Marconi OMS 1200
Technical Product Description
221 02-ZAP 701 25/1 Rev C 2006-08-04
© Ericsson AB 2006
03PHB00004AAV-CUA
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7.4.5.1
Locally Detected Line Failure Events
When a tributary card is removed, the controller function detects a card-out signal and
sends a Forced Slot Fail message to the core card switch function stating which
psuedo-STM-1 interface is affected. The Forced Slot Fail condition is latched in the
core card switch function.
The switch ORs this controller derived interface fail condition with the locally detected
interface parity failure. If either failure condition is active, then any SF/SD signalling
flags on the affected interface, for protected multiplex sections and HO/LO VC
channels, are considered as having failed and are interpreted as SF conditions. An
interface failure also causes AIS to be injected toward the router by the tributary-side
cross connect in all TU-Ns, resulting in AIS being transmitted on all ports cross-
connected to the failed interface.
When a card is replaced into a configured slot, the controller function checks the
validity of the card and after downloading the configuration database sends a Clear
Slot Fail message to the switch. The controller-derived interface failure is then
removed, and provided there is no locally detected interface failure; the SF/SD flags
are again monitored.
Detection of locally received failures on an STM-n section is performed by a
combination of the receiving STM-n unit and the core unit.
Two criteria are used to indicate the status of each section to the protection switching
control mechanism:
•
Signal Fail (SF)
•
Signal Degrade (SD).
The STM-n unit generates these flags and the core unit receives them and uses them
to trigger the next stage of the protection switching sequence.
Each STM-n unit is responsible for monitoring its connected STM-n input. A failure
indication is raised if one, or more, of the following criteria is detected:
•
STM-n Loss of Signal
•
Loss of Frame Alignment
•
MS AIS - bits 6, 7 and 8 of K2 received in state 111.