This attribute is an extension of the Closed User Group (CUG)
facility, as follows:
This attribute, if set to a value of allowed indicates that outgoing
calls (from the DTE to the network) to the open (non-CUG) part of
the network are permitted. It also permits outgoing calls to DTEs
that have Incoming Access capabilities. If set to a value of
disallowed, then such calls cannot be made using this DNA. Such
calls will be cleared by the local DCE.
This attribute corresponds to the CCITT 'Closed User Group with
Outgoing Access' feature for DNAs in that outgoing access is
granted if this attribute is set to a value of allowed.