The FDDI Station Link entity is a subentity of the FDDI Station entity.
   The FDDI Station link subentity provides the management view of LLC and
   the FDDI MAC.   FDDI allows stations to be either single MAC or dual
   MAC and therefore there can be up to two link subentities for each
   station. In most cases, a station has at least one link entity.
   Concentrators may have no link entity and are not addressable on the
   FDDI, though they may be using other communications channels.