We have just enabled "mls qos" and executed default mls qos values.
Can you please explain me in simple words ,what it does ?
COS stands for "class of service" and is l2 only. COS values are from 0 - 7 with 0 being low priority and 7 being high priority. Generally, phones will mark with cos 5 or a dscp value of 46 (EF). There is a cos-dscp mapping that happens outbound on the switch when it sends to the router for the router to see the dscp value that was converted from the internal map on the switch. Once your traffic is tagged at ingress (on switchport), the tag is carried to the output queue on the switch which leads to the router.
Here's something to read:
QoS is a very big topic...