Re: 3650 COS/DSCP to queue mapping

Hi Marc..

thanks a lot for the link.. it clarifies indeed!

btw.. I did some other tests:

*** TEST1 ***

pc1(vlan1) - sw1 - pc2(vlan2)

pc1 side
cos 3
cos overr

mls qos map dscp-cos 24 to 5

I see:

cos3 incoming on pc1 side
cos3 outgoing on pc2 side
dscp24 incoming on pc2 side
dscp24 outogoing on pc2 side

**** TEST2 ***

instead of doing a cos 3 + override I just trusted dscp and sent ping with
ToS 96 from PC1

mls qos map dscp-cos 24 to 5

I see:

dscp24 incoming on pc1 side
dscp24 incoming on pc2 side
dscp24 outogoing on pc2 side
cos instead is always 0.. that makes sense

**** TEST3 ****

I put a sw2 on pc2 side in trunk with sw1
I setup a cos3 + cos override on pc1 side and did some test

mls qos map dscp-cos 24 to 5

I see:
same results than TEST1

therefore.. what I don't see it when cos to dscp to cos it could be
actually used.. as the schema implicitily says it should be never used.

Joe.. could please add your comment? when your scenario could apply?

thanks in advance

On Tue, Sep 4, 2012 at 5:46 PM, marc edwards <renorider_at_gmail.com> wrote:

