Operation
3-6
Round Robin Arbitration (Level 2)
This level makes use of idle time slices. There is a token passed on every time slice
to modules participating in this level of arbitration. Only one module has the
token at any one time slice. If the module assigned to the next time slice is not
requesting then the module with the token will be granted access if it is
requesting. The token is passed to the next highest slot number participating each
time slice.
Lowest Slot Number (Level 3)
This level is only used if the other two levels fail in granting access to the
backplane. If the owner of the token is not requesting, then the lowest slot number
requesting will be granted access. This ensures that a time slice will not be idle if
there are modules requesting access.
Monarch/Slave SmartSwitch 9000 Modules
All modules in an SmartSwitch 9000 chassis that transfer packets across the INB
backplane have identical INB interfaces. However, one of them has to be selected
to perform the backplane arbitration. The lowest slot number module will
automatically be selected as the arbitrator. This module will be called the
Monarch and others will be Slaves to that module. If the Monarch module is
removed from the chassis, a re-election occurs and the module with the lowest
slot number is elected Monarch.