From: Pavel Bykov (slidersv@gmail.com)
Date: Tue Mar 24 2009 - 22:51:12 ART
Your undesrtanding of least-drop is correct. 3560 supports 2Q3T or 1P1Q3T
ingress queuing.
But your configuration is not complete.
By default, thresholds 1,2 and 3 are assigned 100% buffers.
So to differentiate between them, say so th1 is dropped first, then if there
is a lot more traffic still, th2 will be dropped first, and only then th3
will be dropped. (meaning, not dropped at all, unless there is too much
traffic in assigned th3 as well - DSCP 40 and 46 in your case)
This means, use a command something like
mls qos srr-queue input threshold 2 60 80 100
This will assign:
Q2T1 = can use up to 60% of buffers
Q2T2 = can use up to 80% of buffers
Q2T3 = can use up to 100% of buffers (default, you don't have to type 100).
Actually, i'm not sure if you will be able to type the last 100. You may
only be able to enter "mls qos srr-queue input threshold 2 60 80", sine 100
is by default, and as you write "queue-full" meaning nothing can exist in
the queue over this threshold. Maybe it's implicitly set at 100 and is non
configurable... unfortunately can't test right now because it's almost 3
am...
On Tue, Mar 24, 2009 at 4:24 PM, Hunt, Richard (LDN-GIS) <
Richard.Hunt@interpublic.com> wrote:
> Hi,
> Just been setting up QoS on 3560 and wonderd if anyone knew the answer to
> this
> question about srr-queue input dscp-map.
>
> Here's the config line:
> mls qos srr-queue input dscp-map queue 2 threshold 3 40 46
>
> Here's what I think I'm doing. I think that this will map DSCP 40 & 46 to
> input queue number 2 in the last of the 3 thresholds for weighted tail
> drop?
> Now as I understand it, threshold 1 & 2 are configurable and I am
> comfortable
> with that, which is nice. Threshold 3 however is documented in some places
> as
> the "queue-full" threshold. This is a little cryptic to me, I am hoping
> it's
> the queue least likely to suffer drops as it's my priority traffic.
>
> I notice that DSCP 46 and 40 amongst others are in this queue and threshold
> by
> default (I'm just running over it manually so that I can put others in if
> needed) as seen here in an out of the box config
>
> Switch#sh mls qos maps dscp-input-q
> Dscp-inputq-threshold map:
> d1 :d2 0 1 2 3 4 5 6 7 8 9
> ------------------------------------------------------------
> 0 : 01-01 01-01 01-01 01-01 01-01 01-01 01-01 01-01 01-01 01-01
> 1 : 01-01 01-01 01-01 01-01 01-01 01-01 01-01 01-01 01-01 01-01
> 2 : 01-01 01-01 01-01 01-01 01-01 01-01 01-01 01-01 01-01 01-01
> 3 : 01-01 01-01 01-01 01-01 02-02 01-01 01-01 01-01 01-01 01-01
> 4 : 02-03 02-01 02-01 02-01 02-01 02-01 02-03 02-01 01-01 01-01
> 5 : 01-01 01-01 01-01 01-01 01-01 01-01 01-01 01-01 01-01 01-01
> 6 : 01-01 01-01 01-01 01-01
>
> Other DSCP values look after themselves as above.
> The question is about threshold 3 of the input queues and how it works as
> opposed to threshold 1 & 2
>
> Thanks in advance
> Richard.
>
>
>
>
>
>
>
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