"One method of using the priority command for a traffic class is to
specify a bandwidth argument that gives the maximum bandwidth in kpbs.
The other method of using the priority command for a traffic class,
which was introduced in Cisco IOS Release 12.1(5)T, is to specify a
percentage of available bandwidth to be reserved for the priority
queue. The bandwidth value or percentage guarantees the configured
bandwidth to the priority class under worst-case congestion scenarios.
If excess bandwidth is available, the priority class will be allowed
to utilize the bandwidth. If no excess bandwidth is available, the
priority traffic will be constrained to the configured rate via packet
drops. Each individual class that is configured to a bandwidth value
will have its traffic constrained to its individual rate."
Does this answer your question?
Mihai
On Thu, Nov 26, 2009 at 6:00 PM, S Malik <ccie.09_at_gmail.com> wrote:
> Thanks to all for their time and explanation:
>
> Let me ask it again please:
>
> I have four class-maps (1,2,3,4) and under policy-map I use "bandwidth
> percent 25" for the three classes 1,2,3.
> Now for the class-map 4, I configure "priority percent 25".
>
> My question is how Priority will be handled, will the traffic for class-map
> 4 get priority upto 25% of BW and how the traffic in class-map 1,2,3 and
> default -class will be handled under congestion?
>
>
> I have an impression that class 4 will get 25% (due to priority) and extra
> traffic in this class will be dropped, class-maps 1,2,3 will get upto 25% of
> BW as there is no additional BW available and they will get their minimum
> share and traffic in default-class will be dropped as there is no BW
> available. Can some one correct if wrong please?
>
>
> On Wed, Nov 25, 2009 at 11:43 PM, Babatunde Sanda <sbabatunde1_at_ca.rr.com>wrote:
>
>> I forgot to include the " max-reserved-bandwidth 80" under the serial
>> interface
>>
>> INT S0/0
>> max-reserved-bandwidth 80
>> service-policy output INTERNET_TRAFFIC
>>
>>
>>
>> -----Original Message-----
>> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
>> sbabatunde1_at_ca.rr.com
>> Sent: Wednesday, November 25, 2009 7:40 PM
>> To: S Malik; ALL From_NJ
>> Cc: Cisco certification
>> Subject: Re: LLQ with Bandwidth MQC
>>
>> Hello Malik,
>>
>> Here is a quick QOS MQC run down (there is way more to QOS though). The
>> command "max-reserve bandw" is to modify the default reserved bandwidth on
>> interfaces which is 25% of the interface by default. This is needed for the
>> "class-default" (any traffic not explicitly classified for in your
>> configuration. So when you configure traffic with MQC you are actually
>> using the remaining 75% on the interface. You shouldn't have to modify the
>> reserved bandwidth except absolutely necessary because you definitely cannot
>> classify for all traffic. If my memory serves me I think the maximum class
>> recommended is 11 and minimum is 4. So you want to make sure there is
>> bandwidth for this traffic's to use (As usual Cisco will give you the
>> command to shoot yourself in the foot even though they recommend otherwise).
>>
>> When configuring LLQ, you use the command priority percent "bandwidth
>> percent" or priority bandwidth "bandwidth amount". When you do this you are
>> policing the class you specified to the amount in percentage or specified
>> bandwidth amount. In other words this command is saying the traffic will
>> not get more than the amount if congestion happens.
>>
>> On the other hand when you use the "bandwidth percent or bandwidth followed
>> by the bandwidth amount" you are saying to the class "you get this amount
>> if congestion happen and if there is more bandwidth and you need more you
>> can use more.
>>
>> So for example say I want to classify for this 3 traffic voice, video and
>> Gnutella and I want to use 80 percent of the total bandwidth on the
>> interface I will do something like this.
>>
>> TRAFFIC CLASSIFICATION
>>
>> class-map match-any VIDEO
>> match ip dscp 41
>> class-map match-any VOICE
>> match ip dscp ef
>> class-map match-any TRASH
>> match protocol gnutella
>>
>> ACTION
>>
>> policy-map INTERNET_TRAFFIC
>> class VOICE
>> set dscp ef
>> priority percent 33
>> class VIDEO
>> set dscp 41
>> bandwidth percent 10
>> class TRASH
>> set dscp af11
>> bandwidth percent 2
>> class class-default
>> fair-queue
>> random-detect dscp-based
>>
>>
>> APPLICATION
>>
>> INT S0/0
>> service-policy output INTERNET_TRAFFIC
>>
>>
>> Hope this gives you a better insight and encourage you to read more on QOS.
