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Chapter 6: Operation
LAN Performance Verification Level 1 displays the projected
speed capability of the cable. The graph is a result of thousands
of measurements used to project the speed of the cable. This is
one of the most useful and money-saving displays. For instance,
it is possible that some shorter, installed CAT5 cable (rated for
100 Mbps) are capable of communicating at a 1000 Mbps. This
graph will indicate such. Many users conclude their cable testing
with Level 1 and skip the Level 2.
Figure 6-24. Length/Timing summary screen.
Length: The length of the shortest cable pair (in feet). 330 feet
(100 m) is the longest cable allowed by the 802.3 standard.
The LAN Performance Verifier can test cables up to 1250 feet
(381 m) in length.
Propagation delay: The time it takes for a data signal to travel
the length of the cable (in nanoseconds). An abnormally long
propagation delay indicates the cable is “too slow” for the
application. Either the cable itself is too slow or there is an error
in the wiring. The standard allows a maximum 555 nsecs
propagation delay (CAT6 cables).
Skew: The difference in the propagation delay between the
slowest pair and the fastest pair in the cable (in nanoseconds). A
small skew ensures that data, on each pair, will arrive at the
receiver at about the same time. A large skew reading causes
errors. 50 nsecs is the maximum allowable skew.
To continue reviewing, press the down arrow key
q
.
