From: Chris Lewis (chrlewiscsco@gmail.com)
Date: Thu Jun 29 2006 - 14:55:21 ART
Hi Petr,
What I described in my first response holds for both shape average and shape
peak. Unles I am misunderstanding what you wrote, it is not an accurate
description of the operation of shape peak. It is possible to veryify this
with a simple test. Consider the topology below:
R3----ethernet----R1-----128K serial line----R2
Then do an extended ping with low timeout and large packet sizes from R3 to
R2. If you crets a service policy like the test 1 and 2 below, and apply it
outbound on R1 towards R3 (with access-list 1 matching all packets), set the
load interval to 30 on that interface as well, you will then see that both
shape average and shape peak will after a few minutes indicate an output
rate of 62000 bits per second. The disparity with the configured shaped rate
is due to the way one will measure layer 3 bandwidth only.
Test 1
class-map match-all TEST
match access-group 1
!
!
policy-map TEST
class TEST
shape average 64000 8000 8000
Test 2
class-map match-all TEST
match access-group 1
!
!
policy-map TEST
class TEST
shape peak 64000 8000 8000
The net effect is as I described, the difference between shape peak and
shape average only exists if there is credit to be used by the shaper, hence
the CIR achieved by both is the same.
Chris
On 6/29/06, Petr Lapukhov <petr@internetworkexpert.com> wrote:
>
> Correct, Chris.
>
> But AFAIK that rule does not work with "shape peak".
> It always send up Bc+Be every Tc, effectively ending
> with CIR*(1+Bc/Be) rate.
>
> --
>
> Petr Lapukhov, CCIE #16379
> petr@internetworkexpert.com
>
> Internetwork Expert, Inc.
> http://www.InternetworkExpert.com <http://www.internetworkexpert.com/>
> Toll Free: 877-224-8987
> Outside US: 775-826-4344
>
> 2006/6/29, Chris Lewis <chrlewiscsco@gmail.com>:
> >
> > Just a note of caution here. The shaper can only utilize the Be tokens
> if
> credit has been built up, meaning that the shaper has been transmitting at
> below CIR for a period of time. Be does not allow you to constantly
> transmit
> at a rate above CIR, it is only available if traffic has dropped below
> CIR.
> Over time, you should still acerage out at CIR.
>
> Chris
>
>
> On 6/29/06, Elias Chari < elias.chari@gmail.com> wrote:
> >
> > Andy,
> >
> > It is when you configure shape peak 96000 (not average) that you get
> upto
> > 192k.
> >
> > If not specified bc and be default to the same value, then peak = 2*CIR
> as
> > per the formula. Also if only cir and bc are specified the bc value is
> > used
> > for be
> >
> > Rack1R1#sh policy-map int s0/1
> > Serial0/1
> >
> > Service-policy output: testB
> >
> > Class-map: testB (match-all)
> > 0 packets, 0 bytes
> > 5 minute offered rate 0 bps, drop rate 0 bps
> > Match: any
> > Queueing
> > Output Queue: Conversation 265
> > Bandwidth 84 (kbps) Max Threshold 64 (packets)
> > (pkts matched/bytes matched) 0/0
> > (depth/total drops/no-buffer drops) 0/0/0
> > Traffic Shaping
> > Target/Average Byte Sustain
> Excess Interval Increment
> > Rate Limit bits/int bits/int (ms) (bytes)
> > *192000/96000 1992 7968 7968 83 1992*
> >
> > Adapt Queue Packets Bytes Packets Bytes Shaping
> > Active Depth Delayed Delayed Active
> > - 0 0 0 0 0 no
> >
> > Class-map: class-default (match-any)
> > 0 packets, 0 bytes
> > 5 minute offered rate 0 bps, drop rate 0 bps
> > Match: any
> > On 6/29/06, Anderson Mota Alves < mota_anderson@hotmail.com> wrote:
> > >
> > > Hi Petr,
> > >
> > > Based on your explanation below it's more clear to me that you cannot
> > mix
> > > "priority" and "shape" because one is for policing and the other for
> > > shaping purposes.
> > >
> > > But I've been seaching in cisco webpage and from the link below it
> says:
> > >
> > > You can specify two types of traffic shaping; average rate shaping and
> > > peak rate shaping. Average rate shaping limits the transmission rate
> to
> > > the 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)
> > >
> > >
> >
> http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_command_reference_chapter09186a0080087f34.html#wp1077189
> > >
> > >
> > > But how do I know that configuring the "shape average 96000" I can
> send
> > > traffic up to 192 kbps?
> > >
> > > Thanks,
> > >
> > > Andy
> > >
> > > --------------------------------------------------------------------
> > >
> > > From: "Petr Lapukhov" < petr@internetworkexpert.com>
> > > To: "Anderson Mota Alves" <mota_anderson@hotmail.com >,
> > > < ccielab@groupstudy.com>
> > > Subject: Re: Doubt in QoS
> > > Date: Thu, 29 Jun 2006 14:42:55 +0400
> > > >The first one seems to be "almost" correct:
> > > >
> > > >You shape (limit) traffic up to 96kbit here - the only problem
> > > >is "peak" keyword. This configuration actually permits you to send
> > > >traffic up to 192kbit by default. So I would better do something
> > > >like:
> > > >
> > > >...
> > > >class CRITICAL
> > > > shape average 96000
> > > > bandwidth 84
> > > >...
> > > >
> > > >This way you guarantee 84k in case of congestion,
> > > >and limit flow up to 96k in any case.
> > > >
> > > >As for your second example - you can not mix priority and bandwidth:
> > > >
> > > >R6(config-pmap-c)#priority 64
> > > >R6(config-pmap-c)#bandwidth 92
> > > >Must remove priority configuration from this class first.
> > > >
> > > >Also remember that you cannot mix "priority" and "shape",
> > > >and dont forget that "priority" actually police your traffic in
> > > >case of congestion.
> > > >
> > > >Finally, you may choose "police" instead of "shape", with
> > > >your first example. The decision should depend on task wording.
> > > >
> > > >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
> > > >
> > > >----- Original Message ----- From: "Anderson Mota Alves"
> > > ><mota_anderson@hotmail.com>
> > > >To: <ccielab@groupstudy.com>
> > > >Sent: Thursday, June 29, 2006 2:16 PM
> > > >Subject: Doubt in QoS
> > > >
> > > >
> > > >>Hi gurus, The question I need to complish is the following:
> > > >>
> > > >>Which configuration provides the mission-critical traffic class
> > > >>with a
> > > >>minimum
> > > >>
> > > >>bandwidth guarantee of 84 kbps and a maximum upper bandwidth limit
> > > >>of 96
> > > >>
> > > >>kbps?
> > > >>
> > > >>I think I have to solution for this one but I'm not sure if I'm
> > > >>right:
> > > >>
> > > >>policy-map shape
> > > >>class mission-critical
> > > >>bandwidth 84
> > > >>shape peak 96000
> > > >>
> > > >>or
> > > >>
> > > >>policy-map shape
> > > >>class mission-critical
> > > >>priority 64
> > > >>bandwidth 96
> > > >>
> > > >>Could anyone tell me which one I could use? Also I don't know if in
> > > >>order
> > > >>to use the shape peak I need to first configure the shape cir ir
> > > >>order to
> > > >>make sure that this will be the peak above the Cir.
> > > >>
> > > >>Thanks
> > > >>
> > >
> >
> >>_______________________________________________________________________
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> > >
> > >
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