I have some 3560 switches where I have enabled the global qos command "mls qos". When I have this enabled I notice a lot of output drops on some of the slower links. What exactly does the mls qos command do to cause output drops? With it on, I see about a 50 percent decrease in speed over some of our wireless links.
I'm not running using QOS as of right now, but when I want to in the future, do I need the "mls qos" command? If I do, (and I know there is more too it than just "mls qos"), but won't that defeat the purpose of qos, if the global command is just going to slow my links down?
Sorry for digging up an old post, but we just had this same "problem" on one of our blade switches (CBS3130 to be exact).
Also, please correct me if i seem wrong.
Since the traffic is subject to the QoS SRR scheduler and its queues, wouldnt it be subject to the configured thresholds of those queues aswell?
If i recall from a QoS course, the thresholds for the queues are made at the time when there was nothing faster than T1 internet connections. Our output queue for QoS is 100packets large on each threshold/queue, we are currently pushing ~8000pps.
This output is from our problem switch with 'mls qos' enabled, but not used in class-maps or policy-maps or anything such. Just simply enabled.
#sh mls qos interface gi1/0/1 statistics
GigabitEthernet1/0/1 (All statistics are in packets)