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Webcast-Catalyst9k
New Member

QoS threshold

I am trying to understand the command:

mls qos queue-set output 1 threshold

particularly why thresholds can and are set above 100%

It makes no sense to me why it is possible to set drop thresholds above 100% (ios limit is 3200%), the idea is if a queue is at 100% then packets are dropped. Why set a threshold above 100%?

1 REPLY
Cisco Employee

QoS threshold

Hello,

Particular port has some buffer allocated only to it which we can asume to be 100% on that command.

There is also common pool for all the ports. And we can use that by icreasing threshold.

So if port reserved pool is empty - but maximum threshold is not reached - port is allowed to get some buffers from common pool. Until maximum threshold is reached or common pool just become empty due to other ports getting buffers from it simultanenously. If last statement is true for particular port trying to get more buffers for it packet - packet is dropped.

Hope this helps,

Nik

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