From: Skinner, Stephen (Stephen.Skinner@rbs.co.uk)
Date: Sun Apr 15 2007 - 11:29:43 ART
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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