User Manual

ArchitectureNortel Networks Confidential 3–15
S8000/S8002/S8006 BTS Reference Manual
3.2.1.10 ALCO board–oriented defense actions
If there is an ALCO card hardware failure, the CSWM restarts self–tests by means
of the commands available on the O&M bus. If the self–tests are successful, the
ALCO card is considered operational again and the BSC is informed.
3.2.1.11 Gateway switchover management
If there is a gateway failure, the gateways themselves determine state change
(passive ⇔ active). Then the fault signal is transferred to the CSWM via the O&M
bus.
Each gateway can send its status to the CSWM, either after a query from the CSWM
or spontaneously after switchover.
3.2.1.12 Duplex operation between CSWMs
The duplex function manages CSWM equipment redundancy in the BCF. The BSC
only perceives one CSWM at a time.
Redundancy is operated in passive/dynamic mode with hot restart:
The standby processor does not execute the same algorithms as the active
processor and does not receive the same message flow.
The active CSWM sends stable status information to the standby side. If a
problem arises on the active side, the standby CSWM takes over BCF control.
Switchover time includes the time needed to locate the fault, return to a stable
status, and restart processing.
Causes of switchover
Switchover may be triggered by hardware or software resetting. The watchdog
triggers hardware resetting, and software is reset by a software init message.
Hardware resetting may be triggered by the following:
a major hardware fault (CPU, memory units, etc.)
a serious software fault (address error)
Software resetting may be triggered by the following:
a minor hardware fault (switching matrix, internal PCM bus, O&M bus drivers)
a system software fault (dynamic memory overfilling)
Switchover procedure
The switchover procedure can only be performed in a stable system status. In the
event of switchover, the CSWM tries to return to the last stable condition. It checks
that its database (last stable state) and slave processor states (alarm units,
synchronization units, concentrator units, PCM interface units and transmitter
units) are consistent and may reconfigure them.