From: Godswill Oletu (oletu@inbox.lv)
Date: Wed Jun 07 2006 - 22:43:47 ART
Roberto,
Though, I have not checked the question to see if it is shaping or policing,
but if we assume that it is policing as you have just said, I am lost at
how:
Police cir 128000 bc 4000
Will result in a burst, as the original poster indicated. The command above
is just telling the router that, in order not to create a scheduling
concern, please kindly send 4000 bytes per burst or timing interval (Tc).
Bc is committed burst, you have paid for 128Kbps and you are telling the
router to allow you to burst your traffic from 0 to 4000 per timing interval
(Tc), and this commitment is based on your CIR. The concept of burst as we
understand it in everyday English only start coming into play with Be or
excess burst.
Also, if you look at the computation you just did; you are equating CIR to
be the same the same value as Bc, but using different metrics, which might
not be the correct thing to do.
The CIR given was 128kbps, convert this to bytes will be be 128000 / 8 =
16000 bytes and you divided that by 4 to get 1/4Bc (4000 bytes) that was
asked for.
Let assume that a full Bc was asked for instead of 1/4Bc, you see that your
computation will make Bc = 16000 bytes and this is the same amount of
traffic our CIR is allowing us to transmit per second. In a one second
traffic snapshot, the difference between 128kbps and 16000 bytes is the same
as the difference between $1 and 100 cents.
As you can see, that might not be the correct formula to computer Bc either
in policing or in shaping.
HTH
Godswill Oletu
----- Original Message -----
From: "Roberto Fernandez" <rofernandez@us.telefonica.com>
To: "Brian McGahan" <bmcgahan@internetworkexpert.com>; "Godswill Oletu"
<oletu@inbox.lv>; "Leigh Harrison" <ccileigh@gmail.com>; "Andi Bennett"
<bigandibennett@yahoo.com>
Cc: <ccielab@groupstudy.com>
Sent: Wednesday, June 07, 2006 2:21 PM
Subject: RE: FRTS Lab 1 - 7.2 question.
Friends,
Well... checking into 7.2 question of Version 3 WB, it is not a question
about FRTS it is about policing.
With FRTS Bc is bits, but with policing is Bytes, thus 128 kbits/4 = 32
kbits => 4K Bytes
The answer says
Police cir 128000 bc 4000
Best Regards,
Roberto
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Brian McGahan
Sent: Tuesday, June 06, 2006 9:45 AM
To: Godswill Oletu; Leigh Harrison; Andi Bennett
Cc: ccielab@groupstudy.com
Subject: RE: FRTS Lab 1 - 7.2 question.
> I think it has to do the value of the default 'Tc' (the Tc value used
when
> none is supplied) which is 125ms.
In this case yes, but not always. The default Tc is a function
of the CIR. The higher the CIR the lower the maximum (and default) Tc.
Change the "frame-relay cir" value in a map-class with no other values
configured and look at the "show traffic-shape" output. As the CIR goes
up you will see the Tc go down.
HTH,
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987 x 705
Outside US: 775-826-4344 x 705
24/7 Support: http://forum.internetworkexpert.com
Live Chat: http://www.internetworkexpert.com/chat/
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Godswill Oletu
> Sent: Tuesday, June 06, 2006 7:23 AM
> To: Leigh Harrison; Andi Bennett
> Cc: ccielab@groupstudy.com
> Subject: Re: FRTS Lab 1 - 7.2 question.
>
> LH,
>
> Maybe, you are talking about 'fragments' which are in bytes,
otherwise,
> 'CIR' are in bits/second; 'Bc' in Bits and 'Be' in Bits.
>
> I think it has to do the value of the default 'Tc' (the Tc value used
when
> none is supplied) which is 125ms.
>
> Be=(AR- CIR) * Tc/1000
> =(128000 * 125/1000
> =16000
>
> 1/4 Be = Be / 4 = 16000/ 4
> = 4000
>
> My only problem is that, the orignal posted mentioned 'Bc' instead of
> 'Be'.
> I do not see how 'Bc' will result in a Burst, except I am missing
> something
> here or in the question. 'Bc' simply tell us how much need to be
> transmitted
> per timing interval to conform to our 'CIR'; which is in our case
every
> 125ms and to conform to our 'CIR' of 128K, that value is 16000. 'Be'
tell
> us
> that, after fulfilling our allocated quota and we have room, how much
> above
> CIR should we Burst?
>
> Since, the Access Rate (AR) was not given in the task, it is safe to
> assume
> that 'AR' is equal to 'CIR', making both 'Bc' & 'Be' to be equal and
1/4
> of
> Be will be 4000.
>
> Please, set me straight if I am missing something here.
>
> Thanks.
> Godswill Oletu
>
>
> ----- Original Message -----
> From: "Leigh Harrison" <ccileigh@gmail.com>
> To: "Andi Bennett" <bigandibennett@yahoo.com>
> Cc: <ccielab@groupstudy.com>
> Sent: Tuesday, June 06, 2006 6:39 AM
> Subject: Re: FRTS Lab 1 - 7.2 question.
>
>
> > Hey there Andi,
> >
> > CIR is in bits, Bc is in bytes
> >
> > 128,000 / 4 = 32,000 _bits_ per interval
> >
> > 32,000 / 8 = 4,000 _bytes_ per interval
> >
> > Hope that helps a bit,
> >
> > LH
> >
> > Andi Bennett wrote:
> > > Dear group.
> > > Being a bit crap at FRTS can somebody explain the answer to the
Lab
> 1
> 7.2 question.
> > >
> > > 128K CIR and allow for 1/4th for burst.
> > >
> > > How does this come up with bc = 4000 ?
> > >
> > > Am I missing something here?
> > > Cheers
> > > A.
> > >
> > >
> > >
> > > Send instant messages to your online friends
> http://uk.messenger.yahoo.com
> > >
> > >
>
This archive was generated by hypermail 2.1.4 : Sat Jul 01 2006 - 07:57:32 ART