ConnNet

ConnNet was a packet switched data network operated by the Southern New England Telephone Company serving the U.S. state of Connecticut.

ConnNet was the nation's first local public packet switching network when it was launched on March 11, 1985. Users could access services such as Dow Jones News Retrieval, CompuServe, Dialcom, GEnie, Delphi, Eaasy Sabre, NewsNet, PeopleLink, the National Library of Medicine, and BIX. ConnNet could also be used to access other national and international packet networks, such as Tymnet and ACCUNET. Large companies also connected their mainframe computers to ConnNet allowing employees access to the mainframes from home. The network is no longer in operation.

Hardware

The X.25 network was based on hardware from Databit, Inc. consisting of three EDX-P Network Nodes that performed switching and were located in Hartford, New Haven and Stamford. Databit also supplied 23 ANP 2520 Advanced Network Processors each of which provided the system with a point of presence, a network control center and modems. Customers would order leased line connections into the network for host computers running at 4,800 to 56,000 bits per second (bit/s). Terminals would connect over a leased line from 1,200 to 9,600 bit/s synchronous, 300 to 2,400 bit/s asynchronous or using dial-up connections from 300 to 1,200 bit/s. The connection to Tymnet was established over an X.75 based 9,600 bit/s analog link from the ConnNet Hartford node to Tymnet's Bloomfield node.

Operations in Tymshare

Organization

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.

Trouble Tracking

Origins

Trouble reports were initially tracked on pieces of paper. This was until 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[citation needed]). He called the program PAPER after the old manual way of managing trouble tickets. The program grew as features were added to handle customer information, call-back contact information, escalation procedures, and outage statistics.

Company-wide Use

Access to PAPER became critical as more and more functionality was added. 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. Each computer was the size of 5 refrigerators, and had a string of disks that looked like 18 washing machines. Their power supplies produced +5 volts at 200 amps (non-switching) making them expensive to operate.

Major upgrades

In 1996 the DEC PDP-10s that ran Tymnet's trouble-ticket system were replaced by PDP-10 clones from XKL, Inc. They were accessible via TCP/IP as ticket.tymnet.com and token.tymnet.com, by both TELNET and HTTP. 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". The XKL TOAD-1 systems ran a modified TOPS-20. The application was ported to a newer version of the Fortran compiler, and still used the 1022 database.

Decommission

In mid to late 1998, Concert produced an inter-company trouble tracking system for use by both MCI and Concert. This was adopted and the TTS PAPER data necessary for ongoing tickets was re-entered on the new system. TTS was kept up for historical information until the end of the year. In January 1999, both XKL servers (ticket and token) were decommissioned. In late 2003 the hardware left onsite in San Jose was accidentally scrapped by the facilities manager during a scheduled cleanup.

Electronic Data Interchange

EDI

Tymshare EDI, MD Payment Systems Company, MCI EDI Department

Tymshare was one of the pioneers in the EDI field. Under McDonnell Douglas, the Payment Systems Company continued that legacy and maintained its own network monitoring and support group. They used Tandem computers connected to a high speed data link using Tymnet as the connection and translation medium. Tymshare developed a bi-sync modem interface (HSA), a translation module to translate between EBCDIC and ASCII (BBXS), and a highly customized x.25 module (XCOM) to interface with the Tandem computers.

Apparently, there was no TCP/IP equivalent service, so to continue use of this service after the shutdown of Tymnet, an ingenious solution was selected. A special version of Tymnet Engine node code which allows nodes and interfaces to communicate with one another and the rest of the network was created. Instead of relying on the supervisor to validate calls, a table of permitted connections was defined per customer to allow an incoming call to be made from the HSA interface to the BBXS interface to the XCOM interface and on to the Tandem computer. In effect, they created a Tymnet Island consisting of a single Tymnet node that accepted calls for a pre-determined list of clients. No supervisor needed.

These islands of Tymnet have not only outlived the parent company, Tymshare, and the operations company, Tymnet, but also the Tymnet Network itself. As of 2008, these Tymnet Island nodes are still running and doing their jobs.

Tymnet - History

Beginnings: Tymshare

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, Ann & Norm Hardy, Bill Frantz, Joe Rinde, 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 called a "Supervisor" 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. The Varian 620i was also used for the TYMNET nodes. During those first years, Tymshare and its direct customers were the network's only users.

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 Interdata, they started developing Tymnet on 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.

Tymnet, Inc. spun off

In about 1979, Tymnet Inc. was spun off from Tymshare Inc. to continue administration and operation of the network. 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.

