From: Ray Stevens (cisco-guy@rogers.com)
Date: Mon Apr 21 2003 - 21:18:22 GMT-3
This is how I understand it as well. but when reading it indicates that
WRED will drop all packets simulating tail-drop when the queue is full. Is
this refering to when the max-threshold is reashed or not. depending on the
sources I have read sometimes it sounds like the probability denomiintor is
the number of packets dropped when it reaches the min and incrases to
dropping all when at the maximum-threshold, and others say that it will
start dropping a percentage of the marked probabiltiy at minimum nd increase
to full marked proability when at max-threshold.
if the second is correct at what point would WRED start dropping all
packets.
exerpt from ISO Quality Of Service book.
WRED is usually used in the core routers of a network, rather than at the
edge. WRED uses these
precedences to determine how it treats different types of traffic.
When a packet arrives, the following events occur:
1. The average queue size is calculated.
2. If the average is less than the minimum queue threshold, the arriving
packet is queued.
3. If the average is between the minimum queue threshold for that type of
traffic and the maximum
threshold for the interface, the packet is either dropped or queued,
depending on the packet drop
probability for that type of traffic.
4. If the average queue size is greater than the maximum threshold, the
packet is dropped.
This would indicate once it goes over the max treshold it drops all which
would seem like a step increase from say dropping 1 out of 50 at max
threshold and dropping all once it goes over.
Ray Stevens
CCNP, CCDP, SCSA
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
midaskim
Sent: Friday, April 18, 2003 4:03 AM
To: dhuskey@bpop.com
Cc: ccielab@groupstudy.com
Subject: [RE]Re: [RE]random-detect precedence 5 40 60 20 (OUT OF OFFICE)
Thanks..
But I found the answer for my question.
The packet drop probability is based on the minimum threshold, maximum
threshold, and mark probability denominator.
When the average queue depth is above the minimum threshold, RED starts
dropping packets. The rate of packet drop increases linearly as the
average queue size increases until the average queue size reaches the
maximum threshold.
The mark probability denominator is the fraction of packets dropped when
the average queue depth is at the maximum threshold.
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A&8q : Re: [RE]random-detect precedence 5 40 60 20 (OUT OF OFFICE)
3/B% : Fri, 18 Apr 2003 02:09:44 -0500
:83=@L : "David Huskey" <dhuskey@bpop.com>
9^4B@L : <janggulove@hanmail.net>
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