The QLLC entity represents the QLLC protocol on the Peer Server and
   its accessibility by client applications. The Peer Server supports
   a single instance of QLLC. The subordinate entities of the QLLC
   entity are the Port and the Link. Ports exists when a QLLC connection
   is established to an adjacent link station. Ports are dynamically
   created and deleted as client connections are made and broken.
   A Link must exist for each X.25 communication line. The Link defines
   the local link station to the Peer Server and contains the management
   attributes for the operation of all supported station components.
   It also contains information that permits the identification of the
   associated X.25 server component. The Link entity has the Station
   subentity that represents the remote DTE (Data Terminal Equipment
   address) of a station that operates over a particular X.25 logical
   link.