Re: Tc

From: Petr Lapukhov (petr@internetworkexpert.com)
Date: Fri Jun 23 2006 - 01:55:48 ART

Yeah, Cisco IOS has a lot of policing options, that may seem to be
confusing..

Living aside weird CAR behavior, let's stick with MQC policer. We have three

options here

1) Single-rate three-color policer (police)
2) Two-rate three-color policer (police cir, behaves like police w/o
peak-rate)
3) Contro-plane policer (police rate)

For many years people were asking - what burst values should they pick up?
:)
There is no single answer, a pity :) But with MQC Cisco permits you to rely
on it's defaults. E.g. you may simply type "police 1000000" and IOS
will pick up some "default" commited burst size. For instance

policy-map TEST
 class class-default
   police 1000000

Router#show policy-map
  Policy Map TEST
    Class class-default
     police cir 1000000 bc 31250
       conform-action transmit
       exceed-action drop

Default bc here is bitrate*0.250ms/8 bytes.. It seems that default
"capacity" is 0.250 ms but not 0.200ms. Actually, it does not matter
how much is it. The main point is that you may finally omit bursts
and let IOS pick the defaults ;)

HTH

2006/6/23, Victor Cappuccio <cvictor@protokolgroup.com>:
>
> I got lost... Do you QOS Gurus mind to shed a light over here?
> How did you have those values?
>
> Thanks and sorry for the ignorance :S
>
> Victor.
>
>
> -----Mensaje original-----
> De: nobody@groupstudy.com [mailto:nobody@groupstudy.com] En nombre de Petr
> Lapukhov
> Enviado el: Jueves, 22 de Junio de 2006 03:14 p.m.
> Para: Chris Lewis
> CC: Sami; ccielab@groupstudy.com
> Asunto: Re: Tc
>
> Chris,
>
> I guess Sami actually mentions commited burst size with MQC,
> which is 200ms*Bitrate by default, AFAIR :)
>
> 2006/6/22, Chris Lewis <chrlewiscsco@gmail.com>:
> >
> > Sami,
> >
> > Could you explain what you mean by Tc in relation to applying the
> > bandwidth
> > command and how you arrive at the 200ms figure?
> >
> > Chris
> >
> >
> > On 6/22/06, Sami <sy1977@gmail.com > wrote:
> > >
> > > Group,
> > >
> > > What is default Tc for a ethenet interface ? I configured a policy and
> > > used
> > > 50% bandwidth , by caluclation it looks like default tc is 200 ms ? Is
> > > that
> > > correct ?
> > >
> > > R4#show policy-map interface fastEthernet 0/0
> > > FastEthernet0/0
> > >
> > > Service-policy output: Pri
> > >
> > > Class-map: IT (match-all)
> > > 0 packets, 0 bytes
> > > 5 minute offered rate 0 bps, drop rate 0 bps
> > > Match: access-group 81
> > > Queueing
> > > Strict Priority
> > > Output Queue: Conversation 264
> > > Bandwidth 50 (%)
> > > * Bandwidth 50000 (kbps) Burst 1250000 (Bytes)
> > > * (pkts matched/bytes matched) 0/0
> > > (total drops/bytes drops) 0/0
> > >
> > > Class-map: class-default (match-any)
> > > 15 packets, 1849 bytes
> > > 5 minute offered rate 0 bps, drop rate 0 bps
> > > Match: any
> > >
> > > Thanks
> > >
> > >
> _______________________________________________________________________
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>
>
>
> --
> Petr Lapukhov, CCIE #16379
> petr@internetworkexpert.com
>
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-- 
Petr Lapukhov, CCIE #16379
petr@internetworkexpert.com

Internetwork Expert, Inc.
http://www.InternetworkExpert.com
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