From: Hobbs (deadheadblues@gmail.com)
Date: Sat Nov 22 2008 - 16:51:28 ARST
Ok. I think I understand this a little better. Whether you configure "peak"
or "average" the following value is still always CIR. This will always be
the "average rate". You target rate will be set using default values if you
do not specify a Be. And it appears Be = Bc by default.
R3(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
So if you want a peak rate of 512000, there are multiple things you can
configure since you are sending Bc+Be every interval. In fact you can:
1) set peak to 512000, Bc to 5120, Be of 0
2) set peak to 384000, Bc to 3840, Be to 1280
3) set peak to 256000, Bc to 2560, Be to 2560
All of these (and many more combinations) set target rate to 512000.
So if you are not asked to specify Bc or Be and can use any values for them,
there are many correct answers :)
On Sat, Nov 22, 2008 at 10:48 AM, Hobbs <deadheadblues@gmail.com> wrote:
> I have noticed that too. When you configure shape peak, your target rate is
> doubled. In you example it is 1024000bps, but nowhere did you configure
> that. I don't really understand why that is...anybody? I have tested in my
> lab with shape peak 128000. It configures target rate to 256000, and I am
> able to push about ~240 traffic (not exactly 256 for some reason) through
> the interface.
>
>
> On Sat, Nov 22, 2008 at 6:00 AM, Huan Pham <pnhuan@yahoo.com> wrote:
>
>> Hi,
>>
>> I posted a similar question few months ago, and I got a very good answer
>> from Narbik. I also believe his answer is right.
>>
>> http://www.groupstudy.com/archives/ccielab/200806/msg01899.html
>>
>> However, today, I came accross an example in DOC CD, which left me
>> wondering, whether DOC CD example is wrong or not. I did come accross few
>> wrong example in the Doc CD before, and I believe this one is another one.
>>
>> Really need your opinion on this, to clear things up.
>>
>> Here's the link to the DOC CD:
>>
>>
>> http://www.cisco.com/en/US/docs/ios/qos/command/reference/qos_s1.html#wp1014690
>>
>> shape
>>
>> To specify average or peak rate traffic shaping, use the shape command in
>> class-map configuration mode. To remove traffic shaping, use the no form of
>> this command.
>>
>> shape {average | peak} cir [bc] [be]
>>
>> =================================================================
>>
>> 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
>>
>> =================================================================
>>
>>
>> In my opinion, this configuration will give a peak rate of 1024K, instead
>> of 512K.
>>
>> here's the config, and what the show policy interface output:
>>
>>
>> Rack1R1#
>> class-map match-all WWW
>> match protocol http
>>
>> policy-map SHAPE
>> class WWW
>> bandwidth 300
>> shape peak 512000
>>
>> interface Serial0/0
>> service-policy output SHAPE
>>
>> Rack1R1#sh policy-map interface
>> Serial0/0
>> Service-policy output: SHAPE
>> Class-map: WWW (match-all)
>> 0 packets, 0 bytes
>> 5 minute offered rate 0 bps, drop rate 0 bps
>> Match: protocol http
>> 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)
>> 1024000/512000 3200 12800 12800 25 3200
>> Adapt Queue Packets Bytes Packets Bytes Shaping
>> Active Depth Delayed Delayed Active
>> - 0 0 0 0 0 no
>> Class-map: class-default (match-any)
>> 1 packets, 13 bytes
>> 5 minute offered rate 0 bps, drop rate 0 bps
>> Match: any
>>
>>
>> I think the solution should be, following. Any opinion please?
>>
>> bandwidth 300
>> shape peak 300000 37500 26500
>>
>> Rack1R1#show policy-map interface
>> Serial0/0
>> Service-policy output: SHAPE
>> Class-map: WWW (match-all)
>> 0 packets, 0 bytes
>> 5 minute offered rate 0 bps, drop rate 0 bps
>> Match: protocol http
>> 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)
>> 512000/300000 8000 37500 26500 125 8000
>> Adapt Queue Packets Bytes Packets Bytes Shaping
>> Active Depth Delayed Delayed Active
>> - 0 0 0 0 0 no
>> Class-map: class-default (match-any)
>> 293 packets, 64409 bytes
>> 5 minute offered rate 0 bps, drop rate 0 bps
>> Match: any
>>
>>
>> Blogs and organic groups at http://www.ccie.net
>>
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