From: Andy Mrozek (AndyMrozek@yahoo.com)
Date: Sun Jul 18 2004 - 20:53:54 GMT-3
Thanks Bob,
Also I found a good little section in Cisco Press Dqos book on page 262 that
starting discussing how WFQ works on previously classified traffic. So the
way I am perceiving this , is WFQ does NOT have its own built in
classification tools like PQ and CQ , as it dynamically classifies traffic
via flow charachteristics eg... IP source/Dest / transport either tcp/udp
and client port/server port. But if you took say a High Volume flow of
traffic say from a database that backs up to another database via ftp for
example and Tagged that flow with IP Prec "critical" it looks like WFQ will
now take preference over this High Volume flow , as opposed to normal WFQ
operation of providing more bandwidth to lower volume flows such as
Telnet/SNA
-----Original Message-----
From: Bob Sinclair [mailto:bsin@cox.net]
Sent: Sunday, July 18, 2004 4:42 PM
To: Andy Mrozek; ccielab@groupstudy.com
Subject: Re: WFQ Clarification
Andy,
Cisco's implementation of WFQ is IP Precedence - aware. Not sure how it
relates to tail drop, though Odom is usually pretty reliable. Here is a
link to more on the WFQ algorithm:
http://www.cisco.com/warp/public/732/Tech/wfq/
Bob Sinclair
CCIE #10427, CISSP, MCSE
www.netmasterclass.net
----- Original Message -----
From: "Andy Mrozek" <AndyMrozek@yahoo.com>
To: <ccielab@groupstudy.com>
Sent: Sunday, July 18, 2004 5:13 PM
Subject: WFQ Clarification
> Question : Does WFQ -- queuing tool -- act on previously marked layer 3
> headers such as DSCP / Ip Prec
>
> Info Source: In Dqos cisco press book there is the the following quote on
> page 257 : " WFQ differs from PQ and CQ in several significant ways. The
> first and most obvious difference is that WFQ does not allow
classification
> options to be configured. WFQ classifies packets based on flows. A "Flow"
> consists of all packets that have the same source / destination port
numbers
> " end quote.... But then in the table on page 272 where it lists the
> charachteristics of WFQ functions and features it states this : "
> Classifies without configuration , based on source / Destination IP
address
> / port / protocol type (udp/tcp) and TOS. And says it has a modified tail
> drop . Drop policy..
>
>
> I am trying to determine what " Modified Tail Drop" means in the context
of
> Dqos book on page 272 .. And say I mark via CB marking a flow to Critical
> Accounting webserver at 10.10.10.10 and set all packets with IP
destination
> in them with "Critical" IP prec ... Will WFQ look at this flow differently
> than a flow that has the same volume say to a web server that is marked "
> Routine" ????
>
> Thanks
>
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