Tymnet was an international data communications network headquartered in Cupertino, California[citation needed] that used virtual call packet-switched technology and X.25, SNA/SDLC, BSC and Async interfaces to connect host computers (servers) at thousands of large companies, educational institutions, and government agencies.
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.
Unlike the TCP/IP protocol underlying the internet, Tymnet used a circuit switching layout which allowed the supervisors to be aware of every possible end-point.
In its original incarnation, the users connected to nodes built using Varian minicomputers, then entered commands that were passed to the supervisor which ran on a XDS 940 host.
This did have the side effect of making data transfers quite difficult, as bytes from the file would be invisibly "translated" without specific intervention on the part of the user.
Tymnet II was developed to ameliorate the problems outlined above by off-loading some of the work-load from the supervisor and providing greater flexibility in the network by putting more intelligence into the node code.
A Tymnet II node would set up its own "permuter tables", eliminating the need for the supervisor to keep copies of them, and had greater flexibility in handling its inter-node links.
Written in assembly code by LaRoy Tymes for the SDS 940, with architectural design contributions from Norman Hardy, the "Supervisor" was the beginning of the Tymnet network.
In February, 1972, the National Library of Medicine became the first non-Tymshare network customer with a toxicology data base on an IBM 360.
In 1972, Joseph Rinde joined the Tymnet group and began porting the Supervisor code to the 32-bit Interdata 7/32, as the 8/32 was not yet ready.
Tymnet II ran in parallel with the original network, which continued to run on the Varian machines until it was phased out over a period of several years.
This led to the foundation of Tymnet as a wholly owned subsidiary of Tymshare to run a public network as a common carrier within the United States.
McDonnell Douglas acquired Microdata and created MD Information Systems Group (MDISC), expecting to turn Microdata's desktop and server systems along with Tymshare's servers and Tymnet data network into a major player in the Information Services market.
After five years, peace was breaking out in many places in the world and McDonnell Douglas sold off MDNSC and MDFSC at a profit for much needed cash.
British Telecom (BT) wanted to expand and the acquisition of Tymnet, which already a worldwide data network, was projected to help to achieve that goal.
Another project begun a few months before the BT purchase was to migrate the Tymnet code repository from the PDP-10s to Sun systems.
Tymnet was still growing, and at several times reached its peak capacity when some of its customers held network intensive events.
Tymnet usage statistics showed AOL's call capacity was greater than its maximum volume for the duration of the event.
MCI took a different direction and looked to migrate the network protocols to run over TCP/IP and use Sun Microsystems SPARC technology.
The supervisor technology was rewritten in C to run as standard UNIX applications under Sun's Solaris operating system.
Times were changing and the Internet and World Wide Web were becoming a practical and even important part of corporate and personal life.
However, the Tymnet network was still bringing in much cash (in some cases more than current IP-based services), so both BT and MCI needed to keep their customers happy.
Sometime in early March 2004, without ceremony, BT Americas disconnected the last two remaining Tymnet supervisors from the network, effectively shutting it down.
[7] The scandal resulted in the CEO, Bernard Ebbers, being ousted and later brought up on federal charges for conspiracy and securities fraud.
Under McDonnell Douglas, the Payment Systems Company continued that legacy and maintained its own EDI*Net network monitoring and support group.
It is for this reason, that many of the Tymnet projects ran on the Digital Equipment Corporation DECSystem-10 computers that Tymshare offered as timesharing hosts for their customers.
From its earliest days, Tymnet had an on-line and real time network trouble reporting tool called the Consolidator.
It eventually was maintained on two dedicated PDP-10 computers, model KL-1090, accessible via the Tymnet Packet Network as Tymshare hosts 23 and 26.
A low-end workstation from Sun was used as a telnet gateway; it accepted logins from the Tymnet network via x.25 to IP translation done by a Cisco router forwarded to "ticket" and/or "token".
In late 2003 the hardware left onsite in San Jose was accidentally scrapped by the facilities manager during a scheduled cleanup.