Editing Internetworking

{{redirect|Internetwork|the most notable example of an internetwork|Internet}}
{{Short description|Interconnecting different types of computer networks}}

'''Internetworking''' is the practice of [[interconnect]]ing multiple [[computer network]]s.<ref name="PD2012">{{cite book |last1=Peterson |first1=Larry L. |last2=Davie |first2=Bruce S.|date=2012 |title=Computer Networks: a systems approach |publisher=Elsevier, Inc. |isbn=978-0-12-385059-1}}</ref>{{rp|169}} Typically, this enables any pair of [[Host (network)|host]]s in the connected networks to exchange messages irrespective of their hardware-level networking technology. The resulting system of interconnected networks is called an ''internetwork'', or simply an ''internet''.

The most notable example of internetworking is the [[Internet]], a network of networks based on many underlying hardware technologies. The Internet is defined by a unified [[IP address|global addressing system]], [[Network packet|packet]] format, and [[Router (computing)|routing]] methods provided by the [[Internet Protocol]].{{r|CDKB2012|p=103}}

The term ''internetworking'' is a combination of the components ''inter'' (between) and ''networking''. An earlier term for an internetwork is '''catenet''',<ref name="ien48">{{Cite web |author=Vint Cerf |author-link=Vint Cerf |date=July 1978 |title=IEN 48: The Catenet Model for Internetworking |url=https://www.rfc-editor.org/ien/ien48.txt |publisher=[[IETF]] |quote=The term "catenet" was introduced by L. Pouzin in 1974.}}</ref> a short-form of ''(con)catenating networks''.

