From: Montgomery, Jerry (jerry.montgomery@eds.com)
Date: Tue Jul 18 2006 - 18:59:01 ART
Elmer,
Thanks for the link.
I wished the commands associated with shape [shape (class-map) and shape
(policy-map class)] would be more similar especially the part concerning
the calculation of peak rate.
No mention of peak rate calculation under shape (policy-map class).
peak rate = CIR(1+Be/Bc)
Respectfully,
Jerry Montgomery, CCDP, CCNP, CCDA, & CCNA
-----Original Message-----
From: Elmer Hall [mailto:Elmer.Hall@vaci.com]
Sent: Tuesday, July 18, 2006 3:47 PM
To: 'Chris Lewis'; Montgomery, Jerry
Cc: 'Kay D'; ccielab@groupstudy.com
Subject: RE: Shaping Average / Peak vs. Policing
You can specify two types of traffic shaping; average rate shaping and
peak rate shaping. Average rate shaping limits the transmission rate to
the committed information rate (CIR). Using the CIR ensures that the
average amount of traffic being sent conforms to the rate expected by
the network.
Peak rate shaping configures the router to send more traffic than the
CIR. To determine the peak rate, the router uses the following formula:
peak rate = CIR(1+Be/Bc)
Source:
http://www.cisco.com/en/US/products/sw/iosswrel/ps1829/products_feature_
guid
e09186a00801b2405.html
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Chris Lewis
Sent: Tuesday, July 18, 2006 12:07 PM
To: Montgomery, Jerry
Cc: Kay D; ccielab@groupstudy.com
Subject: Re: Shaping Average / Peak vs. Policing
You can define Be as zero to simplify the math if you want to use shape
average also. Shape peak is not widely deployed in user networks.
Chris
On 7/18/06, Montgomery, Jerry <jerry.montgomery@eds.com> wrote:
>
> Good morning, Kay,
>
> I see that Chris Lewis had responded.
>
> I went back and forth trying to understand the difference. The main
> difference is that "shape peak" will send Bc + Be at every time
> interval, whereas "shape average" will send Bc every time and possibly
> Be if credits have been accumulated.
>
> So if you have a question that states limit the traffic to 128k and
> you can not use rate-limiting or policing, then "shape peak 128000" is
> the solution. The reason is that at any time interval you can not
> send more that Bc + Be.
>
> However, whereas "shape average" will send Bc + Be definitely at the
> first of each time interval. As such, at any particular time interval
> the router can transmit at a rate HIGHER than 128000.
>
> That is how I keep it straight.
>
> Now, can you configure "shape average CIR Bc Be" to provide the same
> result as "shape peak 128000"? Definitely, but that requires more
> math than just simply configuring "shape peak 128000" and letting the
> Cisco IOS calculate the appropriate Bc and Be.
>
> Let me know if this helps.
>
> Respectfully,
> Jerry Montgomery, CCDP, CCNP, CCDA, & CCNA
>
> -----Original Message-----
> From: Kay D [mailto:krsna83@gmail.com]
> Sent: Sunday, July 16, 2006 10:41 AM
> To: Montgomery, Jerry
> Cc: Chris Lewis; ccielab@groupstudy.com
> Subject: Re: Shaping Average / Peak vs. Policing
>
>
> Hi ,
> Still confused with whether "shape average " would allow excess
> traffic if credits are available or does it send only in the first
> interval . Please confirm and i can have a good sleep :)
>
> TIA
> Kay D
>
>
> On 7/12/06, Montgomery, Jerry <jerry.montgomery@eds.com> wrote: Chris,
>
> Thanks for the link. The light bulb just came on!!!!
>
> Thanks.
>
>
> Respectfully,
> Jerry Montgomery, CCDP, CCNP, CCDA, & CCNA
>
> -----Original Message-----
> From: Chris Lewis [mailto: chrlewiscsco@gmail.com]
> Sent: Tuesday, July 11, 2006 2:13 PM
> To: Montgomery, Jerry
> Cc: Joe Gagznos; ccielab@groupstudy.com
> Subject: Re: Shaping Average / Peak vs. Policing
>
>
> Please read over the following:
>
> http://www.cisco.com/warp/public/125/traffic_shaping_6151.html
>
> Shape peak does send Bc plus Be at every interval, contrary to my
> initial post.
> If things rae still unclear to you after reading this link, post
again.
>
> Cheers
>
> Chris
>
>
> On 7/11/06, Montgomery, Jerry < jerry.montgomery@eds.com> wrote: Good
> morning, Chris,
>
> What is the main difference between shape average and shape peak?
