TCP Traffic - OS 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 guest, and particularly monitors retransmissions.

Target of the test : A Hyper-V / Hyper-V VDI server

Agent executing the test : An internal agent

Output of the test : For a Hyper-V server, one set of results will be reported for every powered-on VM on the server.

For a Hyper-V VDI server, one set of results will be reported for the user who is currently logged into each virtual desktop on the server

Configurable parameters for the test
Parameter	Description
Test period	This indicates how often should the test be executed.
Host	Specify the HOST for which this test is to be configured.
Port	Specify the port at which the target host is listening. By default, this is NULL
Inside View Using	By default, this test obtains the “inside view” of VMs using the eG VM Agent. Accordingly, the Inside view using flag is set to eG VM Agent by default. The eG VM Agent is a piece of software, which should be installed on every VM on a hypervisor. Every time the eG agent runs this test, it uses the eG VM Agent to pull relevant 'inside view' metrics from each VM. Once the metrics are collected, the eG agent then communicates with each VM agent and pulls these metrics, without requiring administrator privileges. Refer to Configuring the Remote Agent to Obtain the Inside View of VMs for more details on the eG VM Agent.
Domain, Admin User, and Admin Password, and Confirm Password	By default, these parameters are set to none. This is because, by default, the eG agent collects 'inside view' metrics using the eG VM agent on each VM. Domain administrator privileges need not be granted to the eG agent if it uses this default approach to obtain the 'inside view' of Windows VMs.
Report By User	For the Hyper-V monitoring model, the Report By User flag is set to No by default, indicating that by default, the guest operating systems on the Hyper-V server are identified using the hostname specified in the operating system. On the other hand, for the Hyper-V VDI model, this flag is set to Yes by default; this implies that in case of VDI servers, by default, the guests will be identified using the login of the user who is accessing the guest OS. In other words, in VDI environments, this test will, by default, report measures for every username_on_virtualmachinename.
Report Powered OS	This flag becomes relevant only if the report by user flag is set to ‘Yes’. If the Report Powered OS flag is set to Yes (which is the default setting), then this test will report measures for even those VMs that do not have any users logged in currently. Such guests will be identified by their virtualmachine name and not by the username_on_virtualmachinename. On the other hand, if the Report Powered OS flag is set to No, then this test will not report measures for those VMs to which no users are logged in currently.
Report Powered ON	You can set the Report Powered ON status to Yes, so that the test reports an additional measure, Is VM powered on?, revealing whether a guest OS is currently running or not. The default status of this flag is set to Yes for a Hyper-V server. For a Hyper-V VDI server on the other hand, the default status of this flag is No. This is because, in such environments, the virtual desktops will be in the powered-off state most of the time.
Ignore VMs Inside View	Administrators of some high security Hyper-V environments might not have permissions to internally monitor one/more VMs. The eG agent can be configured to not obtain the 'inside view' of such ‘inaccessible’ VMs using the Ignore VMs Inside View parameter. Against this parameter, you can provide a comma-separated list of VM names, or VM name patterns, for which the inside view need not be obtained. For instance, your Ignore VMs Inside View specification can be: xp,lin,win,vista. Here, the * (asterisk) is used to denote leading and trailing spaces (as the case may be). By default, this parameter is set to none indicating that the eG agent obtains the inside view of all VMs on a Hyper-V host by default. Note: While performing VM discovery, the eG agent will not discover the operating system of the VMs configured in the Ignore VMs Inside View text box.
Exclude VMs	Administrators of some virtualized environments may not want to monitor some of their less-critical VMs - for instance, VM templates - both from 'outside' and from 'inside'. The eG agent in this case can be configured to completely exclude such VMs from its monitoring purview. To achieve this, provide a comma-separated list of VMs to be excluded from monitoring in the Exclude VMs text box. Instead of VMs, VM name patterns can also be provided here in a comma-separated list. For example, your Exclude VMs specification can be: xp,lin,win,vista. Here, the * (asterisk) is used to denote leading and trailing spaces (as the case may be). By default, this parameter is set to none indicating that the eG agent obtains the inside and outside views of all VMs on a virtual host by default. By providing a comma-separated list of VMs/VM name patterns in the Exclude VMs text box, you can make sure the eG agent stops collecting 'inside' and 'outside' view metrics for a configured set of VMs.
Ignore WINNT	By default, the eG agent does not support the inside view for VMs executing on Windows NT operating systems. Accordingly, the Ignore WINNT 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 10; in this case, the test will compute/report the Retransmit ratio from VM measure only if more than 10 segments are sent over the network – i.e., if the value of the Segments sent by VM measure crosses the value 10. On the other hand, if the Segments sent by VM measure reports a value less than 10, 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 VMmeasure. You can change this minimum threshold to any value of your choice.

Measurements reported 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.