From: Julius Kinsler (jkinsler@harbortech.com)
Date: Tue May 16 2006 - 10:52:03 ART
This is the same article I was reading yesterday. It so happen to be
that I was trying to do policing on a 3550.
For example I created a policy-map and under the policy map, for the
default class I put in the keyword
police 1000000 <Normal Burst bytes> exceed action drop. I didnt
completely understand the normal burst bytes I just wanted to police at
1Mbps.
When I looked it up I came across the link below and was trying to
interpret this Interval to come up with the normal burst bytes. I came
to believe that this can be an arbitrary number based on the
specifications in a practice lab.
I was doing an IPExpert lab and the answer looked like this:
mls qos
policy-map MyPolice
class class-default
police 1000000 187500 exceed drop
Now I was racking my brain trying to come up with the logic behind the
number "187500" but I believe the number was made up after everything I
read about rate/intervals/and burst as stated below.
Please tell me if I am wrong
Julius
________________________________
From: Petr Lapukhov [mailto:petrsoft@gmail.com]
Sent: Tuesday, May 16, 2006 1:17 AM
To: Chris Lewis
Cc: Julius Kinsler; ccielab@groupstudy.com
Subject: Re: Policing
Chris,
There is an interesting thing they say about 3550 policing:
http://www.cisco.com/en/US/products/hw/switches/ps646/products_tech_note
09186a00800feff5.shtml
Specifically:
---- quote
These parameters control the operation of policing:
- Rate - defines how many tokens are removed at each interval. This
effectively sets
the policing rate. All traffic below the rate is considered in
profile. Supported rates
range from 8 Kbps to 2 Gbps, and increment by 8 Kbps.
- Interval-defines how often tokens are removed from the bucket. The
interval is fixed
at 0.125 milliseconds (or 8000 times per second). This interval cannot
be changed.
- Burst-defines the maximum amount of tokens the bucket can hold at any
time.
Supported bursts range from 8000 bytes to to 2000000 bytes, and
increment by 64 bytes.
---- quote
I wonder if they do actually use *leaky* bucket with 3550 policer and
*token*
bucket (metering) with CAR/IOS Policer..
Petr
2006/5/16, Chris Lewis <chrlewiscsco@gmail.com>:
Julius,
You are mixing two concwpts here. There is no Tc in policing
that adheres to
the shaping formula quoted. Policing does not calculate things
at regular
intervals, it calculates tokens to be credited and removed from
the bucket
based off packet arrival times.
Chris
On 5/15/06, Julius Kinsler <jkinsler@harbortech.com > wrote:
>
> Using the standard equation CIR = Bc / Tc where can I find the
Tc when
> trying to complete this formula?
>
> TIA
> Julius
>
>
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