Tymnet: Международная сеть передачи данных, предшественник Интернета.

Defunct international data communications network
Tymnet was an international data communications network headquartered in Cupertino, California 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. 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 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 international public gateways via Tymnet II protocol and 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.

In its original implementation, the network supervisor contained most of the routing intelligence in the network. 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. Circuits were character oriented and the network was oriented towards interactive character by character full duplex communications circuits. The nodes handled character translation between various character sets, which were numerous at that time. 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 later developed their own custom hardware, the Tymnet Engine, which contained both nodes and a supervisor running on one of those nodes. As the network grew, the supervisor was in danger of being overloaded by the sheer number of nodes in the network, since the requirements for controlling the network took a great part of the supervisor's capacity. Tymnet II was developed in response to this challenge. 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. Data transfers were also possible via "auxiliary circuits".

Tymshare was founded in 1964 as a time sharing company, selling computer time and software packages for users. It had two SDS/XDS 940 computers; access was via direct dial up to the computers. In 1968, it purchased Dial Data, another time sharing service bureau. In 1968, Norm Hardy and LaRoy Tymes developed the idea of using remote sites with minicomputers to communicate with the mainframes. The minicomputers would serve as the network's nodes, running a program to route data. In November 1971, the first Tymnet Supervisor program became operational. 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. One instance of the supervisor would be running at all times and choose a path (circuit) through the network for each new interactive session. The Varian 620i (8K of 16 bit words) was used for the TYMNET nodes. Initially, Tymshare and its direct customers were the network's only users. In February, 1972, the National Library of Medicine became the first non Tymshare network customer with a toxicology data base on an IBM 360. It soon became apparent that the SDS 940 could not keep up with the rapid growth of the network. 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. In 1973, the 8/32 became available, but the performance was disappointing and a crash effort was made to develop a machine that could run Rinde's Supervisor. In 1974, a second, more efficient version of the Supervisor software became operational. The new Tymnet "Engine" software was used on both the Supervisor machines and on the nodes. After the migration to the Tymnet Engine, they started developing Tymnet accounting and other support software on the PDP 10. Tymshare sold the Tymnet network software to TRW, who created their own private network, TRWNET. Tymes and Rinde then developed "Tymnet II". 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. Tymnet II's different method of constructing virtual circuits allowed for much better scalability. In 1996, the third and final version of the Supervisor was written in C for a Sparc multiprocessor work station by Tymes and Romolo Raffo. Node code software was ported from the Tymnet Engine to a Sparc platform by Bill Soley. Up to 10 old style Tymnet Engines were replaced by a single Sparc node in the network switching centers.

In about 1979, Tymnet Inc. was spun off from Tymshare Inc. to continue administration and operation of the Tymnet network and its VAN services. The network continued to grow, and customers who owned their own host computers and wanted access to them from remote sites became interested in connecting their computers to the network. 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. This allowed users to connect their host computers and terminals to the network, and use the computers from remote sites or sell time on their computers to other users of the network, with Tymnet charging them for the use of the network.

In 1993 British Telecom (BT) and MCI Communications (MCI) negotiated what they called the "Deal of the Century", where MCI would take ownership of the US based portions of Tymnet and they would create a 50/50 joint venture called "Concert". (The joint venture was called "NewCo" for more than a year while they decided on a name.) Concert was also aligned with another acquisition of BT, called Syncordia which was headquartered in Atlanta, Ga. Tymnet was then referred to as: The Packet network, the BT/MCI network and Concert Packet switching Services (CPS). As MCI cut away at Tymnet, expecting it to die, it became a cash cow that just wouldn't go away. In May 1994, there were still three DEC KL 10s under TYMCOM X. At this time, the network had approximately 5000 nodes in 30 foreign countries. A variety of protocols can be run over a single packet switching network, and Tymnet's most used protocols were X.25, asynchronous (ATI/AHI), SNA. BT and Concert also continued to develop the network, and after the failure of the "Turbo nodes" to take off, decided to have an outside company add Tymnet protocols to existing hardware used in their frame relay network. Telematics International developed a subset of the Tymnet protocols to run on their ACP/PCP nodes. The Telematics nodes were connected in a mesh network via Frame Relay and appeared to Tymnet as super nodes that were directly connected to as many as 44 other super nodes interconnecting most of Europe, Asia and the Americas as a high speed data network. 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. Funding for this project was at a minimum but the Tymnet engineers believed it was a superior method and proceeded anyway. Times were changing and the Internet and World Wide Web were becoming a practical and even important part of corporate and personal life. Tymnet technology needed improvements to keep pace with TCP/IP and other internet protocols. Both BT and MCI decided not to compete with the Internet, but to convert their customer base to IP based networks and technologies. 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.

