Re: QoS quiz

I know it is the same. This is the configuration that I would have done,
and that I guess many do. But I was surprised when I realized that it
does not work, or at least, it does not work as I thought it would.

Hence the quiz. Either I'm confused (more than likely :) or there is no
easy way to configure what I described. And it does not sound a weird
requirement...

To really protect the voip flows you have to set the priority class in
the parent policy. This will side step the shape buffer.
On the other hand, you will be overrunning your CIR!
Is there any way to have priority + shape work in synch ?
Some kind of shape adapt to "rest of" bandwidth...

-Carlos

David Prall @ 17/06/2011 20:07 -0300 dixit:
> It is the same as your configuration. I didn't include the parent because
> you already had that covered. I used priority percent instead of a bandwidth
> value, because then I can use it across multiple shaper values with only
> needing to change one parameter for different configurations.
>
> 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 6:35 PM
>> To: David Prall
>> Cc: 'Cisco certification'
>> Subject: Re: QoS quiz
>>
>> 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:
>>>>>> http://www.groupstudy.com/list/CCIELab.html
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>> --
>>>> Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina
>> --
>> 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
Blogs and organic groups at http://www.ccie.net