From: CiSco Champ (cischamp2009@gmail.com)
Date: Fri Jan 02 2009 - 11:40:20 ARST
Thanks Scott, well explained the concept behind that. So when ever i need to
calculate bc and be for traffic shaping i will use
Bc = CIR * Tc/1000 and to calculate Be is Be = (AR - CIR) * Tc/1000
and calculation for rate limit will be with below formulas
normal burst = configured rate * (1 byte)/(8 bits) * 1.5 seconds
extended burst = 2 * normal burst
I am confuse because i feel like anyone of two formulas to calculate Bc can
be used for taffic shaping based on task requirement and vice virsa.
In an example of a workbook
AR = 768000bps
CIR = 384000bps
Tc = 125ms
so Bc = CIR x Tc/1000 = 48000
and Be = (AR-CIR) x Tc/1000 = 48000
but in his calculation Be = 96000, it means he used rate-limit formula i,e,
Be = 2 x Normal Burst
Please correct me.
Regards
On Fri, Jan 2, 2009 at 5:12 PM, Scott Morris <smorris@internetworkexpert.com
> wrote:
> The rate-limit command isn't tied to a time interval in the same fashion
> that traffic-shaping it. In traffic shaping, your CIR and Bc are used to
> derive the interval (moving target).
>
> In the rate-limit command, samples are taken every one second and averaged
> over a 5-second period of time. So it's more of a statistical analysis
> than
> any interval-based specific function.
>
> HTH,
>
> Scott
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> CiSco Champ
> Sent: Friday, January 02, 2009 6:33 AM
> To: ccielab@groupstudy.com
> Subject: QOS Formulas
>
> Hi,
>
> Qos parameters calculation like Bc and Be, are there different formulas to
> calculate for FRTS and rate-limit. I am confused like one formula to
> calculate Bc is
>
> Bc = CIR * Tc/1000 and to calculate Be is Be = (AR - CIR) * Tc/1000
>
> other formula i can see on cisco doc is
>
> normal burst = configured rate * (1 byte)/(8 bits) * 1.5 seconds
> extended burst = 2 * normal burst
> Can somene explain when to use one and when other formula, I really
> appreciate
>
> Regards
>
>
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