From: Paul Dardinski (pauld@marshallcomm.com)
Date: Thu Jun 29 2006 - 16:54:53 ART
Can someone explain exactly how the "credit" system works assuming
configuration of shape average? I understand that be is only replenished
when previous bc isn't fulfilled. However, I have heard different things
regarding exactly when the credit is applied. Is it applied if there is
NO traffic in the previous bc or is it applied as a "partial" credit?
(bc - actual = be credit)
PD
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Brian McGahan
Sent: Thursday, June 29, 2006 2:43 PM
To: Chris Lewis; Petr Lapukhov
Cc: Elias Chari; Anderson Mota Alves; ccielab@groupstudy.com
Subject: RE: Doubt in QoS
The difference between them is how Be is accumulated. With
shape average the algorithm uses a system of credit, where Be is only
accumulated if you haven't sent enough Bc. With shape peak the
algorithm uses a system of debit, where Be is sent right off the bat,
and then paid back at a later time. The difference between them is the
delay that the traffic will see inside of the second, but overall you
will still never exceed CIR over a longer term average.
HTH,
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
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> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Chris Lewis
> Sent: Thursday, June 29, 2006 12:55 PM
> To: Petr Lapukhov
> Cc: Elias Chari; Anderson Mota Alves; ccielab@groupstudy.com
> Subject: Re: Doubt in QoS
>
> 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_
re
> ference_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
tt
> p://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
> > > > >>
> > > >
> > >
> >
>
>>______________________________________________________________________
_
> > > > >>Subscription information may be found at:
> > > > >>http://www.groupstudy.com/list/CCIELab.html
> > > >
> > > >
> >
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