Re: Policing - what happens to violate packets?

From: allboutcisco (frenzeus@streamyx.com)
Date: Tue Jun 27 2006 - 01:49:07 ART

Hi Petr,

Below is what i found out:

Rack1R2(config-if)#do sh policy-map QOS_IN
  Policy Map QOS_IN
    Class UDP
     police cir 128000 bc 2000 be 2000
       conform-action transmit
       exceed-action set-prec-transmit 0
Rack1R2(config-if)#
Rack1R2(config-if)#do sh policy-map int f0/0
 FastEthernet0/0

  Service-policy input: QOS_IN (2361)

    Class-map: UDP (match-all) (2362/5)
      0 packets, 0 bytes
      5 minute offered rate 0 bps, drop rate 0 bps
      Match: access-group 101 (2363)
      police:
          cir 128000 bps, bc 2000 bytes <--------------NO be value
        conformed 0 packets, 0 bytes; actions:
          transmit
        exceeded 0 packets, 0 bytes; actions:
          set-prec-transmit 0
        conformed 0 bps, exceed 0 bps

    Class-map: class-default (match-any) (2365/0)
      0 packets, 0 bytes
      5 minute offered rate 0 bps, drop rate 0 bps
      Match: any (2366)
        0 packets, 0 bytes
        5 minute rate 0 bps

It's clear indeed now that even if be value was defined but no violate action was configured,
Be value was not used here.

But as i read thru the link in the doccd where it says "Setting the extended burst value equal to the normal burst value excludes the extended burst capability."
This was actually picked out from IEWBv3 Lab 13 Task8.1 where the task was to convert CAR to MQC CLI. One of the lines are as below:

interface FastEthernet0/0
 rate-limit input access-group 101 128000 2000 2000 conform-action transmit exceed-action set-prec-transmit 0
!
 rate-limit input access-group 102 256000 4000 8000 conform-action transmit exceed-action set-prec-transmit 0

It seems to me that for access-group 101, Bc=Be which means Be should be 0. But from the solution guide, they gave be=2000. But why set be=2000 when there's no violate-action?
  ----- Original Message -----
  From: Petr Lapukhov
  To: allboutcisco
  Cc: Cisco certification
  Sent: Tuesday, June 27, 2006 1:40 AM
  Subject: Re: Policing - what happens to violate packets?

  Here,

  check this link, it explains how actually CAR treats Be value :)
  It's totally different from MQC policer behavior :)

  http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/hqos_c/part20/qchpolsh.htm#wp1000944

  HTH
  --
  Petr Lapukhov, CCIE #16379
  petr@internetworkexpert.com

  Internetwork Expert, Inc.
  http://www.InternetworkExpert.com
  Toll Free: 877-224-8987
  Outside US: 775-826-4344

  2006/6/26, allboutcisco <frenzeus@streamyx.com>:
    Hi Petr,

    Thanks for the reply. What do u mean when u say for CAR ""exceed" action is
    somewhat "random", to simulate RED behavior, and depends on Be-Bc
    "margin"."

    Thanks.

    K

    ----- Original Message -----
    From: "Petr Lapukhov" <petr@internetworkexpert.com>
    To: "allboutcisco" < frenzeus@streamyx.com>
    Cc: "Cisco certification" <ccielab@groupstudy.com>
    Sent: Monday, June 26, 2006 7:43 PM
    Subject: Re: Policing - what happens to violate packets?

> Hmm, since no *violate* action has been defined, Be value is NOT used
> actually. All your traffic that exceeds Bc falls under exceed action.
>
> This behavior is unlike CAR, where you "exceed" action is somewhat
> "random", to simulate RED behavior, and depends on Be-Bc "margin".
>
> HTH
>
> --
> Petr Lapukhov, CCIE #16379
> petr@internetworkexpert.com
>
> Internetwork Expert, Inc.
> http://www.InternetworkExpert.com
> Toll Free: 877-224-8987
> Outside US: 775-826-4344
>
> 2006/6/26, allboutcisco <frenzeus@streamyx.com>:
>>
>> Hi Group,
>>
>> Looking at the config below:
>>
>> Rack1R2#sh run | b policy-map
>> policy-map QOS_IN
>> class UDP
>> police cir 128000 bc 2000 be 2000
>> conform-action transmit
>> exceed-action set-prec-transmit 0
>> class TCP
>> police cir 256000 bc 4000 be 8000
>> conform-action transmit
>> exceed-action set-prec-transmit 0
>>
>> Taking class UDP as an example, policing rate for UDP is 128000bps, with
>> a
>> Bc bucket depth of 2000 bytes & a Be bucket depth of 2000 bytes as well.
>> A
>> bunch of packets arrive, assuming Bc bucket tokens are all used up to
>> transmit & excess packets used up all of Be bucket tokens as well where
>> the
>> excess action is to set prec to 0 then transmit. Now assuming that there
>> are
>> still packets & since no action has been defined for violate - what
>> happens
>> to those packets?
>>
>> Appreciate if someone could advise on this?
>>
>> Thanks.
>>
>> Cheers,
>> K
>>
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