From: alsontra@hotmail.com
Date: Sat Sep 11 2004 - 14:41:49 GMT-3
Hi Taiyi Sun,
Here are my thoughts...
<cisco>
> Q1. if i want to use class base policing to limit the incoming traffic to
300K
The Cisco recommendation is as follows:
"Policing Traffic with CAR
CAR embodies a rate-limiting feature for policing traffic. When policing
traffic with CAR, Cisco recommends the following values for the normal and
extended burst parameters:
normal burst = configured rate * (1 byte)/(8 bits) * 1.5 seconds
extended burst = 2 * normal burst"
Meaning your normal burst should be se to 1.5 * normal rate (in bytes).
The default action on all my routers to use 1/4 of the Cir as the normal
burst value. On all of my switches, you must specify a normal burst. There
appears to be no default, you must give a normal burst value.
<--------------Switches--------------->
SW1(config-pmap-c)#police 300000
% Incomplete command.
<---------------Routers--------------->
R5(config-pmap-c)# police 300000
R5(config-pmap-c-police)#do sh policy-map
Policy Map QOS_TEST
Class class-default
police cir 300000 bc 9375 <------1/4 Cir in bytes
conform-action transmit
exceed-action drop
R5(config-pmap-c-police)# police 100000
R5(config-pmap-c-police)#do sh policy-map
Policy Map QOS_TEST
Class class-default
police cir 100000 bc 3125<------1/4 Cir in bytes
conform-action transmit
exceed-action drop
R5(config-pmap-c-police)# police 6000000
R5(config-pmap-c-police)#do sh policy-map
Policy Map QOS_TEST
Class class-default
police cir 6000000 bc 187500<------1/4 Cir in bytes
conform-action transmit
exceed-action drop
I recall reading something about this CAR default bc behavior, but I can not
find it at the moment. So my above statements regarding the default behavior
of the normal burst value are based on its observed behavior.
>Q3. Is the configuration above correct?
I think this is wrong ---> police 300000 37500 conform-action transmit
exceed-action drop
(normal burst needs to be in
bytes)
I think this is correct ---> police 300000 9375 conform-action transmit
exceed-action drop
or---> police 300000 <cr>
> Q4. When I configured "police 300000" command under policy-map, it's
will show
> "police 300000 9250 9250 conform-action transmit exceed-action drop".
What does
> 9250 mean? And how does it calculate? any response will be
appreciated?
normal burst = configured rate * (1 byte)/(8 bits) * 1.5 seconds
extended burst = 2 * normal burst"
See answer to question 1.
There are a few resident expert in the areas of QOS on this list, perhaps
they will grace us with a more astute explanation. :-)
HTH
Alsontra
----- Original Message -----
From: "Taiyi Sun" <wanwalker2000@yahoo.ca>
To: "Ccie Lab" <ccielab@groupstudy.com>
Sent: Saturday, September 11, 2004 12:25 AM
Subject: about CB policing
> Hi, group,
>
> I have questions about Class Based Policing.
>
> Q1. if i want to use class base policing to limit the incoming traffic to
300K, how
> could i decide the burst-normal and burst-max, how aoubt the exceed action
to take,
> and how to check whether my configuration is correct. Saying to limit
telnet and ftp
> traffic.
> Q2. If the exceed action is remarking, does it mean the remarked packets
can be propagated?
> Here is my configuration:
> ....
> ip cef
> ...
> class-map match-any telnet&ftp
> match protocol telnet
> match protocol ftp
> ...
> policy-map rate_limit
> class telnet&ftp
> police 300000 37500 conform-action transmit exceed-action drop
> .....
> interface s0/0
> ....
> service-policy inpuit rate_limit
> > Q4. When I configured "police 300000" command under policy-map, it's
will show
> "police 300000 9250 9250 conform-action transmit exceed-action drop".
What does
> 9250 mean? And how does it calculate?
> any response will be appreciated?
>
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