How can I tell the type of traffic dropped in a interface

In a normal day operation in a NOC, tipical problem is a port dropping packets.

How can you tell which type of traffic is dropping without sniffing the traffic?

Well, there is a way to how if it is a stp packet, broadcast packet: 

Use the command:

sh platform port-asic stats drop asic 2

 Supervisor TxQueue Drop Statistics
   Queue  0: 0 -> rpc
   Queue  1: 0 -> STP
   Queue  2: 0 -> ipc
   Queue  3: 931 -> Routing protocol
   Queue  4: 0
   Queue  5: 0
   Queue  6: 0
   Queue  7: 0
   Queue  8: 0 -> Broadcast
   Queue  9: 0
   Queue  10: 0  -> igmp snooping