Теленет: Первая коммерческая пакетная сеть в США.

American commercial packet switched network

Telenet was an American commercial packet switched network which went into service in 1975. It was the first FCC licensed public data network in the United States. Various commercial and government interests paid monthly fees for dedicated lines connecting their computers and local networks to this backbone network. Free public dialup access to Telenet, for those who wished to access these systems, was provided in hundreds of cities throughout the United States. The original founding company, Telenet Inc., was established by Bolt Beranek and Newman (BBN) and recruited Larry Roberts (former head of the ARPANet) as President of the company, 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, D. C., then moved to McLean, Virginia. It was acquired by GTE while in McLean, and then moved to offices in Reston, Virginia.

After establishing that commercial operation of "value added carriers" was legal in the U. S., Bolt Beranek and Newman (BBN), who were the private contractors for constructing packet switching nodes (Interface Message Processor) for the ARPANET, set out to create a private sector version. In January 1975, Telenet Communications Corporation announced that they had acquired the necessary venture capital after a two year quest, and on August 16 of the same year they began operating the first public data network.

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 switched fabric among the microprocessors. By contrast, a typical microprocessor based system of the time used a bus; switched fabrics did not become common until about twenty years later, with the advent of PCI Express and HyperTransport. 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. Telenet initially used a proprietary virtual connection host interface. Telenet adopted X.25 shortly after the protocol was published in March 1976. Its X.25 host interface was the first in the industry.

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. Telenet also supported Block Mode Terminal Interfaces (BMTI) for IBM Remote Job Entry terminals supporting the 2780/3780 and HASP Bisync protocols.