Diagnostics and Troubleshooting
8-9
8000-A2-GB20-20 November 1997
Failure Type Action
Error Rate
Threshold
(A trap
message sent if
the Block Error
Rate averaged
over a period of
time exceeds
the selected
value.)
If the Error Rate Threshold is < 10-4, then this alarm is a warning
that the loop has degraded. The actual bit rate should still be above
10 -7. This condition may be temporary due to high temperature or
humidity/rain. It may be permanent due to high noise from
additional digital circuits installed in the same cable bundle.
If the Error Rate Threshold is >10-4, then this alarm is a warning
that the loop has degraded. The actual bit rate may be below 10 -7.
This condition may be temporary or permanent. However, if it
persists, the loop may have to be reengineered for better
performance by performing one of the following:
– Remove bridge taps
– Change cable gauge on a cable section
– Run new cable
– Remove other noise-generating digital circuits from the cable
bundle
Link Down
Threshold
(A trap
message sent if
the number of
DSL link down
events in 15
minutes
exceeds the
selected value.)
If the threshold is set low (1–4), and the link is currently down, then
there may be a loop or RTU problem. Check both.
– Verify that the RTU is powered up, is connected to the loop, and
has passed its Selftest.
– Check the loop for continuity
If the threshold is set low (1–4), and the link is currently up, then an
event had occurred to temporarily knock out the connection. Log
the event and continue normal operation.
If the threshold is set high (> 4), and the link is currently down, then
check the Margin statistics over the past hour and day. If the
numbers are low, there may be a situation where the DSL modems
cannot train. This condition may be temporary or permanent.
However, if it persists, the loop may have to be reengineered for
better performance by performing one of the following:
– Remove bridge taps
– Change cable gauge on a cable section
– Run new cable
– Remove other noise-generating digital circuits from the cable
bundle
If the threshold is set high (> 4) and the link is currently up, then
there may be a loose connection in the loop plant, or the loop is
barely usable. Check the Margin. If the Margin is normal, there may
be a loose connection. If the Margin is low, try reducing the speed
of the DSL port.