Re: QOS Question

Just think:

Q: Where are you applying QoS? What are you trying to accomplish?
A: Normally, we apply QoS to differentiate between traffic aggregates, or
traffic types.

Q: Why do we need to do that at all?
A: Because there might be situations, where there is not enough space for
all

Q: What space?
A: Buffers. Interface Buffers.

That is why we are applying QoS on interface, not globally.
Globally we are defining rules. But to apply them, to make rules work, to do
what they are suppose to, we need to apply them on interface (or wherever
there are buffers: shapers, fabric asics, etc).

A hundred policy-maps will not affect a bit, unless they become
service-policies on a router interface
Same with switches: all the global rules you can imagine are worthless
unless applied on interface

As for mappings, it's a strictly hardware dependent configuration procedure.
Some platforms allow you to specify more mappings globally, some want more
defined at interface level. In your case of what looks like a 6500, there
are parameters that you can specify per car type e.g. 1p3q1t or 2q2t etc,
and then overwrite them at interface level.

On Fri, Apr 10, 2009 at 6:23 PM, Durkin, Michael (H USA) <
michael.durkin_at_siemens.com> wrote:

> Hello Group,
>
> I am trying to understand QOS, I was looking at QOS on a switch and
> found this config:
>
> interface GigabitEthernet4/9
> description XXXXXXXXXXXXXXXXXXX
> switchport
> no ip address
> wrr-queue queue-limit 40 30
> wrr-queue random-detect min-threshold 1 40 80
> wrr-queue random-detect min-threshold 2 70 80
> wrr-queue random-detect max-threshold 1 80 100
> wrr-queue random-detect max-threshold 2 80 100
> wrr-queue cos-map 2 1 4
> wrr-queue cos-map 2 2 6 7
>
> In this case, this is an access port and I am unsure of why there would
> be QOS assigned to this port with no layer three information assigned to
> this port.
>
> Basically I am trying to figure out why you would put this config on an
> interface. Am I just missing the point here?
>
> Thanks group
>
>
>
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