dot1dStpBridgeMaxAge: From RFC1493(Bridge MIB).
The value that all bridges use for MaxAge when
this bridge is acting as the root.
Note that 802.1D-1990 specifies that the
range for this parameter is related to the value of
dot1dStpBridgeHelloTime. The granularity of this
timer is specified by 802.1D-1990 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.