A suite of networking protocols developed by Xerox Corporation’s Palo Alto Research Center (PARC) in the early 1980s. Xerox Network Systems (XNS) is little used today, but it was important in the evolution of other networking protocols, such as IPX/SPX and TCP/IP.
XNS is based on a five-layer model, in contrast to the seven-layer Open Systems Interconnection (OSI) reference model for networking. The layers of the XNS protocol stack are as follows:
XNS has no level that maps to the OSI session layer.