==History==
The first international heterogenous [[resource sharing]] network was developed by the computer science department at [[University College London]] (UCL) who interconnected the [[ARPANET]] with early [[Internet in the United Kingdom#History|British academic networks]] beginning in 1973.<ref name="M. Ziewitz & I. Brown">{{cite book |author=M. Ziewitz & I. Brown |url=https://books.google.com/books?id=QgI1_r61JFQC&pg=PA7 |title=Research Handbook on Governance of the Internet |date=2013 |publisher=[[Edward Elgar Publishing]] |isbn=978-1849805049 |page=7 |access-date=2015-08-16}}</ref><ref>{{Cite journal |last=Kirstein |first=P.T. |date=1999 |title=Early experiences with the Arpanet and Internet in the United Kingdom |url=https://pdfs.semanticscholar.org/4773/f19792f9fce8eacba72e5f8c2a021414e52d.pdf |url-status=dead |journal=IEEE Annals of the History of Computing |volume=21 |issue=1 |pages=38–44 |doi=10.1109/85.759368 |issn=1934-1547 |archive-url=https://web.archive.org/web/20200207092443/https://pdfs.semanticscholar.org/4773/f19792f9fce8eacba72e5f8c2a021414e52d.pdf |archive-date=2020-02-07 |quote=From the outset of the project, we aimed not only to carry out innovative research, but also to provide network services to UK and U.S. groups that wished to cooperate. |s2cid=1558618}}</ref><ref>{{cite news |date=19 November 2003 |title=30 years of the international internet |work=[[BBC News]] |url=http://news.bbc.co.uk/1/hi/technology/3280897.stm |access-date=22 June 2012}}</ref> In the ARPANET, the network elements used to connect individual networks were called [[gateway (telecommunications)|gateways]], but the term has been deprecated in this context, because of possible confusion with functionally different devices. By 1973-4, researchers in France, the United States, and the United Kingdom had worked out an approach to internetworking where the differences between network protocols were hidden by using a common internetwork protocol, and instead of the network being responsible for reliability, as in the ARPANET, the hosts became responsible, as demonstrated in the [[CYCLADES]] network.<ref name=":3">{{cite web|date=27 October 2009|title=The Computer History Museum, SRI International, and BBN Celebrate the 40th Anniversary of First ARPANET Transmission, Precursor to Today's Internet|url=https://www.sri.com/newsroom/press-releases/computer-history-museum-sri-international-and-bbn-celebrate-40th-anniversary|url-status=dead|archive-url=https://web.archive.org/web/20190329134941/https://www.sri.com/newsroom/press-releases/computer-history-museum-sri-international-and-bbn-celebrate-40th-anniversary|archive-date=March 29, 2019|access-date=25 September 2017|publisher=SRI International|quote=But the ARPANET itself had now become an island, with no links to the other networks that had sprung up. By the early 1970s, researchers in France, the UK, and the U.S. began developing ways of connecting networks to each other, a process known as internetworking.}}</ref><ref>{{Cite journal|last1=Cerf|first1=V.|last2=Kahn|first2=R.|date=1974|title=A Protocol for Packet Network Intercommunication|url=https://www.cs.princeton.edu/courses/archive/fall06/cos561/papers/cerf74.pdf|journal=IEEE Transactions on Communications|volume=22|issue=5|pages=637–648|doi=10.1109/TCOM.1974.1092259|issn=1558-0857|quote=The authors wish to thank a number of colleagues for helpful comments during early discussions of international network protocols, especially R. Metcalfe, R. Scantlebury, D. Walden, and H. Zimmerman; D. Davies and L. Pouzin who constructively commented on the fragmentation and accounting issues; and S. Crocker who commented on the creation and destruction of associations.}}</ref><ref>{{cite news|date=13 December 2013|title=The internet's fifth man|work=Economist|url=https://www.economist.com/news/technology-quarterly/21590765-louis-pouzin-helped-create-internet-now-he-campaigning-ensure-its|access-date=11 September 2017|quote=In the early 1970s Mr Pouzin created an innovative data network that linked locations in France, Italy and Britain. Its simplicity and efficiency pointed the way to a network that could connect not just dozens of machines, but millions of them. It captured the imagination of Dr Cerf and Dr Kahn, who included aspects of its design in the protocols that now power the internet.}}</ref> Researchers at [[Xerox PARC]] outlined the idea of [[Ethernet]] and the [[PARC Universal Packet]] (PUP) for internetworking.<ref>{{Cite web |title=8.7 Ethernet and Robert Metcalfe and Xerox PARC 1971-1975 |url=https://historyofcomputercommunications.info/section/8.7/ethernet-and-robert-metcalfe-and-xerox-parc-1971-1975/}}</ref><ref name="Moschovitisp78-9">{{harvnb|Moschovitis|1999|p=[https://archive.org/details/historyofinterne0000unse/page/78/mode/2up 78-9]}}</ref> Research at the [[National Physical Laboratory (United Kingdom)|National Physical Laboratory]] in the United Kingdom confirmed establishing a common host protocol would be more reliable and efficient.<ref>{{Cite book|last=Abbate|first=Janet|author-link=Janet Abbate|url=https://books.google.com/books?id=E2BdY6WQo4AC&pg=PA125|title=Inventing the Internet|date=2000|publisher=MIT Press|isbn=978-0-262-51115-5|pages=125|language=en}}</ref> The ARPANET connection to UCL later evolved into [[SATNET]]. In 1977, ARPA demonstrated a three-way internetworking experiment, which linked a mobile vehicle in [[PRNET]] with nodes in the ARPANET, and, via SATNET, to nodes at UCL. The [[X.25]] protocol, on which [[public data network]]s were based in the 1970s and 1980s, was supplemented by the [[X.75]] protocol which enabled internetworking.

Today the interconnecting gateways are called [[Router (computing)|router]]s. The definition of an internetwork today includes the connection of other types of computer networks such as [[personal area network]]s.

