This attribute indicates the type of DE to CLP mapping that is
performed in the Frame Relay to ATM direction.
A value of preserve indicates that the DE field in the Q.922 core
frame copies to the CLP field of every ATM cell containing the
frame.
A value of always0 indicates that the CLP field of every ATM cell is
always set to 0.
A value of always1 indicates that the CLP field of every ATM cell is
always set to 1.