police cir and police rate commands

BennyLavaBennyLava Posts: 60Member ■■□□□□□□□□
The QoS Exam Certification Guide doesn't mention the 'police rate' command at all and I've been trying to figure out if there is any difference between this and the 'police cir' command (besides the fact that 'police rate' allows you to configure the rate as bps or packets per second, and 'police cir' only allows bps). I found this on Cisco's site which sounds like 'police rate' is meant to be used for control plane policing:
http://www.cisco.com/en/US/docs/ios/qos/command/reference/qos_n1.html#wp1013265

and this on Internetwork Expert's forums which says the same thing (read the last post by Petr Lapukhov):
http://ieoc.com/forums/t/2944.aspx

However I've found that both 'police rate' and 'police cir' are able to be configured in a policy and applied on an interface. Wouldn't the result of using either of the following 2 commands and applying the policy to an interface be the same?
police cir 64000 bc 8000 conform-action transmit exceed-action drop

police rate 64000 burst 8000 conform-action transmit exceed-action drop

Is there any reason not to use 'police rate' on an interface, or is this just two different ways of doing the same thing?

Comments

  • armsvedarmsved Posts: 1Registered Users ■□□□□□□□□□
    Does anyone have an answer to this?

    What is the purpose of policy rate? If it's only control plane, shouldn't that mean it'll only police traffic destined to the router?
  • d4nz1gd4nz1g Posts: 464Member
    hi armsved.

    Police rate is usually used at CoPP policies, and it uses packets per second rate. a CoPP policy is attached to the control plane, not to an interface.

    Ex: policy-map policy
    class class
    police rate 1500 pps

    control-plane
    service-policy input policy

    Police cir is used to define the CIR for a given link (the commited information rate), which is usually defined by bps (you don't contract any service measuring in pps, right?). Usually used along with pir (peak information rate). Read about color aware policing.

    Ex: policy-map policy
    class class
    police cir 1000 pir 3000

    Honestly, I wouldnt know how to answer if you can exchange the usage, because most implementations use it this way.
    However, you are free to test it on a lab.


    Edit: sauce - End-to-End QoS Network Design: Quality of Service for Rich-Media & Cloud Networks, Second Edition, Video Enhanced Edition - Chap 4
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