Public Data Networking before the Internet

Home and Small Private Networks that used the telephone system

CP/M (and MS-DOS) Bulletin Board Services. 1978 was the year of the first, called CBBS, written by Ward Christensen. It employed file transfers via Xmodem, which sent data in 128 byte packets, prefixed with a 3 byte header and suffixed with a 1 or 2 byte checksum. Following 1996 and the mass acceptance of Windows 95 / 98 and Internet Explorer (a free browser for the World Wide Web), BBSes have rapidly declined in popularity. Some of the larger commercial BBSes evolved into Internet Service Providers.

FidoNet was a network that linked these bulletin boards, breaking the world into nodes, hubs (i.e. networks / regions) and five (originally six) zones. Written by Tom Jennings in 1984, it was then used for routing messages (via store and forward) by Bulletin Board networks worldwide. It compressed Netmail and Echomail (public message board) files and sent them at set times via Xmodem. It also connected BBS users to Usenet News via UUCP (Unix to Unix Copy).


Business Networks - US

Compuserve on DEC PDP-10 midrange computers. Started in 1969 as a subsidiary of Golden United Life Insurance by two electrical engineering graduate students.
Providing in-house support, it then developed as an independent business in the computer time sharing industry. Gained number one market share. Purchased by H & R Block in 1980, it was the first online service to offer Internet connectivity, albeit limited access, as early as 1989 when it connected its proprietary e-mail service to allow incoming and outgoing messages to other Internet e-mail addresses.

Second in market share was Prodigy. Started in 1984 by CBS, Sears Roebuck, and IBM (with a GUI interface)

Tymshare / Tymnet was a data communications network in California for large companies, education and govt agencies. Started in 1964. Became the largest commercial network in the United States in its heyday, with nodes in every major US city and a few overseas as well. They used IBM, DEC, and X.25 (ITU) networking protocols. It finally closed in 2004.

Another commercial packet-switching network service was Telenet. Telenet was started by Bolt Beranek and Newman, the Internet engineers, in 1974, as the first packet-switched network service available to the general public. However, it used X.25 networking protocols, where, unlike IP routers, the network switching nodes needed to be aware of every connection. Telenet was taken over by GTE in 1979, then along with United Telecom became part of Sprint in 1986.

Public Data Network — X.25

As mentioned in the preceding paragraph, X.25 uses packet-switched protocols which, like the Internet, transmits data in "packets" but, unlike the Internet, can "know" the status of every connection on the network. It was set up by the International body of Telephone and Telegraph engineers (CCITT), later called the ITU, becoming popularly known as the Public Data Network after publishing its first edition in 1976.

Note, unlike the Internet, which was based chiefly in the US, the ITU was based chiefly in Europe. National Telecom companies used X.25 to market Videotex: e.g. French Telecom's-Minitel, UK Post Office's-Prestel (sold off in 1994) and Australia's-Viatel. It was also used in Automated Teller Machines.

ISDN — Integrated Services Digital Network

In 1988, ISDN, and in particular Broadband-ISDN, was published by the ITU as a new, digital circuit-switched set of standards for the worldwide telephone system, enabling voice data and video to be sent as digital packets over the full range of frequencies accessible over telephone wire. One of the first outcomes of Broadband-ISDN was frame-relay, a stripped down version of X.25 having no error correction for speed and simplicity. Frames that contained errors at the final destination were simply discarded. This frame-relay standard was launched in the U.S. by the "Gang of Four": Cisco, DEC, Stratacom and Northern Telecom in 1990.

Asynchronous Transfer Mode — ATM — and ADSL

While most networks used Ethernet's variable length packets (up to 1500 bytes), in the 1990s the small cell packet switching standard known as ATM (Asynchronous Transfer Mode) slowly grew in popularity at telephone exchanges. Using ATM, each fixed size cell (or packet) contained just 48 bytes of data and 5 bytes of header. Simple, fast. At the downstream end to the customer premises using ADSL along with filters, the telephone line gets divided into three frequency or "information" bands, 0-4kHz carries the voice, 26-138kHz carries digital upload data, and 138-1100kHz carries the digital download data. A weakness though lay in the fact that, without repeaters, the phone company was unable to transmit high frequencies over a long distance. It meant in many cases that 4 kilometres was the maximum limit between the customer premises and the telephone exchange.

Also, due to the initial equipment cost at the telephone exchange, it wasn't until 1999 that DSL (and in particular ADSL) found Internet Service Providers offering broadband Internet service within the US.

In 2000, Telstra launched ADSL (using either Ethernet or ATM) in Australia. It rapidly became the broadband standard for desktops. ATM could now transmit those small 53-byte "cells" to and from the ISP over "always-on" Digital Subscriber Lines.

Lastly, Cable Internet networking

Launched in Australia in 1997 by Telstra-100MB max download then excess fees 35 cents per MB, Optus in 2000-more cheaply no excess fees using the HFC television network, a Hybrid of Fibre-optic cable running to each street cabinet (node), then copper Coaxial cable into each house. With coaxial cable, used for carrying TV channels as well as broadband Internet, the accessible range of frequencies is 1,000 times higher than telephone cable, up to 1 gigahertz, but the Internet channel bandwidth for uploading and downloading data is then shared between about 200 houses per node.

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