From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Fri Jun 04 2004 - 18:40:33 GMT-3
Christian,
This is another matter entirely. In short, in newer IOS the
reservation is absolute based on the interface bandwidth. In older IOS
the reservation is relative based on the available bandwidth (interface
bandwidth * max-reserved-bandwidth).
For more info see this thread:
http://www.groupstudy.com/archives/ccielab/200402/msg01220.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
> Cristian Henry H
> Sent: Friday, June 04, 2004 4:22 PM
> To: Brian McGahan
> Cc: Spolidoro, Guilherme; ccielab@groupstudy.com
> Subject: Re: QoS - Police - Congestion - NoCongestion
>
> 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:
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> > > > >>
> > > >
> > >
> >
>>______________________________________________________________________
> > > _
> > > > >>Please help support GroupStudy by purchasing your study
materials
> > > from:
> > > > >>http://shop.groupstudy.com
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> > > > >
> > > > >
> > > > >
> > >
> >
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