Cambridge Ring (computer network)

{{Short description|Experimental local area network}}

{{Use dmy dates|date=April 2022}}

File:Cambridge Ring.jpg

The Cambridge Ring was an experimental local area network architecture developed at the Computer Laboratory, University of Cambridge starting in 1974{{cite web|url=http://www.cl.cam.ac.uk/conference/EDSAC99/history.html |title=A brief informal history of the Computer Laboratory |publisher=University of Cambridge |date=20 December 2001 |archiveurl=https://web.archive.org/web/20101113213834/http://www.cl.cam.ac.uk/conference/EDSAC99/history.html |archivedate=2010-11-13 |url-status=live }} and continuing into the 1980s. It was a ring network with a theoretical limit of 255 nodes (though such a large number would have badly affected performance), around which cycled a fixed number of packets. Free packets would be "loaded" with data by a sending machine, marked as received by the destination machine, and "unloaded" on return to the sender; thus in principle, there could be as many simultaneous senders as packets.

The network ran over twin twisted-pair cabling (plus a fibre-optic section) at a raw data rate of 10 megabits/sec.{{cite book|title=Proceedings of the seventh symposium on Operating systems principles - SOSP '79|author=Roger Needham|chapter=Systems aspects of the Cambridge Ring |year=1979|pages=82–85|doi=10.1145/800215.806573|isbn=0-89791-009-5 }}

There are strong similarities between the Cambridge Ring and an earlier ring network developed at Bell Labs based on a design by John R. Pierce.John R. Pierce, [https://archive.org/details/bstj51-6-1133/mode/1up Network for Block Switching of Data], Bell System Technical Journal, Vol. 51, No. 6 (July–August, 1972); pages 1133-1145.W. J. Kropfl, [https://archive.org/details/bstj51-6-1147/mode/1up An Experimental Data Block Switching System], Bell System Technical Journal, Vol. 51, No. 6 (July–August, 1972); pages 1147-1165.C. H. Coker, [https://archive.org/details/bstj51-6-1167/mode/1up An Experimental Interconnection of Computers Through a Loop], Bell System Technical Journal, Vol. 51, No. 6 (July–August, 1972); pages 1167-1175. That network used T1 lines at bit rate of 1.544 MHz and accommodating 522 bit messages (data plus address).

People associated with the project include Andy Hopper, David Wheeler, Maurice Wilkes, and Roger Needham.{{cite journal |title= The Cambridge Fast Ring Networking System |author1= Andrew Hopper |author2= Roger Needham |author2-link= Roger Needham |journal= Orl-88-1 |date= 1988 |volume= 37 |issue= 10 |pages= 1214–1223 |doi=10.1109/12.5983 |url= http://www.cl.cam.ac.uk/research/dtg/lce-pub/public/files/tr.88.1.pdf }}{{cite AV media|title=Prof. Andy Hopper - The Cambridge Ring and the Computer Lab|via=YouTube|url=https://www.youtube.com/watch?v=euid1mj7ap8|year=2016|people=Andy Hopper|location=Cambridge, UK|publisher=Centre for Computing History}}

A 1980 study by Peter Cowley reported several commercial implementors of elements of the network, ranging from Ferranti (producing gate arrays), Inmos (a semiconductor manufacturer), Linotype Paul, Logica VTS, MDB Systems, and Toltec Data (a design company who manufactured interface boards).{{cite web|url=https://www.cl.cam.ac.uk/downloads/ring/ring-2005-01.pdf|publisher=Cambridge Computer Lab Ring|year=2005|title=The Ring|pages=12–13}}

In 2002, the Computer Laboratory launched a graduate society called the Cambridge Computer Lab Ring named after the Cambridge Ring.{{cite web|url=https://www.cst.cam.ac.uk/ring|title=Cambridge Computer Lab Ring|year=2024|publisher=Cambridge Computer Laboratory}}