From: Cristian Henry H (chenry@reuna.cl)
Date: Fri Jun 04 2004 - 18:21:36 GMT-3
Brian, but, the policy-map B is setting only the 75% of total bandwith
regarding the default max-reserved-bandwidth. So the class X plus
class-default get the 100% of the 75%. In this case, we have available
another 25% yet of the total bandwidth of the interface, right?. How
this bandwidth is occuped?
Brian McGahan ha escrito:
>
> That simply means that the sum of all non-default classes
> reservations cannot exceed 75% of the bandwidth, interface or available
> depending on the IOS release. Class-default traffic is not guaranteed
> in the case of congestion. The following policies are not the same:
>
> policy-map A
> class X
> bandwidth percent 75
>
> policy-map B
> class X
> bandwidth percent 75
> class class-default
> bandwidth percent 25
>
> Suppose that the output queue is completely full of traffic from
> class X. In the first case, policy-map A, class-default traffic will be
> tail dropped as it attempts to enter the output queue. It is not
> guaranteed admission. In the second case, policy-map B, class-default
> traffic will be admitted and class X traffic in excess of 75% may be
> dropped.
>
> HTH,
>
> Brian McGahan, CCIE #8593
> bmcgahan@internetworkexpert.com
>
> Internetwork Expert, Inc.
> http://www.InternetworkExpert.com
> Toll Free: 877-224-8987 x 705
> Outside US: 775-826-4344 x 705
>
> > -----Original Message-----
> > From: Spolidoro, Guilherme [mailto:Guilherme.Spolidoro@unisys.com]
> > Sent: Friday, June 04, 2004 3:29 PM
> > To: Brian McGahan
> > Cc: ccielab@groupstudy.com
> > Subject: RE: QoS - Police - Congestion - NoCongestion
> >
> > I suggest you go back to the link that I sent before:
> >
> > CBWFQ Bandwidth Allocation
> > The sum of all bandwidth allocation on an interface cannot exceed 75
> > percent of the total available interface bandwidth. The remaining 25
> > percent is used for other overhead, including Layer 2 overhead,
> routing
> > traffic, and best-effort traffic. Bandwidth for the CBWFQ
> class-default
> > class, for instance, is taken from the remaining 25 percent.
> >
> > From:
> >
> http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_configur
> at
> > ion_guide_chapter09186a00800b75a9.html#1001225
> >
> >
> >
> > -----Original Message-----
> > From: Brian McGahan [mailto:bmcgahan@internetworkexpert.com]
> > Sent: Friday, June 04, 2004 3:58 PM
> > To: Spolidoro, Guilherme
> > Cc: ccielab@groupstudy.com
> > Subject: RE: QoS - Police - Congestion - NoCongestion
> >
> >
> > > Therefore, if the traffic from class-default wants/needs to use bw,
> > > there'll always be 25% guaranteed for it
> >
> > No this is not true. Class-default is best-effort unless you
> > manually reserve bandwidth for it. In the case of congestion, traffic
> > that falls into the default-class can still be dropped from the output
> > queue. Routing traffic is treated differently though. See the
> > following document for more information:
> >
> > http://www.cisco.com/warp/public/105/rtgupdates.html
> >
> >
> > HTH,
> >
> > Brian McGahan, CCIE #8593
> > bmcgahan@internetworkexpert.com
> >
> > Internetwork Expert, Inc.
> > http://www.InternetworkExpert.com
> > Toll Free: 877-224-8987 x 705
> > Outside US: 775-826-4344 x 705
> >
> >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> > Of
> > > Spolidoro, Guilherme
> > > Sent: Friday, June 04, 2004 1:37 PM
> > > To: Carlos G Mendioroz; Bob Sinclair
> > > Cc: ccielab@groupstudy.com
> > > Subject: RE: QoS - Police - Congestion - NoCongestion
> > >
> > > Carlos, not sure if I understand your question but the class-default
> > is
> > > always there (implicit) and you cannot reserve more than 75% in all
> > other
> > > classes combined (unless you use the max-reserved-bandwidth
> command).
> > > Therefore, if the traffic from class-default wants/needs to use bw,
> > > there'll always be 25% guaranteed for it (among other things like
> > routing
> > > traffic), otherwise class a can use as much as it is available.
