Re: MLS QOS

All the red marked text (for the list sake, the between asterisk in the
DSCP paragraph) applies to non IP packets. Sure, non IP packets do not
have DSCP to be looked at. But that's the exception, not the rule.

-Carlos

marc edwards @ 26/05/2012 13:55 -0300 dixit:
> This is a good reference diagram for the process:
>
> Step 3
>
>
>
> *mls qos trust* [*cos* |*dscp* | *ip-precedence*]
>
>
>
> Configure the port trust state.
>
> By default, the port is not trusted. If no keyword is specified, the
> default is*dscp*.
>
> The keywords have these meanings:
>
> *cos*Classifies an ingress packet by using the packet CoS value. For
> an untagged packet, the port default CoS value is used. The default port
> CoS value is 0.
>
> *dscp*Classifies an ingress packet by using the packet DSCP value. For
> a non-IP packet, the packet CoS value is used if the packet is tagged;
> for an untagged packet, the default port CoS is used. Internally, *the
> switch maps the CoS value to a DSCP value by using the CoS-to-DSCP map*.
>
> *ip-precedence*Classifies an ingress packet by using the packet
> IP-precedence value. For a non-IP packet, the packet CoS value is used
> if the packet is tagged; for an untagged packet, the default port CoS is
> used. Internally, the switch maps the CoS value to a DSCP value by using
> the CoS-to-DSCP map.
>
>
> On Sat, May 26, 2012 at 9:22 AM, Carlos G Mendioroz <tron_at_huapi.ba.ar
> <mailto:tron_at_huapi.ba.ar>> wrote:
>
> Marc,
> switch don't do "correlation" in any of the meanings of that word I
> know. If you trust COS, then the incoming COS value is used to
> derive the internal DSCP. If you trust DSCOm then incoming DSCP
> value is used instead.
>
> Is it hard for me to offer "evidence" of that in written form. What
> you need to see it is to generate frames with different markings and
> see what happen.
> Medianet QoS docs may help showing it:
>
> http://www.cisco.com/en/US/__docs/solutions/Enterprise/WAN___and_MAN/QoS_SRND_40/QoSCampus___40.html#wp1098549
> <http://www.cisco.com/en/US/docs/solutions/Enterprise/WAN_and_MAN/QoS_SRND_40/QoSCampus_40.html#wp1098549>
>
> -Carlos
>
>
> marc edwards @ 26/05/2012 12:36 -0300 dixit:
>
> /This is the whole point of the previous question! If you use "trust
> DSCP" then the switch will indeed use DSCP and not COS./
> /
>
> /
> Carlos, if trusting DSCP, the switch will use it's mappings to
> correlate
> the packet's DSCP value to the frame's COS value. Switches deal with
> frames, hense the use of COS. Please show me evidence that supports
> otherwise.
>
> Marc
>
> On Sat, May 26, 2012 at 8:25 AM, Carlos G Mendioroz
> <tron_at_huapi.ba.ar <mailto:tron_at_huapi.ba.ar>
> <mailto:tron_at_huapi.ba.ar <mailto:tron_at_huapi.ba.ar>>> wrote:
>
> marc edwards @ 26/05/2012 11:55 -0300 dixit:
>
> 1) doesn't matter because the switch will use it's
> mappings to
> take dscp
> value and convert to associated cos more importantly the
> mappings have
> to be adjusted. either command is good but I would also
> add a
> 'switchpot
> voice vlan XX' putting the phone into another network
> and 'mls
> qos trust
> device cisco-phone'. These commands will put cisco
> phones on another
> vlan and use macros to ensure .1p is set up properly.
>
>
> It does matter.
> It is how you tell the switch to decide which marking is for
> good,
> and ignore the other. cos-to-dscp is only used if you decide to
