This attribute displays whether a PLCP Loss Of Frame (LOF)
failure alarm state has been entered. An LOF failure is declared
when a PLCP LOF defect persists for 2.5 s +/- 0.5 s. An LOF defect
occurs when an OOF (Out of Frame) state persists for more than 1
ms. If the OOF events are intermittent, the LOF defect counter is
decremented at a rate of 1/12 (for DS3 PLCP) or 1/9 (for G.751 E3
PLCP) of the incrementing rate, with all measurements based on a
200 ms polling cycle. An OOF event (also known as a PLCP SEF
event) is declared when an error is detected in both the A1 and A2
octets, or when two consecutive POHIDs are found in error.
OOF is removed when two valid sets of framing octets and two
valid and sequential POHID octets have been found. The LOF
defect is removed when the defect counter reaches zero, i.e. when
OOF events are absent for more than 12 ms (DS3 PLCP) or 9 ms
(G.751 E3 PLCP). LOF failure alarm is cleared when LOF defect is
absent for 10.0 s +/- 0.5 s
The DS3 or E3 component goes into an operational state of disabled
until the LOF failure alarm is cleared. The terminal declaring the
LOF failure alarm will transmit a PLCP RAI signal to the far-end
for the duration of the alarm.
The lofAlarm attribute is always set to off when the DS3 or E3
component has been locked and left offline.