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Chaosnet was first developed by Thomas Knight and Jack Holloway at MIT's AI Lab in 1975 and thereafter. It refers to two separate, but closely related, technologies. The more widespread was a set of computer communication packet-based protocols intended to connect the then-recently developed and very popular (within MIT) Lisp machines; the second was one of the earliest local area network hardware implementations.

The Chaosnet protocol originally used the latter, an implementation over CATV coaxial cable modeled on the early Xerox PARC 3 megabit/second Ethernet, the early ARPANET, and Transmission Control Protocol (TCP). It was a contention-based system intended to work over a 0 - 1000 meter range, that included a pseudo-slotted feature intended to reduce collisions, which worked by passing a virtual token of permission from host to host; successful packet transmissions updated each host's knowledge of which host had the token at that time. Collisions caused a host to fall silent for a duration depending on the distance from the host it collided with. Collisions were never a real problem, and the pseudo-slotting fell into disuse.

Chaosnet's network topology was usually series of linear (not circular) cables, each up to a maximum of a kilometer and roughly 12 clients. The individual segments were interconnected by "bridges" (much in the ARPANET mold), generally older computers like PDP-11s with two network interfaces.

The protocols were also later implemented as a payload that could be carried over Ethernet (usually the later 10 megabit/second variety). Chaosnet was specifically for LANs; features to support WANs were left out for the sake of simplicity.

Chaosnet can be regarded as a contemporary of both the PUP protocols invented by PARC, and the Internet Protocol, and was recognized as one of the other network types (other than "IN") in the Domain Name System. BIND uses a built-in pseudo-top-level-domain in the "CHAOS class" for retrieving information about a running DNS server.[1]

The original GNU Manifesto mentioned that it aimed to, among other things, support the Chaosnet protocol.

Symbolics, a maker of the Lisp machines, licensed the MIT Chaosnet hardware and software implementation from the CADR computer design.

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