> trust COS, otherwise the DSCP goes straight into internal DSCP.
> dscp-to-cos is used on output to create the L2 marking if
> needed.
>
> But you also can use trust extend, which instructs the phone
> (switch) to remark PC's packets (or should I say frames) with a
> given COS. That is the remarking that I was referring to.
>
>
> 2) The Cisco phones will most likely mark both but
> switch will
> only use
> CoS. The DSCP values are adjusted based on the internal
> switch
> mappings.
> This mapping is not ideal left to default values and is
> typically fixed
> manually. I don't know why cisco just didn't make it
> default.
> ... This
> command : 'mls qos map cos-dscp 0 8 16 24 32 46 48 56'
> is used
> in global
> config to map EF (IP precedence 5) to the dscp value 46.
>
>
> What do you mean by "switch will only use COS" ?? This is
> the whole
> point of the previous question! If you use "trust DSCP" then the
> switch will indeed use DSCP and not COS.
>
> The mapping is older than DSCP, at least older than any DSCP
> usage
> standarization, I would guess.
>
> -Carlos
>
>
> You are taking the right steps for Catalyst QoS good luck!
>
> HTH
>
> Marc
>
> On Sat, May 26, 2012 at 5:04 AM, Carlos Mendioroz
> <tron_at_huapi.ba.ar <mailto:tron_at_huapi.ba.ar>
> <mailto:tron_at_huapi.ba.ar <mailto:tron_at_huapi.ba.ar>>
> <mailto:tron_at_huapi.ba.ar <mailto:tron_at_huapi.ba.ar>
> <mailto:tron_at_huapi.ba.ar <mailto:tron_at_huapi.ba.ar>>>> wrote:
>
> COS fpr sure.
> Phones mark COS & DSCP but only remark COS, so if
> you want
> tp extend the
> trust border, you have tp trust COS.
> -Carlos
>
> --
> Carlos Mendioroz <tron_at_acm.org <mailto:tron_at_acm.org>
> <mailto:tron_at_acm.org <mailto:tron_at_acm.org>>
> <mailto:tron_at_acm.org <mailto:tron_at_acm.org> <mailto:tron_at_acm.org
> <mailto:tron_at_acm.org>>>>
>
>
>
> -----Original message-----
> From: Vincent Tay <vtay.75_at_gmail.com
> <mailto:vtay.75_at_gmail.com>
> <mailto:vtay.75_at_gmail.com <mailto:vtay.75_at_gmail.com>>
> <mailto:vtay.75_at_gmail.com <mailto:vtay.75_at_gmail.com>
> <mailto:vtay.75_at_gmail.com <mailto:vtay.75_at_gmail.com>>>>
> To: "Ccielab_at_groupstudy.com
> <mailto:Ccielab_at_groupstudy.com> <mailto:Ccielab_at_groupstudy.com
> <mailto:Ccielab_at_groupstudy.com>__>
> <mailto:Ccielab_at_groupstudy.com <mailto:Ccielab_at_groupstudy.com>
> <mailto:Ccielab_at_groupstudy.com
> <mailto:Ccielab_at_groupstudy.com>__>__>"
> <ccielab_at_groupstudy.com <mailto:ccielab_at_groupstudy.com>
> <mailto:ccielab_at_groupstudy.com <mailto:ccielab_at_groupstudy.com>__>
> <mailto:ccielab_at_groupstudy.com <mailto:ccielab_at_groupstudy.com>
> <mailto:ccielab_at_groupstudy.com
> <mailto:ccielab_at_groupstudy.com>__>__>>
> Sent: Sat, 26 May 2012, 05:36:38 GMT+00:00
> Subject: MLS QOS
>
> Hi all,
>
> I got the below questions to clarify.
>
> 1) When a cisco VoIP phone is connected to a switchport,
> which is
> better?
> mls qos trust dscp or mls qos trust cos?
>
> 2) The cisco phone will mark cos or dscp value or
> both? If
> mls qos trust
> cos is use, must i map the cos 5 to dscp 46 manually?
>
> Regards
> Vincent Tay
>
>
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>
> --
> Carlos G Mendioroz <tron_at_huapi.ba.ar
> <mailto:tron_at_huapi.ba.ar> <mailto:tron_at_huapi.ba.ar
> <mailto:tron_at_huapi.ba.ar>>> LW7
> EQI Argentina
>
>
>
> --
> Carlos G Mendioroz <tron_at_huapi.ba.ar <mailto: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