Re: QoS quiz

Just to be sure, and because my previous test was in an old platform
(2600Xm running 12.4.9T), I just tested it again with 15.1.1T on
a 2811.

policy-map child
  class voice
     priority 500
   set dscp ef
  class class-default
   set dscp default
     bandwidth remaining percent 100
policy-map parent
  class class-default
     shape average 1000000
   service-policy child

And now it works. Cool.
On the other hand, I would have thought that this worked before, back in
the time when 15.0 (or 12.4.20) did not exist.
Oh well, seems nothing should be taked for granted.

-Carlos

Alexei Monastyrnyi @ 20/06/2011 09:23 -0300 dixit:
> Well, according to the docs shaping uses FIFO by default which can be
> changed to either WFQ or any queuing under nested service-policy.
>
> http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6558/white_paper_c11-481499.html
>
> Default Queuing Implementation for the Shape Feature
>
> When you configure the shape command in a class, the default queuing
> behavior for the shape queue is FIFO instead of WFQ. You can configure
> the bandwidth, fair-queue, or service-policy commands in shape class to
> achieve different queuing behaviors.
>
> I can test it in our prof of concept lab but I am quite sure it will
> play out exactly that way or else it would be quite a miss by Cisco :-)
>
> Cheers,
> A.
>
>
>
> On 6/20/2011 9:57 PM, Carlos G Mendioroz wrote:
>> Alexei,
>> what you describe is what would happen with only one policy at the port,
>> which is not the case. When you have parent/child, you basically
>> "create" a serial setup where the parent output becomes the child input.
>>
>> The parent is doing shapping for ALL traffic without classification.
>> And it's a FIFO queue. So when it kicks in (rate above shape rate) you
>> start delaying all traffic.
>>
>> Don't take my word, test it. May be there's some way to make it work,
>> but I don't know it!
>>
>> -Carlos
>>
>> Alexei Monastyrnyi @ 20/06/2011 05:23 -0300 dixit:
>>> Carlos
>>> I don't think this is the case.
>>>
>>> In case of shaping buffer not empty the packet which is about to
>>> egress would go into scheduler and based on its marking it would be
>>> placed into the right queue, in you case in either LLQ or the
>>> class-default one. Now if it is a voice packet scheduled for LLQ it
>>> will egress as soon as it can regardless of class-default queue being
>>> full or not (well, up to the priority XYZ value, where it will be
>>> policed, and we are not taking serialization into account here as all
>>> is happening at FE speed).
>>>
>>> So I reckon your voice traffic should be just fine. I may be missing
>>> something so please correct me if I am wring.
>>>
>>> Cheers
>>> A.
>>>
>>>
>>> On 6/18/2011 8:35 AM, Carlos G Mendioroz wrote:
>>>> The problem with this configuration, which AFAIK is "by the book",
>>>> is that it does not protect the Voip stream.
>>>>
>>>> If you have a data stream that is going over your shape rate,
>>>> the shape buffer will be full and your voip traffic has to cross it!
>>>> (Read, you will have jitter at best, lost packets more than likely)
>>>>
>>>> -Carlos
>>>>
>>>> David Prall @ 17/06/2011 18:49 -0300 dixit:
>>>>> Carlos,
>>>>> So I would do:
>>>>> Class-map match-all voice
>>>>> Match protocol rtp
>>>>> Match dscp ef
>>>>> Policy-map child
>>>>> Class voice
>>>>> Priority percent 25
>>>>> Class class-default
>>>>> Bandwidth remaining percent 100
>>>>> Set dscp 0
>>>>>
>>>>> David
>>>>>
>>>>> --
>>>>> http://dcp.dcptech.com
>>>>>
>>>>>
>>>>>> -----Original Message-----
>>>>>> From: Carlos G Mendioroz [mailto:tron_at_huapi.ba.ar]
>>>>>> Sent: Friday, June 17, 2011 5:40 PM
>>>>>> To: David Prall
>>>>>> Cc: 'Cisco certification'
>>>>>> Subject: Re: QoS quiz
>>>>>>
>>>>>> Right.
>>>>>> This is *one* thing I left out. All traffic should be marked.
>>>>>> -Carlos
>>>>>>
>>>>>> David Prall @ 17/06/2011 18:31 -0300 dixit:
>>>>>>> You are matching on RTP, is all RTP already marked EF? You are using
>>>>>> shape
>>>>>>> average to provide artificial back-pressure at 2Mbps. You have
>>>>>> provided for
>>>>>>> 500Kbps within the 2Mbps so you will be fine as long as the carrier
>>>>>> is
>>>>>>> providing priority for the RTP traffic, if they are providing
>>>>>> priority for
>>>>>>> EF then you need to confirm that the application is setting EF or
>>>>>> remark the
>>>>>>> traffic on your own to EF. You also need to confirm that the traffic
>>>>>> that is
>>>>>>> not RTP, is not marked EF, otherwise the SP will put it into
>>>>>>> their EF
>>>>>> queue
>>>>>>> along with your RTP EF traffic, so remarking the class-default to 0
>>>>>> may help
>>>>>>> here.
>>>>>>>
>>>>>>> David
>>>>>>>
>>>>>>> --
>>>>>>> http://dcp.dcptech.com
>>>>>>>
>>>>>>>> -----Original Message-----
>>>>>>>> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On
>>>>>>>> Behalf
>>>>>> Of
>>>>>>>> Carlos G Mendioroz
>>>>>>>> Sent: Friday, June 17, 2011 5:05 PM
>>>>>>>> To: Cisco certification
>>>>>>>> Subject: QoS quiz
>>>>>>>>
>>>>>>>> Easy one, I would think.
>>>>>>>>
>>>>>>>> Say you have a wan link provided over metro (i.e. access rate is
>>>>>> well
>>>>>>>> over your contracted BW) and you want to apply QoS to protect your
>>>>>>>> Voip.
>>>>>>>>
>>>>>>>> You have 2Mbps contract, 25% limit on EF marked traffic.
>>>>>>>>
>>>>>>>> Will this config do the right thing (i.e. protect your voip traffic
>>>>>>>> from jitter caused by your data) ?
>>>>>>>>
>>>>>>>> class-map voice
>>>>>>>> match protocol rtp
>>>>>>>>
>>>>>>>> policy-map child
>>>>>>>> class voice
>>>>>>>> priority 500
>>>>>>>> class class-default
>>>>>>>> bandwidth remaining percent 100
>>>>>>>>
>>>>>>>> policy-map parent
>>>>>>>> class class-default
>>>>>>>> shape average 2000000
>>>>>>>> service-policy child
>>>>>>>>
>>>>>>>> inferface fastEthernet0/0
>>>>>>>> service-policy output parent
>>>>>>>>
>>>>>>>> --
>>>>>>>> Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina
>>>>>>>>
>>>>>>>>
>>>>>>>> Blogs and organic groups at http://www.ccie.net
>>>>>>>>
>>>>>>>>
>>>>>> _______________________________________________________________________
>>>>>>
>>>>>>>> Subscription information may be found at:
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>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>> --
>>>>>> Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina
>
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-- 
Carlos G Mendioroz  <tron_at_huapi.ba.ar>  LW7 EQI  Argentina
Blogs and organic groups at http://www.ccie.net