From: Ahmed Mamoor Amimi (mamoor@xxxxxxxx)
Date: Tue Feb 12 2002 - 17:41:18 GMT-3
can u explain something about DSCP value .... what is that and wat is the
value for use
-Mamoor
----- Original Message -----
From: Leah Lynch <leah_lynch@lucent.com>
To: 'Ahmed Mamoor Amimi' <mamoor@ieee.org>; <ccielab@groupstudy.com>
Sent: Wednesday, February 13, 2002 1:25 AM
Subject: RE: CAR and WRED
> That's pretty close:
>
> Short answer:
>
> CAR is a DiffServ packet marking/classification application based on value
> in TOS header. It is very configurable and allows you to change the value
of
> the IP precedence bit or DSCP value based on conform or exceed statements
> which are configurable.
>
>
> WRED is based on RED (that goes based on Nagle algorithm) where WRED uses
> the value of TOS header to drop packet proactively based on their weight
> (kind of like WFQ) WRED will drop a percentage of packets once congestion
> has been detected on the interface. WRED is used to avoid congestion by
> forcing TCP flows to backoff using TCP windowing.
>
> This doc explains a lot about the differences between the two.
>
>
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fqos
> _c/qcfintro.htm
>
> This is also covered in Cisco IOS Quality of Service and the Configuration
> guide but a lot has changed since that was written (and since IOS 12.2). I
> personally like the Documentation CD contents best.
>
> Hope that helps.
>
> Leah Lynch
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Ahmed Mamoor Amimi
> Sent: Tuesday, February 12, 2002 11:42 AM
> To: ccielab@groupstudy.com
> Subject: CAR and WRED
>
>
> my thinking about CAR and WRED :
>
> CAR
> By CAR u can set normal and max burst then tell if the rate drop from
> normal then apply precedence or drop or ATM-CLP or QoS or trasmit.
> General assumption:
> set min xxx
> max xxx
> if min<flow of packet
> then
> drop or clp or prec or qos or transmit
> end
>
>
> WRED
> Use the random-detect command to enable WRED, which randomly discards
> packets during congestion based on IP precedence settings
> General assumption:
> if RED<flow of packet
> then
> {(set precedence 0-7) and (threshold 1-4096)}
> or
> set precedence to rsvp packets
>
>
>
> my thinking is that they both are some what same but CAR is more flexible
as
> it gives u the upper and lower bond of limit
> to traffic.
>
>
> -Mamoor
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