2. For Labeled Ethernet frame ( without .1P ) , how the internal DSCP value is mapped, and how can this internal DSCP value rewrite EXP value on Egress.
Dot1q packets will use COS (Class Of Service) marking for QoS and the 7600 has internal cos-dscp maps.
Once the dscp value is obtained, it will use another map for exp-dscp maps.
You can see your current maps with the command show mls qos maps
You may need to modify the default maps as they are incorrect, for instance COS 5 is mapped to DSCP 40 where it should be DSCP 46.
You should modified your default map with this command:
mls qos map cos-dscp 0 8 16 24 32 46 48 56
mls qos map exp-dscp 0 8 16 24 32 46 48 56
mls qos map ip-prec-dscp-dscp 0 8 16 24 32 46 48 56