From: Ahsan Mohiuddin (ahsan.mohiuddin@gmail.com)
Date: Tue Jul 15 2008 - 16:41:03 ART
Hello Guys,
when you put in a Bc value, you are actually affecting the Tc (there is no
direct way of setting the Tc). So in Roger's config, "frame-relay bc"
command is not required because it will be automatically calculated (from
default Tc of 125 ms) by IOS:
Bc = CIR x Tc
= 512000 kbps x 125 ms
= (512000 x 125) / 1000
= 64000
Be will be = (AR - CIR) x Tc
= (1500000 - 512000) x 125 ms
= 123500
Note that 1.5 Mbps is 1500000 bps and not 1536000.
Check out this very good post by Brian McGahan on FRTS:
http://www.groupstudy.com/archives/ccielab/200304/msg01159.html
And one from cisco
Kind regards,
Ahsan
On Tue, Jul 15, 2008 at 5:08 PM, Fahad Khan <fahad.khan@gmail.com> wrote:
> By default TC = 125 ms and can be 10 ms mininum, by lowering this value ,
> one can have greater number of TCs with lower BC value. I think when the
> question does not shed light over TC, we sould not worry about this default
> value.
>
> Plz correct me if I am wrong
>
> Thanks and regards,
> On Tue, Jul 15, 2008 at 4:57 AM, GAURAV MADAN <gauravmadan1177@gmail.com>
> wrote:
>
> > HI All
> >
> > Can someone Please clearify on Tc stuff as well .
> > Bc = Tc * CIR .. The example that Roger mentioned ; he has considered
> > the Tc as 125 msec .
> >
> > Can someone please clearify under what conditions can we safely assume
> > this value ?
> >
> > Thnx in advance
> > Gaurav Madan.
> >
> > On Tue, Jul 15, 2008 at 4:19 PM, Roger RPF <rpf@bluemail.ch> wrote:
> > > Hi group,
> > >
> > > I need some confidence in FRTS with an example. I know it is a "hot
> > > discussed" topic and I catched a lot from all the discussions, but I'm
> > still
> > > not 100% certain about "my calculation". Below a task which I tried to
> > solve
> > > with FRTS and CB-Traffic shaping.
> > >
> > > The task is: Target transmission rate is 512Kbps but I'm allowed to
> burst
> > up
> > > to port speed (1.5Mbps = AR = 1536000).
> > >
> > > So with FRTS I would do:
> > >
> > > map-class frame-relay shape
> > > frame-relay cir 512000 (target rate)
> > > frame-relay bc 64000 (CIR/Tc)
> > > frame-relay be 128000 (Ar/Tc - Bc)
> > >
> > > So the same stuff with Class Based shaping:
> > >
> > > policy-map shape
> > > class class-default
> > > shape peak 512000 64000 128000 (calculation is the same as with FRTS)
> > >
> > >
> > > _______________________________________________________________________
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> >
> > _______________________________________________________________________
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> >
> >
> >
> >
> >
>
>
> --
> *FAHAD KHAN
>
> BE Computer Systems NED,
>
> CCNA,CCDA,CCNP,FOUNDFE,CLSE,QOS,JNCIA,JNCIS,MCP,CCIE (Written)
>
> Systems Support Engineer, Premier Systems (Pvt) limited,
>
> Karachi, Pakistan
>
> 92-321-2370510.*
>
>
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