> > >
> > >
> > > Bob, I guess we all learn something new everyday, rigth? :-)
> > >
> > > For some reason I always understood that the exceed/overflow traffic
> > from
> > > a given class would dispute the remaining of the bw with the
> overflow
> > of
> > > all other classes by using the WFQ algorithm, where packets with
> > higher IP
> > > Precedence get more bw.
> > >
> > > Doesn't sound like this is the case. Please visit the following
> link:
> > >
> > >
> >
> http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_configur
> > at
> > > ion_guide_chapter09186a00800b75a9.html#1009161
> > >
> > >
> > >
> > > Thanks.
> > >
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: Carlos G Mendioroz [mailto:tron@huapi.ba.ar]
> > > Sent: Friday, June 04, 2004 10:23 AM
> > > To: Bob Sinclair
> > > Cc: Spolidoro, Guilherme; ccielab@groupstudy.com
> > > Subject: Re: QoS - Police - Congestion - NoCongestion
> > >
> > >
> > > Me too. (inter class WFQ that is)
> > >
> > > I've been told that there is sort of priority to bandwidth assigned
> > > classes wrt non bandwidth assigned classes.
> > > So if you have class a bw 10% and class-default w/o bw, enough class
> a
> > > traffic can starve the rest of the link.
> > >
> > >
> > > Bob Sinclair wrote:
> > >
> > > > Guiherme,
> > > >
> > > > According to Wendell Odom in his book Cisco DQOS, the CBWFG
> > algorithm is
> > > not
> > > > published. I have a hard time seeing how it could be
> > precedence-based,
> > > like
> > > > WFQ. Do you have a reference you can share?
> > > >
> > > > Thanks!
> > > >
> > > > Bob Sinclair
> > > > CCIE #10427, CISSP, MCSE
> > > > www.netmasterclass.net
> > > >
> > > >
> > > > ----- Original Message -----
> > > > From: "Spolidoro, Guilherme" <Guilherme.Spolidoro@unisys.com>
> > > > To: <ccielab@groupstudy.com>
> > > > Sent: Friday, June 04, 2004 9:32 AM
> > > > Subject: RE: QoS - Police - Congestion - NoCongestion
> > > >
> > > >
> > > >
> > > >>The word that should be used with CBWFQ is not reserve but
> > guarantee.
> > > >>
> > > >>When you type the bandwidth percent 25 command on the class,
> what's
> > > gonna
> > > >
> > > > happen is that CBWFQ will guarantee at least 25% of the bw for
> this
> > > class
> > > > during congestion.
> > > >
> > > >>If there's no congestion, the bw command will never kick off. It's
> > used
> > > >
> > > > only during congestion, meaning it's basically a technology used
> to
> > > empty
> > > > the queues (when used with the bw statement).
> > > >
> > > >>If there's enough bw for everyone, there's no reason to guarantee
> > > >
> > > > anything, right?
> > > >
> > > >>If this class doesn't need to use 25% or more (let's say it's
> using
> > only
> > > >
> > > > 10%), the rest of the classes can use the remaining of the bw (the
> > other
> > > 15%
> > > > that this class doesn't need).
> > > >
> > > >>CBWFQ uses the WFQ algorithm, meaning that packets from the
> > different
> > > >
> > > > classes that have the highest IP Precedence will be the ones to
> > benefit
> > > more
> > > > from that. Let me give you an example:
> > > >
> > > >>class a = streaming video (ip prec 4)
> > > >>class b = bulk data (ip prec 1)
> > > >>class c = voip (ip prec 5)
> > > >>class default-class = anything else (ip prec 0)
> > > >>
> > > >>Class c has 25% of the bw guarantee for it, but might need only
> 10%
> > at a
> > > >
> > > > given time.
> > > >
> > > >>Class a has 5% of the bw guarantee for it, but might need more
> than
> > that
> > > >
> > > > at a given time.
> > > >
> > > >>Class b has 5% of the bw guarantee for it, but might need more
> than
> > that
> > > >
> > > > at a given time.
> > > >
> > > >>class default-class has 25% of the bw guarantee for it by default,
> > but
> > > >
> > > > might need more than that at a given time.
> > > >
> > > >>If there's congestion on the link, class c (voip) will get the 10%
> > that
> > > it
> > > >
> > > > needs. Classes a, b and the default-class' overflow will compete
> for
> > the
> > > > remaining bandwidth. They will use at least the bw that is on the
> > > command
> > > > plus whatever they can get.
> > > >
> > > >>Class a's overflow will be able to get more bw than class b and
> the
> > > >
> > > > default-class' overflows.
