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STCLive PM NETQ-Q2Q : Why do I see variations in the number of packets sent in a 5min interval?


Because the number of times the NETQ-Q2Q test is run in a 5minute interval varies, the number of sent packets and received packets will vary by a set amount.
NETQ-Q2Q testing in STCLive PM is performed between two probes. One probe sends the packets and the other reflects them back. The sending probe then measures the returning packets.
Because of the nature of testing between two probes, STCLive PM NETQ-Q2Q uses the “original” Net Quality test (TST-ECHO), rather than the newer TST-ECHO-PM.
It is the difference between the way these two commands collect the data that is the cause of the variations in the number of packets sent and received.
The TST-ECHO command is a one shot test that reports the results via the command line.  It will run multiple times during the 5 minute reporting interval of STCLive PM. The results of all the tests run during this time, are aggregated into a lump sum and reported at the end of the 5 minute interval. While the reporting of the results are strictly synchronized to PM’s 5 minute window, the running of the tests themselves are not synchronized to the window. As a result,  there are more packets sent in one reporting interval and less the next because the test was able to run more times in one reporting interval and less times the next.
On the other hand, the TST-ECHO-PM command reports the results back in 5min intervals in a file via the cpy-mem command. They are already collected and summed up in one report. This provides a more uniform set of results as opposed to how TST-Echo's results are collected.
Because the TST-ECHO command can run between 1-3 tests in a 5 minute interval, the number of packets that are sent and received may vary by double or even triple in a 5 minute period. 
The way to confirm that this is what is causing the variations in sent and received packets, check the STCLive PM comm logs for the switch with the suspected problem. In the comm log there will be results for the TST-ECHO command. These results will have a line with “PACKETS-SENT=” in them – see below.
Check the <totSent> number and verify that value meets these 2 criteria:
Is <totSent> equal the number reported by PM?
Is <totSent> exactly half (or a third) the number reported by PM?
If either of the two conditions is met, then what is happening is that the number of packets sent and received varies because of the number of times that test was able to run in that 5 minute window.
Below is an example of a NETQ-Q2Q test using 1518 frame size with a duration of 5secs. This frame size generates 4055 packets per test. Notice that sometimes the frames sent/recv are 4055 and sometimes 8110 (or 4055 x 2) and sometimes they are 12165 (4055 x 3).   This is because the test runs between 2 and 3 times in a 5 minute interval.  


Product : VW Controller PM Classic,VW Controller T&D Classic,STCLive