From: Gregory Gombas (ggombas@gmail.com)
Date: Tue Sep 04 2007 - 14:09:51 ART
Thanks Victor,
So if I had to summarize, using PIR has two benefits:
1. Gives a more consistent traffic pattern (as opposed to guessing
when burst will be allowed or not allowed based on refilling of the
token bucket.
2. Allows you to color traffic that is out of profile (but I'm not
sure how that aspect differs from a single rate, tri color policer).
Is that correct?
If anyone can elaborate on point 2 please feel free to chime in here.
Thanks,
Greg
On 9/4/07, Victor Cappuccio <vcappuccio@ccbootcamp.com> wrote:
>
>
>
> Recommended Book for this
>
> Tim Szigeti, CCIE No. 9794, Christina Hattingh
> Copyright (c) 2005 Cisco Systems, Inc.
> Published by:
> Cisco Press
> 800 East 96th Street
> Indianapolis, IN 46240 USA
>
> Excellent to have in the book self or in safari
>
>
> Two-Rate Three-Color Marker/Policer
>
> The single-rate three-color marker/policer was a significant improvement for
> policers, in that it made allowance for temporary traffic bursts (as long as
> the overall average transmitted rate was equal to or below the CIR).
> However, the variation in the number of accumulated excess burst credits
> could cause a degree of unpredictability in traffic flows. To improve on
> this, a two-rate three-color marker/policer was defined in RFC 2698. This
> policer addresses the peak information rate (PIR), which is unpredictable in
> the RFC 2697 model. Furthermore, the two-rate three-color marker/policer
> allows for a sustainable excess burst (negating the need to accumulate
> credits to accommodate temporary bursts) and allows for different actions
> for the traffic exceeding the different burst values.
>
> The two-rate three-color marker/policer was introduced in Cisco IOS Software
> Release 12.2(4)T and uses the following parameters to meter the traffic
> stream:
>
> PIR Peak information rate, the maximum rate that traffic ever is allowed
>
> PBS Peak burst size, the maximum size of the first token bucket
>
> CIR Committed information rate, the policed rate
>
> CBS Committed burst size, the maximum size of the second token bucket
>
> Tp Token count of CBS, the instantaneous number of tokens left in the PBS
> bucket
>
> Tc Token count of EBS, the instantaneous number of tokens left in the CBS
> bucket
>
> B Byte size of offered packet
>
> The two-rate three-color policer also uses an algorithm with two token
> buckets, but the logic varies slightly. Instead of transferring unused
> tokens from one bucket to another, this policer has two separate buckets
> that are filled each second with two separate token rates. The first bucket
> is filled with the PIR number of tokens and the second bucket is filled with
> the CIR number of tokens. In this model, the Be works the same as the Bc,
> except for the PBS bucket (not the CBS bucket). This means that Be
> represents the peak limit of traffic that can be sent during a subsecond
> interval.
>
> The logic varies further in that the initial check is to see whether the
> traffic is within the PIR. Only then is the traffic compared against the
> CIR. (In other words, a violate condition is checked for first, then an
> exceed condition, and finally a conform condition, which is the reverse of
> the logic of the previous model.)
>
>
> thanks,
> Victor Cappuccio.-
> - CCSI# 31452
>
> CCBOOTCAMP - A Cisco Sponsored Organization (SO)
> vcappuccio@ccbootcamp.com
> Toll Free: 877-654-2243
> Direct: +1-702-968-5100 = Outside the USA
> FAX: +1-702-446-8012
> YES! We take Cisco Learning Credits!
> Training And Remote Racks: http://www.ccbootcamp.com
>
> Register to win a free iPhone!
> http://www.ccbootcamp.com/iphone.html
>
>
>
> -----Original Message-----
> From: Gregory Gombas [mailto:ggombas@gmail.com]
> Sent: Tue 04-Sep-07 7:28 AM
> To: Victor Cappuccio
> Cc: groupstudy
> Subject: Re: When to use PIR?
