The value that all bridges use for ForwardDelay
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
ctPvstStpBridgeMaxAge. 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.