Metrodata ATM CBR DSU, User Manual

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TEST & TROUBLESHOOTING
76-02-031E 74
8. 4 Troubleshooting
This Section deals with common problems encountered while commissioning ATM CBR
DSUs, as well as fault isolation during normal operation.
Step 1: Establish And Verify the CBR Link
a) Check that the power LED is lit. If it is not, the mains fuse is suspect.
b) If the LINE MAJOR alarm LED is on, try swapping the BNC connections.
c) If the LINE MAJOR alarm remains on, try looping the BNC connections on the DSU using
a short piece of BNC cable. If the MAJOR alarm LED goes off then the cabling or
configuration is faulty. Check the cabling and then check the port configuration at either end
of the link. Pay particular attention to the framing and line coding options.
d) If the LINE MAJOR alarm goes off, check the status of the MINOR alarm LED.
e) If the LINE MINOR alarm LED is on, check that the PABX is configured correctly.
Step 2: Establish and verify the ATM UNI Link
Repeat steps a) to d) for the ATM UNI port, noting that there is only a single LED for both
UNI MAJOR and UNI MINOR alarms.
If the ATM UNI fault LED is on, check that the connected ATM UNI port has no MAJOR
alarms, check that the
AIS FORWARDING and RAI FORWARDING options are configured
correctly, and that the HEC COSET and PAYLOAD SCRAMBLING options are compatible
with those of the ATM switch port.
If the LINE MINOR alarm LED goes out but problems persist, check that the peak cell rate
of the connected ATM port has been set so that the buffer in the ATM CBR DSU is not
overrun
Step 3: Configuration problems
As these ATM CBR DSUs are used in a variety of locations and with many different
manufacturers equipment it is impossible for us to cover all eventualities here, so please
consult the other Manufacturer’s Operating Manual for further information.