Average rate of Exp On-Off source

[Loh Kok Jeng <elelohkj@leonis.nus.edu.sg>]

Hi,

If I have an Exponetial On-Off source with the following parameters, what
is the average rate?
	packet size = 500 bytes
	burst time  = 500ms
	idle time   = 500ms
	peak rate   = 100kb/s

I did a few simple tests and calculated the average rate of such a source
over 50s.  I got 30.4504kb/s consistently.  Shouldn't the average be about
50kb/s?