Internet History of 1970s


Nodes are added to the ARPANET at the rate of one per month.

Programmers Dennis Ritchie and Kenneth Thompson at Bell Labs complete the UNIX operating system on a spare DEC minicomputer. UNIX combines many of the time-sharing and file-management features offered by Multics and wins a wide following, particularly among scientists.

Bob Metcalfe builds a high-speed (100 Kbps) network interface between the MIT IMP and a PDP-6 to the ARPANET. It runs for 13 years without human intervention. Metcalfe goes on to build another ARPANET interface for Xerox PARC’s PDP-10 clone (MAXC).

DEC announces the Unibus for its PDP-11 minicomputers to allow the addition and integration of myriad computer-cards for instrumentation and communications.

In December, the Network Working Group (NWG) led by Steve Crocker finishes the initial ARPANET Host-to-Host protocol, called the Network Control Protocol (NCP).


The ARPANET begins the year with 14 nodes in operation. BBN modifies and streamlines the IMP design so it can be moved to a less cumbersome platform than the DDP-516. BBN also develops a new platform, called a Terminal Interface Processor (TIP) which is capable of supporting input from multiple hosts or terminals.

The Network Working Group completes the Telnet protocol and makes progress on the file transfer protocol (FTP) standard. At the end of the year, the ARPANET contains 19 nodes as planned.

Intel’s release of the 4004, the first ‘computer on a chip,’ ushers in the epoch of the microprocessor. The combination of memory and processor on a single chip reduces size and cost, and increases speed, continuing the evolution from vacuum tube to transistor to integrated circuit.

Many small projects are carried out across the new network, including the demonstration of an aircraft-carrier landing simulator. However, the overall traffic is far lighter than the network’s capacity. Something needs to stimulate the kind of collaborative and interactive atmosphere consistent with the original vision. Larry Roberts and Bob Kahn decide that it is time for a public demonstration of the ARPANET. They choose to hold this demonstration at the International Conference on Computer Communication (ICCC) to be held in Washington, DC, in October 1972.


The ARPANET grows by ten more nodes in the first 10 months of 1972. The year is spent finishing, testing and releasing all the network protocols, and developing network demonstrations for the ICCC.

At BBN, Ray Tomlinson writes a program to enable electronic mail to be sent over the ARPANET. It is Tomlinson who develops the ‘user@host’ convention, choosing the @ sign arbitrarily from the non-alphabetic symbols on the keyboard. Unbeknownst to him, @ is already in use as an escape character, prompt, or command indicator on many other systems. Other networks will choose other conventions, inaugurating a long period known as the e-mail ‘header wars.’ Not until the late 1980s will ‘@’ finally become a worldwide standard.

Following the lead of Intel’s 4004 chip, hand-held calculators ranging from the simple Texas Instruments four-function adding machines to the elaborate Hewlett-Packard scientific calculators immediately consign ordinary slide rules to oblivion.

Xerox PARC develops a program called Smalltalk, and Bell Labs develops a language called ‘C.’

Steve Wozniak begins his career by building one of the best-known ‘blue boxes;’ tone generators that enable long-distance dialing while bypassing the phone company’s billing equipment.

The ICCC demonstrations are a tremendous success. One of the best known demos features a conversation between ELIZA, Joseph Weizenbaum’s artificially-intelligent psychiatrist located at MIT, and PARRY, a paranoid computer developed by Kenneth Colby at Stanford. Other demos feature interactive chess games, geography quizzes, and an elaborate air traffic control simulation. An AT&T delegation visits ICCC but leaves in puzzlement.


Thirty institutions are connected to the ARPANET. The network users range from industrial installations and consulting firms like BBN, Xerox PARC and the MITRE Corporation, to government sites like NASA’s Ames Research Laboratories, the National Bureau of Standards, and Air Force research facilities.

The ICCC demonstrations prove packet-switching a viable technology, and ARPA (now DARPA, where the ‘D’ stands for ‘Defense’) looks for ways to extend its reach. Two new programs begin: Packet Radio sites are modeled on the ALOHA experiment at the University of Hawaii designed by Norm Abramson, connecting seven computers on four islands; and a satellite connection enables linking to two foreign sites in Norway and the UK.

Bob Kahn moves from BBN to DARPA to work for Larry Roberts, and his first self-assigned task is the interconnection of the ARPANET with other networks. He enlists Vint Cerf, who has been teaching at Stanford. The problem is that ARPANET, radio-based PRnet, and SATNET all have different interfaces, packet sizes, labeling, conventions and transmission rates. Linking them together is very difficult.

Kahn and Cerf set about designing a net-to-net connection protocol. Cerf leads the newly formed International Network Working Group. In September 1973, the two give their first paper on the new Transmission Control Protocol (TCP) at an INWG meeting at the University of Sussex in England.

Meanwhile, at Xerox PARC, Bob Metcalfe is working on a wire-based system modeled on ALOHA protocols for Local Area Networks (LANs). It will become Ethernet.


Ethernet is demonstrated by networking Xerox PARC’s new Alto computers.

