Tymnet

Tymnet was an international data communications network headquartered in Cupertino, California that used virtual call packet switched technology and X.25, SNA/SDLC, ASCII and BSC interfaces to connect host computers (servers) at thousands of large companies, educational institutions, and government agencies. Users typically connected via dial-up connections or dedicated asynchronous connections. The business consisted of a large public network that supported dial-up users and a private network business that allowed government agencies and large companies (mostly banks and airlines) to build their own dedicated networks. The private networks were often connected via gateways to the public network to reach locations not on the private network. Tymnet was also connected to dozens of other public networks in the United States and internationally via X.25/X.75 gateways.

As the Internet grew and became almost universally accessible in the late 1990s, the need for services such as Tymnet migrated to the Internet style connections, but still had some value in the Third World and for specific legacy roles. However the value of these links continued to decrease, and Tymnet shut down in 2004.

Tymnet offered local dial-up modem access in most cities in the United States and to a limited degree in Canada, which preferred its own DATAPAC service.

Users would dial into Tymnet and then interact with a simple command-line interface to establish a connection with a remote system. Once connected, data was passed to and from the user as if connected directly to a modem on the distant system. For various technical reasons, the connection was not entirely "invisible", and sometimes required the user to enter arcane commands to make 8-bit clean connections work properly for file transfer.

Tymnet was extensively used by large companies to provide dial-up services for their employees who were "on the road", as well as a gateway for users to connect to large online services such as CompuServe or The Source.

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