From: Carlos G Mendioroz (tron@huapi.ba.ar)
Date: Wed Jun 02 2004 - 14:30:36 GMT-3
Yup,
I may be wrong but AFAIK, all QOS thing is done internally at "layer 3",
called internal DSCP value, so if incoming traffic has layer 2 markings,
it is converted to layer 3, and then on output it is againg converted to
layer 2 if needed.
That in turn implies that you have to decide which markings are you to
believe (layer 2 or layer 3) on input.
There is a default switchwide CoS and per interface default CoS (used if
not trusting incoming markings) that are converted to DSCP via
CoS-to-DSCP table. There is also a IPPrecedence-to-DSCP to be used if
trusting IP Preceddence on input.
Chris Larson wrote:
> I have not tested it out but I think that the 3550 has a default layer 2 CoS
> to layer 3 DSCP mapping. Therefore if you configure QoS and an ethernet
> frame is CoS marked then the default is to map the CoS into the appropriate
> DSCP and you would see the ToS value changed in the packet.
>
>
> ----- Original Message -----
> From: "Peng Zheng" <zpnist@yahoo.com>
> To: <Brent.Bowers@cox.com>; <tomasz.szymanski@trecom.pl>
> Cc: <ccielab@groupstudy.com>
> Sent: Wednesday, June 02, 2004 1:56 AM
> Subject: RE: A Question about 3550 QoS
>
>
>
>>Can anyone verify this because I don't have access to
>>a 3550?
>>
>>--- Brent.Bowers@cox.com wrote:
>>
>>>In my testing on a 3550 it does actually change the
>>>TOS bits. If you have access to a 3550 please test
>>>it out and check it against a packet analyzer to
>>>verify the change.
>>>
>>>-----Original Message-----
>>>From: nobody@groupstudy.com
>>>[mailto:nobody@groupstudy.com]On Behalf Of Peng
>>>Zheng
>>>Sent: Tuesday, June 01, 2004 3:01 PM
>>>To: Bowers, Brent (CCI-San Diego);
>>>tomasz.szymanski@trecom.pl
>>>Cc: ccielab@groupstudy.com
>>>Subject: RE: A Question about 3550 QoS
>>>
>>>I think this will set cos, not ip precedence. Am I
>>>wrong?
>>>
>>>--- Brent.Bowers@cox.com wrote:
>>>
>>>>mls qos cos 5
>>>>mls qos cos override
>>>>
>>>>Should do the trick...
>>>>
>>>>
>>>>
>>>>-----Original Message-----
>>>>From: nobody@groupstudy.com
>>>>[mailto:nobody@groupstudy.com]On Behalf Of Tomasz
>>>>Szymanski
>>>>Sent: Tuesday, June 01, 2004 1:49 PM
>>>>To: Peng Zheng
>>>>Cc: ccielab@groupstudy.com
>>>>Subject: Re: A Question about 3550 QoS
>>>>
>>>>I tried some examples today and watched the
>>>
>>>packets
>>>
>>>>with Ethereal.
>>>>
>>>>class class-default will not match ip traffic (I
>>>>don't know why but it
>>>>didn't work)
>>>>
>>>>
>>>>Peng Zheng wrote:
>>>>
>>>>
>>>>>Requirement: on port fa 0/6, it is in Vlan 10,
>>>
>>>set
>>>
>>>>ip
>>>>
>>>>>preference of all traffic from that port to
>>>>
>>>>critical.
>>>>
>>>>>Can I use this?
>>>>>
>>>>>policy-map TEST
>>>>>class class-default
>>>>>set ip preference critical
>>>>>
>>>>>int fa 0/6
>>>>>switch access vlan 10
>>>>>switch mode access
>>>>>service-policy input TEST
>>>>>
>>>>>Thanks for any reply.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
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>>
>>
>>
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>
>
> _______________________________________________________________________
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-- Carlos G Mendioroz <tron@huapi.ba.ar> LW7 EQI Argentina
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