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

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 Thu Apr 15 2010 - 16:00:31 ART