From: Tom Young (gitsyoung@xxxxxxxxxxx)
Date: Sun Jul 21 2002 - 11:29:58 GMT-3
I am very interested in the calculation of Tc, Could I set
it for a Frame-Relay? Or it should be decided by provider?
And the default is 0.125s in everywhere of the world?
Thanks
--- David Luu <wicked01@ix.netcom.com> $B$+$i$N%a%C%;!<%8(B
$B!'(B
> "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>
>
=== message truncated ===
This archive was generated by hypermail 2.1.4 : Sat Sep 07 2002 - 19:36:38 GMT-3