An ATM address mask associated with the LEC ATM
address of this entry. Bits in this mask that are set
to zero indicate that corresponding bit locations in
the comparison ATM address are to be ignored for the
purposes of matching. A mask of all zeros would be
the trivial case of having all comparisons match while
a mask of all ones indicates that the two ATM
addresses must match exactly. This object is useful
due to the fact that ATM addresses are a composite
negotiated by the switch and connected device. Wild
carding the prefix of an addresses indicates a
preference of where a LEC is to join regardless of
what switch it is attached from. Wildcarding the ESI
and selector byte indicates that a LEC is to join a
certain ELAN based on what switch it is attached to.