Re: Legacy adaptive FRTS question

Thank you Petr, thank you Guys, now I get it, things make sense.

Even I work every day with all this stuff, now I realize that I was far away
of really understand the shaping algorithm.

Cheers.....

On Sun, Aug 9, 2009 at 6:56 PM, Petr Lapukhov
<petr_at_internetworkexpert.com>wrote:

> Hi,
>
> Here is the problem that many people face understanding the shaping
> algorithm. The fact is that "sending" rate is an averaged "fictious"
> value. The actual "real" variables are Bc and Tc - shaper sends at
> most Bc bits every Tc milliseconds. Every burst is being sent at the
> interface access rate (physical rate). Effectively, CIR=Bc/Tc is the
> value that appears as a result of averaging across multiple Tc, not
> the "real" sending rate.
>
> Now for adaptive shaping. When Frame-Relay layer detects congestion
> via some means (signaling or interface congestion) it needs to bring
> the "average" CIR to MinCIR. The are two ways to do that per the
> formula CIR=Bc/Tc
>
> 1) Shrink Bc in size
> 2) Increase Tc duration
>
> Most of the times it makes sense to decrease Bc (not messing with
> latency), which FRTS does using a back-off algorithm. Upon every
> congestion notification message received, Bc is decremented until it
> is small enough to safisfy MinCIR=Bc/Tc. By default, MinCIR=CIR/2 and
> thus FRTS will shrink the burst size to half of the configured value
> while responding to congestion.
>
> Once again, remember, even if you set frame-relay traffic rate with
> FRTS commands, you effectively encode Bc and Tc which are used by the
> shaper's scheduler!
>
> HTH,
>
> --
> Petr Lapukhov, petr_at_INE.com
> CCIE #16379 (R&S/Security/SP/Voice)
>
> Internetwork Expert, Inc.
> http://www.INE.com <http://www.ine.com/>
> Toll Free: 877-224-8987
> Outside US: 775-826-4344
>
>
> 2009/8/9 Victor <cisco.all.stuff_at_gmail.com>:
> > Hello People,
> >
> > Many thanks for your answer but maybe I'm still confused.
> >
> > My question is:
> >
> > In the case of FRTS adaptive, how I should calculate the Bc, using the
> CIR
> > configured or the minCIR??
> >
> > Bc=CIR*Tc ====== OR ====== Bc=minCIR*Tc ???
> >
> > I've seen both ways in different documents.
> >
> > Cheers..... Johan Victor.
> >
> >
> >
> > On Sun, Aug 9, 2009 at 4:24 PM, Bryan Bartik <bbartik_at_ipexpert.com>
> wrote:
> >
> >> Victor,
> >>
> >> Sending rate is reduced to the mincir. Check this link out:
> >>
> >>
> >>
> http://www.cisco.com/en/US/docs/ios/12_2t/12_2t4/feature/guide/ft_afrts.html
> >>
> >> On Sun, Aug 9, 2009 at 11:42 AM, Victor <cisco.all.stuff_at_gmail.com
> >wrote:
> >>
> >>> Hello Guys,
> >>>
> >>> Today my head is a mess, I've been re-reading some documentation about
> the
> >>> subject topic and I realized I've a big confusion, since different
> author
> >>> deal with this in a little different way. My question is:
> >>>
> >>> Bc calculation for adaptive shaping is based on CIR or MINCIR??
> >>>
> >>> Thanks in advance for you help.
> >>>
> >>> Cheers.... Johan Victor
> >>>
> >>>
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> >>
> >>
> >> --
> >> Bryan Bartik
> >> CCIE #23707 (R&S), CCNP
> >> Sr. Support Engineer - IPexpert, Inc.
> >> URL: http://www.IPexpert.com <http://www.ipexpert.com/> <
> http://www.ipexpert.com/>
> >
> >
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Received on Sun Aug 09 2009 - 19:46:13 ART