Internetworking

Internetworking is the practice of interconnecting multiple computer networks, such that any pair of hosts in the connected networks can exchange messages irrespective of their hardware-level networking technology. The resulting system of interconnected networks are 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 global addressing system, packet format, and routing methods provided by the Internet Protocol. The term internetworking is a combination of the components inter (between) and networking. An earlier term for an internetwork is catenet, a short-form of (con)catenating networks. Internetworking 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 networks via some sort of wide area network. The first international heterogenous resource sharing network was the 1973 interconnection of the ARPANET with early British academic networks through the computer science department at University College London (UCL). In the ARPANET, the network elements used to connect individual networks were called gateways, but the term has been deprecated in this context, because of possible confusion with functionally different devices. By 1973-4, researchers in the United States, the United Kingdom and France 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. Research at the National Physical Laboratory in the United Kingdom confirmed establishing a common host protocol would be more reliable and efficient. The ARPANET connection to UCL later evolved into SATNET.