Troubleshooting guide

Section 5, User Interface Guide - UIG-530, M13 Loopbacks
61186003L1-1D 5-89
CSU Loopback
A Channel Service Unit (CSU) Loopback enables the M13 MUX to generate a CSU loop-up
pattern (00001...) for 6 seconds towards the T1 CSU attached to the selected T1 line. After 6
seconds have elapsed, the pattern stops and incoming network traffic passes through to the
CSU device. If the CSU device responded to the CSU loop-up pattern, the CSU device returns
all data back towards the network. When Data Mode is selected, a loop-down pattern
(001001....) is generated towards the CSU for 6 seconds.
CSU Loopback w/BERT
A CSU Loopback w/BERT enables the M13 MUX to test the local T1 loop to the CSU with a
user-selected Bit Error Rate (BERT) pattern. When CSU Loopback w/BERT is selected, the
M13 MUX initiates a CSU loopback towards the CSU attached to the selected T1 line similar to
the CSU Loopback test. After starting the CSU loop-up pattern with the 6-second pattern, the
M13 MUX stops sending the CSU loop-up pattern and begins sending the selected BERT
pattern towards the CSU. If the CSU device responded to the CSU loop-up pattern, the M13
MUX checks the incoming pattern for errors. Selecting Data Mode stops the transmission of
the BERT pattern and starts transmission of a loop-down pattern.
NOTE
When in either CSU Loopback or CSU Loopback w/BERT, only the
DATA MODE for the T1 under test can be selected. Selecting any
other option results in an error message being displayed.
NIU Loopback
A Network Interface Unit (NIU) Loopback enables the M13 MUX to generate a NIU loop-up
pattern (00011...) for 6 seconds towards the NIU attached to the selected T1 line. After 6
seconds have elapsed, the pattern stops and incoming network traffic passes through to the
NIU device. If the NIU device responded to the NIU loop-up pattern, the NIU device returns all
data back towards the network. When Data Mode is selected, a loop-down pattern
(0011100111...) is generated towards the NIU for 6 seconds.
NIU Loopback w/BERT
A NIU Loopback w/BERT enables the M13 MUX to test the local T1 loop to the NIU with a
user-selected BERT pattern. The BERT pattern is selected from the MX2820 Loopbacks menu.
When NIU Loopback w/BERT is selected, the M13 MUX initiates a NIU loopback towards the
NIU attached to the selected T1 line similar to the NIU Loopback test. Six seconds after
starting the NIU loop-up pattern, the M13 MUX stops sending the NIU loop-up pattern and
begins sending the selected BERT pattern towards the NIU. If the NIU device responded to the
NIU loop-up pattern, the M13 MUX checks the incoming pattern for errors. Additional menu
items appear to show: the state of pattern synchronization, the error count, and a clear error
count option. Selecting Data Mode stops the transmission of the BERT pattern and starts
transmission of a loop-down pattern.