From: Paglia, John (USPC.PCT.Hopewell) (JPaglia@xxxxxxxxxxxxx)
Date: Tue Jul 16 2002 - 17:42:42 GMT-3
OK, now I'm getting confused on this point, because when I read Cisco
Documentation, I was led to believe that the Be is ONLY sent during the
first time cycle. Thus, for example....
125 ms
max= 64k
CIR= 48k
mincir= 24k
I was thinking that if the above is true, that...
Bc= 6k (48k/8 (1sec*.125))
Be= 16k (max-above formula)
6k (Bc) * 8 # of time cycles) + 16k (remainder sent in first time cycle) =
64K
Please assist,
Pags
> -----Original Message-----
> From: Carlos G Mendioroz [SMTP:tron@huapi.ba.ar]
> Sent: Tuesday, July 16, 2002 3:34 PM
> To: Guoqi Cui
> Cc: David Luu; Ahmed Mamoor Amimi; Bruce Williams; Lab Candidate;
> ccielab@groupstudy.com
> Subject: Re: FRTS want to nail it down !!
>
> Guoqi Cui wrote:
> >
> > As I understand CIR and BE are in different unit.
>
> Yes indeed.
>
> > We can not say set BE=32000 bps. BE should be in
> > unit of bits. As for the example, 32000 is the extra
> > link speed to handle extra traffic beyond CIR. The
> > formula to calculate BE is: (AR-CIR)*Tc. Tc is one
> > slot time interval. You can set BE higher than
> > (AR-CIR)*Tc, what is the use of it? Sinece AR is the
> > maximum rate the link can provide, after garantee CIR
> > only (AR-CIR) left.
>
> There is only AR - CIR left but in each Tc!
> You can use your "excess burst" in many Tc's.
>
> As I said in the example, even though you have only 4000
> bits left to transmit above CIR, you can actually transmit
> one full minute at AR given that you have enough Be.
>
> Please take the time to make the experiment.
> Or read some book (e.g. Tannenbaum's computer metworks)
> about the dual leaky bucket algorithm. That's what it is.
>
> Regards,
>
> >
> > As for David, you set BE as 32000bps, this is
> > different from BE's definition, you give a rate, BE
> > should be in bits.
> >
> > --- Carlos G Mendioroz <tron@huapi.ba.ar> wrote:
> > > David,
> > > I think this is not quite right, or I am
> > > misunderstanding you.
> > >
> > > To be safe, it is ok to set Be to a value >> AR/Tc.
> > >
> > > It is my understanding that Be is how much data you
> > > can transmit over
> > > your CIR,
> > > as you "eat" burst tokens. But you can eat them in
> > > more than one Tc.
> > >
> > > Here an example everyone can run to see the
> > > difference:
> > >
> > > CIR = 32 kbps
> > > Bc = 4000 b
> > > Tc = .125 s (automatically computed)
> > > Be = 1920000 b
> > > Ar = 64 kbps (Access rate, i.e. clockrate)
> > >
> > > This will transmit at 64kbps for one minute and then
> > > drop to 32k.
> > > Try it with ttcp, send 60 x 8192 bytes, it will take
> > > some 75 seconds...
> > >
> > > http://www.cisco.com/warp/customer/125/21.shtml has
> > > more info.
> > >
> > > Regards,
> > >
> > >
> > > David Luu wrote:
> > > >
> > > > like i said in a previous post...
> > > > "Be" sends excess data in the FIRST interval if
> > > there are enough tokens, it
> > > > does not send it in the other intervals
> > > >
> > > > take the bottom example...
> > > > port speed = 64000bps
> > > > cir = 32000bps
> > > > mincir = 16000bps
> > > > bc = 4000bps
> > > > be = 32000bps
> > > >
> > > > first we will start off with "Bc", to get "Bc" we
> > > divide 1 second (1000ms)
> > > > by the time interval (which is 125ms in this
> > > case), which is 1000ms divided
> > > > by 125ms = 8...this gives us 8 intervals, so a
> > > 32000bps cir divided by 8
> > > > gives us a "Bc" of 4000bps
> > > >
> > > > again, "Be" sends excess data in the FIRST
> > > interval if there are enough
> > > > tokens, it does not send it in the other
> > > intervals...to send data at the
> > > > maximum rate the port can handle, we take the port
> > > speed of 64000bps minus
> > > > the cir of 32000bps...this leaves us with 32000bps
> > > to send in the first
> > > > interval...
