This attribute indicates the type of CLP to DE mapping that is
performed in the ATM to Frame Relay direction.
A value of preserve indicates that the DE field of the Q.922 Core
frame is set when one or more ATM cells belonging to an AAL5
frame have their CLP field set.
A value of always0 indicates that the DE field of the Q.922 Core
frame is always set to 0.
A value of always1 indicates that the DE field of the Q.922 Core
frame is always set to 1.