[nsp] QoS on Cat 4K Super II

[sgsubs at vdata.co.uk]

Hi,
I'm trying to implement a basic level of QoS on a Cat 4k with a Supervisor II running CatOs 7.2(2)

My understanding of the QoS implementation on these boxes is that all ports are trusted ports, the CoS mapping relates to 802.1p
field in the 802.1q header, this must be marked before entering the switch, if unmarked then the frame will be marked with the
default CoS, 0 by default.

On the ingress to the switch the frames I want to prioritise I mark as 802.1p CoS 6, the queues I have configured as follows:

set qos map 2q1t 1 1 cos 0-1
set qos map 2q1t 1 1 cos 2-3
set qos map 2q1t 1 1 cos 4-5
set qos map 2q1t 2 1 cos 6-7

So the queues look like this:

TEST-MS1> (enable) sh qos info runtime
Run time setting of QoS:
QoS is enabled
All ports have 2 transmit queues with 1 drop thresholds (2q1t).
Default CoS = 0
Queue and Threshold Mapping:
Queue Threshold CoS
----- --------- ---------------
1     1         0 1 2 3 4 5
2     1         6 7

All CoS 6 & 7 frames go into queue 2, so I expect the frames in queue 2 to go first, the threshold for each queue is hard coded at
1, then it starts to tail drop.

My question is if the queue depth is 1, as soon as you see any congestion then you will start dropping straight away from both
queues? Is there any value in configuring QoS on these switches, in tests I have not been able to see any gain. Has anyone
successfully implemented QoS on these switches?

Thanks in advance...

Regards,

Steven


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