Basic QOS question

[ernest.johnson]

Can someone expland to me what will these lines do for the qos on my switch.I am not a QOS person and I woul like to know.

Thanks

mls qos srr-queue output cos-map queue 4 threshold 3  0 1

mls qos srr-queue output dscp-map queue 4 threshold 3 0 10

[John Blakley]

These lines map cos values 0 1 to threshold 3 and dscp values 0 and 10 to threshold 3 of queue 4. Threshold 3 is 100% full drop when the outbound queues get full. There are 3 thresholds and they use weighted tail drop. Thresholds 1 and 2 are configurable, but threshold 3 is not. From the looks of it, it seems that whoever did the mapping decided that cos 0 1 and dscp 0 10 didn't need to be dropped until the 100% threshold was met. It's hard to tell without seeing the rest of the config, but I believe generally you'd want your higher cos and dscp values in threshold 3.

HTH,

John