BBN recruits Larry Roberts to direct a new venture, called Telenet, which is the first public packet-switched service. Roberts’ departure creates a crisis in the DARPA IPTO office.

DARPA has fulfilled its initial mission. Discussions about divesting DARPA of operational responsibility for the network are held. Because it is DARPA-funded, BBN has no exclusive right to the source code for the IMPs. Telenet and other new networking enterprises want BBN to release the source code. BBN argues that it is always changing the code and that it has recently undergone a complete rewrite at the hands of John McQuillan. Their approach makes Roberts’ task of finding a new director for IPTO difficult. J.C.R. Licklider agrees to return to IPTO from MIT on a temporary basis.

In addition to DARPA, The National Science Foundation (NSF) is actively supporting computing and networking at almost 120 universities. The largest NSF installation is at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. There, scientists use a home-built ‘remote job entry’ system to connect to NCAR’s CDC 7600 from major universities.

Bob Kahn and Vint Cerf publish "A Protocol for Packet Network Interconnection" in the May 1974 issue of IEEE Transactions on Communications Technology. Shortly thereafter, DARPA funds three contracts to develop and implement the Kahn-Cerf TCP protocol described in their paper, one at Stanford (Cerf and his students), one at BBN (Ray Tomlinson), and one at University College London (directed by Peter Kirstein and his students).

Daily traffic on the ARPANET exceeds 3 million packets.


The ARPANET geographical map now shows 61 nodes. Licklider arranges its administration to be turned over to the Defense Communications Agency (DCA). BBN remains the contractor responsible for network operations. BBN agrees to release the source code for IMPs and TIPs.

The Network Working Group maintains its open system of discussion via RFCs and e-mail lists. Discomfort grows with the bureaucratic style of DCA.

The Department of Energy creates its own net to support its own research. This net operates over dedicated lines connecting each site to the computer centers at the National Laboratories.

NASA begins planning its own space physics network, SPAN. These networks have connections to the ARPANET so the newly developed TCP protocol begins to get a workout. Internally, however, the new networks use such a variety of protocols that true interoperability is still an issue.


DARPA supports computer scientists at UC Berkeley who are revising a Unix system to incorporate TCP/IP protocols. Berkeley Unix also incorporates a second set of Bell Labs protocols, called UUCP, for systems to use dial-up connections.

Seymour Cray demonstrates the first vector-processor supercomputer, the CRAY-1. The first customers include Lawrence Livermore National Laboratory, Los Alamos National Laboratory, and NCAR. The CRAY-1 hardware is more compact and faster than previous supercomputers. No wire is more than 4 feet long, and the clock period is 12.5 nanoseconds (billionths of a second). The machine is cooled by freon circulated through stainless steel tubing bonded within vertical wedges of aluminum between the stacks of circuit boards (Cray patents the bonding process). The CRAY-1’s speed and power attract researchers, who want access to it over networks.

Vint Cerf moves from Stanford to DARPA to work with Bob Kahn on networking and the TCP/IP protocols.


Steve Wozniak and Steve Jobs announce the Apple II computer. Also introduced are the Tandy TRS-80 and the Commodore Pet. These three off-the-shelf machines create the consumer and small business markets for computers.

Cerf and Kahn mount a major demonstration, ‘internetting’ among the Packet Radio net, SATNET, and the ARPANET. Messages go from a van in the Bay Area across the US on ARPANET, then to University College London and back via satellite to Virginia, and back through the ARPANET to the University of Southern California’s Information Sciences Institute. This shows its applicability to international deployment.

Larry Landweber of the University of Wisconsin creates THEORYNET providing email between over 100 researchers and linking elements of the University of Wisconsin in different cities via a commercial packet service like Telenet.


The appearance of the first very small computers and their potential for communication via modem to dial up services starts a boom in a new set of niche industries, like software and modems.

Vint Cerf at DARPA continues the vision of the Internet, forming an International Cooperation Board chaired by Peter Kirstein of University College London, and an Internet Configuration Control Board, chaired by Dave Clark of MIT.

The ARPANET experiment formally is complete. This leaves an array of boards and task forces over the next few years trying to sustain the vision of a free and open Internet that can keep up with the growth of computing.


Larry Landweber at Wisconsin holds a meeting with six other universities to discuss the possibility of building a Computer Science Research Network to be called CSNET. Bob Kahn attends as an advisor from DARPA, and Kent Curtis attends from NSF’s computer research programs. The idea evolves over the summer between Landweber, Peter Denning (Purdue), Dave Farber (Delaware), and Tony Hearn (Utah).

In November, the group submits a proposal to NSF to fund a consortium of eleven universities at an estimated cost of $3 million over five years. This is viewed as too costly by the NSF.

USENET starts a series of shell scripts written by Steve Bellovin at UNC to help communicate with Duke. Newsgroups start with a name that gives an idea of its content. USENET is an early example of a client server where users dial in to a server with requests to forward certain newsgroup postings. The server then ‘serves’ the request.