Need help understanding QoS Config

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May 14th, 2009
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Hello,


I'm having trouble with the configs mean on a qos queue, here is a snapshot of our 6500 switch.


mls qos

mls qos map cos-dscp 0 10 18 24 34 46 48 56

mls qos srr-queue input bandwidth 90 10

mls qos srr-queue input threshold 1 70 100

mls qos srr-queue input threshold 2 70 100

mls qos srr-queue input dscp-map queue 1 threshold 1 46

mls qos srr-queue input dscp-map queue 2 threshold 2 48 56

mls qos srr-queue output dscp-map queue 1 threshold 2 46

mls qos srr-queue output dscp-map queue 2 threshold 1 24

mls qos srr-queue output dscp-map queue 2 threshold 2 56

mls qos srr-queue output dscp-map queue 2 threshold 3 48

mls qos srr-queue output dscp-map queue 3 threshold 1 34 36 38

mls qos srr-queue output dscp-map queue 3 threshold 2 26 28 30

mls qos srr-queue output dscp-map queue 3 threshold 3 32

mls qos srr-queue output dscp-map queue 4 threshold 1 8 9 11 13 15 16 17 19

mls qos srr-queue output dscp-map queue 4 threshold 1 20 21 22 23 25 27 29 31

mls qos srr-queue output dscp-map queue 4 threshold 1 40 41 42 43 44 45 47

mls qos srr-queue output dscp-map queue 4 threshold 2 10 12 14

mls qos srr-queue output dscp-map queue 4 threshold 3 0

mls qos queue-set output 1 threshold 1 75 200 100 400

mls qos queue-set output 1 threshold 2 75 150 100 400

mls qos queue-set output 1 threshold 3 75 150 50 400

mls qos queue-set output 1 threshold 4 50 150 50 400

mls qos queue-set output 1 buffers 15 20 25 40



Now if I'm reading this correctly the top line means we are using the CoS to determine the DSCP values. And the preceding lines are showing what threshold values the traffic is being assigned to. However what i'm not understanding is the output threshold values (the last 5 lines in the snapshot). What exactly are these values telling me? I know this is a pretty basic question but i'm still trying to wrap my head around QoS. Thanks



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drolemc Wed, 05/20/2009 - 07:23
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These values are queue-id drop-threshold1 drop-threshold2 reserved-threshold maximum-threshold.

You guarantee availability of the buffers, set drop thresholds, and configuring the maximum memory allocation of the queue-set by using the following global configuration command.


mls qos queue-set output (qset-id) threshold (queue-id drop-threshold1 drop-threshold2 reserved-threshold maximum-threshold).


Each threshold value is a percentage of the queue's allocated memory.


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