From: David Luu (wicked01@xxxxxxxxxxxxx)
Date: Tue Jul 16 2002 - 20:05:59 GMT-3
something i need clarification on...
"The amount of excess data allowed to be sent during first Tc interval in
bits once credit is built up. Configure Be only if the Frame Relay CIR
value is less than the AR. For PVCs carrying voice packets, the Be must be
set to zero to ensure best possible voice quality. The router only bursts
(Be) when there are tokens in the token bucket. The token bucket does not
accrue tokens unless the amount of traffic being sent out is less than the
CIR. The router can only burst for the first Tc, after which the token
bucket is empty. The value of Be by default is zero bits."
using the same example below...
say you put your Be to 4k that was derived from the formula instead of the
32k that i said...
keep in mind that Bc is 4k as well which equals CIR/8 intervals...
so even with a Be of 4k you will still be over your CIR and their will be
no tokens to accumulate...
whenever you burst you empty the token bucket...
so i would assume that you can send a "burst excess" of less than what you
configured
just the first time around with a higher "Be" you can send more
At 07:30 PM 7/16/2002 -0300, Carlos G Mendioroz wrote:
>David,
>the problem is that Be will be exhausted after one second. If you don't
>go
>below CIR, then you will not be able to transmit any more excess bursts.
>
>With your params (AR=64kbps,CIR=32kpbs,Bc=4000, Ec=32000) , a ttcp
>of 60x8192bytes takes 125 seconds. That's an efective 32kbps.
>
>
>
>David Luu wrote:
> >
> > "Be" should be written in bits, i got carried away typing bps at the
> time...
> >
> > i said that "Be" is sent out in the FIRST interval of EVERY SECOND if
> > enough tokens are available...
> >
> > "burst excess" can be sent out in more than 1 interval, but it CANT take
> > place in the SAME second...assuming a Tc of 125ms which gives us 8
> > intervals PER second, it can be sent out on the 1st, 9th, 17th, etc
> > interval, the 1st interval will take place in the 1st second, the 9th
> > interval will take place in the 2nd second, the 17th interval will take
> > place in the 3rd second...
> >
> > now for the Be=(AR-CIR)*Tc...
> > assume AR=64kbps, CIR=32kbps, and a Tc of 125ms
> > this would make Be = 4kb according to the formula you are using
> > now do CIR+Be=36kb, remember that Be is sent ONCE a second if enough tokens
> > are available
> > so the max you can send in 1 second is 36kb
> > you are not effectively using your AR...64kb-36kb=28kb of room to burst
> >
> > to burst from your CIR to AR you would want to use a Be of 32kb
> > now CIR+Be=64kb=AR
> >
> > At 04:33 PM 7/16/2002 -0300, Carlos G Mendioroz wrote:
> > >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
> > > > > > > > >
> > > > > > > >
> > > > >
This archive was generated by hypermail 2.1.4 : Sat Sep 07 2002 - 19:36:33 GMT-3