|
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. The measures
made by this test are as
follows:
| Measurement |
Description |
Measurement
Unit |
Interpretation |
| Segments_recvd |
The rate at which segments are received by the
server |
Segments/Sec |
|
| Segments_sent |
The rate at which segments are sent to clients
or other servers |
Segments/Sec |
|
| Retransmits |
The rate at which segments are being
retransmitted by the server to clients/other servers |
Segments/Sec |
|
| Retransmit_ratio |
The ratio of the rate of date 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 a 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 lossy 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.
|
|