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Measurements for jitter, loss, round-trip times, and handshake-round-trip times, are made by the CNA USTAT modules.
Tests were conducted by introducing 100 ms and 1,000 ms delays into packet transit times in a lab network. These artificial latency figures were selected as representative of normal delays through the live Internet due to such factors as traffic load, bottlenecks, and down segments. As latency increases, the number of retransmissions rise and more state needs to be maintained in individual handshakes, thereby reducing performance.
As a general “rule of thumb”, each USTAT of the device can handle the following rates:
For the device, the same numbers apply, but keep in mind that it has only one USTAT, so its measurement capacity is divided among the links being measured.
If you mix the different types of probes, then you will need to factor in the limits that each imposes on the system (e.g., at 400 UDP probes per second, the USTAT would have room for roughly 100 TCP probes per second).
You should also take into consideration the engine module measurement capacity (see the next section), as it is not productive to allow the USTATs to generate more measurements than the engine is able to handle.
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