From: WorkerBee (ciscobee@gmail.com)
Date: Sat Apr 14 2007 - 22:40:51 ART
It says the bandwidth is minimum gurantee to 384kbps
but set the CIR to 512kbps.
When I configured it, this is my result:
#### Configuration ####
policy-map TEST
class class-default
bandwidth 384
shape peak 512000
interface FastEthernet0/1
ip address 155.1.5.5 255.255.255.0
service-policy output TEST
#### Verification ####
R5#show policy-map TEST
Policy Map TEST
Class class-default
Bandwidth 384 (kbps) Max Threshold 64 (packets)
Traffic Shaping
Peak Rate Traffic Shaping
CIR 512000 (bps) Max. Buffers Limit 1000 (Packets)
When you apply to the interface, show policy-map interface f0/1
Traffic Shaping
Target/Average Byte Sustain Excess Interval Increment
Rate Limit bits/int bits/int (ms) (bytes)
1024000/512000 3200 12800 12800 25 3200
So to explain the target rate
Tc = 25ms , so in 1 sec = 40 intervals
each interval can send 3200 bytes = 3200 x 8 = 25600 bits
therefore, for 40 intervals = 25600 x 40 = 1024000 which is equal to the
target rate
So in my opinion, this is not right. The question says shape peak to 512k.
It can actually send above the peak of 512kbps since the target rate is
1024000 bps.
Did I get it wrong somewhere?
On 4/15/07, Jo Johnson <groupstudyjo@gmail.com> wrote:
>
> 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_gui
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_guide
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?
> > >
> > >
> > _______________________________________________________________________
> > > Subscription information may be found at:
> > > http://www.groupstudy.com/list/CCIELab.html
> >
> > _______________________________________________________________________
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Tue May 01 2007 - 08:28:35 ART