Re: Help - Catalyst 3560/3750 QoS

Emir,

1- Where did you get this from? it simply marks down some traffic to CS1.
This could happen due to many reasons including in case of excess traffic.

2- There is no absolute optimal logic in this topic. It all depends on what
you are going to use it for and how?

There are different best practices to implement QoS in converged networks
out there. If you'd like to see a nice example my recommendation would be
the AutoQoS feature of IOS. Apply it and see how it sets various parameters;
they're usually pretty good but again, "optimum" is what you have to figure
out and not necessarily what you see in best practices.

* You can find some good examples in "End to end qos network design" By Tim
Szigeti and the last chapters of QoS for IP telephony by Odom.

HTH

Kambiz Agahian

CCIE Instructor/Consultant
M.Eng Telecom, CCIE# 25341, CCSI# 33326, MCSE, MCSA

On Mon, Aug 23, 2010 at 3:38 PM, emir d souza <emir979_at_gmail.com> wrote:

> Hi experts!!
>
> I'm having a tough time understanding the logic behind some of the QOS
> configs for the 2970/3560/3750.
>
> 1. Why on earth would we want DSCP 0 to be remarked (upwards) to CS1
> (Scavenger) as I thought that the whole idea behind remarking to mark
> traffic downwards?
>
> <mls qos map policed-dscp 0 24 to 8>
>
>
> 2. Are the ingress policing values below optimal? (got them from SRND) and
> why is the burst set to 8000 for all policed values?
>
>
> I'm would rather do egress policing on the uplink going to the SP switch
> rather than having to think about correct individual ingress values for
> each
> port and then calculate the aggregrated bw towards the uplinks, but these
> switches don't support egress policing.
>
> Is there a better way?
>
> CAT2970(config) #mls qos map cos-dscp 0 8 16 24 32 46 48 56
> ! Modifies CoS-to-DSCP mapping to map CoS 5 to DSCP EF
> CAT2970(config) #mls qos map policed-dscp 0 24 to 8
> ! Excess VVLAN & DVLAN traffic will be remarked to Scavenger (CS1)
> CAT2970(config) #
> CAT2970(config) #
> CAT2970(config) #class-map match-all VVLAN-VOICE
> CAT2970(config-cmap) # match access-group name VVLAN-VOICE
> CAT2970(config-cmap) #
> CAT2970(config-cmap) #class-map match-all VVLAN-CALL-SIGNALING
> CAT2970(config-cmap) # match access-group name VVLAN-CALL-SIGNALING
> CAT2970(config-cmap) #
> CAT2970(config-cmap) #class-map match-all VVLAN-ANY
> CAT2970(config-cmap) # match access-group name VVLAN-ANY
> CAT2970(config-cmap) #
> CAT2970(config-cmap) #
> CAT2970(config-cmap) #policy-map IPPHONE+PC-BASIC
> CAT2970(config-pmap) #class VVLAN-VOICE
> CAT2970(config-pmap-c) # set ip dscp 46 ! DSCP EF (Voice)
> CAT2970(config-pmap-c) # police 128000 8000 exceed-action drop
> ! Only one voice call is permitted per switchport VVLAN
> CAT2970(config-pmap-c) #class VVLAN-CALL-SIGNALING
> CAT2970(config-pmap-c) # set ip dscp 24 ! DSCP CS3 (Call-Signaling)
> CAT2970(config-pmap-c) # police 32000 8000 exceed-action
> policed-dscp-transmit
> ! Out-of-profile Call-Signaling is marked down to Scavenger (CS1)
> CAT2970(config-pmap-c) #class VVLAN-ANY
> CAT2970(config-pmap-c) # set ip dscp 0
> CAT2970(config-pmap-c) # police 32000 8000 exceed-action
> policed-dscp-transmit
> ! Unauthorized VVLAN traffic is marked down to Scavenger (CS1)
> CAT2970(config-pmap-c) #class class-default
> CAT2970(config-pmap-c) # set ip dscp 0
> CAT2970(config-pmap-c) # police 5000000 8000 exceed-action
> policed-dscp-transmit
> ! Out-of-profile data
>
>
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Received on Mon Aug 23 2010 - 15:54:42 ART