Friday, February 20, 2009

CAR and Policing

CAR is proprietry to cisco where as policing supports RFC 2697. Rate-Limit is used for the implementation of CAR where as police command is used for policing. CAR works on single tocken bucket where as Policing works seperate token buckets for burst. CAr supports two coloring which is confirm and exceed action where as policing supports three coloring which is confirm,exceed and violate action. One major advantage of using policing is that you can remark the packets where as CAR doesnot support the same feature.

How to configure rate limit
rate-limit input 1536000 288000 576000 conform-action transmit exceed-action drop
rate-limit output 1536000 288000 576000 conform-action transmit exceed-action drop

How to configure policingpolicy-map MPLSVPN
class MPLS police 16000 2000 2000 conform-action transmit exceed-action drop

interface fastethernet 0/0 service-policy output MPLSVPN

Cisco recommends using the following formulas when calculating the normal and extended burst parameters in case of car.
normal burst (in bytes) = configured rate (in bits per second) * (1 byte)/(8 bits) * 1.5 seconds extended burst = 2 * normal burst

shivlu jain

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1 comment:

john said...

what a nice post car & policing,i like it