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A College Job and Its Impact on the Direction of Ethernet

It is a given that Ethernet is a fundamental building block of today’s Internet. From local area networks in the 1980s to cable modems in the 1990s to today’s fiber-to-the-home and WiFi networks, Ethernet is a common thread in the evolution of broadband.1 But would there have been a thread if not for the insight of someone who had a college job installing MATV (Master Antenna Television) networks for schools in Michigan?

In a 4/13/22 IEEE Silicon Valley History webinar regarding the early history of Ethernet, Dr. Robert Metcalfe (3Com founder) credits Dr. David Liddle for suggesting the use of a Jerrold tap as a way to connect to a shared coaxial cable. In that webinar, Metcalfe characterized this non-invasive method of accessing the coaxial cable as one of three key technologies they employed as the basis for the first Ethernet.

The Impact of a Summer Job #

In the above interview, Liddle explains that his experience with coaxial cable and the Jerrold tap stemmed from his college job setting up networks for distributing television channels within schools.2 His work was part of the Midwest Program for Airborne Television Instruction (MPATI), which, in a nutshell, broadcast pre-recorded instructional videos to schools in six Midwestern states.

The intent of MPATI was “to bring the best educational programming to a large number of schools, even the most geographically isolated and economically disadvantaged.classrooms.” An illustration of this pre-satellite broadcast transmission network, which covered approximately 127,000 square miles, is provided at approximately 1:44 in the above video. This network could be considered a precursor to Cable in the Classroom as well as statewide fiber optic-based educational networks, such as Ohio SchoolNet.3

Liddle’s insight into the characteristics of coaxial cable networking sped the development of Ethernet in the 1975 to 1980 period. Liddle went on to become Vice President and General Manager, Office Systems, of the Office Products Division for the Xerox Corporation. He was part of a troika, that included Intel’s Robert Noyce and DEC’s Gordon Bell, who unveiled Ethernet at the February 10th, 1982 event at New York City’s World Trade Center (PDF).

Xerox and PARC – “The Architects of Information” #

In the above interview, Liddle explains that the vision of Xerox CEO Peter McColough was for this dominant copier company to be, “The architects of information.” This simple statement provided a great deal of freedom for Xerox’s PARC team to, paraphrasing Liddle’s colleague Alan Kay, “predict the future by inventing it.

The charter of PARC, founded by Xerox in 1970, was to create the office of the future. In addition to Ethernet, some of PARC’s notable inventions include laser printing, the graphical user interface, and natural language processing. PARC’s influence is far-reaching as its inventions are part of virtually every technology produced today.

Kay was one of the “extra special” people that made up PARC’s all-star team of scientists and engineers. The youthful age of this team reflected the nascent era of computer science in the early 1970s. Team members were involved with emerging technologies, such as ARPANET (PDF), plasma displays, and interface devices. Liddle sums up what made PARC special in this 1996 interview:

“The PARC environment fostered an important collision of ideas: interconnected peer computers controlled by individuals; spatial, gestural, and nonverbal interaction techniques; and extremely high-quality typographical text and graphics.”

Bringing Design to Software – Chapter 2: Design of the Conceptual Model

One gets a sense in talking to Liddle and his former colleagues of a work environment and camaraderie that brought out the best of an extremely talented team.4 All members contributed their expertise, whether gained in academics or, in the example given by David Liddle, from a summer job.

Interview Highlights: #

01:28 – Liddle provides an overview of his summer job designing and aligning microwave dishes as part of an early form of distance learning, MPATI.

04:05 – The coaxial cable and taps from his summer job were the inspiration for Ethernet.

06:11 – Liddle explains how he was a staff member of PARC when he suggested using coaxial cables and taps. In 1975, he moved to the System Development Division to commercialize PARC’s inventions.

07:31 – Xerox’s provided PARC freedom to research and invent. Liddle indicates that the vision of being “The architects of information,” proved quite useful in focusing their research and development.

09:18 – The PARC team was young because computer science was a relatively new academic discipline. This group was also intimately familiar with things like ARPANET and the work of Douglas Engelbart and his colleagues in creating the On-Line System (NLS)

12:45 – Some of Liddle’s pre-PARC work included research on plasma displays for Owens-Illinois. This gave him an appreciation for the importance of graphics in computing. He expresses his appreciation for the University of Toledo as that was one of the few programs with a Ph.D. program that students could attend at night.

15:30 – Liddle advises college engineering students, who are looking for a summer job, to prioritize getting a feel for their career as opposed to striving for the greatest near-term financial rewards. He has career advice for those engineers who know what they want to do (established companies) and those who don’t (start-up environments).

21:50 – The discussion shifts to the FTC’s 1975 consent decree that required Xerox to license certain patents and abandon certain marketing practices.


References #

1 The thread tying cable television (CATV) and Ethernet weaves itself through the history of both technologies. As heard in the above interview, coaxial cable and associated taps were a key building block for the first Ethernets. Later, the underlying Ethernet technology became the basis for cable modems, standards (DOCSIS), and the introduction of the first commercially successful residential broadband networks. Those last-mile connections provided the foundation for the commercial success of WiFi (or Radio Ether, as Bob Metcalfe characterized it in his 1973 internal PARC memorandum proposing Ethernet).

2 Founded in 1948 by Milton Shapp, Jerrold was the first manufacturer of equipment designed specifically for the cable television industry.

3 Purdue has additional background on its pivotal role in providing the DC-6s that served as the airborne broadcast towers.

4 This 1988 interview with David Liddle provides additional detail about PARC, his work on plasma screens, and his experience working on MPATI.

5 A report referenced in this December 21 1981 Computerworld article predicts “Ethernet will fail in 2 years…headed for the worst failure in Xerox history.” Liddle rightly suggested the report was inaccurate and incomplete.

Author Ken Pyle, Managing Editor

By Ken Pyle, Managing Editor

Ken Pyle is Marketing Director for the Broadband Forum. The mission of this 25+-year-old non-profit “is to unlock the potential for new markets and profitable revenue growth by leveraging new technologies and standards in the home, intelligent small business, and multi-user infrastructure of the broadband network.”

He is also co-founder of Viodi, LLC and Managing Editor of the Viodi View, a publication focused on the rural broadband ecosystem, autonomous vehicles, and electric aviation. He has edited and produced numerous multimedia projects for NTCA, US Telecom and Viodi. Pyle is the producer of Viodi’s Local Content Workshop, the Video Production Crash Course at NAB, as well as ViodiTV. He has been intimately involved in Viodi’s consulting projects and has created processes for clients to use for their PPV and VOD operations, as well authored reports on the independent telco market.

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