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 Oracle LDoms server

Agent deploying the test : An internal agent

Outputs of the test : One set of results for each powered-on guest on the Oracle LDoms server being monitored.

Configurable parameters for the test
Parameter	Description
Test period	How often should the test be executed
Host	The host for which the test is to be configured.
Port	The port number at which the specified host listens. By default, the port is NULL.
Domain	Specify the domain within which the virtual guests reside. Since the Oracle LDoms server supports only Oracle and Linux guests, this parameter should always be set to none.
Admin User	This test connects to each virtual guest and collects status and resource usage statistics from the guest. In order to do so, the test must be configured with user privileges that allow a remote connection to the virtual guest from the Oracle host. If a single user has access to all the guest domains on the Oracle server, specify the name of that user against Admin User, and specify his password against Admin Password. On the other hand, if the user credentials vary from one guest to another, then multiple Admin Users and Admin Passwords might have to be specified for every Oracle LDoms server being monitored. To help administrators provide these user details quickly and easily, the eG administrative interface embeds a special configuration page. To access this page, simply click on the Click here hyperlink that appears just above the parameters of this test in the test configuration page. To know how to use the special page, refer to Configuring Users for VM Monitoring.
Admin Password	The password of the Admin User needs to be provided here. Here again, if multiple passwords need to be specified, then follow the procedure detailed in Configuring Users for VM Monitoring.
Confirm Password	Confirm the password by retyping it here. Here again, if multiple passwords need to be confirmed, then follow the procedure detailed in Configuring Users for VM Monitoring.

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.