Using Bit Error Rate Tests - Cisco ASR 1000 Configuration Manual

Chapter 20 Troubleshooting the Serial SPAs

Using Bit Error Rate Tests

BERT (Bit-Error Rate Testing) is used for analyzing quality and for problem resolution of digital
transmission equipments. BERT tests the quality of an interface by directly comparing a pseudorandom
or repetitive test pattern with an identical locally generated test pattern.
The BERT operation is data-intensive. Regular data cannot flow on the path while the test is in progress.
The path is reported to be in alarm state when BERT is in progress and restored to a normal state after
BERT has been terminated.
BERT is built into most of the serial SPAs. With BER tests, you can test cables and signal problems in
the field.
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BERT operation is data-intensive. Regular data cannot flow on the path while the test is in progress. The
Note
path is reported to be in alarm state when BERT is in progress and restored to a normal state after BERT
has been terminated.
There are two categories of test patterns that can be generated by the onboard BER test circuitry:
pseudorandom and repetitive. Pseudorandom test patterns are exponential numbers and conform to the
CCITT/ITU O.151 and O.153 specifications; repetitive test patterns are all zeros, all ones, or alternating
zeros and ones.
A description of the test patterns follows:
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For the 2-Port and 4-Port Channelized T3 SPA, you can configure individual T1 lines to run BER
tests, but only one BER test circuit exists for all 28 T1 lines. Hence, only one BER test can be run
on a single T3 port at any given time.
For the 8-port Channelized T1/E1 SPA, there are six framer-assisted BERT engines, and six BER
tests may run concurrently.
For the 1-Port Channelized OC-3/STM-1 SPA and 1-Port Channelized OC-12/STM-4 SPA, you can
run a maximum of 27 concurrent tests across all paths on the SPA.
Pseudorandom test patterns:
2^15 (per CCITT/ITU O.151)
–
2^20 (per CCITT/ITU O.153)
–
2^23 (per CCITT/ITU O.151)
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QRSS (quasi-random signal sequence) (per CCIT/ITU O.151)
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Repetitive test patterns:
– All zeros (0s)
– All ones (1s)
– Alternating zeros (0s) and ones (1s)
Cisco ASR 1000 Series Aggregation Services Routers SIP and SPA Software Configuration Guide
Using Bit Error Rate Tests
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