From: Nguyen, Thai (Thai.Nguyen@xxxxxxxxxxxxxx)
Date: Thu Jun 20 2002 - 22:04:48 GMT-3
Hi all,
Thank you everyone for responding to my question. I would like clarify my
understanding.
FRTS is implemented to prevent a router pumping too much traffic into the FR
network
and traffic gets dropped into the frame-relay without any feedback from the
FR network
to the router.
Let's consider the following scenario:
Router A AR=64K, CIR=32 (service provider value or minCIR)
=========================================================
AR=96
Router C
=========================================================
Router B AR=64 CIR=32 (service provider value or minCIR)
If no FRTS is not configured, Router C can send to Router B at its AR rate
(ie 128K).
Data will properly get delivered to the last FR switch connecting to router
B
but some of the traffic will get dropped because router B's AR is only 64K.
To prevent data getting dropped, FTRS is configured on router C so
that router A only send traffic router B at 64K rate.
Note traffic also can get dropped at Router C end when the aggregated rate
of Router A, eg 128K, and router B is exceeded router C's AR (ie 96K)
When having VoIp traffic, it is recommended to set the CIR = minCIR.
The minCIR is only used when adaptive shaping is used ie BECN.
I think Cisco could have used different term for their CIR, eg average rate.
-----Original Message-----
From: David Luu [mailto:wicked01@ix.netcom.com]
Sent: Friday, June 21, 2002 7:05 AM
To: MADMAN; Anthony Pace
Cc: dmadlan@interprise.com; Katson Yeung; Ahmed Mamoor Amimi; Nguyen,
Thai; 'Erhan Kurt'; Michael Popovich; CCIE GROUPSTUDY
Subject: Re: FRTS
i believe Anthony is referring to the traffic-shap rate command where
everything is done in 1 argument...this command assumes you have a Tc
interval of 125ms and is configured on kbps instead of the time intervals
At 02:58 PM 6/20/2002 -0500, MADMAN wrote:
>Anthony Pace wrote:
> >
> > But if each map-class has a CIR and MINCIR, don't I want each one to
> > have only a peice of the pie? If I read you correctly you would want
> > all 8 map-classes to have a CIR of 1544 so that they "may" use all the
> > bandwidth if there were no congestion and a MINCIR of say 128 so that
> > if every spoke had traffic we would diveid it up. Is that correct?
>
> In a nutshell, yes. Otherwise your basically screwing yourself out of
>potential bandwidth. If you happen to be going in and out of the same
>frame switch, no NNI, you can often get well above your CIR for a
>sustained time.
>
> > Also does the command wjere traffic shaping parms are all on one line
> > express the Bc abd Be different than if you put thme seperatly in a
> > map-class?
>
> Not sure what you mean.
>
> Dave
> >
> > Anthony Pace
> >
> > On Thu, 20 Jun 2002 13:45:53 -0500, "MADMAN" <dave@interprise.com>
> > said:
> > >
> > >
> > > Anthony Pace wrote:
> > > >
> > > > I also keep seeing this reference to setting the CIR to the port
speed
> > > > in all the CCO an in all the books and in these posts. I guess I
will
> > > > adhere to this in the lab since I am seeing that this CCIE effort is
> > > > more theory than practical, however, what I have observed in real
life
> > > > is that traffic shaping is used when many, many logical circuits
> > > > inhabit a phisical link (ATM or FRAME). In the case of frame-relay,
if
> > > > the hub has 1544 kbps and 8 pvc's with 8 class's and each spoke has
64k
> > > > on each of their circuits,how can the CIR be 1544 on every map
class.
> > > > Isn't the idea to carve up the bandwidth amongst the spokes?
> > > >
> > > If you have a 1.544M circuit and you configure FRTS CIR for say 128K
> > > you will have effectively limited yourself to a max of 128K and will
> > > not
> > > be able to burst at a higher rate. Yes you want to shape when needed
> > > but you also want to burst when the bandwidth is available.
> > >
> > > Dave
> > >
> > > > Anthony Pace
> > > >
> > > > On Thu, 20 Jun 2002 22:31:25 +0800 (HKT), "Katson Yeung"
> > > > <kyeung@mail.hkcix.com> said:
> > > > > Thanks Mamoor, that is correct.
> > > > >
> > > > > One more question about the CIR.
> > > > >
> > > > > According to all the materials I read, the recommended value for
> CIR is
> > > > > set it to Access-rate. So, there is a question:
> > > > >
> > > > > R1s0 ------ FR -------- s0R2
> > > > >
> > > > > R1s0 = 1.544Mbps
> > > > > R2s0 = 128kbps
> > > > > CIR = 64k. (I know it is = mincir, irrelevent to the question,
> but list
> > > > > it
> > > > > out anyway.)
> > > > >
> > > > >
> > > > > At R1,
> > > > > should I set the CIR as 1544000 or 128000?
> > > David Madland
> > > Sr. Network Engineer
> > > CCIE# 2016
> > > Qwest Communications Int. Inc.
> > > dave@interprise.com
> > > 612-664-3367
> > >
> > > "Emotion should reflect reason not guide it"
> > >
> >
> > --
> > Anthony Pace
> > anthonypace@fastmail.fm
> >
> > --
> > http://fastmail.fm
> > - Ever wonder why we aren't named snailmail.sm?
>
>--
>David Madland
>Sr. Network Engineer
>CCIE# 2016
>Qwest Communications Int. Inc.
>dave@interprise.com
>612-664-3367
>
>"Emotion should reflect reason not guide it"
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