Chaosnet (1981) | Hacker News Reader

Chaosnet (1981)

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101 pointsRGBCube15 comments

https://bitsavers.trailing-edge.com/pdf/mit/ai/AIM-628_chaos...

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Related. Others?

A Short History of Chaosnet (2018) - https://news.ycombinator.com/item?id=36079416 - May 2023 (5 comments)

A Short History of Chaosnet - https://news.ycombinator.com/item?id=29927718 - Jan 2022 (1 comment)

Chaosnet Network Protocol - https://news.ycombinator.com/item?id=20972236 - Sept 2019 (11 comments)

Chaosnet - https://news.ycombinator.com/item?id=19623831 - April 2019 (12 comments)

A Short History of Chaosnet (2018) - https://news.ycombinator.com/item?id=19480577 - March 2019 (6 comments)

Short History of Chaosnet - https://news.ycombinator.com/item?id=18107136 - Sept 2018 (5 comments)

Chaosnet, a memo from July 1981 - https://news.ycombinator.com/item?id=6787665 - Nov 2013 (1 comment)

Is this the same CHAOS that can be in IP packets as protocol 0x10?

Yes, and in DNS messages as class 3.

Get your public IP from cloudflare over chaos dns: dig @1.1.1.1 ch txt whoami.cloudflare +short

Yes, and in Ethernet frames as EtherType 0x0804.

As a reminder, CHAOS protocol is valid over IPv6 as well.

"The transmission medium of Chaosnet is called the ether. Physically it is a coaxial cable, of the semi-rigid 1/2 inch low-loss type used for cable TV, with 75-ohm termination at both ends. At each network node a cable transceiver is attached to the cable. A 10-meter flat cable connects the transceiver to an interface which is attached to a computer’s I/O bus."

[...]

"The transceiver receives a differential digital signal from the computer interface and impresses it onto the cable as a level of about 8 volts for a 1, or 0 volts (open circuit) for a 0, through a very fast VMOS power FET. When the cable is idle it is held at 0 volts by the terminations. This simple-minded unipolar scheme is adequate for the medium cable lengths and transmission speeds we are using. The transceiver monitors the cable by comparing it against a reference voltage, and returns a differential signal to the interface. In addition, it detects interference (another transceiver transmitting at the same time as this one) and informs the interface."

Seems like the above would be all that's necessary for the simplest possible "built around first principles" local LAN, if someone wanted to experiment with an early Ethernet-like system...

Anyway, great article!

It is. This is what they mean by an aether - a wire connecting several computers so that any of them can send an electrical signal they will all receive. Ethernet was named after this, but doesn't use an ether any more.

In this design you need a way to make computers take turns. CSMA/CD is the stupidest: wait until nobody is transmitting before you transmit, and if two nodes start transmitting at the same moment, both abort.

Chaosnet in active use, mostly on emulators: https://chaosnet.net/

Lispm, PDP-10, PDP-11, VAX.

Should not be confused with Chaos VPN, a predecessor to dn42 for linking nstworks of the Chaos Computer Club.

It says it was inspired by Ethernet, and while modern Ethernet might have some significant differences of course, what were the differences between Chaosnet and the Ethernet of the time?

Chaosnet was inspired by the experimental 3 Mbits/s Ethernet in use at Xerox PARC at the time. Experimental Ethernet has a 8-bit node address; Chaosnet has 16 bits, of which 8 is network and another 8 is the node. The Chaosnet data rate is 4 Mbits/s.

On top of the hardware protocol, Chaosnet also defined the higher-level transport and session layer protocol. Applications are addressed by a name string rather than a port number; e.g. "TELNET" instead of 23. This protocol was retained when the NIC hardware was replaced with stock Ethernet.

I only know of this because the CADR emulator supports an emulated version of it.

It is also capable of doing it over the wire.

Woaw! You could use a space cadet keyboard with this!!1!

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