From: Nathasha Aleyevka (naleyevka@yahoo.com)
Date: Wed Feb 18 2004 - 11:35:20 GMT-3
Cisco DQOS Exam Certification Guide
ISBN:1587200589
By Wendell Odom, Michael Cavanaugh
Packet Man-Is this the book you mentioned?
Thank you
Packet Man <ccie2b@hotmail.com> wrote:
yasser,
You are correct. I also found some other things which I had forgotten. (My
brain is a leaking bucket).
Keep tihs in mind.
Tc doesn't always = 1/8 second. Tc= Bc/cir and remember (unlike I did)
that Bc is in Bytes and cir is in bits.
Also, and this is again counter intuitive. The 3rd parameter isn't really
Be, it's Be + Bc. So, if Bc and Be look like they're the same (for example,
the parameters are 128000 4000 4000), what that really means is that Be = 0.
So, using those same parameters, Tc = 4000 / 16000 = 1/4 second
Get the book DQOS. He has the best explanations and examples of this stuff.
HTH
>From: "Yasser Aly"
>To: ccie2b@hotmail.com, ccielab@groupstudy.com
>Subject: RE: Limiting ICMP using CAR
>Date: Tue, 17 Feb 2004 19:15:13 -0500
>
>
>Hi Packet Man,
>
> Bc and Be are configured in Bytes not bits. I am not sure about whether
>it is per Tc or not.
>
>Needs clarification.
>
>Regards,
>Yasser
>
>>From: "Packet Man"
>>To: blackyeyes00@hotmail.com, ccielab@groupstudy.com
>>Subject: RE: Limiting ICMP using CAR
>>Date: Tue, 17 Feb 2004 18:27:11 -0500
>>
>>Yasser,
>>
>>I think the issue you might be having is due to the different units used
>>for the different parameters. Remember that the 1st parameter, cir, is in
>>bits per SECONDS while the Bc and Be are in bits per Tc which is 1/8 of a
>>second.
>>
>>So, 128,000 kbps dvided by 8 = 16,000 = bits per interval, Tc. To allow
>>for a burst of 1/4 of this rate, divide by 4. 16,000 / 4 = 4000.
>>
>>Now, given the requirements you stated, I think the answer that was
>>provided is wrong. I think it should be
>> CIR Bc Be
>>rate-limit output access-group 100 128000 16000 4000 conform-action
>>transmit exceed-action drop
>>
>>Hopefully, if I'm mistaken, someone will immediately say so and point out
>>my mistake. (It wouldn't be the 1st time)
>>
>>HTH
>>
>>
>>>From: "Yasser Aly"
>>>Reply-To: "Yasser Aly"
>>>To: ccielab@groupstudy.com
>>>Subject: Limiting ICMP using CAR
>>>Date: Tue, 17 Feb 2004 18:07:34 -0500
>>>
>>>Hi group,
>>>
>>> The task is as follows: Configure E0/0 such that ICMP traffic is
>>>limited to 128Kbps.
>>>Allow for a burst of 1/4th of this rate.
>>>
>>>
>>>The answer for this question was as follows:
>>>
>>>acess-group 101 permit icmp any any
>>>!
>>>interface Ethernet0/0
>>>rate-limit output access-group 100 128000 4000 4000 conform-action
>>>transmit exceed-action drop
>>>
>>>I am confused why Bc and Be were set this way. Would you kindly explain
>>>and give more detail on general concepts used when configuring Bc and Be
>>>while using CAR.
>>>
>>>Regards,
>>>Yasser
>>>
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>>
>
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