CUG (Closed User Group) information.
The structure of the CUG information consists zero or
more groups (number of groups can be derived from the
OCTET STRING data type of this MIB attribute) of COI
structure information. Each COI structure consists of
a COI group number (4-byte integer) and a COI list.
Each COI list consists of a length field (4-byte integer)
which specifies the number of bytes of COI bit-encoded
information belonging to this group and the COI information
structure. COI information structure is a bit mask field
where each bit from left to right represents whether this
X.121 address belongs to a particular COI number within this
COI group number.
wfFrSwLocalX121AddrCUG defaults to zero COI groups which
means no CUG related information and hence this local
wfFrSwLocalX121Address is allowed to communicate with
all users.