Certain other namespaces and associated protocol families are supported but not documented yet because they are not often used. PF_NS refers to the Xerox Network Software protocols. PF_ISO stands for Open Systems Interconnect. PF_CCITT refers to protocols from CCITT. `socket.h' defines these symbols and others naming protocols not actually implemented.
PF_IMPLINK is used for communicating between hosts and Internet Message Processors. For information on this, and on PF_ROUTE , an occasionally-used local area routing protocol, see the GNU Hurd Manual (to appear in the future).