Xerox Network Systems

Xerox Network Systems. It was a comprehensive suite of network protocols developed at the Xerox PARC research facility during the 1970s. Designed to enable distributed computing and resource sharing over Ethernet, it provided a complete alternative to the emerging Internet protocol suite. The system's layered architecture and pioneering protocols significantly influenced the development of modern computer networking.

Overview

Developed by researchers including David Boggs, Robert Metcalfe, and John Shoch, the system was integral to the vision of the office of the future. It was created alongside the invention of the Ethernet local area network technology, providing the necessary software to make the hardware useful. The suite aimed to facilitate transparent access to resources like file servers and network printers across a distributed network of Xerox Alto workstations. Its development represented one of the first complete implementations of a high-level protocol stack for a local area network, predating the widespread adoption of TCP/IP in that environment.

Architecture

The architecture followed a clear layered model, pre-dating the OSI model and influencing its development. Its core was the Internetwork Datagram Protocol, which provided connectionless, best-effort packet delivery across an internetwork, analogous to the Internet Protocol. Above this, the Sequenced Packet Protocol offered reliable, connection-oriented data streams, similar in function to the Transmission Control Protocol. The highest layers included protocols for specific applications, such as the Courier remote procedure call protocol for distributed computation and the Clearinghouse directory service for network name management. This structured separation of concerns between network, transport, and application layers became a fundamental principle for subsequent network designs, including the Department of Defense's protocol suite.

Protocols

The protocol suite was extensive and feature-rich. The Internetwork Datagram Protocol handled routing and fragmentation across interconnected networks. The Sequenced Packet Protocol managed session establishment, flow control, and reliable data transfer. For file access, the File Access Protocol enabled workstations to interact with remote storage, while the Printing Protocol standardized network printing. The Courier remote procedure call protocol defined a standard for executing procedures on remote machines, a concept later adopted in systems like Sun Microsystems's Open Network Computing RPC. The Clearinghouse protocol provided a distributed, replicated name service for mapping user-friendly names to network addresses, a precursor to services like the Domain Name System.

Implementation and deployment

Primary implementation occurred within the Xerox Alto and Xerox Star product ecosystems at research sites and within the corporation itself. The protocols were embedded into the Pilot operating system that ran on Alto workstations, enabling seamless network interaction. While commercial success was limited outside of Xerox due to proprietary nature and the rise of TCP/IP, the system saw substantial internal use for over a decade. It was demonstrated publicly in influential settings, showcasing live document collaboration and printing, which impressed visitors from companies like Apple Inc. and Microsoft. Key development and debugging tools, such as network packet analyzers, were also created specifically for this environment at Xerox PARC.

Influence and legacy

Its legacy is profound, as it served as a direct blueprint and proof-of-concept for many subsequent networking technologies. The AppleTalk protocol suite from Apple Inc. borrowed heavily from its simple, service-oriented design for local area networks. Engineers from Xerox PARC, such as those who founded 3Com, carried its design principles into the commercial Ethernet market. The Internet Engineering Task Force's development of certain TCP/IP application protocols was informed by its capabilities. Furthermore, the concept of a distributed name service in Clearinghouse directly inspired the architecture of the Domain Name System. The work demonstrated the practicality of networked personal computing, influencing the entire trajectory of the personal computer industry.

Category:Network protocols Category:Xerox Category:Computer networking