dummynet pipe burst

[Adailton Milhorini]

How to works dummynet burst..

I read on man ipfw,

    burst size
              If the data to be sent exceeds the pipe's bandwidth limit (and
              the pipe was previously idle), up to size bytes of data are
              allowed to bypass the dummynet scheduler, and will be sent as
              fast as the physical link allows.  Any additional data will be
              transmitted at the rate specified by the pipe bandwidth.  The
              burst size depends on how long the pipe has been idle; the 
effec-
              tive burst size is calculated as follows: MAX( size , bw *
              pipe_idle_time).


but don´t show sample...
  pipe_idle_time?????????????

any sample for explain ...

thank you...

Adailton Milhorini