From: Sean C (Upp_and_Upp@hotmail.com)
Date: Sun May 22 2005 - 16:17:49 GMT-3
Hi Zeng,
I believe you are looking at the DQOS book - ISBN# 1-58720-058-9
Bruce is referring to the new QoS book - ISDN# 1-58720-124-0
Both books are authored by Odom and Cavanaugh. The book Bruce is referring
to is the 2nd edition of the book you are referencing.
Please note - in the 1st edition & the 2nd edition - both books use the same
example
1st edition - pg393
2nd edition - pg387
-all traffic policed at 96kbps
-Bc of 1 second's worth of traffic allowed
-Be of 0.5 second's worth of traffic is allowed
-traffic that violates is dropped
-traffic that exceeds the contract is marked down to DSCP Be
-traffic that conforms to the contract is forwarded with no re-marking.
but the solutions and accompanying explanation are not the same:
1st edition (pg 393-4):
police cir 96000 bc 12000 be 18000.......
"The excess burst configuration parameter actually defines the Bc and Be
value combined, in bytes. So, the value is configured at 18000, which is
6000 bytes more than Bc."
2nd edition (pg 388-9:)
police cir 96000 bc 12000 be 6000....
"The excess-burst configuration parameter is 6000 bytes, or half of Bc."
To further complicate the issue - in the 2nd edition, the 1st sentence on pg
389 actually looks like if was copy and pasted from the 1st edition by
stating 'police cir 96000 bc 12000 be 18000...' even though the example on
pg 388 uses 'be 6000'
Interestingly, the 1st edition's errata does not address this. And it does
not appear there is an errata for the 2nd edition yet.
HTH (if it doesn't confuse you),
Sean
----- Original Message -----
From: "ccie zeng" <ccie.candidate@gmail.com>
To: "Andrew B. Caslow" <abcaslow@netmasterclass.net>
Cc: "simon hart" <simon.hart@btinternet.com>; <ccielab@groupstudy.com>
Sent: Sunday, May 22, 2005 2:48 PM
Subject: Re: Bc and Be
> Hi Andrew:
> according to pg,393 in DQOS book, it says all traffic is policed at
> 96kbps,
> Bc of 1 seconds worth of traffic is allowed(12000bytes), Be of 0.5
> seconds worth of traffic is allowed(6000bytes), Then when you look at
> the configuration at next page, you will see it configure be as 18000,
> not 6000.
>
> Did I misunderstood your statement?
> Thanks
> Zeng
>
>
> On 5/22/05, Andrew B. Caslow <abcaslow@netmasterclass.net> wrote:
>> Simon,
>>
>> Regarding the CB-police command, the Bc and Be create two separate and
>> distinct token buckets. You can have a Be that is equal to or even less
>> than
>> the Bc and you will still be able to have an excess burst. This is
>> central
>> to the operation of the single-rate three-color-marker. If you have the
>> Wendell Odom book, check out pages pp 388-393. He has a couple of
>> examples
>> where Be is set to a value less than Bc. Odom also has a nice summary on
>> CB-Police parameters on pp. 405-406.
>>
>> I hope all is well.
>>
>> -Bruce
>>
>> -----Original Message-----
>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>> simon hart
>> Sent: Sunday, May 22, 2005 4:40 AM
>> To: ccie zeng; Cisco certification
>> Subject: RE: Bc and Be
>>
>> Zeng,
>>
>> You are right. If you configure both bc and be to the same value there
>> is
>> no extended burst. In order to achieve your stated goal, then bc 1000
>> and
>> be 2000 would be correct.
>>
>> Be careful when using these police commands, I would recommend that you
>> always use the ? prompt to determine whether you need to enter bits or
>> bytes.
>>
>> Also the relationship between bc and be is different when using Traffic
>> shaping. When traffic shaping any value of be will be the absolute value
>> of
>> the burst.
>>
>> HTH
>>
>> Simon
>>
>> -----Original Message-----
>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
>> ccie zeng
>> Sent: 22 May 2005 09:30
>> To: Cisco certification
>> Subject: Bc and Be
>>
>>
>> Hi:
>> Could anyone clarify to me, when I asked to configure normal burst
>> size 1000 bytes, and excess burst size 1000 bytes for CAR or CB
>> policing, should I configure like this ".....bc 1000 be 2000" or just
>> "...bc 1000 be 1000".
>>
>> Based on my understanding if Be is configured as 1000, then there is
>> no excess burst, is that right?
>>
>> Thanks
>> Zeng
>>
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