Tcp Traffic - AVD Test

Since most popular applications rely on the TCP protocol for their proper functioning, traffic monitoring at the TCP protocol layer can provide good indicators of the performance seen by the applications that use TCP. The most critical metric at the TCP protocol layer is the percentage of retransmissions. Since TCP uses an exponential back-off algorithm for its retransmissions, any retransmission of packets over the network (due to network congestion, noise, data link errors, etc.) can have a significant impact on the throughput seen by applications that use TCP. This test monitors the TCP protocol traffic to and from an Azure Virtual Desktop, and particularly monitors retransmissions.

Target of the test : An Azure Virtual Desktop

Agent deploying the test : An internal agent

Outputs of the test : One set of results for the chosen Session Host / Azure Virtual Desktop

Configurable parameters for the test
Parameters	Description
Test Period	How often should the test be executed.
Host	The host for which the test is to be configured.
Port	The default port is NULL.
Segments Sent Min	Specify the minimum threshold for the number of segments sent/transmitted over the network. The default value is 10; in this case, the test will compute/report the TCP retransmit ratio measure only if more than 10 segments are sent over the network. On the other hand, if less than 10 segments are sent, then the test will not compute/report the TCP retransmit ratio measure. This is done to ensure that no false alerts are generated by the eG Enterprise system for the TCP retransmit ratio measure. You can change this minimum threshold to any value of your choice.
Trace	By default, the Trace flag is set to No. This indicates that the test does not report any detailed diagnostics by default. However, if unusually high TCP traffic is flowing into the Azure virtual desktop , then you may want to know where this traffic is coming from. For deep-dive insights into the incoming TCP traffic of the target virtual desktop, you need to enable the detailed diagnosis capability of the test. For this, set the Trace flag to Yes. Note: This test will report detailed metrics only if the Trace flag is set to Yes and the Detailed Diagnosis flag is set to On. If either or both these flags are turned off, then the test will not report detailed statistics.
Event Capture Interval in Secs	This parameter is applicable only when the Trace flag is set to Yes and the Detailed Diagnosis flag is set to On. By default, the value of this parameter is set to 30 seconds. This setting ensures that the detailed diagnosis of the test reports on only the TCP traffic that flows into the virtual desktop during the last 30 seconds of a measurement period. However, you can override the default value of this parameter as per your requirement.
Detailed Diagnosis	To make diagnosis more efficient and accurate, the eG Enterprise 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
Segments received	Indicates the rate at which segments are received by the virtual desktop.	Segments/Sec	If the value of this measure is unusually high, then use the detailed diagnosis of the measure to know the source of the unusual traffic. Note: Detailed diagnostics will be available only if the Trace flag and the Detailed Diagnosis flag of this test are enabled.
Segments sent	Indicates the rate at which segments are sent to clients or other virtual desktops.	Segments/Sec
Retransmits by VM	Indicates the rate at which segments are being retransmitted by the virtual desktop.	Segments/Sec
Retransmit ratio from VM	Indicates the ratio of the rate of data retransmissions to the rate of data being sent by the virtual desktop.	Percent	Ideally, the retransmission ratio should be low (< 5%). Most often retransmissions at the TCP layer have significant impact on application performance. Very often a large number of retransmissions are caused by a congested network link, bottlenecks at a router causing buffer/queue overflows, or by lousy network links due to poor physical layer characteristics (e.g., low signal to noise ratio). By tracking the percentage of retransmission, an administrator can quickly be alerted to problem situations in the network link(s) to the virtual desktop that may be impacting the service performance.