Perhaps the most glaring reason that Tymnet is dead and Internet lives on is that Tymnet was a technology to make money fast and the money spent on development was always in light of a short financial planning horizon. While available raw bandwidth was doubling every year, there was little development investment for Tymnet to exploit the resulting opportunities. Tymnet started out serving 110 b/s customers and never got much beyond 1200 b/s customers. Tymnet paid its way nearly from the beginning. I think it made a lot of money for its investors, originally Tymshare. Internet, by contrast, was highly subsidized with little attention to economy. Internet succeeded also because it was open and various organizations made money by advancing the foundational technologies. Tymnet was always proprietary; if someone else had seen a way to spend $1,000,000 on developing a new switching node, there would have been no possible business plan to do so. The polycentrism of Internet won. Tymnet developers were smart but few. We did not think in terms of multi million dollar projects. We were hard pressed to respond to all of the available business opportunities. We had neither the temperamental inclination nor the money to become big.

Internet stemmed from Arpanet which was more of a laboratory experiment than a commercial venture. As it became Internet it was unleashed, both from the AUP (Authorized Usage Policy) and the rules for interfacing new hardware and software. The technology was largely dominated by the best of the providers some of whom had much more money than Tymshare or those who operated Tymnet towards the end of the century. Internet was limited only by the money and imagination of the best of many entrants. Tymnet remained limited to a single organization.

Internet exploded mainly because there was a huge niche for it. The traditional carriers were well aware of the plummeting costs of moving bits but their plan was to reduce end-user prices by only a few percent per year. They still had many billions of dollars of equipment on their books set to be amortized over 40 years. The public utility commissions who had been largely responsible for these long amortizations were thus perhaps comfortable in preserving monopoly pricing even when their charter was principally to prevent this. Internet was an end-run around the PUC’s as the ARPA net seemed outside their grasp. Perhaps some of the real heroes were those who saw it coming and kept their mouths shut until it was too late. It is a pity about the widows and orphans with AT&T stock, but not having Internet would be a much bigger pity.

McDonnell Douglas bought Tymshare, including Tymnet in 1984. McDonnell Douglas sold Tymnet to BT in 1989. In 1994 BT and MCI together launched Concert Communications Services which was a $1 billion joint venture between the two companies. This was built on Tymnet which had not developed a great deal beyond what Tymshare had produced, except in scale. Conversations with some of those who worked on the technology during these later years leads me to think that there was not much spent on development in those times. Tymnet had become a very successful cash cow and a technological dead end.

MCI shut down their Tymnet at the end of March 2003, and BT shut down the remaining part sometime between Feb 13th and March 6th of 2004.

It would have taken vision and vigorous development to move Tymnet along the trajectory allowed by the burgeoning available bandwidth and concomitant customer demand. This article has many details about the later corporate Tymnet arrangements.

Norman Hardy. 2007

Greenstein’s epilog describes the nature of the genesis of Internet—a situation that Tymnet lacked.

Steve Crocker speaks of the origins of Internet.