From: Hewie (whewetson@gmail.com)
Date: Sun Apr 15 2007 - 12:40:14 ART
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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