This attribute, if set to allowed indicates that outgoing calls (from
the DTE into the network) can be made using this particular Cug. If
set to a value of disallowed, then outgoing calls cannot be made
using this Cug - such calls will be cleared by the local DCE.
This attribute corresponds to the ITU-T 'Outgoing Calls Barred'
feature for Cugs in that outgoing calls are barred if this attribute is
set to a value of disallowed.