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Measures reported by TcpTrafficTest
This test monitors the TCP protocol traffic to and from a server. Since most popular applications (Web servers, Citrix, Databases, Application servers, etc.) 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.
Outputs of the test : One set of results for each host system monitored
The measures made by this test are as follows:
| Measurement |
Description |
Measurement Unit |
Interpretation |
| Segments_recvd |
Indicates the rate at which segments are received by the server. |
Segments/Second |
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| Segments_sent |
Indicates the rate at which segments are sent to clients or other servers. |
Segments/Second |
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| Retransmits |
Indicates the rate at which segments are being retransmitted by the server to clients/other servers. |
Segments/Second |
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| Retransmit_ratio |
Indicates the ratio of the rate of data retransmissions to the rate of data being sent by the server to clients/other servers. |
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 server, an administrator can quickly be alerted to problem situations in the network link(s) to the server that may be impacting the service performance. |
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