Editing Message switching (section)

== History ==
[[Western Union]] operated a message switching system, [[Plan 55-A]], for processing [[telegrams]] in the 1950s.<ref>{{Citation|last=Transfilm|title=Telegram for America|date=1956|url=https://archive.org/details/Telegram1956|access-date=2021-03-16}}</ref> [[Leonard Kleinrock]] wrote a doctoral thesis at the [[Massachusetts Institute of Technology]] in 1962 that analyzed queueing delays in this system.<ref>{{cite thesis|author=Kleinrock, Leonard|date=December 1962|title=Message Delay in Communication Nets with Storage (PhD thesis)|url=http://dspace.mit.edu/bitstream/handle/1721.1/11562/33840535.pdf|location=Cambridge|publisher=Massachusetts Institute of Technology|type=Thesis}}</ref> 

Message switching was built by Collins Radio Company, Newport Beach, California, during the period 1959–1963 for sale to large airlines, banks and railroads. 

The original design for the [[ARPANET]] was [[Wesley A. Clark|Wesley Clark's]] April 1967 proposal for using [[Interface Message Processor|Interface Message Processors]] to create a message switching network.<ref>{{Cite web|url=https://www.forbes.com/sites/gilpress/2015/01/02/a-very-short-history-of-the-internet-and-the-web-2/|title=A Very Short History Of The Internet And The Web|last=Press|first=Gil|website=Forbes|language=en|access-date=2020-02-07|quote=Roberts’ proposal that all host computers would connect to one another directly ... was not endorsed ... Wesley Clark ... suggested to Roberts that the network be managed by identical small computers, each attached to a host computer. Accepting the idea, Roberts named the small computers dedicated to network administration ‘Interface Message Processors’ (IMPs), which later evolved into today’s routers.}}</ref><ref>{{Cite web|url=https://web.stanford.edu/dept/SUL/library/extra4/sloan/mousesite/EngelbartPapers/B1_F20_CompuMtg.html|title=SRI Project 5890-1; Networking (Reports on Meetings).[1967]|website=web.stanford.edu|access-date=2020-02-15|quote=W. Clark's message switching proposal (appended to Taylor's letter of April 24, 1967 to Engelbart)were reviewed.}}</ref><ref>{{Cite book|last=Roberts|first=Lawrence|date=1967|title=Multiple Computer Networks and Intercomputer Communications|chapter=Multiple computer networks and intercomputer communication|chapter-url=https://people.mpi-sws.org/~gummadi/teaching/sp07/sys_seminar/arpanet.pdf|pages=3.1–3.6|doi=10.1145/800001.811680|s2cid=17409102|quote=Thus the set of IMP's, plus the telephone lines and data sets would constitute a message switching network}}</ref> After the seminal meeting at the first ACM [[Symposium on Operating Systems Principles]] in October 1967, where [[Roger Scantlebury]] presented [[Donald Davies]] work and referenced the work of [[Paul Baran]], [[Lawrence Roberts (scientist)|Larry Roberts]] incorporated [[packet switching]] into the design.<ref name=":1">{{Cite web|url=https://www.forbes.com/sites/gilpress/2015/01/02/a-very-short-history-of-the-internet-and-the-web-2/|title=A Very Short History Of The Internet And The Web|last=Press|first=Gil|website=Forbes|language=en|access-date=2020-01-30}}</ref>

The [[SITA (business services company)|SITA]] High-Level Network (HLN) became operational in 1969, handling data traffic for airlines in real time via a message-switched network over [[common carrier]] [[Leased line|leased lines]].<ref>{{cite conference |last=Chretien |first=G.J. |author2=Konig, W.M. |author3=Rech, J.H. |date=1973 |title=The SITA Network |url=http://rogerdmoore.ca/PS/SITAB.html |location=Sussex, United Kingdom |publisher=Noordhoff International Publishing |pages=373–396 |archive-url=https://web.archive.org/web/20131020140241/http://rogerdmoore.ca/PS/SITAB.html |archive-date=2013-10-20 |book-title=Proceedings of the NATO Advanced Study Institute on Computer Communication Networks |url-status=dead}}</ref><ref name="Roberts19782">{{cite web |last1=Roberts |first1=Dr. Lawrence G. |date=November 1978 |title=The Evolution of Packet Switching |url=http://www.packet.cc/files/ev-packet-sw.html |url-status=dead |archive-url=https://web.archive.org/web/20160324033133/http://www.packet.cc/files/ev-packet-sw.html |archive-date=24 March 2016 |access-date=5 September 2017 |quote=Almost immediately after the 1965 meeting, Donald Davies conceived of the details of a store-and-forward packet switching system}}</ref> It was organised to act like a packet-switching network.<ref name="Roberts1978">{{cite web |last1=Roberts |first1=Dr. Lawrence G. |date=November 1978 |title=The Evolution of Packet Switching |url=http://www.packet.cc/files/ev-packet-sw.html |url-status=dead |archive-url=https://web.archive.org/web/20160324033133/http://www.packet.cc/files/ev-packet-sw.html |archive-date=24 March 2016 |access-date=5 September 2017 |quote=Almost immediately after the 1965 meeting, Donald Davies conceived of the details of a store-and-forward packet switching system}}</ref>

Message switching systems are nowadays mostly implemented over packet-switched or circuit-switched [[Telecommunications network|data networks]]. Each message is treated as a separate entity. Each message contains addressing information, and at each switch this information is read and the transfer path to the next switch is decided. Depending on network conditions, a conversation of several messages may not be transferred over the same path. Each message is stored (usually on hard drive due to RAM limitations) before being transmitted to the next switch. Because of this it is also known as a '[[store and forward]]' network. Email is a common application for message switching. A delay in delivering email is allowed real-time data transfer between two computers.