Tag Archives: Packet switching

The Failure of AT&T’s Advanced Communications System (ACS)

Today, it’s hard to find any information on AT&T’s failed packet-switched network of the late 1970s and early 1980s. AT&T’s History of Network Switching page doesn’t mention it. It’s one of the most costly engineering failures of all time, so it’s understandable that today’s AT&T (which is really a renamed Southwestern Bell) wants to forget about it. It was a project that was always just 90 days away from going on-line. In 1979, hopes were high:

The Advanced Communications System (ACS) is AT&T’s new, all-encompassing data service which will compete directly with SBS and XTEN. . . AT&T expects to have 137,000 ACS business customers by 1983.1

By 1981, hopes had dimmed slightly:

Although behind schedule, AT&T’s ACS (Advanced Communications System) should begin operation soon.2

800px-Boeing_307_in_Elliott_BaySometime thereafter, AT&T’s Advanced Communications System, brainchild of its vaunted Bell Labs, with over a thousand engineers aboard, sank beneath the surface, never to be mentioned again, like a malformed stepchild. They seem to have destroyed virtually all documentation of this disaster: no schematics, no mockups, no prototypes, no photos, no nothing. Apparently when you’re a monopoly, you can waste billions of dollars, and remain in business.

What happened?

I remember reading about this great new network in the late 1970s, and since its failure to appear, wondered what happened. Recently I found a description of this catastrophe. Colin Berkshire’s post-mortem report emphasizes the importance of good system architecture; patching of subsystems will never overcome poor system design. I’m surprised that design reviews at Bell Labs didn’t nip this dud in the bud.

Finally, here’s the story

And now, for your reading pleasure, learn how AT&T wasted over a billion dollars on their idea of a packet-switched network: How the Bell System Missed the Internet, by Colin Berkshire.


  1. Computer Technology: A Forecast For the Future, by William J. Kubitz, Associate Professor, Department of Computer Science, University of Illinois, Urbana-Champaign, published in 1979, page 148
  2. Computer-based national information systems: technology and public policy, by United States Congress’ Office of Technology Assessment, published in 1981, under “The Data Communication Industry” heading.

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© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695

Learn about the Internet’s infrastructure

An FC/PC fiber-optic connector
photo: Srleffler
Author of new book, Tubes, interviewed.

The Internet knits today’s society together, yet most of us aren’t familiar with exactly what comprises “The Cloud”. Last month, NPR’s Terry Gross interviewed Andrew Blum, the author of a new book, Tubes, A Journey to the Center of the Internet. The book explores the hardware infrastructure that instantly transports data across the globe. Ms. Gross asks the questions that any layperson would ask, and the author replies with amusing stories of his adventures inside the Internet’s data centers, points of presence, repeater huts, and cross-connect centers.

I found Mr. Blum’s descriptions to be easy to understand. I’ve worked inside similar facilities and don’t think that I could describe their components so clearly.

Much of the Internet is built atop older telephone and telegraph infrastructure. (Likewise, American highways are built atop the trails that were blazed by Indians a thousand years ago.) Fiberoptic cable often shares the conduit, cable trays, and trenches where 100-year old lead-sheathed oil-impregnated paper-insulated copper cable still resides.

Click here to read the brief article and/or listen to the 25 minute interview.

Visit my website: http://russbellew.com
© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695