QOS - RED

From: Ruhann (groupstudy@ru.co.za)
Date: Tue Mar 31 2009 - 16:42:21 ART


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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