>
> Thanks,
>
> But how does that different from:
> exceed action set-dscp
> violate action set-dscp
>
> ?
> On 9/4/07, Victor Cappuccio <vcappuccio@ccbootcamp.com> wrote:
> > I found this Link very interesting about the topic
> http://www.juniper.net/techpubs/software/junos/junos74/swconfig74-cos/html/cos-tcm2.html#1196011
> >
> > With colorblind policing, all packets are evaluated by the CIR. If a
> packet exceeds the CIR, it is evaluated by the PIR.
> >
> >
> > thanks,
> > Victor Cappuccio.-
> > - CCSI# 31452
> >
> > CCBOOTCAMP - A Cisco Sponsored Organization (SO)
> > vcappuccio@ccbootcamp.com
> > Toll Free: 877-654-2243
> > Direct: +1-702-968-5100 = Outside the USA
> > FAX: +1-702-446-8012
> > YES! We take Cisco Learning Credits!
> > Training And Remote Racks: http://www.ccbootcamp.com
> >
> > Register to win a free iPhone!
> http://www.ccbootcamp.com/iphone.html
> >
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com on behalf of Gregory Gombas
> > Sent: Tue 04-Sep-07 6:54 AM
> > To: groupstudy
> > Subject: When to use PIR?
> >
> > Hey Folks,
> >
> > When configuring policing, when is it necessary to use PIR?
> >
> > From what I understand PIR allows you continuosly send traffic at a
> > rate above your CIR (as opposed to occasional burst) but if that is
> > that case, why not just set your CIR to that higher value?
> >
> > For example, if your CIR is 256k and PIR is 512k, the policer will
> > allow you to send continously at 512k, correct? If that is the case,
> > then why not just set your PIR to 512k?
> >
> > Thanks,
> > Greg
> >
> >
> _______________________________________________________________________
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html
> >
> >
> >
>
>
> From: Gregory Gombas [mailto:ggombas@gmail.com]
> Sent: Tue 04-Sep-07 7:28 AM
> To: Victor Cappuccio
> Cc: groupstudy
> Subject: Re: When to use PIR?
>
> Thanks,
>
> But how does that different from:
> exceed action set-dscp
> violate action set-dscp
>
> ?
> On 9/4/07, Victor Cappuccio <vcappuccio@ccbootcamp.com> wrote:
> > I found this Link very interesting about the topic
> http://www.juniper.net/techpubs/software/junos/junos74/swconfig74-cos/html/cos-tcm2.html#1196011
> >
> > With colorblind policing, all packets are evaluated by the CIR. If a
> packet exceeds the CIR, it is evaluated by the PIR.
> >
> >
> > thanks,
> > Victor Cappuccio.-
> > - CCSI# 31452
> >
> > CCBOOTCAMP - A Cisco Sponsored Organization (SO)
> > vcappuccio@ccbootcamp.com
> > Toll Free: 877-654-2243
> > Direct: +1-702-968-5100 = Outside the USA
> > FAX: +1-702-446-8012
> > YES! We take Cisco Learning Credits!
> > Training And Remote Racks: http://www.ccbootcamp.com
> >
> > Register to win a free iPhone!
> http://www.ccbootcamp.com/iphone.html
> >
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com on behalf of Gregory Gombas
> > Sent: Tue 04-Sep-07 6:54 AM
> > To: groupstudy
> > Subject: When to use PIR?
> >
> > Hey Folks,
> >
> > When configuring policing, when is it necessary to use PIR?
> >
> > From what I understand PIR allows you continuosly send traffic at a
> > rate above your CIR (as opposed to occasional burst) but if that is
> > that case, why not just set your CIR to that higher value?
> >
> > For example, if your CIR is 256k and PIR is 512k, the policer will
> > allow you to send continously at 512k, correct? If that is the case,
> > then why not just set your PIR to 512k?
> >
> > Thanks,
> > Greg
> >
> >
> _______________________________________________________________________
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html
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