As far as I understand ARPANET and NPL shared the goal to make data transmission scalable and reliable over large distances between many computers/networks. Of course to make the internet today, cascade of advances such as packet switching, NCP, later TCP/IP protocols were invented. Then ethernet, modems, routers, switches came into existence.

Ignoring internet, today we plug our ethernet cable into our routers/switch to create a LAN that can communicate with our other computer devices. But I wonder did people do this before ARPANET/NPL? Maybe with different types of hardware/protocol?

Edit: narrowed my question, and thanks for all the answers, interesting convos too. I suppose the history is that people already could connected computers with other computers just before the internet was born. Although, they were less standardized and more from proprietary software/hardware designed not with the thought to scale at large distances. All up until ARPANET and many other institutions which took a step forward to figure out solutions to the scalable/security problems, and eventually the internet was born under better circumstances.

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    Modems were around much earlier than IP or any sort of LAN-like networking. One computer sends bits and the other receives them, that's it. Nov 15, 2022 at 20:00
  • @NateEldredge Thank you ! may I ask, if modems were able to allowed exchanges of bits already, then what made it different for ARPANET and NPL has done to achieve this goal of connecting computers with each other over long distances? quick read, i found an example of modem usage - 'modems in US...Sage air-defense system in 1958 which connected terminals at various airbases...' Is it the packet switching that added reliability/efficiency + TCP/IP protocols that really spark the Internet connection expansion?
    – cozycoder
    Nov 15, 2022 at 20:31
  • Modern computers, LANs, and inter-networks all developed simultaneously, since communication (vice computation) was always the main point.
    – Brian H
    Nov 15, 2022 at 20:53
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    the kind of thing you did with modems was point-to-point communication between two machines directly connected (via the phone) and also it was program-directly-to-program. there were no "operating system network services". networking added direct operating system functionality that any program could use, routing where you could go over a "network" to get to any addressable machine (not just the machine you dialed up over the phone network), and more.
    – davidbak
    Nov 15, 2022 at 21:09
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    @SolomonSlow - I believe you're talking about UUCP? Why, yes. Yes I am.
    – davidbak
    Nov 15, 2022 at 22:02

3 Answers 3


This question seems to be mostly about what we did for LANs before ethernet.

Sure, we had local area networks, even if we did not call them that.

Assuming a bunch of computers not too far apart physically (like in the same air-conditioned room), you can connect them together with point-to-point links. Said links were most often serial synchronous links, but parallel links were known (faster), as well as serial asynchronous links (slower). Modems were not needed for such connections.

You can even connect computers at some distance like that, typically by renting a wire from your country's PTT. The cost of that wire depended on speed and probably distance. You'll need modems for this, since the PTT network is designed for voice. We didn't necessarily think that was any different to a "LAN"; the only difference was greater latency (which can affect datalink protocol design). That is, it is still "a network" rather than two connected networks.

If you had appropriate routing software, A could talk to B even if there was no wire directly between A and B. But desirable redundancy meant you had some nodes with multiple wires, which meant multiple interfaces (each probably costing a few thousand dollars).

DECnet was originally built on point-to-point connections in the 1970s. DEC itself had a worldwide DECnet network for engineering use. One such point-to-point connection involved a satellite link from Cornwall, England, to somewhere in Massachusetts, USA.

  • There was another common form of local area network. You'd grab some data on a magtape, or deck or cards, and walk it over to the other computer in the lab, or down the hall, or in the next building. The other computer was farther than you could walk? Not LAN. That computer was on the WAN. (You gave the tape to the mailroom guy and he drove it over.)
    – davidbak
    Nov 15, 2022 at 23:23
  • Oh, I was one of those networks at school. I collected the Fortran card decks, walked to the post office, and mailed them to Imperial College to be run on their 7094. A couple of days later, you'd get your listing ("Syntax error at line 2. Execution deleted.") back.
    – dave
    Nov 16, 2022 at 0:18
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    To @davidbak's point: This was known as "sneaker net".
    – njuffa
    Nov 16, 2022 at 9:13
  • @njuffa - yeah but I wanted to riff on LAN and WAN from the question ...
    – davidbak
    Nov 16, 2022 at 15:36

The underlying idea of ARPANET, or Ethernet, and many other computer networking technologies, is packets. Small standardized blocks of data that are forwarded around from machine to machine, under software control. Over this base layer of packets, virtual circuits are created between programs running on different computers. This allows a single communication link to serve many uses simultaneously, and to communicate with computers, by forwarding and routing, even if a direct link to that machine does not exist.

Point-to-point links between two computers to exchange data date to at least the mid-1950s. This was usually directly by serial cable or modem. An appropriate configuration of hardware and software that would allow several such links to create a packet-based network would turn out to be ARPANET. Packets and routing and virtual circuits are what distinguishes ARPANET or similar networking technologies from simply communicating over a modem, where only the two machines at each end can stream data directly to each other. ARPANET was not the only early attempt at a packet-based network, but it was certainly the most successful.

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    One of the earliest uses of point-to-point connections was "Remote Job Entry". The RJE station, likely a small computer dedicated to this task, with card reader and line printer, could submit jobs to The Big Mainframe at the other end of the wire.
    – dave
    Nov 15, 2022 at 22:29

The early arpanet was composed entirely of Interface Message Processors (IMPS) and Terminal Interface Processors (TIPS).

An IMP connected one (or more? I'm not sure) computers to the arpanet, while a TIP connected multiple computer terminals to remote arpanet hosts via the TELNET protocol. All of the dedicated, long-distance phone lines that comprised the network "backbone" ran between the IMPS and the TIPs.

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