Editing Chaosnet

{{Short description|Local area networking technology}}
'''Chaosnet''' is a [[local area network]] technology. It was first developed by [[Tom Knight (scientist)|Thomas Knight]] and Jack Holloway at [[Massachusetts Institute of Technology|MIT's]] [[MIT AI Lab|AI Lab]] in 1975 and thereafter. It refers to two separate, but closely related, technologies.<ref>{{harvnb|Moon|1981|p=2}}</ref> The more widespread was a set of [[computer]] communication packet-based [[protocol (computing)|protocols]] intended to connect the then-recently developed and very popular (within MIT) [[Lisp machine]]s; the second was one of the earliest [[local area network]] (LAN) hardware implementations.

==Origin==
The Chaosnet protocol originally used an implementation over [[CATV]] coaxial cable modeled on the early [[Xerox PARC]] {{nowrap|3 megabit/second}} [[Ethernet]],<ref>{{harvnb|Moon|1981|p=2}}</ref> the early [[ARPANET]], and [[Transmission Control Protocol]] (TCP). It was a contention-based system intended to work over a {{nowrap|0–1000 meter}} range,<ref>{{harvnb|Moon|1981|p=3}}</ref> 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.<ref>{{harvnb|Moon|1981|pp=6–8}}</ref> Collisions were never a real problem, and the pseudo-slotting fell into disuse.

Chaosnet's network topology was usually a 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-11]]s with two network interfaces.<ref>{{harvnb|Moon|1981|p=3, 14}}</ref>

The protocols were also later implemented as a payload that could be carried over Ethernet (usually the later {{nowrap|10 megabit/second}} variety). Chaosnet was specifically for LANs; features to support [[Wide area network|WANs]] were left out for the sake of simplicity.<ref>{{harvnb|Moon|1981|p=1}}</ref>

Chaosnet can be regarded as a contemporary of both the [[PARC Universal Packet|PUP]] protocols invented by PARC, and the [[Internet Protocol]] (IP), and was recognized as one of the other network classes (other than "[[Internet|IN]]" and "[[Hesiod (name_service)|HS]]") in the [[Domain Name System]].{{Ref RFC|1034|rsection=3.6}} [[BIND]] uses a built-in pseudo-top-level-domain in the "CHAOS class" for retrieving information about a running DNS server.<ref>{{Cite web |url=http://www.bind9.net/manual/bind/9.3.2/Bv9ARM.ch06.html#builtin |title=BIND 9 version 9.3.2 Manual / User Guide |access-date=2009-10-28 |archive-date=2006-07-18 |archive-url=https://web.archive.org/web/20060718215648/http://www.bind9.net/manual/bind/9.3.2/Bv9ARM.ch06.html#builtin |url-status=dead }}</ref>

==Chaosnet protocol==
The Chaosnet protocol identifies hosts by 16-bit addresses, 8 bits of which identify the subnet, 8 bits of which identify the host within the subnet.<ref>{{harvnb|Moon|1981|p=10}}</ref> The basic protocol was a full-duplex reliable packet transmission between two user processes. The packet contents could be treated as bytes of 8 or 16 bits, with support for other word sizes provided by higher-level protocols. The connection was identified by a combination of the 16-bit addresses of each host and a 16-bit "connection index" assigned by each host to maintain uniqueness. "Controlled" packets within a connection were identified by a 16-bit packet number, which was used to deliver controlled packets reliably and in order, with re-transmission and flow control.  "Uncontrolled" packets were not retransmitted, and were used at a lower level to support the flow-control and re-transmission. Chaosnet also supported "BRD" broadcast packets to multiple subnets.<ref>{{harvnb|Moon|1981}}</ref>

Initial establishment of the connection was made using "contact names." These names identified the network service and higher-level protocol. For example, "STATUS" was the contact name which requested basic network statistics from a host. "TELNET" was a contact name for the Arpanet TELNET protocol. "FILE" was a contact name for the Lisp Machine network file service. Other contact names included "SUPDUP", "MAIL", "NAME" for the Arpanet Finger protocol, "TIME", "SEND" for interactive messaging, "ARPA" for a gateway service to Arpanet. "DOVER" was the contact name for sending print jobs to Chaosnet hosts with a [[Xerox Dover]] printer attached (an early [[laser printer]]).<ref>{{harvnb|Moon|1981}}</ref> Developers could easily experiment with new protocols by inventing new contact names. In [[Incompatible Timesharing System|ITS]], a new server for that protocol could be installed by creating a link to the program in the location DSK:DEVICE;CHAOS <cname> where <cname> was up to six letters of the contact name.

Simple transactions could be completed by a single "RFC" packet containing a contact name, answered by a single "ANS" packet with the relevant information. For example, an RFC to contact name "TIME" would result in a single ANS packet containing a 32-bit number indicating the time.<ref>{{harvnb|Moon|1981}}</ref>
 
The original [[GNU Manifesto]] mentioned that it aimed to, among other things, support the Chaosnet protocol.

[[Symbolics]], a maker of the [[Lisp machine]]s, licensed the [[MIT]] Chaosnet hardware and software implementation from the [[Lisp machine|CADR]] computer design.

==Notes==
{{Reflist}}

==References==
{{refbegin}}
*{{cite tech report |last=Moon |first=David A. |author-link=David A. Moon |date=June 1981 |series=MIT AI Memos (1959–2004) |number=AIM-628 |url=https://dspace.mit.edu/handle/1721.1/6353 |title=Chaosnet |institution=Massachusetts Institute of Technology Artificial Intelligence Laboratory }}
* {{cite web |url=http://groups.csail.mit.edu/mac/ftpdir/its/sysdoc.tar.gz |title=CHAOS ORDER (chaord.57)|access-date= June 12, 2013}} Online documentation from the ITS SYSDOC; directory
{{refend}}

==External links==
* [http://docstore.mik.ua/univercd/cc/td/doc/product/software/ssr83/rpc_r/48381.htm Cisco's Implementation of Chaosnet]
* [http://lkml.iu.edu/hypermail/linux/net/0104.3/0050.html Chaosnet implementations] {{Webarchive|url=https://web.archive.org/web/20211009171245/http://lkml.iu.edu/hypermail/linux/net/0104.3/0050.html |date=2021-10-09 }}
* [http://gopher.quux.org:70/Archives/usenet-a-news/FA.works/81.07.13_ucbvax.2264_fa.works.txt Another reference to AI Memo 628]
* [http://bitsavers.trailing-edge.com/pdf/mit/ai/AIM-628_chaosnet.pdf A better scan of AI Memo 628 than the one below] (pdf)
* [https://web.archive.org/web/20170706144931/ftp://publications.ai.mit.edu/ai-publications/500-999 Another place to get AI Memos 500 to 999] (FTP)
* [http://chaosnet.sourceforge.net/ Chaosnet (Linux source driver)]

[[Category:Local area networks]]