Usenet History: How the hardware problem was solved?

  • webmaster
  • 30 Mar 2021

The initial plan

When Dukenet initially conceptualized Usenet, the planners had three things in mind.

  • They wanted a way by which they could send local administrative messages.
  • Their goal was to create a system that was networked. (The idea incidentally came from grad students of the University).
  • UUCP would be used to ensure communication between sites. UUCP was the only option they had with sites run on Unix. They only needed a single dial-up modem port to run UUCP.

Running UUCP

Running UUCP called for a single dial-up modem port. The issue here was about the dialing. Someone had to make the call and pay the charges. Auto-dial modems did not exist (the Hayes Smartmodem came much later. The leased Bell autodialer was too expensive. Usenet was an unstructured project. Buying a modem was itself an issue. Paying monthly lease charges would not be workable. The solution planned was to use an acoustic coupler, which could act as the interface device. The solution was what Duke could afford.

The solution developed by the grad students worked like this:

  • The phone handset had to be put into tight-fit cups. The electronic part had to be connected to the computer.
  • The computer received the bits after which the coupler would send sounds through a speaker from where it went to the microphone of the handset.
  • Similarly, the mike in the coupler listened to noises that corresponded to the bits. The mike then sent voltage signals to the computer.
  • Since sounds were used to connect to the telephonic network, there would be no objection from the telephone company. AT&T did object later, but they fell in line.

The Dialing problem

When the dialing happened manually, this solution worked well. All that had to be done was to pick the handset, make the call, and placed the handset in the coupler. An issue remained, which was how the computer would do the dialing. The connection from the coupler to the computer happened through the RS-232 standard. The modem pins were five in number. They were ground, CD (carrier detect), transmit, receive, and DTR (Data Terminal Ready).

When the modem connected with the computer, i.e.: when the serial port was opened, the DTR signal would be sent. When the modem was connected, a ‘carrier detect’ signal would be sent. When the connection at the other end dropped, the modem then dropped CD. The signal then returned to the calling program. The solution was using a DTR signal. It helped solve Duke CS’s needs.

Duke implemented this solution successfully. Prof. Steven Bellovin of Columbia University liked the idea and thus created his variant. The following is a description of Prof. Bellovin’s variant:

  • An open relay was put with the phone in series to simulate the on-hook (when the landline handset was not in use).
  • The DTR signal was used when the computer needed to use the modem.
  • The DTR line was wired so it would close the relay and out the phone line off-hook. The moment the computer opened the device, the phone would be off-hook. When the computer closed the device, the phone would again be on-hook. It was a smart solution to manage this issue.

Prof. Bellovin then created a driver program. The program controlled the DTR line. The driver program ensured the modem, as well as the dialer, were seen as two different devices by UUCP.

Now came the last and most serious problem, who would foot the bill? During those times phone calls were pretty expensive. Calling during normal working hours would be extremely expensive. Phone calls in the evening would cost lesser and night calls the lowest.

The solution worked out was that Duke would take the responsibility for the calls since they had the autodialer. Any site wanting to join the network had to get a modem with an auto-answer feature and pay Duke. It was decided that the system would make calls at night and keep it to not more than two times to keep expenses at a minimum.

This plan called for money to be exchanged. There would be a spike in the phone bills. Duke had to receive as well as process payments from other sites. Usenet happened because it had the official sanction. It also materialized because the faculty members valued innovations by graduate students.

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