In 1997 talks were underway for British Telecom (BT) to acquire MCI. The deal fell through, and in September, 1998 MCI was acquired by WorldCom after they made a better offer for the company. Actually, the Worldcom offer was nearly identical to the BT offer, but where BT planned to buy out MCI shares of stock, WorldCom offered a stock swap which was more attractive to the stockholders. Worldcom took control in September 1998 and dissolved the BT/MCI alliance as of October 15, 1998.

With the alliance gone, BT and MCI/Worldcom began the process of unraveling and separating their extensive voice and data communications systems. Concert created Project Leonardo to separate the BT and MCI/Worldcom voice and data networks. At times over the next five years, advancements were made or stalled due to BT and MCI management negotiating and renegotiating the terms of their contractual obligations to each other made during the alliance. At times, things came to a standstill, or decisions made were reversed, and some reversed again at a later time. Parts of the project were to migrate customers from X.25 to IP based networks, while others created a duplicate set of services so that both Concert and MCI could separately continue to run and manage their own portions of the network. Accounting data for network usage was also shared by the two companies and had to be separated before clients could be billed properly.

In 2000 BT then went searching for another alliance, and created a new "Concert" alliance between BT and AT&T Corporation, moving the headquarters to Atlanta, Georgia. This alliance did not help the negotiations between BT and MCI Worldcom as their partners from MCI and AT&T were corporate enemies. For Tymnet, the data network portion of the split, and the "CPS Leonardo" project, the split was never fully realized. Instead, MCI Worldcom completed their migration of services from Tymnet to IP based services in March 2003 and disconnected their supervisor nodes and their portion of the network on March 31, 2003. British Telecom continued to run the network using their own supervisor and other utility nodes until February 2004 when their last customer was able to move all of its customers to other access services. BT and AT&T dissolved their Concert alliance on September 30, 2003, and the remaining BT assets were combined with BTNA assets into BT Americas, Inc. Sometime in early March 2004, without ceremony, BT Americas disconnected the last two remaining Tymnet supervisors from the network, effectively shutting it down.

Worldcom executives were involved in a financial scandal. In June 2002, Worldcom admitted to nearly 4 billion dollars of incorrect accounting. The scandal resulted in the CEO, Bernard Ebbers, being ousted and later brought up on federal charges for conspiracy and securities fraud. The scandal sent the stock price down to ten cents per share. A month after the revelation of accounting "mishaps", Worldcom filed for bankruptcy. In less than a year, the remains of MCI was sold for $6.7B bid to what is today known as Verizon Business, a division of Verizon. Verizon had been formed in 2000 when Bell Atlantic, one of the Regional Bell Operating Companies, merged with GTE. Prior to its transformation into Verizon, Bell Atlantic had merged with another Regional Bell Operating Company, NYNEX, in 1997.

On January 31, 2005, SBC Communications announced that it would purchase AT&T Corp. for more than $16 billion. Shortly thereafter the name was changed to AT&T Inc. to distinguish itself from AT&T Corp.

In operation, Tymshare's Data Networks Division was responsible for the development and maintenance of the network and Tymnet was responsible for the administration, provisioning and monitoring of the network. Each company had their own software development staff and a line was drawn to separate what each group could do. Tymshare development engineers wrote all the code which ran in the network, and the Tymnet staff wrote code running on host computers connected to the network. 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. Tymnet operations formed a strategic alliance with the Tymshare PDP 10 TYMCOM X operating systems group to assist them in developing new network management tools.

From its earliest days, Tymnet had an on line and real time network trouble reporting tool called the Consolidator. That, along with the network node interrogation capabilities (known as Snap or Snapshot), provided unique and real time operation of the network. However, trouble reports were initially tracked on a traditional paper ticket system. This was until Bill Scheible, a manager at Tymnet, wrote a small FORTRAN IV program to maintain a list of problem reports and track their status in a System 1022 database (a hierarchical database system for TOPS 10 published by Software House). 1022 was a hierarchical database system which could be accessed via third generation languages such as Fortran and COBOL; it also had its own 4GL.

Software House, the company that trademarked and brought 1022 to market also marketed a VAX counterpart, System 1032. Software House was acquired by Computer Corporation of America. Software House released
System 1032 for Digital Equipment Corporation's 32 bit VAX systems. Version 1.5 (1984) added EBCDIC support. System 1032 was acquired by Computer Corporation of America (CCA) in 1992. In 2010, Rocket Software acquired CCA's products, including System 1032. Rocket continue to develop and maintain System 1032 for the OpenVMS operating system. Like 1022, it had a Host Language Interface (HLI).