Traffic Policing : Rate-Limit or MQC Policing

Example : limiting icmp traffic to 128kbps with a permitted burst during 1/4th of the rate

Legacy traffic policing using the command rate-limit

access-list 110 permit icmp any any
access-list 110 permit ip any any

interface e0/0
rate-limit 110 128000 4000 4000 conform-action transmit exceed-action drop

128000 bps : rate-limit
4000 bytes : normal rate that could be sent at clock rate (bucket size every timeslot)
4000 bytes : exceed rate that could be sent at clock rate

Bc = Be so there is no exceed burst

Verification

show interface rate-limit


traffic policing using MQC

Cef must be activated

class-map match-all CAR
match protocol icmp

policy-map CAR
class CAR
police cir 128000 bc 4000

interface e0/0
service-policy out CAR

128000 : rate limit
4000 : normal rate that could be sent at clock rate
Be : 0

Verification

show policy-map interface


Differences

- Legacy CAR : configured Bc should include Be (Bc = excess_bits + Be)
- MQC CAR use a default Bc of 2xBe if not configured
- MQC CAR : configured Bc doesn't include Be ( Bc = excess_bits)