Definitions:
Errored Second (ES):
A one-second time interval in which one or more bit errors occurs.
Severely Errored Second (SES):
A one-second interval in which the bit error ratio exceeds 10
-3
.
Unavailable Second (UAS):
A circuit is considered to be unavailable from the first of at least ten consecutive SES. The circuit
is available form the first of at least ten consecutive seconds which are not SES.
Available Second (AS):
A one-second time interval in which no bit errors occur.
Errored Free Second (EFS):
A one-second time interval in AS during which no errors and no pattern slips have been
detected.
Evaluation according to ITU-T G.826
G.826 recommendation makes provision for higher bit rates and allows in-service measurement using the evaluation of block
errors.
The following are evaluated: ES, SES, BE, BBE, and UAS.
Pass/Fail result depending on path allocation of 0.1 to 100%.
In-service measurement (ISM)
Simultaneous in-service measurement of “near end” and “far end” of a selected path:
Out-of-service measurement (OOS)
Out-of-service measurement using bit errors in a test pattern
Definitions:
Errored second (ES):
A one-second time interval containing one or more errored blocks.
Severely Errored Second (SES):
A one-second time interval in which more than 30% of the blocks are errored
Block Error (BE):
A block containing one or more errored bits.
Background Block Error (BBE):
An errored block that is not a SES .
Unavailable second (UAS):
A circuit is considered to be unavailable from the first of at least ten consecutive SES. The circuit
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