Re: 3650 COS/DSCP to queue mapping

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:
>>> >> >> > >>http://www.groupstudy.com/list/CCIELab.html
>>> >> >> > >
>>> >> >> > >
>>> >> >> > > Blogs and organic groups at http://www.ccie.net
>>> >> >> > >
>>> >> >> > >
>>> >> ______________________________________________________________________
>>> >> >> > > _ Subscription information may be found at:
>>> >> >> > > http://www.groupstudy.com/list/CCIELab.html
>>> >> >> > >
>>> >> >> > >
>>> >> >> > >
>>> >> >> > >
>>> >> >> > >
>>> >> >> > >
>>> >> >> > >
>>> >> >> >
>>> >> >> >
>>> >> >> >
>>> >> >> > --
>>> >> >> > 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
>>> >> >> >
>>> >> >> >
>>> >>
>>> _______________________________________________________________________
>>> >> >> > Subscription information may be found at:
>>> >> >> > http://www.groupstudy.com/list/CCIELab.html
>>> >> >> >
>>> >> >> >
>>> >> >> > Blogs and organic groups at http://www.ccie.net
>>> >> >> >
>>> >> >> >
>>> >>
>>> _______________________________________________________________________
>>> >> >> > Subscription information may be found at:
>>> >> >> > http://www.groupstudy.com/list/CCIELab.html
>>> >> >>
>>> >> >>
>>> >> >> Blogs and organic groups at http://www.ccie.net
>>> >> >>
>>> >> >>
>>> _______________________________________________________________________
>>> >> >> Subscription information may be found at:
>>> >> >> http://www.groupstudy.com/list/CCIELab.html
>>> >>
>>> >>
>>> >> Blogs and organic groups at http://www.ccie.net
>>> >>
>>> >>
>>> _______________________________________________________________________
>>> >> Subscription information may be found at:
>>> >> http://www.groupstudy.com/list/CCIELab.html
>>>
>>>
>>> Blogs and organic groups at http://www.ccie.net
>>>
>>> _______________________________________________________________________
>>> Subscription information may be found at:
>>> http://www.groupstudy.com/list/CCIELab.html

Blogs and organic groups at http://www.ccie.net
Received on Tue Sep 04 2012 - 10:46:35 ART