Tymnet

Tymnet was an international data communications network headquartered in San Jose, California that utilized virtual call packet switched technology and used 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 async 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 was officially shut down in 2004.

Network

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.

Organization and functionality

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 point in 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".

Accessing the Network

Asynchronous Access

Users could use modems on the Public Switched Telephone Network to dial TAC ports, calling either from "dumb" terminals or from computers emulating such terminals. Organizations with a large number of local terminals could install a TAC on their own site, which used a dedicated line, at up to 56 kbit/s, to connect to a switch at the nearest Telenet location. Dialup modems supported had a maximum speed of 1200 bit/s, and later 4800 bit/s.

Computer Access

Computers supporting the X.25 protocol could connect directly to switching centers. These connections ranged from 2.4 to 56 kbit/s.

Other Access Protocols

Telenet supported remote concentrators for IBM 3270 family intelligent terminals, which communicated, via X.25, to Telenet-written software that ran in IBM 370x series front-end processors.

PC Pursuit

In the late 1980s, Telenet offered a service called PC Pursuit. For a flat monthly fee, customers could dial into the Telenet network in one city, then dial out on the modems in another city to access bulletin board systems and other services. PC Pursuit was popular among computer hobbyists because it sidestepped long-distance charges. In this sense, PC Pursuit was a forerunner of Voice over IP services.

Cities accessible by PC Pursuit

City Code	Area Code(s)	City
AZPHO	602	Phoenix, Arizona
CAGLE	818	Glendale, California
CALAN	213	Los Angeles, California
CODEN	303	Denver, Colorado
CTHAR	203	Hartford, Connecticut
FLMIA	305	Miami, Florida
GAATL	404	Atlanta, Georgia
ILCHI	312, 815	Chicago, Illinois
MABOS	617	Boston, Massachusetts
MIDET	313	Detroit, Michigan
MNMIN	612	Minneapolis, Minnesota
NCRTP	919	Research Triangle Park, North Carolina
NJNEW	201	Newark, New Jersey
NYNYO	212, 718	New York City
OHCLV	216	Cleveland, Ohio
ORPOR	503	Portland, Oregon
PAPHI	215	Philadelphia, Pennsylvania
TXDAL	214, 817	Dallas, Texas
TXHOU	713	Houston, Texas
WIMIL	414	Milwaukee, Wisconsin

Telenet

Telenet was a packet switched network which went into service in 1974. It was the first publicly available commercial packet-switched network service.

The original founding company, Telenet Inc., was established by Larry Roberts (former head of the ARPANet), and Barry Wessler. GTE acquired Telenet in 1979. It was later acquired by Sprint and called "Sprintnet". Sprint migrated customers from Telenet to the modern-day SprintLink IP network, one of many networks composing today's Internet. Telenet had its first offices in downtown Washington DC, then moved to McLean, Virginia. It was acquired by GTE while in McLean, and then moved offices in Reston, Virginia.

Under the various names, the company operated a public network, and also sold its packet switching equipment to other carriers and to large enterprise networks.

Coverage

Originally, the public network had switching nodes in seven US cities:

* Washington, D.C. (network operations center as well as switching)
* Boston, MA
* New York, NY
* Chicago, IL
* Dallas, TX
* San Francisco, CA
* Los Angeles, CA

The switching nodes were fed by Telenet Access Controller (TAC) terminal concentrators both colocated and remote from the switches. By 1980, there were over 1000 switches in the public network. At that time, the next largest network using Telenet switches was that of Southern Bell, which had approximately 250 switches.

Internal Network Technology

The initial network used statically-defined hop-by-hop routing, using Prime commercial minicomputers as switches, but then migrated to a purpose-built multiprocessing switch based on 6502 microprocessors. Among the innovations of this second-generation switch was a patented arbitrated bus interface that created a switching fabric, a shared bus in modern terms, among the microprocessors.

Most interswitch lines ran at 56 kbit/s, with a few, such as New York-Washington, at T1 (i.e., 1.544 Mbit/s). The main internal protocol was a proprietary variant on X.75; Telenet also ran standard X.75 gateways to other packet switching networks.

Originally, the switching tables could not be altered separately from the main executable code, and topology updates had to be made by deliberately crashing the switch code and forcing a reboot from the network management center. Improvements in the software allowed new tables to be loaded, but the network never used dynamic routing protocols. Multiple static routes, on a switch-by-switch basis, could be defined for fault tolerance. Network management functions continued to run on Prime minicomputers.

Its X.25 host interface was the first in the industry and Telenet helped standardize X.25 in the CCITT.