Tcp Traffic - VM 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 a Windows virtual desktop on the cloud, and particularly monitors retransmissions.

Target of the test : A Windows virtual desktop on the cloud

Agent deploying the test : A remote agent

Outputs of the test : One set of results for each user_on_poweredonvirtualdesktop

Configurable parameters for the test
Parameter Description

Test Period

How often should the test be executed.

Host

The nick name of the Cloud Desktops component for which this test is to be configured.

Port

Refers to the port at which the specified host listens to. By default, this is NULL.

Inside View Using

To obtain the 'inside view' of performance of the cloud-hosted Windows desktops - i.e., to measure the internal performance of the Windows virtual desktops - this test uses a light-weight eG VM Agent software deployed on each of the desktops. Accordingly, this parameter is by default set to eG VM Agent (Windows).

Report Powered OS

This flag is relevant only for those tests that are mapped to the Inside View of Desktops layer. If this flag is set to Yes (which is the default setting), then the 'inside view' tests will report measures for even those Windows virtual desktops that do not have any users logged in currently. Such desktops will be identified by their name and not by the username_on_virtualdesktopname. On the other hand, if this flag is set to No, then this test will not report measures for those Windows virtual desktops to which no users are logged in currently.  

Is Cloud VMs

Since this test runs for a 'Cloud Desktops' component, this flag is set to Yes by default.

Segments Sent Min

Specify the minimum threshold for the number of segments sent/transmitted over the network. The default value is 25; in this case, the test will compute/report the Retransmit ratio from VM measure only if more than 25 segments are sent over the network – i.e., if the value of the Segments sent by VM measure crosses the value 25. On the other hand, if the Segments sent by VM measure reports a value less than 25, then the test will not compute/report the Retransmit ratio from VM measure. This is done to ensure that no false alerts are generated by the eG Enterprise system for the Retransmit ratio from VM measure. You can change this minimum threshold to any value of your choice.

Measurements made by the test
Measurement Description Measurement Unit Interpretation

Segments received by VM

Indicates the rate at which segments are received by the guest.

Segments/Sec

 

Segments sent by VM

Indicates the rate at which segments are sent to clients
or other guests

Segments/Sec

 

Retransmits by VM

Indicates the rate at which segments are being retransmitted by the guest

Segments/Sec

 

Retransmit ratio from VM

Indicates the ratio of the rate of data retransmissions to the rate of data being sent by the guest

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 retransmissions at a guest, an administrator can quickly be alerted to problem situations in the network link(s) to the guest that may be impacting the service performance.