Network Control Program

Network Control Program
Name	Network Control Program
Developer	Bolt, Beranek and Newman, University of California, Los Angeles, Stanford Research Institute
Introduced	0 1970
Purpose	Host-to-host protocol for the ARPANET
Based on	Interface Message Processor concept
Replaced by	TCP/IP

Network Control Program. It was the foundational host-to-host protocol suite that enabled resource sharing and communication across the early ARPANET. Developed in the late 1960s and early 1970s, it provided the essential software layer that allowed disparate host computers to connect to the network's packet-switched backbone. Its implementation was a critical step in realizing the vision of a robust, distributed computer network, paving the way for modern internetworking.

Overview

The Network Control Program served as the primary communications protocol stack for hosts on the ARPANET, functioning as an intermediary between the user applications and the network hardware. It was responsible for establishing connections, managing data flow, and handling errors between different host machines, such as those at the University of Utah and the Massachusetts Institute of Technology. This software suite abstracted the complexities of the underlying Interface Message Processor subnet, allowing researchers at institutions like Carnegie Mellon University to focus on developing applications. Its design embodied the end-to-end principle that would become central to later network architectures.

Development and history

The development was spearheaded by the Network Working Group, an informal collective of researchers from key ARPANET sites. Early specifications and concepts were outlined in documents like RFC 1, authored by Steve Crocker of the University of California, Los Angeles. Significant contributions came from teams at Bolt, Beranek and Newman, which built the Interface Message Processor, and the Stanford Research Institute under the direction of Douglas Engelbart. The protocol's first official specification was published in 1970, with subsequent refinements documented in a series of Request for Comments memos that guided its evolution through the early years of the ARPANET.

Technical design and operation

The technical architecture was built around a connection-oriented model, establishing virtual circuits between host processes before data exchange. It operated above the Host-to-IMP Protocol, which managed communication with the local Interface Message Processor. Key components included mechanisms for flow control, sequence number management, and retransmission to ensure reliable data delivery across the network. The software was typically implemented as a complex, interrupt-driven subsystem within a host's operating system, such as the TOPS-10 on DEC PDP-10 computers. This design required close integration with a host's input/output and process scheduling facilities.

Role in the ARPANET

It was indispensable for the operation of early network services and experiments, enabling foundational applications like Telnet for remote login and the File Transfer Protocol for data sharing. Research projects at the University of Illinois Urbana-Champaign and the Xerox Palo Alto Research Center relied on its consistent interface to develop collaborative tools. The protocol facilitated the first large-scale demonstration of the ARPANET at the International Conference on Computer Communication in 1972, showcasing applications like Air Traffic Control simulations. Its stability allowed the network to expand from the original four nodes to dozens across the United States and internationally to locations like University College London.

Transition to TCP/IP

The limitations in supporting interconnected networks, or internetworking, became apparent during experiments linking the ARPANET with packet radio and SATNET systems. This challenge motivated Vint Cerf and Bob Kahn to develop a more flexible, internetworking protocol suite, leading to the creation of the Transmission Control Protocol and Internet Protocol. A pivotal demonstration during the 1977 National Computer Conference proved TCP/IP's superiority for cross-network communication. A mandated transition plan for the ARPANET was set on January 1, 1983, known as Flag Day (computing), after which it was permanently supplanted by the TCP/IP protocol suite.

Legacy and influence

Its legacy is profound, as it established crucial paradigms for reliable data communication in wide-area networks. The experience gained from its development and deployment directly informed the design of TCP/IP, particularly in concepts of host-to-host reliability and connection management. Key figures involved in its creation, such as Jon Postel and Vint Cerf, played leading roles in the Internet Engineering Task Force and the stewardship of the Internet Assigned Numbers Authority. The protocol's history is preserved in the early Request for Comments archive, providing a vital record of the ARPANET's experimental culture and the foundational principles of the modern Internet.

Category:ARPANET Category:Network protocols Category:History of the Internet