Xerox Network System
(XNS) A proprietary network architecture developed by the Xerox Office Systems Division of Xerox corporation at Xerox PARC in the late 1970s/early 1980s to run on LAN (Ethernet) and WAN networks. The XNS protocol stack provided routing and packet delivery.
XNS has strong parellels to TCP/IP in that the network layer, IDP, is roughly equivalent to IP. RIP has the same functions (and obviously name) as the routing information protocol, RIP. SPP, a connectionless transport layer protocol, is similar to UDP. PEP is also in the transport layer but is connection-oriented and similar to TCP.
XNS denotes not only the protocol stack, but also an architecture of standard programming interfaces, conventions, and service functions for authentication, directory, filing, e-mail, and remote procedure call. XNS is also the name of Xerox's implementation.
Many PC networking companies, such as 3Com, Banyan, Novell, and Ungermann-Bass Networks used or use a variation of XNS as their primary transport protocol. XNS was desigined to be used across a variety of communication media, processors, and office applications. UB, (now a part of Tandem Computers) adopted XNS in developing its Net/One XNS routing protocol.