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networking, history A United States-wide commercial computer
network, created by Tymshare, Inc. some time before 1970,
and used for remote login and file transfer. The network
public went live in November 1971.
In its original implementation, it consisted of fairly simple
circuit-oriented nodes, whose circuits were created by
central network supervisors writing into the appropriate
nodes' "permuter tables". The supervisors also performed
login validations as well as circuit management. Circuits
were character oriented and the network was oriented toward
interactive character-by-character full-duplex
communications circuits.
The network had more than one supervisor running, but only one
was active, the others being put to sleep with "sleeping pill"
messages. If the active supervisor went down, all the others
would wake up and battle for control of the network. After
the battle, the supervisor with the highest pre-set priority
would dominate, and the network would then again be controlled
by only one supervisor. (During the takeover battle, the net
consisted of subsets of itself across which new circuits could
not be built). Existing circuits were not affected by
supervisor switches.
There was a clever scheme to switch the echoing function
between the local node and the host based on whether or not a
special character had been typed by the user. Data transfers
were also possible via "auxiliary circuits".
The Tymshare hosts (which ran customer code) were SDS 940,
DEC PDP-10, and eventually IBM 370 computers. Xerox
XDS 940 might have been used if Xerox, who bought the design
for the SDS 940 from Scientific Data Systems, had ever built
The switches were originally Varian Data Machines 620i. The
Interdata 8/32 was never used because the performance was
disappointing. The TYMNET Engine, based loosely on the
Interdata 7/32, was developed instead to replace the Varian
620i. in the early 1990s, newer "Turbo" nodes based on the
Motorola 68000 began to replace the 7/32s. These were later
replaced with SPARCs.
PDP-10s supported (and still do in 1999) cross-platform
development and billing.
Tymshare, Inc. originally wrote and implemented TYMNET to
provide nationwide access for their time-sharing customers.
La Roy Tymes booted up the public TYMNET in November of 1971
and, as of March 2002, it had been running ever since without
a single system crash.
TYMNET was the largest commercial network in the United States
in its heyday, with nodes in every major US city and a few
overseas as well. Tymshare acquired a French subsidiary,
SLIGOS, and had TYMNET nodes in Paris, France.
Tymshare sold the TYMNET network software to TRW, who
created their own private network (which was not called
TYMNET). In about 1979, TYMNET Inc. was spun off from
Tymshare, Inc. to continue administration and development of
the network.
TYMNET outlived its parent company Tymshare and was acquired
by MCI. As of May 1994 they still ran three DEC KL-10s
under TYMCOM-X, although they planned to decommission them
The original creators of TYMNET included: Ann Hardy, Norm
Hardy, Bill Frantz. La Roy Tymes (who always insisted that
his name was NOT the source of the name) wrote the first
supervisor which ran on the 940. Joe Rinde made many
significant technical and marketing contributions. La Roy
wrote most of the code of the network proper. Several others
wrote code in support of development and administration. Just
recently (1999) La Roy, on contract, wrote a version of the
supervisor to run on SPARC hardware.