I am monitoring an interface on a cisco 3925 router. its a gig interface that is statically set to 100 meg/full duplex.  The actual port speed subscribed to from the carrier is 20 megabits up/down.

on our traffic graph we are getting spikes up to 100 meg or higher some times that throws off the view of the graph.  From the carriers perspective they are shaping it down so theirs no way we could receive over 20 megabits at a time.  Can someone help me understand why we are getting these spikes showing up in the graph? On the interface configuration on the router we have the bandwidth set 20 megabits, and in NFA we changed the In Speed and Out Speed to be 20000000 bits/sec.