From: Julius Kinsler (jkinsler@harbortech.com)
Date: Tue May 16 2006 - 16:22:53 ART
Chris/Petr or anyone else..
When dealing in the MQC on a 3550, what exactly is this "Normal Burst
Size"? What does it represent? how fast tokens replenish the bucket at
an interval, the size of the bucket? What?
Julius
________________________________
From: Chris Lewis [mailto:chrlewiscsco@gmail.com]
Sent: Tuesday, May 16, 2006 3:14 PM
To: Petr Lapukhov
Cc: Julius Kinsler; ccielab@groupstudy.com
Subject: Re: Policing
Petr,
Your test would indeed show that policing does not work in that
configuration, however I would not classify it as the default class
being useless.
The issue is that for egress policing to work, you need to classify on
ingress to set the internal dscp value. The internal DSCP value is the
only thing that can be used to classify packets for egress policing on
the 3550.
There are lots of caveats with using MQC constructs on the 3550, it is
quite limited in its support.
Chris
On 5/16/06, Petr Lapukhov <petrsoft@gmail.com> wrote:
Julius,
While I'm trying to get my mind in full sync with that topic,
let me note, that "class-default" is useless with catalyst 3550.
You need to police within specific class, matching either
IP or non-IP traffic. If you need to police both types to a
single
rate, you should use aggregate policer.
Just try setting policer's rate/burst to minimal values within
"class-default", and do a simple ping test, to see that
traffic
is not policed in that configuration.
HTH
Petr
2006/5/16, Julius Kinsler <jkinsler@harbortech.com>:
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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