From: Petr Lapukhov (petrsoft@gmail.com)
Date: Sun Jun 04 2006 - 09:05:19 ART
Pierre,
unfortunately, I have not much time to write thorough explanation,
but I do recommend you to look at the following links:
http://www.cisco.com/en/US/tech/tk39/tk824/technologies_tech_note09186a00800c9699.shtml
http://www.cisco.com/en/US/tech/tk39/tk824/technologies_tech_note09186a0080093d62.shtml#
http://www.cisco.com/en/US/tech/tk543/tk544/technologies_tech_note09186a0080094612.shtml
They may give you some good insight on how CBWFQ actually works, and how
that
"ureservable" bandwidth is used. Just remember the key idea - "bandiwidth"
is just
a weighting factor for undelying WFQ algorithm.
HTH
Petr
2006/6/4, Pierre-Alex <paguanel@hotmail.com>:
>
> I have labed point number 2 and I my statement is actually wrong!
>
> With the configuration as is, the router will refuse the commands because
> the
> available bandwidth is actually 75% of the interface bandwidth .
>
> ( I think I got confused because when I did the test with shapping, I was
> abled to use 100% of the shapped rate. )
>
>
> ----- Original Message -----
> From: Pierre-Alex
> To: ccielab@groupstudy.com
> Sent: Sunday, June 04, 2006 11:38 AM
> Subject: QoS default-class - oversubscription
>
>
> I need a quick "yes" or "no" + quick optional comments on the following
> points .
>
> Theses are deductions I have made from several readings on CCO and
> research
> in the group-study archives.
>
> I just want to make sure I am not inventing wrong rules here ...
>
>
> 1. QoS bandwidth usage is calculated based on L3 packet size.
>
> 2. On non-7500 + platforms: 25% of the interface bandwidth SHOULD be
> left
> aside for overhead traffic, including Layer 2 (frame? overhead), control
> traffic (routing,cdp,snmp etc ...), and best-effort traffic. This traffic,
> and
> in particular NON IP traffic, will be allocated to the DEFAULT-CLASS .
>
> Because the 25% is a recommendation and is NOT enforced by the routers
> when
> using absolute bandwidth values. Nothing prevents me from doing the
> following
> and starve my overhead traffic.
>
> interface s 0/0
> bandwidth 100
>
> policy a
> class 1
> bandwidh 90
> class 2
> banwith 10
> clas-class default
>
> 3. The command "maximum bandwith-percent xx" is only releavant when
> using
> configurations with "bandwidth percent" .
> When left to the default maximum bandwith-percent 75 of interface
> bandwidth
> and when using "bandwidth percent " type configurations, then the overhead
> is
> taken care off.
> When changed to maximum bandwith-percent 100 then care must be taken to
> leave enough in the default class for overhead traffic.
>
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