Re: calculating burst size for "mls qos aggregate-policer" on

just be aware that burst size should never be less than the max
non-fragmented packet size...so typically the smallest burst should be
around 1500 bytes atleast..

the burst size for 1Mbps comes 250 bytes which is less than the max
packet size, so you should use a burst of 1500 minimum.

(Note: 1Mbps = 1000000bits, the conversion to multiple of 1024
applies between bits and bytes, between bits and Mbits, it stays 1000)

Swap
#19804

On Mon, Apr 19, 2010 at 10:19 PM, Persio Pucci <persio_at_gmail.com> wrote:
> anybody?
>
> On Thu, Apr 15, 2010 at 4:00 PM, Persio Pucci <persio_at_gmail.com> wrote:
>
>> hi folks,
>>
>> I am trying to determine burst sizes for policies to be used on a Cat6500
>> using mls qos aggregate-policer, but I am not confident on the numbers I am
>> getting.
>>
>> For instance, for a 1mbps (1024000bps) policy, I would use a CIR of 1024000
>> bps. The Cat6500 literature (
>> http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SXF/native/configuration/guide/qos.html#wp1726251) says
>> that the Tc is 1/4000sec (0.25ms). For that Tc, I would have to use:
>>
>> CIR=Bc/Tc
>>
>> 1024000=Bc/(1/4000)
>>
>> Bc=1024000*(1/4000)
>>
>> Bc=256
>>
>>
>> That being 256 bits. Considering the normal burst size field asks for a
>> value in bytes, that makes 256/8=32 bytes, making my config line:
>>
>> mls qos aggregate-policer 1mbps 1024000 32 32 conform-action transmit
>>> exceed-action drop violate-action drop
>>
>>
>> The burst value does not sound reasonable for me. Wanted to check with you
>> guys if I am missing something here.
>>
>> Persio
>
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Received on Mon Apr 19 2010 - 23:00:46 ART