Overview… latency diagnostics
Latency measurements are available for each received test payload TID value.
Latency measures the time-in-transit of a packet from transmitter to receiver. There are a variety of last/first-bit modes selectable on the “PORT PROPERTIES” panel. The source port and the receiving port are required to be in the same chassis.
The receiving port accumulates the average latency for all the packets belonging to a particular TID, and logs the minimum and maximum values:
It is also possible to obtain latencies for individual packets by using the capture mechanism.
The absolute values of the latency measurements are not truly indicative of latency in the system under test, because for instance the test module transceivers will add some latency of their own.
This can be compensated out by connecting a cable directly between the two ports, running some traffic, and pressing the “Calibrate” button. This redefines the minimum latency as zero, by setting the latency offset value which is part of the port-level properties.