From: Bit Gossip (bit.gossip@chello.nl)
Date: Mon May 21 2007 - 15:56:05 ART
Group,
I have done a quick test to confirm the behaviour of 'shape average' vs
'shape peak': below the figures and here the results:
- with standard setting for Bc and Be -> 'shape average 256000' shapes @
256kbps while 'shape peak 256000' shapes @ 512kbps
- with Be=0 -> shape peak = shape average
Thanks,
bit.
Baseline:
serial link with clockrate 2015232 and no shaping configured:
R3#show int s4/3 | i second output rate
30 second output rate 864000 bits/sec, 198 packets/sec
~~~~~~~~~~~~~~~~~~~~~~~~~~
shape average 256000
~~~~~~~~~~~~~~~~~~~~~~~~~~
R3#show policy-map int s4/3
Serial4/3
Service-policy output: SHAPE
Class-map: class-default (match-any)
9230 packets, 5046624 bytes
30 second offered rate 248000 bps, drop rate 0 bps
Match: any
Traffic Shaping
Target/Average Byte Sustain Excess Interval Increment
Rate Limit bits/int bits/int (ms) (bytes)
256000/256000 1984 7936 7936 31 992
~~~~~~~~~~~~~~~~~~~~~~~~~~
shape peak 256000
~~~~~~~~~~~~~~~~~~~~~~~~~~
R3#show policy-map int s4/3
Serial4/3
Service-policy output: SHAPE
Class-map: class-default (match-any)
34492 packets, 18871214 bytes
30 second offered rate 456000 bps, drop rate 0 bps
Match: any
Traffic Shaping
Target/Average Byte Sustain Excess Interval Increment
Rate Limit bits/int bits/int (ms) (bytes)
512000/256000 1984 7936 7936 31 1984
~~~~~~~~~~~~~~~~~~~~~~~~~~
shape peak 256000 7936 0
~~~~~~~~~~~~~~~~~~~~~~~~~~
R3#show policy-map int s4/3
Serial4/3
Service-policy output: SHAPE
Class-map: class-default (match-any)
64692 packets, 35386586 bytes
30 second offered rate 244000 bps, drop rate 0 bps
Match: any
Traffic Shaping
Target/Average Byte Sustain Excess Interval Increment
Rate Limit bits/int bits/int (ms) (bytes)
256000/256000 992 7936 0 31 992
----- Original Message -----
From: "maureen schaar" <maureen.schaar@gmail.com>
To: "Hewie" <whewetson@gmail.com>
Cc: "Mike O" <mikeeo@email.msn.com>; "Skinner, Stephen"
<Stephen.Skinner@rbs.co.uk>; <ccielab@groupstudy.com>
Sent: Monday, April 16, 2007 11:51 AM
Subject: Re: shape average vs shape peak
>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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