The value that all bridges use for MaxAge when
this bridge is acting as the root. Note that
802.1d/D9 specifies that the range for this
parameter is related to the value of
dot1dStpBridgeHelloTime. The granularity of this
timer is specified by 802.1d/D9 to be 1 second.
An agent may return a badValue error if a set is
attempted to a value which is not a whole number
of seconds.