From: maureen schaar (maureen.schaar@gmail.com)
Date: Mon Apr 16 2007 - 06:51:48 ART
I would like to add something that may not be obvious from the doccd
(and I had to research myself to fully understand). When using shape
average, there can be bursting above the cir for 1 Tc, but only after
accumulating credit. Credit (or tokens) are accumulated by sending
below the cir. The next Tc, the the left-over tokens from the previous
Tc can be used for bursting upto the Be. So this means bursting for a
very very short period, whereas shape peak allows bursting for long
periods (as long as bandwidth is available).
As far as Hewie's answer to ' obtain a throughput up to a peak of 512
kbps', I would not use shape peak 256000, but shape peak 512000. The
target rate in this case is 512000 (the average rate = cir = 256000).
As long as bandwidth is available, 512000 will be sent, so this is the
throughput (indeed it is 2xCIR when using the defaults).
HTH
Maureen
On 4/15/07, Hewie <whewetson@gmail.com> wrote:
> Hi,
>
> Some more from Cisco
>
> The Be allows more than the Bc to be sent during a time interval under
> certain conditions. Therefore, DTS provides two types of shape commands: *
> average* and *peak*. When shape average is configured, the interface sends
> no more than the Bc for each interval, achieving an average rate no higher
> than the CIR. When shape peak is configured, *the interface sends Bc plus Be
> bits in each interval*
>
> So according to the formula peak rate = CIR(1+Be/Bc) and the output of 'show
> policy-map interface' the peak rate 'could' be CIR x 2, therefore I think
> the COD is incorrect by using 'shape peak 512000' to obtain a throughput *up
> to* a peak of 512 kbps, it should be 'shape peak 256000' to obtain a
> throughput up to a peak of 512 kbps
>
> Will be good to hear some more comments :-)
>
> Hewie
>
>
> On 4/15/07, Mike O <mikeeo@email.msn.com> wrote:
> >
> > Here is an output from the router. If you do shape peak 512000 you
> > actually
> > are allowing 1024000 bps. If you do shape peak 256000 that actually gives
> > you a peak output of 512k.
> >
> > Scott, Brad or the Brians can you chime in?
> >
> >
> >
> >
> >
> > policy-map PEAK
> > class SHAPE
> > bandwidth 300
> > shape peak 512000
> > !
> > Router#sh policy-map interface s0/0
> >
> > Serial0/0
> >
> > Service-policy output: PEAK
> >
> > Class-map: SHAPE (match-any)
> > 0 packets, 0 bytes
> > 5 minute offered rate 0 bps, drop rate 0 bps
> > Match: ip precedence 1
> > 0 packets, 0 bytes
> > 5 minute rate 0 bps
> > Traffic Shaping
> > Target/Average Byte Sustain Excess Interval Increment
> > Rate Limit bits/int bits/int (ms) (bytes)
> > 1024000/512000 3200 12800 12800 25 3200
> >
> > !
> > !
> > policy-map PEAK
> > class SHAPE
> > bandwidth 300
> > shape peak 256000
> >
> > Router#sh policy-map interface s0/0
> >
> > Serial0/0
> >
> > Service-policy output: PEAK
> >
> > Class-map: SHAPE (match-any)
> > 0 packets, 0 bytes
> > 5 minute offered rate 0 bps, drop rate 0 bps
> > Match: ip precedence 1
> > 0 packets, 0 bytes
> > 5 minute rate 0 bps
> > Queueing
> > Output Queue: Conversation 265
> > Bandwidth 300 (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)
> > 512000/256000 1984 7936 7936 31 1984
> >
> >
> > ----- Original Message -----
> > From: "Skinner, Stephen" <Stephen.Skinner@rbs.co.uk>
> > To: <ccielab@groupstudy.com>
> > Sent: Sunday, April 15, 2007 10:29 AM
> > Subject: RE: shape average vs shape peak
> >
> >
> > >I too would like to know the answer ,
> > >
> > > Taking another CCO example
> > >
> > > The following example uses peak rate shaping to ensure a bandwidth of
> > 300
> > > kbps but allow throughput up to 512 kbps if enough bandwidth is
> > available
> > > on
> > > the interface:
> > >
> > > bandwidth 300
> > > shape peak 512000
> > >
> > > This seems to set an arbitrary amount..
> > >
> > > But if as Cisco has stated ..
> > >
> > > 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)
> > >
> > > Then how did they come up with the figure above.
