From: John (jgarrison1@austin.rr.com)
Date: Sun Jul 13 2008 - 11:43:32 ART
Narbik,
Wouldn't you consider the way "WFQ" treats traffic based on virtual time a
weighting mechanisim?
Thank you for the formula. I think I am starting to get it. The formula you
gave me is how WFQ weights the packets, and does not determine the bandwidth?
I don't get the set number, is that a constant that is used in all WFQ ip
precedence algorithms? Badnwidth is determined by "bandwidth /
X(0+1)+X(1+1)........X(7+1) " depending on how many packets are in the queue
and what their precedence is?
Thanks to all for the info
----- Original Message -----
From: Narbik Kocharians
To: Anthony Sequeira
Cc: Joseph Brunner ; John ; ccielab@groupstudy.com
Sent: Saturday, July 12, 2008 9:05 PM
Subject: Re: WFQ
WFQ without the weight should be fair-queuing; the weight aspect of the WFQ
comes in when traffic is set with IP Precedence levels.
The formula that WFQ uses is as follows:
If packets are 1500 Bytes and the IP Precedence is set to 0, then:
[32384 / (IP Precedence + 1)] X 1500 = 32384 / (0 + 1) = 48,576,000
The 32384 is a set number.
If packets are 1500 Bytes and the IP Precedence is set to 1, then:
[32384 / (IP Precedence + 1)] X 1500 = 32384 / (1 + 1) = 24,288,000
Note the packets with IP Precedence of 1 appear to be half the size of
packets with IP Precedence of 0 and therefore they will receive twice as much
bandwidth as the packets that are set with IP Precedence level of 0.
On Sat, Jul 12, 2008 at 4:01 PM, Anthony Sequeira
<Anthony_Sequeira@skillsoft.com> wrote:
In the context of the CCIE Lab, not much to worry about here. WFQ is one
of those "legacy" queuing mechanisms that does a good enough job to be
the default for "low speed" interfaces still. It will indeed prevent a
"top talker" from squeezing out a "low talker". <I think that was a
Seinfeld episode!>
There are some configurable parameters like the Congestive Discard
Threshold and the number of Dynamic Queues, but one of the main problems
with this queuing mechanism is that it does not support fixed bandwidth
guarantees. If you want to ensure your voice traffic gets 256K across
your WAN, this tool falls short.
Class Based Weighted Fair Queuing came along and addresses the
shortcomings of this mechanism. And then Low Latency Queuing further
improved upon that. These are the Lab topics I would focus on.
Interestingly, another place you see WFQ used today is in a LLQ config
for the "catch all other traffic" class of class-default.
I hope these comments helped you.
Anthony J Sequeira
#15626
www.freeiestuff.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Joseph Brunner
Sent: Saturday, July 12, 2008 4:38 PM
To: 'John'; ccielab@groupstudy.com
Subject: RE: WFQ
Much to learn about google have you still...
http://nislab.bu.edu/sc546/sc441Spring2003/wfq/wfq.htm
Much Mystery there will be until you search with keywords correct
Answers to questions find you will on this link and others.
google
cisco wfq scheduler
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
John
Sent: Saturday, July 12, 2008 4:35 PM
To: ccielab@groupstudy.com
Subject: WFQ
I don't know why I have a hard time getting this, but lets see if I have
this
right.
WFQ will give low volume traffic "better treatment" then high volume
traffic.
It does this through some mysterious algorithm that I can't seem to
find.
WFQ
is the default for all interfaces under E1 speeds. WFQ works with ip
precedence and RSVP. WFQ is flow based. I cannot change the behaviour
of
WFQ
through configuration. There are some QOS features I cannot configure
on an
interface with WFQ.
Thats what I get. I would appreciate comments on anything I missed or
got
wrong
_______________________________________________________________________
Subscription information may be found at:
http://www.groupstudy.com/list/CCIELab.html
_______________________________________________________________________
Subscription information may be found at:
http://www.groupstudy.com/list/CCIELab.html
No virus found in this incoming message.
Checked by AVG - http://www.avg.com
Version: 8.0.138 / Virus Database: 270.4.9/1548 - Release Date:
7/12/2008 7:40 AM
_______________________________________________________________________
Subscription information may be found at:
http://www.groupstudy.com/list/CCIELab.html
--
Narbik Kocharians
CCSI#30832, CCIE# 12410 (R&S, SP, Security)
www.Net-Workbooks.com
Sr. Technical Instructor
This archive was generated by hypermail 2.1.4 : Mon Aug 04 2008 - 06:11:54 ART