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Chaosnet was the name for both an internetworking protocol family, and an early LAN technology, both invented at the MIT AI Laboratory; the latter was the LAN on which the protocol first ran.

The LAN was a CSMA-CD system modeled on the Xerox PARC 3 megabit/second Experimental Ethernet, running over cable TV coaxial cable (using standard CATV connectors to connect the transceivers; not vampire taps, as on the Experimental Ethernet).

The protocol was later made to run over standard 10 megabit/second Ethernet, which largely supplanted the Chaosnet hardware. (On Ethernet, the Address Resolution Protocol is required to provide mappings from 16-bit Chaos addresses to the 48-bit addresses used by Ethernet.)

The protocol provided a reliable byte stream service, but also had a datagram mode.


Chaosnet was initially called CAIOSnet.


Historically, the protocol ran only directly on LANs, with no encapsulation on hardware Chaosnet; on Ethernet, EtherType 0x0804 was used. Protocol 16. was allocated for carrying CHAOS packets in Internet Protocol, but it is not clear if this was ever actually used then.

Currently, emulated Chaosnet also uses:

There is a bridge/router that understands all these, written by Bjorn Victor.


Hardware, and simulations

External links

  • AI memo 628 - Includes chapters on ITS, TOPS-20, Lisp Machine, and Unix implementations.
  • SYSDOC;CHAORD > - Initial design
  • MOON;AMBER > - Another Moon document
  • Chaosnet - Detailed descriptions of both the hardware system, and the protociol(s)
  • CHAOS; - hardware interface designs, etc.
  • Chaosnet wiki - central sire for a global emulated Chaosnet