Re: QoS question

Adrian,
to better understand your example, you should post the policy too.

You say "the phone DSCP EF marking is not overwritten by the policy-map"
but I would expect it to, given that the policy actually calls for
a remark.

I don't ubderstand your last paragraph. The PC marking, if any, will
be cleared (reset to 0) by the phone AFAIK. Remember that there's always
a mark at L3, there's no way to tell apart a "marked as 0" or
unmarked, if that term is ever used.

-Carlos
Firm believer that confusion is the beginning of wisdom :)

Lazar Adrian @ 9/04/2010 9:10 -0300 dixit:
> Hi Carlos,
>
> Thanks for your prompt answer.
> As I really needed to know what is the exact behavior in this case I have
> tested it using a 3560 switch and a cisco phone.
> The original IOS on the switch (1-2 years old) didn't even permit the
> service-policy input command on the interface at the same time with "mls qos
> trust device cisco-phone".After I upgraded to the latest 3560 IOS,
> 12.2(53)SE, the behavior changed dramatically. Now I was permitted to put
> the two commands on the same interface and after capturing some traffic it
> seems the phone DSCP EF marking is not overwritten by the policy-map I
> defined (which was not marking the voice packets with DSCP EF).
> To summarize, below are the commands I used to configure the interface:
>
> mls qos trust cos
> mls qos trust device cisco-phone
> service-policy input QoS_Marking
>
> As this was a user/phone port those commands had the effect of letting the
> DSCP EF mark of the phone to go through untouched by the policy and mark the
> user traffic according to the policy (seemed that "mls qos trust cos "
> command didn't apply to user traffic ).
>
> Best Regards,
>
> Adrian
>
> On Thu, Apr 8, 2010 at 12:52 PM, Carlos G Mendioroz <tron_at_huapi.ba.ar>wrote:
>
>> Adrian,
>> ip traffic is always marked with some code, that should give you a clue.
>> But if it does not, then it depends on the logic of the policy, but
>> you can remark if you will. In your terms, the policy has precedence.
>>
>> "mls qos trust device" only disables the wiping of the incoming mark.
>>
>> It's a litle more complicated than that in fact. You need to have
>> "mls qos trust dscp" in place, and that initializes the internal QoS
>> marking to that of the incoming IP dscp. Then if "trust device" is
>> added, the initialization is replaced with 0 if the connected device
>> is not a cisco phone. Then comes your policy to change whatever, and
>> last and option to leave the initial marking alone when sending.
>> To top it, this is architecture dependent.
>>
>> HTH,
>> -Carlos
>>
>> Lazar Adrian @ 8/04/2010 6:29 -0300 dixit:
>>> Hi guys,
>>>
>>> I have a simple QoS implementation with one policy-map marking the
>> traffic
>>> inbound coming from a user or IP phone (I have a general port config, so
>>> same port config no matter if a PC or phone connects to it).
>>> Now, my question is related to the precedence of "mls qos trust device
>>> cisco-phone" and "service-policy QoS_Marking inbound" commands. What I
>> want
>>> to know and I haven't found this information anywhere is, if my phone
>> sends
>>> DSCP EF marked traffic will the policy-map mark it down ? So the matter
>>> resumes to what command has precedence over the other.
>>>
>>> Thank you,
>>>
>>> Adrian
>>>
>>> PS: Disregard the previous mail, I accidentally hit the send button too
>>> early :)
>>>
>>>
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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