The usage control parameter (UPC):

A.
Protects the network and its service guarantees from sources which violate their traffic contract

B.
Sets up SVC’s usage control for an ATM switch

C.
Shapes traffic usage so that the ATM switch will not discard cells

D.
All of the above

Explanation:
UPC enforces a contract between the user and the network about the nature of the connection. This prevents any one user from causing excessive congestion that would degrade the quality of service provided to the other users. It is necessary to determine what is the worst traffic a user can inflict on the network while still abiding by UPC. The Leaky Bucket Algorithm is commonly used to implement the UPC function.