>
> http://www.cisco.com/en/US/docs/switches/lan/catalyst3750x_3560x/software/release/12.2_58_se/configuration/guide/swqos.html#wp1023954
>
>
> Chart really says it all. What I find interested and (supporting your
> view) is the fact that DSCP-to-CoS is never used....
>
>
> On Tue, Sep 4, 2012 at 9:04 AM, marc edwards <renorider_at_gmail.com> wrote:
>
>> So on those thoughts.... We need to trust dscp. trusting cos throughout
>> will bypass switch from looking at dscp markings. trusting dscp will make
>> switch look into packet to see dscp markings and use mappings to convert a
>> cos value. This should hit the dscp-cos map and reference values from
>> altered config.
>>
>> Marc
>>
>>
>> On Tue, Sep 4, 2012 at 8:55 AM, marc edwards <renorider_at_gmail.com> wrote:
>>
>>> So... looks like you are tagging frames on PC NIC? Where is vlan 1 vlan
>>> 2 config or are these PC's in same VLAN/subnet? Where is 'mls qos trust
>>> cos' on fa 0/2?
>>>
>>> Marc
>>>
>>>
>>> On Tue, Sep 4, 2012 at 8:46 AM, ccie99999 <ccie99999_at_gmail.com> wrote:
>>>
>>>> Command was like: MLS qos map dscp-cos 24 to 5
>>>>
>>>> Show mls QoS dscp-cos shows it's mapped correctly
>>>> Il giorno 04/set/2012 17:35, "marc edwards" <renorider_at_gmail.com> ha
>>>> scritto:
>>>>
>>>> > can you please provide command entered for dscp-cos map config?
>>>> >
>>>> > On Tue, Sep 4, 2012 at 8:31 AM, ccie99999 <ccie99999_at_gmail.com>
>>>> wrote:
>>>> >
>>>> >> I did cos 3 + cos override on pc1 side and trust dscp on pc2 side.
>>>> >> I can't do a show mls qos maps now but I set up a dscp24 to cos5
>>>> mapping.
>>>> >>
>>>> >>
>>>> >>
>>>> >> On Tue, Sep 4, 2012 at 3:30 PM, marc edwards <renorider_at_gmail.com>
>>>> wrote:
>>>> >>
>>>> >> > Can either of you do a sh mls qos maps? Also, please show access
>>>> >> > interfaces config. My hunch is that the dscp-cos map hasn't been
>>>> >> changed to
>>>> >> > refelect dscp 24 as cos 05. I am also curious to see if you have
>>>> trusted
>>>> >> > cos or dscp on access. That will change things.
>>>> >> >
>>>> >> > Regards,
>>>> >> >
>>>> >> > Marc
>>>> >> >
>>>> >> >
>>>> >> > On Tue, Sep 4, 2012 at 8:23 AM, ccie99999 <ccie99999_at_gmail.com>
>>>> wrote:
>>>> >> >
>>>> >> >> I've labbed this (cos3->dscp24->cos5) and I see I receive cos3 on
>>>> the
>>>> >> >> second pc as well as dscp24.
>>>> >> >>
>>>> >> >> pc1(vlan1) - sw - pc2(vlan2)
>>>> >> >>
>>>> >> >> (I do trust cos on pc2 interface side).
>>>> >> >>
>>>> >> >> I guess it's fine I see dscp24.. don't understand why I see cos3.
>>>> >> >>
>>>> >> >> thanks
>>>> >> >>
>>>> >> >>
>>>> >> >> On Tue, Sep 4, 2012 at 12:33 PM, gp <gs4me2me_at_gmail.com> wrote:
>>>> >> >>
>>>> >> >> > Hi Joe,
>>>> >> >> >
>>>> >> >> > I tried lab what you wrote, and not have result that I
>>>> expected. So I
>>>> >> >> have
>>>> >> >> > one question; in your opinion what cos value will have frame
>>>> when
>>>> >> leave
>>>> >> >> > switch: cos 3 or cos 5?
>>>> >> >> >
>>>> >> >> > I had cos 3, that confuse me.
>>>> >> >> >
>>>> >> >> > Thanks
>>>> >> >> >
>>>> >> >> >
>>>> >> >> > -----Original Message-----
>>>> >> >> > From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On
>>>> >> Behalf Of
>>>> >> >> > Joe
>>>> >> >> > Astorino
>>>> >> >> > Sent: Thursday, August 30, 2012 6:34 PM
>>>> >> >> > To: Anthony Sequeira
>>>> >> >> > Cc: Matt Eason; Cisco certification
>>>> >> >> > Subject: Re: 3650 COS/DSCP to queue mapping
>>>> >> >> >
>>>> >> >> > Hi Matt,
>>>> >> >> >
>>>> >> >> > Anthony answered your question simply and correctly, but I just
>>>> >> wanted
>>>> >> >> to
>>>> >> >> > add some things that helped me understand this. Like Anthony
>>>> said,
>>>> >> >> > whatever
>>>> >> >> > you trust is basically how the switch determines the queue at a
>>>> high
>>>> >> >> level,
>>>> >> >> > but at a deeper level there are a few different mappings going
>>>> on.
>>>> >> >> Let's
>>>> >> >> > assume you trust CoS. You would have:
>>>> >> >> >
>>>> >> >> > - CoS to DSCP mapping INTERNAL to the switch
>>>> >> >> > - DSCP to CoS mapping INTERNAL to the switch
>>>> >> >> > - CoS to output queue mapping
>>>> >> >> >
>>>> >> >> > The point I am making is that even though a frame comes in with
>>>> a
>>>> >> >> > particular
>>>> >> >> > CoS value, that value COULD change internally based on the
>>>> internal
>>>> >> >> > COS-DSCP
>>>> >> >> > and DSCP-COS, and the frame COULD be queued based on the value
>>>> >> derived
>>>> >> >> from
>>>> >> >> > the internal mappings and not on the original value. Let's
>>>> look at
>>>> >> some
>>>> >> >> > example output for a second
>>>> >> >> >
>>>> >> >> > Here are some mapping tables for cos-dscp, dscp-cos and
>>>> cos-output-q
>>>> >> on
>>>> >> >> a
>>>> >> >> > 3750 switch. Note these are probably not default values because
>>>> this
>>>> >> is
>>>> >> >> a
>>>> >> >> > production switch.
>>>> >> >> >
>>>> >> >> > Here is the COS to DSCP mapping:
>>>> >> >> >
>>>> >> >> > switch#sh mls qos maps cos-dscp
>>>> >> >> > Cos-dscp map:
>>>> >> >> > cos: 0 1 2 3 4 5 6 7
>>>> >> >> > --------------------------------
>>>> >> >> > dscp: 0 8 16 24 32 40 48 56
>>>> >> >> >
>>>> >> >> > Here is the DSCP to CoS mapping
>>>> >> >> >
>>>> >> >> > switch#sh mls qos map dscp-cos
>>>> >> >> > Dscp-cos map:
>>>> >> >> > d1 : d2 0 1 2 3 4 5 6 7 8 9
>>>> >> >> > ---------------------------------------
