Re: QOS - RED

By looking at the question, this is the answer in my opinion:

random-detect precedence 5 50 70 4 :)

So you answered correctly, but your assumption:

"As the Q depth increases so will the random drops, up until Q=70 where 4/4
will be dropped?" was incorrect because Q=70 => you drop 1 out of 4 not
taildrop which is (4 out of 4)

Best regards,
George

On Wed, Apr 1, 2009 at 8:34 AM, Ruhann <groupstudy_at_ru.co.za> wrote:

> In the above Q, what wouldyou use as your MPD to meet the requirement :)
>
>
> On Wed, Apr 1, 2009 at 12:19 AM, George Roman <georgeroman_at_gmail.com>wrote:
>
>> Hi Ruhann,
>>
>> Here is how this works:
>>
>> -when you reach the lower limit (50 packets in your case) in the Q you
>> start dropping packets than as bigger your queue gets you will be more
>> aggressive on your drop (this drop is proportional to the value you set for
>> the MPD).
>> -When you reach higher limit (70 packets in your case) you will drop with
>> the value you are set for the MPD. In your case if the value is 4 (this is
>> the denominator) you will drop 1 out of 4 packets from the queue.
>> After you exceed 70 packets you have taildrop.
>>
>> Best regards,
>> George
>>
>>
>>
>>
>> On Tue, Mar 31, 2009 at 10:42 PM, Ruhann <groupstudy_at_ru.co.za> wrote:
>>
>>> Hi peoples
>>>
>>> I would like to double check something I dont agree with.
>>>
>>> The question states as follow:
>>> Congestion Avoidance:
>>>
>>> - Configure R6 to randomly drop packets before congestion occurs on the
>>> Serial interface output queue.
>>> - Ensure that traffic marked with critical precedence will not be
>>> dropped
>>> unless there are 50 packets in the output queue.
>>> - If there are 70 critical packets in the output queue, R6 should
>>> randomly drop 4 out of every 16 of these packets.
>>> - In the case that there are more than 70 critical packets in the
>>> output
>>> queue, they should all be dropped.
>>> - Do not use any MQC commands to accomplish this task.
>>>
>>>
>>> My solution to this was as follow:
>>> interface Serial0/0
>>> random-detect
>>> random-detect precedence 5 50 70 4
>>>
>>> My question is about the MPD value to be worked out here.
>>> How I understand this, to work out your MPD value you take 1/MPD to see
>>> the
>>> initial stage of RED,
>>> in this example 4/16 = 1/4 , so the MPD=4
>>> thus 1 in every 4 packets will be randomly dropped when RED kick in
>>> (Q=51).
>>>
>>> As the Q depth increases so will the random drops, up until Q=70 where
>>> 4/4
>>> will be dropped?
>>>
>>> Am I understanding this right, Cause the answer to this question was the
>>> MPD
>>> =8
>>> ie : random-detect precedence 5 50 70 8
>>>
>>> Please share you though and point me right if im wrong. :)
>>> --
>>> <ruhann>
>>>
>>>
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>>
>
>
> --
> <ruhann>

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Received on Wed Apr 01 2009 - 10:12:20 ART