SRTTi+1 is the new computed value, and α is a constant between 0 and 1 that controls how rapidly the SRTT adapts to change. The retransmission time-out (RTOi), the amount of time the sender will wait for a given packet to be acknowledged, is computed from SRTTi. The formula is:

RTOi = β x SRTTi

Here, β is a constant, greater than 1, chosen such that there is an acceptably small probability that the round-trip time for the packet will exceed RTOi.

Server smoothed round trip time - SRTT:

Indicates the RTT (round-trip time or screen lag time) of this user, smoothed over the server side connection. 

msecs

Session duration:

Indicates the total duration of all sessions of this user.

Mins

Compare the value of this measure across users to know which user has interacted with the virtual desktops for the longest time.

Use the detailed diagnosis of the Desktop launches measure to know which desktops are currently accessed by the user.

Figure 8 : The detailed diagnosis of the Desktop launches measure of the HDX Desktop Users test