From: Mingzhou Nie (mnie@xxxxxxxxx)
Date: Tue May 14 2002 - 01:16:55 GMT-3
Nick's reply basically is the recap of following techtip.
http://www.cisco.com/warp/public/125/traffic_shaping_6151.html
remember mincir, not cir, is the one guaranteed by service provider.
--- Michael Kilpatrick <mjkilpat@yahoo.com> wrote:
> Great info... thanks.
>
> ----- Original Message -----
> From: "Nick Shah" <nshah@connect.com.au>
> To: "Bezverkhi, Serguei" <Serguei.Bezverkhi@hp.com>; "Michael
> Kilpatrick"
> <mjkilpat@yahoo.com>
> Cc: <ccielab@groupstudy.com>
> Sent: Monday, May 13, 2002 12:54 AM
> Subject: Re: Generic Traffic Shaping - Fatkid Lab #461 / FRTS
>
>
> > Correction & Apologies(my answer was incorrect)... but this is what
> I
> found
> > in the archives, It has come from Patrick @ cisco systems. It seems
> to
> make
> > more sense when you read thru it...
> >
> > ----Pat's original mail----
> > This should help!
> >
> > Terminology:
> >
> > Tc = Bc/Cir ! time interval (the internalized version of Tc where
> the
> > time interval can't exceed 125ms)
> >
> > CIR = Average rate you want to send out (This is generally not the
> > same as the CIR you get from your provider unless you aren't
> > allowed to send above CIR) This is measured in bits/second.
> > Bc = Amount of data to send per each Tc interval. This is
> > measured in bits.
> > (this also gets internalized and real amount of data sent per
> > interval is expressed in bytes by the "increment" variable).
> > Be = Amount of excess data allowed to be sent during first
> > interval once credit is built up. Also measured in bits.
> >
> > Mincir = Minimum amount of data to be sent during periods of
> congestion.
> > This defaults to half of CIR.
> >
> > Interval = Bc/CIR with the maximum size being 125ms.
> >
> > byte increment = Bc/8 . Must be > 125. Upper side has no bound
> > or limitation except if interval is locked at 125ms.
> >
> > limit = byte increment + Be/8 (measured in bytes)
> >
> >
> --------------------------------------------------------------------
> >
> > OK let me throw some numbers in which may help explain this better.
> >
> > Let's say you have a frame relay link with following parameters:
> >
> > Physical port speed 64KB
> > CIR = 16KB (In this case I mean CIR your provider has guarenteed
> > you in their network)
> >
> > Now let's say your provider has told you that you can send data on
> your
> PVC
> > up to port speed as long as there is no congestion in their network
> but
> that
> > when there is congestion they will only guarantee you CIR on your
> PVC.
> >
> > Here is what you should configure on the router:
> >
> > encap frame-relay
> > ip address 10.10.10.1 255.255.255.0
> > frame-relay traffic-shaping
> > frame-relay map ip 10.10.10.2 200 broadcast
> > frame-relay interface-dlci 200
> > class 64KB
> >
> > //snip//
> >
> > Nick
> > map-class frame-relay 64KB
> > frame-relay cir 64000 ! This is rate you want to normally
> send at
> > when
> > there is no congestion
> > frame-relay bc 8000 ! This is amount you will send per
> interval.
> > rule of thumb is to make it 1/8 CIR
> > frame-relay be 0 ! This is extra amount to send in
> first
> > interval. In this case you are
> already
> > sending at port speed so this
> should be 0.
> > frame-relay mincir 16000 ! This is what you will slow down to
> during
> > congestion. This should be set to
> your
> true
> > CIR that your provider has
> guarenteed you
> > when
> > there is congestion in their
> network
> >
> > *Note that BECN Response(ie dropping down when receiving BECNs) is
> > enabled by default in 11.2
> >
> > Now here are a couple of other numbers that are used in traffic
> shaping:
> >
> > Tc= Bc/CIR where Tc is the measurement interval. This value
> should
> > be no larger than 1/8 second for good shaping to
> take
> affect.
> >
> > So in above example Tc = 8K/64K = 1/8 second
> >
> > So basically here is what you would see transmitted in 1/8 second
> intervals:
> >
> > 8000(Bc+Be), 8000(Bc), 8000, 8000, 8000, 8000, 8000, 8000
> >
> > which equals 64000bits/second.
> >
> > Now if you actually had a 128KB port speed but you left all numbers
> the
> same
> > except you changed Be = 64000 then here is what you would see.
> >
> > 72000, 8000, 8000, 8000 ....
> >
> > You would keep sending at Bc(8000) until you had an idle interval
> or only
> a
> > partially used interval and you built up credit again. The maximum
> credit
> > you
> > can build up is Be.
> >
> >
> > -----Original Message-----
> > From: Bezverkhi, Serguei <Serguei.Bezverkhi@hp.com>
> > To: Michael Kilpatrick <mjkilpat@yahoo.com>
> > Cc: ccielab@groupstudy.com <ccielab@groupstudy.com>
> > Date: Monday, 13 May 2002 1:43
> > Subject: RE: Generic Traffic Shaping - Fatkid Lab #461
> >
> >
> > >Hello,
> > >
> > >I think this should meet the requirements
> > >
> > >traffic-shape group 101 16000 2000 14000
> > >
> > >16000 it is CIR, so we guarantee 16kb
> > >2000 it is Bc, just number of bit sent
> > >14000 it is Be, so it can burst up to 30kbps but no more, and even
> after
> > >30kb burst it will be able to send 16kbps.
> > >
> > >What do you think about this calculations??
> > >
> > >Serguei
> > >
> > >-----Original Message-----
> > >From: Michael Kilpatrick [mailto:mjkilpat@yahoo.com]
> > >Sent: May 12, 2002 8:43 PM
> > >To: ccielab@groupstudy.com
> > >Subject: Generic Traffic Shaping - Fatkid Lab #461
> > >
> > >
> > >In Fatkid Lab #461, can someone please verify the given solution
> for
> > >item #5.
> > >
> > >Item #5 says:
> > >5. Configure R3 so that users on the Token Ring segment get at
> least 16K
> > >of bandwidth, but not more than 32K, for their telnet traffic, and
> the
> > >remaining bandwidth for everything else.
> > >
> > >And the given solution is:
> > >interface Serial0
> > > traffic-shape group 101 16000 32000 32000 1000
> > >access-list 101 permit tcp any any eq telnet
> > >
> > >Please correct me if I am wrong, but it seems to me that this does
> > >nothing to guarantee users get at least 16K of bandwidth. In
> addition,
> > >this traffic-shape command would allow bursts up to the 64k
> access-rate
> > >and would apply a tc interval of 2 seconds which would be very
> > >inefficient.
> > >
> > >I think the solution should read:
> > >interface Serial 0
>
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