A.Incorrect VPI and VCI configuration
B.Noise， gain hits， or other transmission problems on the data link equipment
C.ATM cells are dropped due to incorrect ATM routing in the service provider.
D.A faulty or failing ATM interface.
E.Cells are dropped due to traffic policing in the ATM cloud on one or more virtual circuits attached to theATM interface

A.CBWFQ
B.CB-WRED
C.LLQ
D.Custom Queueing
E.WRR Queueing