QOS - "police cir" vs "police rate"

Hello Experts,

What is the difference between "police cir" and "police rate" ?
Both policy-maps below are supposed to:
Up to 30%: transmit.
Exceeding traffic up to 40%: mark dscp 2
Above 40%: drop

For me the look the same:

policy-map CIR
 class WWW
   police cir percent 30 pir percent 40
     conform-action transmit
     exceed-action set-dscp-transmit 2
     violate-action drop

policy-map RATE
 class WWW
   police rate percent 30 peak-rate percent 40
     conform-action transmit
     exceed-action set-dscp-transmit 2
     violate-action drop

Blogs and organic groups at http://www.ccie.net
Received on Mon Feb 01 2010 - 22:06:56 ART