This attribute specifies the type of CLP to DE mapping that is
performed in the ATM to Frame Relay to direction.
When preserve is selected, 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.
When always0 is selected, the DE field of the Q.922 Core frame is
always set to 0.
When always1 is selected, the DE field of the Q.922 Core frame is
always set to 1.