This variable limits the number of multicast frames forwarded
by this port over a 1 second interval. The minimum threshold
limit may vary between platforms, but can be determined by multiplying
this value by the swSysBridgePortReceiveMulticastLimitMultiplier
value. For example if this value equals 2, and the
swSysBridgePortReceiveMulticastLimitMultiplier equals 1000 then no
more than 2000 multicast frames per second will be forwarded by this port.
The default value for this object is zero which an infinite rate.