Overview#Xerox Network Systems (XNS]) is a computer networking protocol suite developed by Xerox within the Xerox Network Systems Architecture.
Xerox Network Systems provided general purpose network communications, internetwork routing and packet delivery, and higher level functions such as a reliable stream, and Remote Procedure Calls.
Xerox Network Systems predated and influenced the development of the Open Systems Interconnection (OSI) networking model, and was very influential in local area networking designs during the 1980s. Xerox Network Systems had little impact on TCP-IP, however, which was designed earlier.
Xerox Network Systems was based on the earlier (and equally influential) PARC Universal Packet (PUP) suite from the late 1970s. Some of the protocols in the Xerox Network Systems suite were lightly modified versions of the ones in the PUP suite. Xerox Network Systems added the concept of a network number, allowing larger networks to be constructed from multiple smaller ones, with routers controlling the flow of information between the networks.
The protocol suite specifications for Xerox Network Systems were placed in the Public Domain in 1977. This helped Xerox Network Systems become the canonical Local Area Networking protocol, copied to various degrees by practically all networking systems in use into the 1990s. Xerox Network Systems was used unchanged by 3Com's 3+Share and Ungermann-Bass's Net/One. Xerox Network Systems was also used, with modifications, as the basis for Novell INC NetWare, and Banyan VINES. Xerox Network Systems was used as the basis for the AppleNet system, but this never commercialized; a number of Xerox Network Systems's solutions to common problems were used in AppleNet's replacement, AppleTalk.