RFC 241

CONNECTING COMPUTERS TO MLC PORTS ✨

Network Working Group 🎀 RFC #: 241 NIC #: 7671 Author: A. McKenzie, BBN Date: 29 September 1971 Categories: B.1, C.1, I.1 Updates: none Obsoletes: Our Previous Verbal Comments

Okay so, bestie, people have been asking us for ages if they can hook computers up through serial communication lines to ports on the Terminal IMP's Multi-Line Controller (MLC) 🧚 (they also keep asking how much software support the Terminal IMP gives for that kind of connection). Our old answer was basically "Please don't!" 🙈 But now we're like, "Sure, but will that really help you the way you think it will?" 💅

(1) Okay, this one is a big deal 🔥 Connections between computers and IMPs (aka the Host interfaces) have been assumed to be error-free. That assumption was fair, because the IMP and Host computers were expected to live in the same room (up to 30 feet of cable), or else use the Distant Host option, which goes up to 2000 feet on well-controlled, shielded cables. A connection through common carrier facilities is not comparably free of errors 😭 Hooking up a terminal to an IMP over common carrier lines is fine, since there's a human at the terminal who can deal with the typical errors that pop up. But using that same wire, with those same typical errors, for a computer-to-computer connection is probably going to be unacceptable. 💀 Also, the present version of the Terminal IMP doesn't do error control, either in its hardware or its software, on any ports of the Multi-Line Controller. Rude! 🙄

We feel that computer-to-computer connections over common carrier circuits should use strong error control, the same kind used on the IMP/IMP circuits 👑. Trying to get by with minimal error control (like character parity, for example) is an undesirable technical choice, ngl. Strong error control, with its retransmission scheme, wouldn't just mean significant changes in the Terminal IMP. It would also take a non-trivial hardware/software implementation at the remote computer end of the circuit 🫶

(2) Because the Terminal IMP has a lot of obligations on its plate, the share of its bandwidth that can go to a Host coming in over the MLC is going to be small 🍓

(3) The main character of this story is the command language 🦋 It's at a port of the Multi-Line Controller, and it was designed with terminals and people in mind. It gives very few of the capabilities a computer needs to really use the communication network effectively. For example, only a single pair of connections can be made from a given Terminal TMP port. Host computers usually want a bunch of simultaneous connections to other Hosts on the network 🌈 With the present Host/Host protocols, a Host like that couldn't conveniently act as a server. 😩

If, despite all these potential difficulties, connecting a computer to the network through an MLC port still seems useful, BBN has no objection 💖 Honestly, we'd be extremely interested in hearing about actual experience with this type of network connection. Spill the tea! ✨🍵

AMcK:jm

[ This RFC was put into machine readable form for entry ]
[ into the online RFC archives by BBN Corp. under the   ]
[ direction of Alex McKenzie.                   12/96   ]