From: Vincent Mashburn (vmashburn@fedex.com)
Date: Tue Oct 24 2006 - 15:00:53 ART
It is my understanding that Be only gets transmitted only if excess
bandwidth is available, even in shape peak. So, if your transmitted
traffic totally saturates the entire token bucket at a particular
interval (Tc), then there is no room to use the Be, so the transmitted
Be is 0 (the entire Bc is used). However, if the Bc did not take the
entire bucket for that interval, the Be is allowed to be used until the
excess bandwidth is used up. Now for Shape average, this Be is
calculated based on the previous intervals (Tc) information whereas the
shape peak allows the Be to transmitted based on the current intervals
(Tc) information. This is how I understand it. Please add any
additional info to this that you can.
Thanks
Vince Mashburn
Voice / Data Engineer
901-263-5072
CCVP, CCNP, CCDA,Network +
Cisco IP Telephony Support Specialist
Cisco IP Telephony Operations Specialist
-----Original Message-----
From: Alexei Monastyrnyi [mailto:alexeim@orcsoftware.com]
Sent: Tuesday, October 24, 2006 12:47 PM
To: Vincent Mashburn
Cc: Cagri Yucel; Group study
Subject: Re: Shape average and shape peak
Hi Wincent.
When adding to Bc we definitely increase Tc with the same CIR... but
under the hood... Odom in DQOS Guide says "shape average" behavior is
the same as normal GTS behavior, i.e spending Be after "a long period of
inactivity" during which Be is being accumulated, whereas "shape peak"
spends tokens from Be on every Tc.
If we spend tokens from Be at each and every Tc and our traffic profile
is not lower than conform rate, i.e >=CIR all the time, where do we get
Be accumulated from?
I have a feeling that this Be is not the same as normal traffic-shaping
Be... It is just a sort of extra credit we've got to be able to burst
more at each Tc ... without increasing a Tc...
Does it make any sense?
A.
Vincent Mashburn wrote:
> This is a common question. To answer the question, refer back to the
> formula: CIR = bc/tc.
>
> For shape peak, bc + be is sent every interval, but the formula is
still
> CIR = bc / tc. For shape average, bc is sent every interval, and the
> formula is still CIR = bc / tc.
>
> So, say you have a CIR of 64000, bc = 8000 and be = 16000.
> Using shape average:
>
> 64000 = 8000 / tc ==> tc = 125ms.
>
> Using shape peak:
>
> 64000 = 8000 / tc ==> tc = 125ms
>
> Using shape average by setting bc = bc + be
>
> 64000 = 24000 / tc ==> tc = 375ms.
>
> So, as you can see, it is different.
> Hope this helps.
>
> Vince Mashburn
> Voice / Data Engineer
> 901-263-5072
> CCVP, CCNP, CCDA,Network +
> Cisco IP Telephony Support Specialist
> Cisco IP Telephony Operations Specialist
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Cagri Yucel
> Sent: Tuesday, October 24, 2006 4:49 AM
> To: Group study
> Subject: Shape average and shape peak
>
> I am sure I am missing a bit here but on the Cisco Doc it says
>
> shape average sends Bc bits in each interval
> shape peak sends Bc+Be bits in each interval
>
> So what's the point of having a different command ? Isn't it the same
> thing
> if I set shape average with a Bc equal to Bc+Be of shape peak ?
>
> Thanks
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