This attribute specifies the DE to CLP mapping that is performed in
the Frame Relay to ATM direction. This is used as the default for all
the connections on the interface.
When preserve is selected, the DE field in a Q.922 core frame
copies to the ATM CLP field of every cell containing the
information of that frame.
When always0 is selected, the CLP field of every generated ATM
cell is always 0.
When always1 is selected, the CLP field of every generated ATM
cell is always 1.