From: Edmundo Bodero (bodero.edmundo@googlemail.com)
Date: Fri Dec 02 2005 - 19:23:30 GMT-3
Hi Bob,
Thanks for your reply. There is a document called QoS FAQ in which Cisco
applies the CAR formula to the police command.
http://www.cisco.com/en/US/tech/tk543/tk545/technologies_q_and_a_item09186a00
800cdfab.shtml
Maybe it is just wrong. What do you think?.
Cheers,
Edmundo
On 12/2/05, Bob Sinclair <bob@bobsinclair.net> wrote:
>
> 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 <bodero.edmundo@googlemail.com>
> *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
>
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