>
> I am trying to answer the following scenario:
>
> Limit all traffic leaving FA0/0 with IP Precedence of 128K. Do not
> use policing or rate-limiting.
>
> Sometimes I convince myself that "shape average 128000 16000 0" is the
> answer (assuming Tc=125ms). And then sometimes I convince myself that
> "shape peak 128000" is the answer (default to Bc and Be).
>
> Any inside as to what the difference between "shape average" and
> "shape peak" are?
>
> Also, can you send me a link regarding Be being sent in addition to Bc
> on the first interval of a second only? I did not find that
> information explicitly stated.
>
> Thanks in advance.
>
> Respectfully,
>
> Jerry Montgomery
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of Chris Lewis
> Sent: Wednesday, July 05, 2006 9:27 AM
> To: Joe Gagznos
> Cc: ccielab@groupstudy.com
> Subject: Re: Shaping Average / Peak vs. Policing
>
>
> Shape average does not allow Bc + Be to be sent every interval.
>
> Shape average allows Be to be sent in addition to Bc on the first
> interval of a second only, also the shaper needs to have built up
> credit in previous intervals to use Be. The effect of Be in shape
> average is to allow the shaper to achieve CIR over a long period of
> time, accommodating periods of lull where less than CIR is sent in one
> second,
>
>
> with an additional Be amount of data in a later period should the
> credit be available and the shaper needing to send more data.
>
> Chris
>
>
> On 7/4/06, Joe Gagznos < joegagznos@comcast.net> wrote:
> >
> > I am trying to find another way to limit outbound traffic through an
> > interface similar in manner to policing. I understand that
> > functionally the two are different. With shaping you are going to
> > be queuing excess traffic to a predetermined rate where with
> > policing you are going to be
> executing
> > some kind of action on traffic that exceeds the contract (usually
> > dropping).
> >
> > For comparison purposes, I have configured shaping and policing on
> > two
>
> > separate subinterfaces in the following manner:
> >
> > interface Ethernet0/0.1
> > encapsulation dot1Q 10
> > ip address 10.1.1.1 255.255.255.0
> > service-policy output shape
> >
> > interface Ethernet0/0.2
> > encapsulation dot1Q 20
> > ip address 10.1.2.1 255.255.255.0
> > service-policy output police
> >
> > Both interfaces are configured to limit traffic to no more than 2.5
> > Mbps as
> > follows:
> >
> > policy-map police
> > class class-default
> > police 2500000 conform-action transmit exceed-action drop
> >
> > policy-map shape
> > class class-default
> > shape average 2500000
> >
> > What I find is that the shaping interface initializes the parameters
> > as
> > follows:
> >
> > R1#sh policy-map interface e0/0.1
> > Ethernet0/0.1
> >
> > Service-policy output: shape
> >
> > Class-map: class-default (match-any)
> > 19 packets, 1729 bytes
> > 5 minute offered rate 0 bps, drop rate 0 bps
> > Match: any
> > Traffic Shaping
> > Target/Average Byte Sustain
> > Excess Interval Increment
> > Rate Limit bits/int bits/int
> (ms)
> > (bytes)
> > 2500000/2500000 15000 60000 60000 24 7500
> >
> > Adapt Queue Packets Bytes Packets Bytes
> Shaping
> > Active Depth Delayed Delayed
Active
> > - 0 19 1729 0 0 no
> >
> > A couple things to note here - Be is initialized to the same value
> > as Bc of 60000 (or 7500 bytes). The byte limit is 15000 bytes,
though.
> > This must mean that the byte limit is initialized to Bc+Be=15000.
> > With a 24 ms interval, does this mean that the interface will send 5
> > Mbps (15000 * 8 bits / byte * 1 sec/.024 = 5000000) instead of the
> > contracted 2.5 Mbps?
> If
> > shape average is allowing the interface to transmit Bc+Be each
> interval,
> > then how does this differ from configuring shape peak which
> accomplishes
> > the
> > same thing?
> >
> > With policing it appears that things are much more straightforward.
> >
> > R1#sh policy-map int e0/0.2
> > Ethernet0/0.2
> >
> > Service-policy output: police
> >
> > Class-map: class-default (match-any)
> > 107 packets, 7473 bytes
> > 5 minute offered rate 0 bps, drop rate 0 bps
> > Match: any
> > police:
> > cir 2500000 bps, bc 78125 bytes
> > conformed 63 packets, 4305 bytes; actions:
> > transmit
> > exceeded 0 packets, 0 bytes; actions:
> > drop
> > conformed 0 bps, exceed 0 bps
> >
> > Thanks for any response!
> >
> > Joe Gagznos
> >
> > ____________________________________________________________________
> > __
>
>
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>
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