> > >
> > > Many thanks in advance
> > >
> > > Stephen Skinner
> > >
> > >
> > > mail: Stephen.Skinner@rbs.co.uk
> > >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]
> > > Sent: 15 April 2007 01:50
> > > To: WorkerBee
> > > Cc: Mike O; ccielab@groupstudy.com
> > > Subject: Re: shape average vs shape peak
> > >
> > > *** WARNING : This message originates from the Internet ***
> > >
> > > Hi all,
> > >
> > > I cut out an example from the hyperlink that was referenced. Can anyone
> > > explain why the solution uses *shape peak 512000* when peak rate =
> > > CIR(1+Be/Bc)?
> > >
> > >
> > > Thanks!
> > >
> > >
> > > *CBWFQ in Conjunction with GTS Example *
> > >
> > > The following example uses CBWFQ at the interface and shapes the traffic
> > > before it is queued to CBWFQ.
> > >
> > > In this example, two classes are definedcust1 and cust2. The class
> > cust1
> > > is
> > > ensured a bandwidth of 256 kbps, and the output is shaped to 384 kbps.
> > The
> > > class cust2 is ensured a bandwidth of 384 kbps, but if enough bandwidth
> > is
> > > available on the interface, the class can obtain throughput up to a peak
> > > of
> > > 512 kbps.
> > >
> > > Figure
> > > 1<
> > http://www.cisco.com/en/US/products/sw/iosswrel/ps1834/products_feature_gu
> > > i
> > > de09186a00800800fc.html#wp1025976>illustrates
> > > this example.
> > >
> > > Figure 1 CBWFQ in Conjunction with GTS
> > >
> > > The following commands are used to configure this example:
> > >
> > > Router(config)# *policy-map shape-cbwfq*
> > >
> > > Router(config-pmap)# *class cust1*
> > >
> > > Router(config-pmap-c)# *shape average 384000*
> > >
> > > Router(config-pmap-c)# *bandwidth 256*
> > >
> > > Router(config-pmap)# *class cust2*
> > >
> > > Router(config-pmap-c)# *shape peak 512000*
> > >
> > > Router(config-pmap-c)# *bandwidth 384*
> > >
> > > Router(config-pmap-c)# *configure terminal*
> > >
> > > Router(config)# *interface Serial 3/3*
> > >
> > > Router(config-if)# *service out shape-cbwfq*
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > On 4/14/07, WorkerBee <ciscobee@gmail.com> wrote:
> > >>
> > >> Specifying Average Rate or Peak Rate Traffic Shaping Design Rule
> > >> ================================================
> > >>
> > >> Traffic shaping limits the rate of transmission of data.
> > >>
> > >> 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) >> peak = CIR + [Be/Tc] which is more than
> > >> CIR.
> > >>
> > >> where:
> > >>
> > >> Be is the Excess Burst rate.
> > >>
> > >> Bc is the Committed Burst rate.
> > >>
> > >> Peak rate shaping allows the router to burst higher than average rate
> > >> shaping. However, using peak rate shaping, the traffic sent above the
> > >> CIR (the delta) has the potential of being dropped if the network
> > >> becomes congested.
> > >>
> > >> If your network has additional bandwidth available (over the
> > >> provisioned CIR) and the application or class can tolerate occasional
> > >> packet loss, that extra bandwidth can be exploited through the use of
> > >> peak rate shaping. However, there may be occasional packet drops when
> > >> network congestion occurs. If the traffic being sent to the network
> > >> must strictly conform to the configured network provisioned CIR, then
> > >> you should use average traffic shaping.
> > >>
> > >> R6(config-pmap-c)#shape ?
> > >>
> > >> average configure token bucket: CIR (bps) [Bc (bits) [Be
> > >> (bits)]],
> > >> send out Bc only per interval
> > >>
> > >> peak configure token bucket: CIR (bps) [Bc (bits) [Be
> > >> (bits)]],
> > >> send out Bc+Be per interval
> > >>
> > >>
> > >>
> > >>
> > >
> >
> http://www.cisco.com/en/US/products/sw/iosswrel/ps1834/products_feature_guid
> > > e
> > > 09186a00800800fc.html#wp1019894
> > >>
> > >>
> > >> On 4/14/07, Mike O <mikeeo@email.msn.com> wrote:
> > >> > I'm a little confused on these. Does shape average just use Bc and
> > >> > peak
> > >> uses
> > >> > Bc and Be? I'm trying to figure out why you would use one over the
> > >> other?
> > >> >
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