>>>> >> >> > 0 : 00 00 00 00 00 00 00 00 01 01
>>>> >> >> > 1 : 01 01 01 01 01 01 02 02 02 02
>>>> >> >> > 2 : 02 02 02 02 03 03 03 03 03 03
>>>> >> >> > 3 : 03 03 04 04 04 04 04 04 04 04
>>>> >> >> > 4 : 05 05 05 05 05 05 05 05 06 06
>>>> >> >> > 5 : 06 06 06 06 06 06 07 07 07 07
>>>> >> >> > 6 : 07 07 07 07
>>>> >> >> >
>>>> >> >> > Finally, here is the CoS to output queue mapping
>>>> >> >> >
>>>> >> >> > switch#sh mls qos map cos-output-q
>>>> >> >> > Cos-outputq-threshold map:
>>>> >> >> > cos: 0 1 2 3 4 5 6 7
>>>> >> >> > ------------------------------------
>>>> >> >> > queue-threshold: 2-1 2-1 3-1 3-1 4-1 1-1 4-1 4-1
>>>> >> >> >
>>>> >> >> >
>>>> >> >> > Let's just look at CoS 3 for example. We see that CoS 3 is
>>>> mapped to
>>>> >> >> DSCP
>>>> >> >> > 24. In turn DSCP 24 is mapped right back to CoS 3 in the DSCP
>>>> to COS
>>>> >> >> > mapping. In turn, CoS 3 is put into output queue 3, threshold
>>>> 1.
>>>> >> >> > Fine. So in this case, it comes in as CoS 3 and is queued
>>>> based on
>>>> >> CoS
>>>> >> >> 3
>>>> >> >> > because we trust CoS and because the DSCP-COS mapping is sort of
>>>> >> >> "synced".
>>>> >> >> > But...what if you went in and mucked with the DSCP-COS mapping
>>>> >> >> internally
>>>> >> >> > such that DSCP 24 was no longer mapped back to CoS 3? What if
>>>> it was
>>>> >> >> > re-mapped to CoS 5 ?
>>>> >> >> >
>>>> >> >> > So you COULD have the frame come in as CoS 3 ...internally we
>>>> go CoS
>>>> >> 3
>>>> >> >> > --> DSCP 24, then DSCP 24 to CoS 5 then queued based on CoS 5
>>>> >> >> >
>>>> >> >> > These are intricate details, but when you are studying for the
>>>> lab, I
>>>> >> >> think
>>>> >> >> > it is important to get to the dirty details! Best of luck and
>>>> I hope
>>>> >> >> this
>>>> >> >> > helps you out.
>>>> >> >> >
>>>> >> >> >
>>>> >> >> >
>>>> >> >> > On Thu, Aug 30, 2012 at 10:45 AM, Anthony Sequeira
>>>> >> >> > <terry.francona_at_gmail.com> wrote:
>>>> >> >> > > Hi Matt!
>>>> >> >> > >
>>>> >> >> > > What an AWESOME question. While the documentation does not
>>>> make it
>>>> >> >> > > clear, the value that you trust on ingress, in your example,
>>>> CoS,
>>>> >> is
>>>> >> >> > > the marking that is used in the appropriate default queue
>>>> mapping
>>>> >> >> > > table on the egress port.
>>>> >> >> > >
>>>> >> >> > > Anthony Sequeira, CCIE, CCSI, VCP
>>>> >> >> > > http://www.stormwind.com
>>>> >> >> > > Twitter: @compsolv
>>>> >> >> > > Facebook: http://www.facebook.com/compsolv
>>>> >> >> > >
>>>> >> >> > >
>>>> >> >> > >
>>>> >> >> > > On 8/29/12 9:11 PM, "Matt Eason" <matt.d.eason_at_gmail.com>
>>>> wrote:
>>>> >> >> > >
>>>> >> >> > >>Hi Guys,
>>>> >> >> > >>
>>>> >> >> > >>
>>>> >> >> > >>
>>>> >> >> > >>Can you help clarify the following. If I have a switchport
>>>> >> configured
>>>> >> >> > >>on a
>>>> >> >> > >>3560 to trust CoS inbound, that cos value is then mapped to an
>>>> >> >> > >>internal DSCP value via the COS>DSCP map. That s fine.
>>>> >> >> > >>
>>>> >> >> > >>
>>>> >> >> > >>
>>>> >> >> > >>Does this switch then determine the output queue from the
>>>> original
>>>> >> CoS
>>>> >> >> > >>value or the internal DSCP value which was assigned by the
>>>> switch?
>>>> >> I
>>>> >> >> > >>see both a DSCP>Output queue map and a COS>Output queue map
>>>> >> exists.
>>>> >> >> > >>
>>>> >> >> > >>
>>>> >> >> > >>
>>>> >> >> > >>Thanks,
>>>> >> >> > >>
>>>> >> >> > >>
>>>> >> >> > >>
>>>> >> >> > >>Matt
>>>> >> >> > >>
>>>> >> >> > >>
>>>> >> >> > >>Blogs and organic groups at http://www.ccie.net
>>>> >> >> > >>
>>>> >> >> >
>>>> >>
>>>> >>______________________________________________________________________
>>>> >> >> > >>_ Subscription information may be found at:
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>>>> >> >> > >
>>>> >> >> > >
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>>>> >> >> > >
>>>> >>
>>>> ______________________________________________________________________
>>>> >> >> > > _ Subscription information may be found at:
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>>>> >> >> > >
>>>> >> >> > >
>>>> >> >> > >
>>>> >> >> > >
>>>> >> >> > >
>>>> >> >> > >
>>>> >> >> > >
>>>> >> >> >
>>>> >> >> >
>>>> >> >> >
>>>> >> >> > --
>>>> >> >> > Regards,
>>>> >> >> >
>>>> >> >> > Joe Astorino
>>>> >> >> > CCIE #24347
>>>> >> >> > http://astorinonetworks.com
>>>> >> >> >
>>>> >> >> > "He not busy being born is busy dying" - Dylan
>>>> >> >> >
>>>> >> >> >
>>>> >> >> > Blogs and organic groups at http://www.ccie.net
>>>> >> >> >
>>>> >> >> >
>>>> >>
>>>> _______________________________________________________________________
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>>>> >> >> >
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>>>> >>
>>>> _______________________________________________________________________
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>>>> >> >>
>>>> >> >>
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>>>> >> >>
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>>>> >>
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>>>> >>
>>>> _______________________________________________________________________
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>>>>
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Received on Wed Sep 05 2012 - 05:07:39 ART