>>
>>
>> Good luck.
>> ---- S Malik <ccie.09_at_gmail.com> wrote:
>> > All,
>> > I have deliberately configured three classes with BW statement under a
>> > policy-map so that it consume 75% of BW.
>> >
>> > Fourth class I configured with priority %25. Now I could configure
>> > service-policy out on interface by changing "max-reserve bw 76%.
>> >
>> > I think, BW 25% command under policy-map means minimum 25% and priority
>> 25%
>> > means upto 25%.
>> >
>> > What I like to confirm is that if I keep max-reserve BW 76% then only 1%
>> of
>> > BW will be used for LLQ?
>> >
>> > On Wed, Nov 25, 2009 at 11:39 AM, ALL From_NJ <all.from.nj_at_gmail.com>
>> wrote:
>> >
>> > > If you have configured more bandwidth than what is avail, you will see
>> the
>> > > error message telling you that you do not have enough. You can use the
>> > > max-reserv command to alter what is available for your configuration.
>> > >
>> > > The link:
>> > >
>> > >
>> http://www.cisco.com/en/US/docs/ios/qos/command/reference/qos_m1.html#wp1039174
>> > >
>> > > By default you can only configure up to 75% of the bandwidth. Use this
>> > > command when you want to configure more. In your example, 24% would
>> still
>> > > be available for class-default, aka ... unnamed traffic that does not
>> match
>> > > your class-maps.
>> > >
>> > > The percent command will be a percentage of the available bandwidth.
>> The
>> > > above link can also be used for looking up these commands as well.
>> > >
>> > > IMO, the percentage commands are very good when you are offering a
>> service
>> > > to another or when you want to standardize a QoS config.
>> > >
>> > > For example, network management traffic will always get at least 5% of
>> the
>> > > bandwidth or biz traffic will always get 40% of bandwidth etc ...
>> > >
>> > > Some service providers might offer different service levels at
>> different
>> > > prices. An example of these might look like:
>> > >
>> > > VoIP always get 25%
>> > > Net Management always gets 5%
>> > > Ip Prec 3 might always get 30%
>> > > IP Prec 4 .... gets 15%
>> > > etc ...
>> > >
>> > > If you are a service provider, you can apply these configs to any link
>> and
>> > > maintain the same service levels regardless of the actual bandwidth of
>> the
>> > > link. Voip will still always get 25% whether it is on a T1 or T3 ...
>> > >
>> > > Does this make sense? I hope my examples are clear (many times I
>> confuse
>> > > myself :-))
>> > >
>> > > HTH,
>> > >
>> > > Andrew Lee Lissitz
>> > > .
>> > > On Wed, Nov 25, 2009 at 11:18 AM, S Malik <ccie.09_at_gmail.com> wrote:
>> > >
>> > >> ALL,
>> > >>
>> > >> if I have three classes of traffic each with 25% of minimum BW and 4th
>> > >> class
>> > >> of traffic with priority percent 25 then all I need for the
>> service-policy
>> > >> command to go through under interface is "max-reserve bw 76%".
>> > >>
>> > >> My question is that in this case only 1% of BW will be allocated to
>> the
>> > >> traffic which is configured for LLQ?
>> > >>
>> > >>
>> > >> Blogs and organic groups at http://www.ccie.net
>> > >>
>> > >>
>> _______________________________________________________________________
>> > >> Subscription information may be found at:
>> > >> http://www.groupstudy.com/list/CCIELab.html
>> > >>
>> > >>
>> > >>
>> > >>
>> > >>
>> > >>
>> > >>
>> > >>
>> > >
>> > >
>> > > --
>> > > Andrew Lee Lissitz
>> > > all.from.nj_at_gmail.com
>> >
>> >
>> > Blogs and organic groups at http://www.ccie.net
>> >
>> > _______________________________________________________________________
>> > Subscription information may be found at:
>> > http://www.groupstudy.com/list/CCIELab.html
>>
>>
>> Blogs and organic groups at http://www.ccie.net
>>
>> _______________________________________________________________________
>> Subscription information may be found at:
>> http://www.groupstudy.com/list/CCIELab.html
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
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Received on Thu Nov 26 2009 - 20:52:16 ART
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