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Making Measurements
Measuring Error Analysis
In-service G.826 analysis allows setting a Path Unavailable Seconds (PUAS)
threshold. If the threshold is set and a PUAS count in excess of the threshold is
measured a FAIL result is displayed.
The PUAS threshold is unaffected by the Path Allocation.
M.2100, M.2110, M.2120 Analysis
(Option 003 only)
Previously ITU-T G.821 was the only international recommendation available to
measure the quality of a communications link. ITU-T G.821 was originally an out-
of-service measurement and analysis for commissioning a link and troubleshooting
during severe disruption. The commissioning test was a one-month out-of-service
test based on errored and severely errored seconds. A one-month test with the
subsequent loss of revenue is clearly unacceptable.
Due to demand ITU-T G.821 also evolved into proprietary methods for in-service
testing based on FAS and code errors. Demand for high quality leased lines meant
an in-service performance standard, closer to real conditions and allowing
comparisons between providers, was required.
The ITU-T M.2100 series was specifically defined to provide a clear indication of
link quality, for service providers using long term performance analysis. "Bringing
into Service" and "repair criteria" analysis were also included.
M.2100 analysis is based on frame errors and provides Error Seconds (anomaly),
Severely Errored Seconds (defect) and Unavailability results for receive and
transmit directions. Transmit results are only available for 2 Mb/s signals with CRC
framing. Out-of-service testing is only available for the receive direction. M.2110 is
an out-of-service measurement for "bringing into service" testing of paths. A
15 minute BER test is performed and if this is error free, a 24 hour M.2110 test is
performed. If the 24 hour M.2110 test displays PASS (S1 limit not reached) the path
can be returned to service. If FAIL is displayed (S2 limit reached or exceeded) the
15 minute BER test should be repeated, If ? (UNCERTAIN) is displayed (result
between the S1 and S2 limits) run the 7 day BIS test.
The PASS, FAIL and UNCERTAIN parameters are determined by the S1 and S2
limits which are user selectable.
BIS Objective (BISO)
UNACCEPTABLE
S2
REGION OF UNCERTAINTY
S1
BRING INTO SERVICE
6-7
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