JDS Uniphase IP Video Test Option HST-3000, Руководство пользователя

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Chapter 9 Troubleshooting
Resolving problems
HST-3000 Ethernet Testing User’s Guide
253
While running a
Ping test, through-
put and perfor-
mance test results
do not seem to
reflect the true state
of the circuit. After running a Ping test,
bandwidth utilization, delay
measurements, and other
test results seem to indicate
that the circuit is experienc-
ing significant utilization and
performance problems.
This occurs for a variety of
reasons:
– Routers on the circuit
and the target computer
itself may impose a limit
on how many ICMP echo
packets to process per
second. Echo packets
that exceed the limits are
discarded.
– ICMP echo packets are
often given a lower prior-
ity by devices on the cir-
cuit. As a result, round-
trip time for Ping packets
can be different than that
experienced by true traf-
fic which is given a
higher priority.
– Traffic shaping does not
occur until enough pack-
ets flow through the cir-
cuit. Isolated packets,
such as Ping packets,
may not experience the
same pace experienced
by real application pack-
ets. Therefore, transmit-
ting ping packets, even
at a continuous rate, pro-
vides a poor indication of
real IP throughput.
In most instances, you
should configure and trans-
mit a true load of traffic to
measure throughput and
verify performance. Run the
Layer 2 Traffic,
Layer 3 Traffic, or
Layer 4 Traffic test as appro-
priate.
Table 14 Problems and resolutions (Continued)
Problem Description Resolution