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Chapter 5
Fault Tolerance
As previously mentioned, you can cluster multiple AT-3600 Series Repeaters
in the same chassis, where they will all operate together as a single logical
concentrator. You manage the entire department concentrator (via the
management agent) from the Master AT-3600 module. Modules are numbered
from 1 through 8, top to bottom, in the chassis.
The
Master
is defined to be the module in the lowest numbered (physically
the topmost) occupied slot position. Typically this is slot 1, but it could be slot
2 if slot 1 is vacant, etc. The other AT-3600 modules in the same backplane are
called
Slaves
.
The first Slave in the hub watches over the Master and can take over the
Master’s functions if necessary: this special module is called the
Backup
. This
module is defined as the one occupying the next higher numbered slot
position after the Master.
Department Concentrator Reconfiguration
Each module in a department concentrator of multiple AT-3600 Series
Repeaters knows its own slot position within the chassis, and which other slot
positions are occupied. From this information, each module determines
whether it should act in the capacity of a Master, Backup or Slave. This
process is called
role determination
.
Role determination occurs as soon as you power up or reset the department
concentrator. Each module then begins to operate in its appropriate capacity.
In addition, all of the modules constantly check the configuration of the
department concentrator. If anything changes, role determination is repeated
to make sure each module is performing its appropriate function. If you
remove or add any modules, the entire department concentrator will readjust
itself to the new configuration as necessary. Configuration changes will be
detected and the new role determination performed in less than two seconds.
