Automatic Performance Tests
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7.1.2. Latency
This test determines the latency inherent in the DUT / SUT. The initial data rate is
based on the results of the throughput test. Typically, packets are timestamped using
the SLA payload (See section 4.1.4, See section 4.4.6), and the time they take to travel
through the DUT / SUT is measured.
In order to determine the latency you usually first measure the throughput for the DUT /
SUT at each of the defined frame sizes, and send a stream of frames through the
DUT / SUT at the determined throughput rate to a specific destination. If you don’t
measure throughput the latency will be measured at the nominal capacity for the
transmission medium.
The time at which this frame is completely transmitted is recorded, and this will be
timestamp A. The receiver of the test equipment must recognize the tag information in
the frame stream and record the reception time of the tagged frame. This will be
Trial duration (s.) This value corresponds with the duration of a single through-
put trial test expressed in seconds. Each algorithm test cycle
contains one trial. The equipment transmits test traffic during
the time specified by this setting before deciding by means
the analysis of the number of lost frames whether to continue
or not.
Some equipments may need some time before they start
dropping frames. If the trial duration is too short this may
cause the estimated throughput to be larger than it will in sta-
tionary transmission conditions.
Max. frame loss (%) The equipment decides whether it is operating above or
below the actual DUT / SUT throughput by comparing the
number of transmitted and received frames. It decides that
the current transmission rate is higher than the real through-
put if the frame loss ratio is larger than the Max.frame loss
(%) configured here. In the same way, the tester decides that
the current test rate is smaller than the actual throughput if
the computed frame loss ratio is smaller than the Max. frame
loss (%).
Table 7.1: RFC 2544 Throughput Test Settings
Setting Description
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