TYMNET

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

any.

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

soon.

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.

The name TYMNET was suggested by Vigril Swearingen in a weekly

meeting between Tymshare technical and marketing staff in

about 1970.

.

[E-mail from La Roy Tymes]

(2002-11-26)