Tymnet
A data network that began as Tymshare's way of reaching its time-sharing customers and ended up as one of the world's largest public packet networks.
Tymshare sold computer time in the 1970s, and its customers needed to reach the machines without calling long distance. LaRoy Tymes designed the network around 1971: small nodes in cities across the US that gathered terminal traffic and passed it on to the central computers. Unlike the ARPANET, routing was decided centrally, by a supervisor that worked out every connection.
The network opened up to other services and became one of the big public X.25 carriers, serving databases, banks and airlines. McDonnell Douglas bought Tymshare in 1984, and the network later passed to BT. It was also a favourite of 1980s hackers, who learned that a local dial-up number could lead almost anywhere.