by Darius Kazemi, August 18 2019

In 2019 I'm reading one RFC a day in chronological order starting from the very first one. More on this project here. There is a table of contents for all my RFC posts.

Enter the minicomputer

RFC-230 is titled “Toward Reliable Operation of Minicomputer-Based Terminals on a TIP”. It's authored by Thomas N. Pyke, Jr. of the National Bureau of Standards.

The technical content

This RFC is about the Terminal IMP (TIP). Recall that the TIP is an Interface Message Processor that a teletype terminal can connect to in order to access services on the ARPANET, such that a user doesn't need to own a gigantic, expensive computer in order to do so.

The author's issue with the TIP is:

  1. that it only allows for character-oriented transmission, as opposed to line-oriented (see RFC-89 and RFC-139 for more on this problem)
  2. it offers no error control

In 1971 teletype terminals are starting to be replaced with “minicomputers”, which are more like the personal computers that we use today in that they contain, well, an actual computer inside them and they aren't just a souped-up typewriter. You can write programs on a minicomputer and everything.

A terminal user is expected to enter a command, see the result, and then determine if there was an error. But if the user is a minicomputer, the human may simply write a piece of software that then talks to the TIP. This data is going to be processed so quickly by the minicomputer that a human can't really debug every single interaction. Hence the need for error control.

Similarly, if the flow of data is going to be (human → minicomputer → TIP) instead of (human → terminal → TIP), then it makes sense for the TIP to accept huge blocks of data at once instead of getting a character-by-character transmission. Character-by-character makes a lot of sense when a human is typing things, but again, we are now in a situation where a computer is talking to a computer and there is no point in pretending that one of the computers is as slow at processing data as a human.

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About me

I'm Darius Kazemi. I'm an independent technologist and artist. I do a lot of work on the decentralized web with ActivityPub, including a Node.js reference implementation, an RSS-to-ActivityPub converter, and a fork of Mastodon, called Hometown. You can support my work via my Patreon.