From: Daniel Cisco Group Study (danielcgs@imc.net.au)
Date: Mon Mar 31 2003 - 06:41:04 GMT-3
Colin,
A very interesting explanation.....
I never saw it in this light. I guess that the success of this method would really depend on what your telco does at their end....
Have you come across anything in CCO regarding this method (apart from the networkers pdf)? I'd be very interested.
Daniel
-----Original Message-----
From: Colin Barber [mailto:Colin.Barber@telewest.co.uk]
Sent: Sunday, 30 March 2003 03:41
To: Daniel Cisco Group Study; CCIE FUN; ccielab@groupstudy.com
Subject: RE: Traffic-shaping question
You need to remember that the output of the TS algorithm does not go
directly to the output interface but to the output buffers. So in the
example by CCIE FUN although the amount of data output in the first time
interval is too much to be transmitted within that time period, the router
will buffer the traffic and send it in the following time intervals. After
the full 1 second has passed all data will have been transmitted and you
have achieved the full line bandwidth.
There are many references within books and CCO that will show both of your
methods. There is no right or wrong method it just depends on the actual
question. If it asks you to achieve full line speed over a 1 second period
then clearly CCIE FUN's example is correct. If it asks you to achieve full
line speed only for the first time period then Daniel's method is correct.
If we are talking about the CCIE lab then ask the proctor. Explain the two
methods and ask them if they would prefer you use a particular method. If
they ask you read the question then there should be something there to make
you select the correct method for that scenario.
If you are not able to decide the method to use then I would recommend using
the method that is show in the CCIE power presentations which is basically
CCIE FUN's method:
http://www.cisco.com/networkers/nw02/presos/pws/docs/PS-570.pdf
page 66/188
Colin
-----Original Message-----
From: Daniel Cisco Group Study [mailto:danielcgs@imc.net.au]
Sent: 29 March 2003 09:30
To: CCIE FUN; Daniel Cisco Group Study; ccielab@groupstudy.com
Subject: RE: Traffic-shaping question
Firstly,
In the following command:
frame-relay be 16000
be is specified in bits....
Router(config-map-class)#frame-relay be ?
<0-16000000> Applied to both Incoming/Outgoing Be, Bits
in Incoming Be (Frame-Relay SVC only)
out Outgoing Be
<cr>
Secondly,
If you look carefully at the first 125msec time interval, we transmit 2000 +
6000 = 8000 bits. (Like you said below)
That's 8000 bits in 125msec, which actually translates to 64000bps (for a
period of 125ms).
Thus, you are able to burst in the first time interval, all the way to
64000bps. Every time interval after that, we transfer only 6000 bits per
125ms interval - ie 48000bps.
You are correct in saying that the net rate is 50kbps (for the entire 1 sec
period). But keep in mind that because you have no tokens left in the bucket
after this 1 sec period, you won't be bursting in the next 1 sec period....
ie you'll be stuck on cir of 48kbps until some point later when you transmit
at less than this rate (and you begin to accumulate tokens in the bucket).
Hope I haven't confused the issue. The best way to understand this is using
the token bucket analogy (which I'll leave up to you or to another colleague
to dig up a good URL for...)
Daniel
-----Original Message-----
From: CCIE FUN [mailto:ccieexam2002@yahoo.com]
Sent: Saturday, 29 March 2003 13:50
To: Daniel Cisco Group Study; ccielab@groupstudy.com
Subject: RE: Traffic-shaping question
Daniel
Be is in bits per second.
The Be value calculated by you is correct, however it
2000Bits per time interval(125ms)
so ultimately the Be for 1 sec(125 ms * 8) is
2000 * 8 = 16000bps.
Yes you can only burst for the first time interval
however if you use the value of 2000
then here is what is transmitted in 1sec
2000(be)+6000(bc)=8000-1st time interval
(125ms)
6000(bc)--2nd time interval(125ms)
6000(bc)--3nd time interval(125ms)
6000(bc)--4th time interval(125ms)
6000(bc)--5th time interval(125ms)
6000(bc)--6th time interval(125ms)
6000(bc)--7th time interval(125ms)
6000(bc)--8th time interval(125ms)
so the total is 50Kbps
But the port speed is 64Kbps this means we can burst
upto 64Kbps. so how do i get to that?
My understanding was that the router will send
send the full Be amount during the first time
interval.
and remaining 7 time interval it will be only Bc.
so adding all that i get the net result of 64000.
i am getting too confused with this now.i hope my
understanding is correct.
because i have been getting varying solutions for this
one.
--- Daniel Cisco Group Study <danielcgs@imc.net.au>
wrote:
> Shouldn't be=2000 ?
>
> (AR - CIR) / 8
>
> (64000 - 48000) / 8
>
> You are using a 125ms time interval, and you can
> only burst in the first one. Also, be is in bits,
> not bps.
>
> Daniel
>
> -----Original Message-----
> From: CCIE FUN [mailto:ccieexam2002@yahoo.com]
> Sent: Saturday, 29 March 2003 02:54
> To: ccielab@groupstudy.com
> Subject: Traffic-shaping question
>
>
> Hello all,
> I have traffic-shaping question and i have also
> mentioned the solution i used.
>
> please help me out to identify if it's correct and
> what commands are useful to determine that the
> traffic
> shaping is going to work as configured.
>
> Here is the question:
> 1.The router R5 has two PVC's going R1 and R13 each
>
> has CIR of 48Kbps and burst size of 64Kbps.
>
> 2. The circuit from R5 to the frame-relay switch is
> provisioned at a speed of 64Kbps.
>
> 3. If BECN's are recieved, R5 needs to throttle back
>
> back the PVC's to 32Kbps.
>
> 4. Using CIR, Bc and Be configure traffic-shaping on
>
> R5.
>
> Now here is my config for Router R5 relevant to
> Traffic-shaping. I have not shown any frame-maps or
> IP
> information for clarity purposes.
>
> !
> interface s0
> encap fram
> no arp fram
> no fram inv
> frame-relay traffic-shaping
> frame-relay class Shape
> !
> map-class frame-relay Shape
> frame-relay cir 48000
> frame-relay bc 6000
> frame-relay be 16000
> frame-relay mincir 32000
> frame-relay adaptive-shaping becn
>
>
>
> Now my question is do i need to configure R1 and R13
> for shaping even if it is not mentioned in the
> Question.
>
> Also is my solution correct.
>
>
> Thanks for your help.
>
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