From: Bob Sinclair (bob@bobsinclair.net)
Date: Fri Dec 02 2005 - 18:03:26 GMT-3
Edmundo,
The Class-Based policer calculates burst as RATE/32. Which represents 1/4
seconds worth of traffic, converted to bytes. Odom discusses this in his
book, but I do not know of any good Cisco docs on it. This is VERY different
from CAR, which has a rule of thumb which suggests that Bc should be 1.5
seconds worth and Be should be twice that.
The theory behind police burst values suggests that the bursts should allow a
full TCP window at the configured rate. The window is calculated as RATE
times Round Trip Time / 8 to convert to bytes. This would suggest that by
default Cisco assumes a 250 ms RTT.
What should you configure in real life? The value that best permits your flow
to approximate the desired profile. This will be determined empirically.
What should you configure in the lab? You should could configure precisely
what is asked. If burst values are not specified, then use the defaults. If
you have any doubt, ask the proctor.
HTH,
Bob Sinclair
CCIE #10427, CCSI 30427
www.netmasterclass.net
----- Original Message -----
From: Edmundo Bodero
To: ccielab@groupstudy.com
Sent: Friday, December 02, 2005 2:24 PM
Subject: police command values
Hi group,
A quick question,
When we use the police command under a policy map, is the bc and be
recommended formula for CAR still valid?. I mean, if we use
police 256000 48000 96000 is that correct?, and if that is so, why Cisco
chooses different default values (they don't follow their own rule!). I
checked the archives and found one mention to it (Brian), but I could not
find any definitive document in the Cisco documentation.
Thanks for your help,
Edmundo
_______________________________________________________________________
Subscription information may be found at:
http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Mon Jan 09 2006 - 07:07:50 GMT-3