> > > >
> > > > if we were to have a "Be" of 4000bps, the max rate
> > > we can send is cir + be
> > > > (32000+4000), which equals 36000bps, remember that
> > > "Be" is only sent out in
> > > > the FIRST interval if there are available tokens
> > > >
> > > > with a Tc of 125ms, it gives us 8 intervals
> > > > with a Tc of 10ms, it gives us 100 intervals
> > > >
> > > > once again i have to stress this, "Be" is only
> > > sent out in the FIRST
> > > > interval if tokens are available...with a Tc of
> > > 125ms or 10ms, "Be" will
> > > > still only be sent out ONE time every second
> > > (1000ms)
> > > >
> > > > hope this clears up any confusion you may have
> > > with "Be" and "Bc"
> > > >
> > > > At 01:33 AM 7/16/2002 +0500, Ahmed Mamoor Amimi
> > > wrote:
> > > > >aaaahhhh !! atleast ur with me... heheheeh...
> > > this is what i have beening
> > > > >saying but not getting a very difinite answer
> > > from the group why they have
> > > > >used 32000 as be in power session. if bc is
> > > multipy by 0.125 then be should
> > > > >also be multiply by 0.125 ... why 1 sec
> > > > >
> > > > >-Mamoor
> > > > >
> > > > >
> > > > >----- Original Message -----
> > > > >From: Guoqi Cui <guoqicui@yahoo.com>
> > > > >To: Bruce Williams
> > > <bruce@williamsnetworking.com>; Lab Candidate
> > > > ><labccie@yahoo.com>; Ahmed Mamoor Amimi
> > > <mamoor@ieee.org>
> > > > >Cc: <ccielab@groupstudy.com>
> > > > >Sent: Monday, July 15, 2002 9:49 PM
> > > > >Subject: RE: FRTS want to nail it down !!
> > > > >
> > > > >
> > > > > > The FRTS parameters are quite confusing.
> > > > > > CIR, MINCIR is in unit of bps
> > > > > > BC, BE is in unit of bits
> > > > > >
> > > > > > If BE is set as: port_speed minus-cir
> > > > > > it will hava a unit of bps,
> > > > > >
> > > > > > Do Tc is assumed to be 1 sec?
> > > > > >
> > > > > > For this case( Tc=0.125 sec),
> > > > > >
> > > > > > BE should be set as 32000/8=4000.
> > > > > >
> > > > > >
> > > > > > --- Bruce Williams
> > > <bruce@williamsnetworking.com>
> > > > > > wrote:
> > > > > > > If the available bandwidth is 32000, then
> > > dont we
> > > > > > > still need to multiply it
> > > > > > > by .0125 to get the bits per Tc?
> > > > > > >
> > > > > > > -----Original Message-----
> > > > > > > From: nobody@groupstudy.com
> > > > > > > [mailto:nobody@groupstudy.com]On Behalf Of
> > > > > > > Lab Candidate
> > > > > > > Sent: Sunday, July 14, 2002 1:03 AM
> > > > > > > To: Ahmed Mamoor Amimi
> > > > > > > Cc: ccielab@groupstudy.com
> > > > > > > Subject: Re: FRTS want to nail it down !!
> > > > > > >
> > > > > > >
> > > > > > > Mamoor,
> > > > > > >
> > > > > > > This is obvious, since you said the port
> > > speed is
> > > > > > > 64000 and cir is 32000,
> > > > > > > if you want to utilized the most of your
> > > available
> > > > > > > bandwidth for burst
> > > > > > > purpose, the be would be equal to port_speed
> > > minus
> > > > > > > cir, hence 32000 bps.
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > I was reading the power-session 2002, here
> > > on page
> > > > > > > 66 they have given the
> > > > > > > values like :
> > > > > > >
> > > > > > > Port Speed: 64000 Bps
> > > > > > > CIR : 32000 Bps (Average Rate of Traffic
> > > Without
> > > > > > > Congestion)
> > > > > > > Mincir: 16000 Bps (Average Rate of Traffic
> > > With
> > > > > > > Congestion)
> > > > > > > Bc: 4000 Bps (Amount of Data Sent Per
> > > Interval)
> > > > > > > Be: 32000 Bps (Amount of Excess Allowed Once
> > > Credit
> > > > > > > Has Built Up)
> > > > > > >
> > > > > > > interface Serial0
> > > > > > > ip address 10.10.10.1 255.255.255.0
> > > > > > > encapsulation frame-relay
> > > > > > > frame-relay traffic-shaping
> > > > > > > frame-relay class ccie
> > > > > > >
> > > > > > > map-class frame-relay ccie
> > > > > > > frame-relay adaptive-shaping becn
> > > > > > > frame-relay cir 32000
> > > > > > > frame-relay mincir 16000
> > > > > > > frame-relay bc 4000
> > > > > > > frame-relay be 32000
> > > > > > >
> > > > > > > Can someone explain why Be = 32000 , why not
> > > Be =
> > > > > > > 32000 * 0.125 = 4000
> > > > > > >
> > > > > >
> > >
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