The maximum number of hosts in the top N table.
When the associated hostTopNRequestedSize object is
created or modified, the probe should set this
object as closely to the requested value as is
possible for the particular implementation and
available resources. The probe must not lower this
value except as a result of a set to the associated
hostTopNRequestedSize object.
Hosts with the highest value of hostTopNRate shall be
placed in this table in decreasing order of this rate
until there is no more room or until there are no more
hosts.