From: Roger RPF (rpf@bluemail.ch)
Date: Tue Jul 15 2008 - 17:19:24 ART
Hi Ahsan,
Thanks for that and for the interesting links, I'll go through them. It's my
fault I was to unclear with the AR. The task which I was referring to in my
question, asked about full line speed T1, which is 1.544Mbps but, as I got
from another discussion on this list, one should use 1.536Mbps (if I got
that right).
Regarding the Bc value which the router will "automatically calculate", how
to do that with CB shaping? I mean, as far as I can see that, it is not
possible to configure Be if you did not configure Bc before, isn't it?
regards
Roger
Von: Ahsan Mohiuddin [mailto:ahsan.mohiuddin@gmail.com]
Gesendet: Dienstag, 15. Juli 2008 21:41
An: Fahad Khan; GAURAV MADAN; Roger RPF
Cc: Cisco certification
Betreff: Re: FRTS conversion
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
http://www.cisco.com/en/US/tech/tk713/tk237/technologies_configuration_examp
le09186a00800942f8.shtml/
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)
> >
> >
> > _______________________________________________________________________
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html
>
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
>
>
>
>
>
-- *FAHAD KHANBE 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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