From: Darren Johnson (dazza_johnson@yahoo.co.uk)
Date: Fri Jan 11 2008 - 14:28:55 ARST
Hey all. Please see my take on your answers:
1. The average queue depth is how many packets are currently in the queue
waiting to be transmitted (when there is congestion). If no congestion, this
should be 0.
2. Think about this. If the interface starting dropping packets only when
the maximum-threshold was reached, how could it 'selectively' drop packets
on precedence/dscp? The queue is at maximum, so all packets are dropped. By
stating a minimum threshold, you are saying at this point there is suffice
congestion to warrant dropping packets selectively. By selectively, I mean
you may want to start dropping low priorirty packets when the queue depth is
10 packets deep. After this point low priority packets are randomly dropped.
For high priority packets, you may want to drop only when the average queue
depth is 50. This way, low priority packets get randomly dropped earlier and
only if heavy congestion is experienced do we drop high priority packets?
Make sense? (Please note: I chose simple easy to understand values above and
now real-life figures).
Take it easy
Dazzler
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Steven Hodgson
Sent: 10 January 2008 05:25
To: abdul muhammed; Cisco certification
Subject: RE: Need Explanation on WRED
You don't really have an average queue length. You have a 3 areas that
traffic can fall into:
1. under the min-threshold - traffic is safe
2. between the min threshold and max-threshold - traffic may be dropped
according to mark-prob-denom
3. over the max-threshold - traffic will be dropped
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
abdul muhammed
Sent: Wednesday, January 09, 2008 3:38 AM
To: Cisco certification
Subject: Need Explanation on WRED
Hi,
in configuring WRED using Random-detect interface command based on IP
precedence where the Precedence, Min-threshold, Max-threshold and
Mark-prob--denominator parameters are deployed.
1. what does my average queue length represent:
2. why should packet be drop when my average queue lenght equals the
Min-threshold and not just when it equal the Max threshold for that
precedence.
I need explanation on this.
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