=== Catenet ===
Catenet, a short-form of ''(con)catenating networks,'' is obsolete terminolgy for a system of [[packet-switched]] communication networks interconnected via [[Gateway (telecommunications)|gateways]].<ref name="ien48" />

The term was coined by [[Louis Pouzin]], who designed the [[CYCLADES]] network, in an October 1973 note circulated to the [[International Network Working Group]],<ref>{{Cite journal |last1=Russell |first1=Andrew L. |last2=Schafer |first2=Valérie |date=2014 |title=In the Shadow of ARPANET and Internet: Louis Pouzin and the Cyclades Network in the 1970s |url=https://www.jstor.org/stable/24468474 |journal=Technology and Culture |volume=55 |issue=4 |pages=893–894 |issn=0040-165X |jstor=24468474}}</ref><ref name=":02">{{Cite journal |last=McKenzie |first=Alexander |date=2011 |title=INWG and the Conception of the Internet: An Eyewitness Account |journal=IEEE Annals of the History of Computing |volume=33 |issue=1 |pages=66–71 |doi=10.1109/MAHC.2011.9 |issn=1934-1547 |s2cid=206443072}}</ref> which was published in a 1974 paper "''A Proposal for Interconnecting Packet Switching Networks"''.<ref>''A Proposal for Interconnecting Packet Switching Networks'', L. Pouzin, Proceedings of EUROCOMP, Brunel University, May 1974, pp. 1023-36.</ref> Pouzin was a pioneer of internetworking at a time when ''network'' meant what is now called a [[local area network]]. Catenet was the concept of linking these networks into a ''network of networks'' with specifications for compatibility of addressing and routing. The term was used in technical writing in the late 1970s and early 1980s,<ref>{{Cite web |title=catenet - Google Search |url=https://www.google.com/search?udm=36&q=catenet&safe=active&ssui=on |access-date=2025-04-28 |website=www.google.com}}</ref> including in [[Request for Comments|RFCs]] and [[Internet Experiment Note|IENs]].<ref>{{Cite web |title=Google Search |url=https://www.google.com/search?q=catenet+site:https://www.rfc-editor.org/&safe=active&ssui=on |access-date=2025-04-28 |website=www.google.com}}</ref> Catenet was gradually displaced by the short-form of the term internetwork, ''internet'' (lower-case ''i''), when the [[Internet Protocol]] spread more widely from the mid 1980s and the use of the term internet took on a broader sense and became well known in the 1990s.<ref>{{Cite web |title=Google Books Ngram Viewer |url=https://books.google.com/ngrams/graph?content=catenet,internet&year_start=1970&year_end=1995&corpus=en&smoothing=3&case_insensitive=false |access-date=2025-04-28 |website=books.google.com |language=en}}</ref><ref>{{Cite IETF |RFC=1011}}</ref><ref>{{Cite IETF |RFC=1087}}</ref><ref>{{Cite IETF |RFC=1392}}</ref><ref>{{Cite IETF |RFC=1462}}</ref><ref>{{Cite IETF |RFC=1935}}</ref><ref>{{Cite IETF |RFC=1958}}</ref><ref>{{Cite IETF |RFC=2002}}</ref>

== Interconnection of networks ==
Internetworking, a combination of the components ''inter'' (between) and ''networking'', started as a way to connect disparate types of networking technology, but it became widespread through the developing need to connect two or more [[local area network]]s via some sort of [[wide area network]].

To build an internetwork, the following are needed:<ref name="CDKB2012">{{cite book|last1=Coulouris|first1=George|title=Distributed Systems: Concepts and Design|last2=Dollimore|first2=Jean|last3=Kindberg|first3=Tim|last4=Blair|first4=Gordon|date=2012|publisher=Addison-Wesley|isbn=978-0-13-214301-1}}</ref>{{rp|103}} A standardized scheme to [[Network address|address]] packets to any host on any participating network; a standardized [[Communication protocol|protocol]] defining format and handling of transmitted packets; components interconnecting the participating networks by [[routing]] packets to their destinations based on standardized addresses.

Another type of interconnection of networks often occurs within enterprises at the [[link layer]] of the networking model, i.e. at the hardware-centric layer below the level of the TCP/IP logical interfaces. Such interconnection is accomplished with [[network bridge]]s and [[network switch]]es. This is sometimes incorrectly termed internetworking, but the resulting system is simply a larger, single [[subnetwork]], and no internetworking [[Communications protocol|protocol]], such as [[Internet Protocol]], is required to traverse these devices. However, a single computer network may be converted into an internetwork by dividing the network into segments and logically dividing the segment traffic with routers and having an internetworking software layer that applications employ.

