internetworking

Internetworking is the practice of interconnecting multiple computer networks. Typically, this enables any pair of hosts 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 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 is the practice of interconnecting multiple computer networks. Typically, this enables any pair of hosts 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 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. ==History== The first international heterogeneous resource sharing network was developed by the computer science department at University College London (UCL), which interconnected the ARPANET with early British academic networks beginning in 1973. 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 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. Researchers at Xerox PARC outlined the idea of Ethernet and the PARC Universal Packet (PUP) for internetworking. Research at the National Physical Laboratory in the United Kingdom found that establishing a common host protocol would be more reliable and efficient. 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 networks were based in the 1970s and 1980s, was supplemented by the X.75 protocol, which enabled internetworking. Today, the interconnecting gateways are called routers. The definition of an internetwork today includes the connection of other types of computer networks, such as personal area networks. ==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 standards. Despite a 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. ==See also== History of the Internet ==References==

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