> > > >
> > > >>By the end, you might see something like this:
> > > >>
> > > >>Class c only needed 10% and that's what it got.
> > > >>Class a ended up getting 35% of the total bw.
> > > >>Class b ended up getting 25% of the total bw.
> > > >>Class default-class ended up getting 30% of the total bw.
> > > >>
> > > >>Not sure if this is a good example, but the idea is that all the
> > > overflows
> > > >
> > > > will leave the queue faster or slower according to their IP
> > > Precedence...
> > > >
> > > >>Without making it more confusing than it has to be, there are
> other
> > > >
> > > > options on CBWFQ (besides the bw command):
> > > >
> > > >>- priority = new version of the low latency queue, typically used
> > for
> > > voip
> > > >
> > > > or interactive video. Instead of putting the packets in the queue,
> > it
> > > sends
> > > > directly to the interface (except for the overflow) In our
> example,
> > you
> > > > could it on class c.
> > > >
> > > >>- policy = new version of the old CAR. Let you limit the traffic
> > that
> > > the
> > > >
> > > > class can use either for inbound or outbound. I personally don't
> > like it
> > > > because the way it works (basically drops the excess) causes too
> > many
> > > > retransmissions.
> > > >
> > > >>- shape = new version of the old traffic shape. Let you limit the
> > > traffic
> > > >
> > > > that the class can use for outbound only. I use extensive here and
> > it
> > > works
> > > > very well.
> > > >
> > > >>I know this address a lot more than what you asked but I hope
> others
> > on
> > > >
> > > > the list can benefit from it.
> > > >
> > > >>
> > > >>-----Original Message-----
> > > >>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On
> Behalf
> > Of
> > > >>gladston@br.ibm.com
> > > >>Sent: Friday, June 04, 2004 8:51 AM
> > > >>To: ccielab@groupstudy.com
> > > >>Subject: QoS - Police - Congestion - NoCongestion
> > > >>
> > > >>
> > > >>Dear Group,
> > > >>
> > > >>Does Police within CBWFQ reserve a bandwidth when there is no
> > congestion
> > > >
> > > > and when there is congestion?
> > > >
> > > >>For example, to reserve 25% of the bandwidth to traffic from
> > 10.100.5.0
> > > to
> > > >
> > > > 10.200.6.0:
> > > >
> > > >>Class-map p-100.5.0
> > > >> Match access-group name p-100.5.0
> > > >>!
> > > >>policy QOS
> > > >>class p-100.5.0
> > > >>police 10000 1000 conform-action transmit exceed-action drop
> > > >>!
> > > >>interface ser 1
> > > >> service-policy output QOS
> > > >>
> > > >>
> > > >>If so, why should one use bandwidth and policy within the same
> > class?
> > > >>
> > >
> >
> >>______________________________________________________________________
> > _
> > > >>Please help support GroupStudy by purchasing your study materials
> > from:
> > > >>http://shop.groupstudy.com
> > > >>
> > > >>Subscription information may be found at:
> > > >>http://www.groupstudy.com/list/CCIELab.html
> > > >>
> > >
> >
> >>______________________________________________________________________
> > _
> > > >>Please help support GroupStudy by purchasing your study materials
> > from:
> > > >>http://shop.groupstudy.com
> > > >>
> > > >>Subscription information may be found at:
> > > >>http://www.groupstudy.com/list/CCIELab.html
> > > >
> > > >
> > > >
> >
> _______________________________________________________________________
> > > > Please help support GroupStudy by purchasing your study materials
> > from:
> > > > http://shop.groupstudy.com
> > > >
> > > > Subscription information may be found at:
> > > > http://www.groupstudy.com/list/CCIELab.html
> > > >
> > >
> > > --
> > > Carlos G Mendioroz <tron@huapi.ba.ar> LW7 EQI Argentina
> > >
> > >
> >
> _______________________________________________________________________
> > > Please help support GroupStudy by purchasing your study materials
> > from:
> > > http://shop.groupstudy.com
> > >
> > > Subscription information may be found at:
> > > http://www.groupstudy.com/list/CCIELab.html
>
> _______________________________________________________________________
> Please help support GroupStudy by purchasing your study materials from:
> http://shop.groupstudy.com
>
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
-- Cristian E. Henry REUNAE-mail: chenry@reuna.cl Fono: 56-2-3370336
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