The Internet Protocol is designed to provide an [[Reliability (computer networking)|unreliable]] (not guaranteed) [[Packet switching|packet service]] across the network. The architecture avoids intermediate network elements maintaining any state of the network. Instead, this function is assigned to the endpoints of each communication session. To transfer data reliably, applications must utilize an appropriate [[transport layer]] protocol, such as [[Transmission Control Protocol]] (TCP), which provides a [[reliable stream]]. Some applications use a simpler, connection-less transport protocol, [[User Datagram Protocol]] (UDP), for tasks which do not require reliable delivery of data or that require real-time service, such as [[video streaming]]<ref name="Teare">
{{cite book
 |last=Teare 
 |first=Diane 
 |title=Designing Cisco Networks 
 |publisher=Cisco Press 
 |date=July 1999 
 |location=Indianapolis 
 |url=http://www.cisco.com/en/US/tech/tk1330/tsd_technology_support_technical_reference_chapter09186a0080759781.html 
 |archive-url=https://web.archive.org/web/20070207144013/http://cisco.com/en/US/tech/tk1330/tsd_technology_support_technical_reference_chapter09186a0080759781.html 
 |url-status=dead 
 |archive-date=2007-02-07 
}}</ref> or voice chat.

==Networking models==
Two architectural models are commonly used to describe the protocols and methods used in internetworking. The [[Open System Interconnection]] (OSI) reference model was developed under the auspices of the [[International Organization for Standardization ]] (ISO) and provides a rigorous description for layering protocol functions from the underlying hardware to the software interface concepts in user applications. Internetworking is implemented in the [[Network Layer]] (Layer 3) of the model.

The [[Internet Protocol Suite]], also known as the TCP/IP model, was not designed to conform to the OSI model and does not refer to it in any of the normative specifications in [[Request for Comments]] and [[Internet standard]]s. Despite similar appearance as a layered model, it has a much less rigorous, loosely defined architecture that concerns itself only with the aspects of the style of networking in its own historical provenance. It assumes the availability of any suitable hardware infrastructure, without discussing hardware-specific low-level interfaces, and that a host has access to this local network to which it is connected via a link layer interface.

For a period in the late 1980s and early 1990s, the network engineering community was polarized over the implementation of competing protocol suites, commonly known as the [[Protocol Wars]]. It was unclear which of the OSI model and the Internet protocol suite would result in the best and most robust computer networks.<ref name="ieee201703">{{cite magazine|author=Andrew L. Russell|date=30 July 2013|title=OSI: The Internet That Wasn't|url=https://spectrum.ieee.org/osi-the-internet-that-wasnt|magazine=[[IEEE Spectrum]]|volume=50|issue=8}}</ref><ref>{{Cite web|title=Rough Consensus and Running Code' and the Internet-OSI Standards War|url=https://www2.cs.duke.edu/courses/common/compsci092/papers/govern/consensus.pdf|last=Russell|first=Andrew L.|publisher=IEEE Annals of the History of Computing}}</ref><ref>{{Cite book|last1=Davies|first1=Howard|url=https://books.google.com/books?id=DN-t8MpZ0-wC&q=%22protocol+wars%22&pg=PA106|title=A History of International Research Networking: The People who Made it Happen|last2=Bressan|first2=Beatrice|date=2010-04-26|publisher=John Wiley & Sons|isbn=978-3-527-32710-2|language=en}}</ref>

==See also==
*[[History of the Internet]]

==References==
{{Reflist}}

==Sources==
* {{cite book |last1=Moschovitis |first1=Christos J. P. |title=History of the Internet: A Chronology, 1843 to the Present |date=1999 |publisher=ABC-CLIO |isbn=978-1-57607-118-2 |url=https://archive.org/details/historyofinterne0000unse }}

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[[Category:Network architecture]]