Qos policing

Unanswered Question
Dec 19th, 2008

Hi,

A quick question about policing I'm trying to understand the parameters from my policy-map and wondered what the following means

class 4mbps-at5-No1

police cir 4000000 pir 6000000 be 750000

conform-action transmit

exceed-action transmit

violate-action drop

I take it as follows

committed information rate - this is 4meg which this traffic is committed to getting during times of congestion the traffic matching class 4mbps-at5-No1 will get 4000000 if it requires it during congestion.

Then PIR, is this the policed rate which the router will allow the traffic to reach if there is no congestion?

Also be when does this come into effect?

Also when does the router decide to enforce this policing what is the threshold?

I will try and find some docs to read up on all this but was hoping someone can give me a quick answer.

thanks

Chris

I have this problem too.
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Joseph W. Doherty Fri, 12/19/2008 - 11:40

A policer doesn't detect or directly react to congestion. It monitors a traffic tranmission rate and does things depending on monitored speed vs. policer parameter settings.

CIR is the specified long term transmission rate.

PIR is the specified short term burst transmission rate.

Be (and Bc; not in your example) isn't easy to explain in a "quick answer" beyond it concerns the measurement periods for PIR (likewise Bc for CIR). You might want to read:

http://www.cisco.com/en/US/docs/ios/12_2t/12_2t4/feature/guide/ft2RTplc.html

or

http://www.cisco.com/en/US/docs/ios/12_0s/feature/guide/12s_cap.html

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