Internetworking is the practice of interconnecting multiple
computer network
A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ...
s,
such that any pair of
host
A host is a person responsible for guests at an event or for providing hospitality during it.
Host may also refer to:
Places
* Host, Pennsylvania, a village in Berks County
People
*Jim Host (born 1937), American businessman
* Michel Host ...
s 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
The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...
, a network of networks based on many underlying hardware technologies. The Internet is defined by a unified
global addressing system,
packet
Packet may refer to:
* A small container or pouch
** Packet (container), a small single use container
** Cigarette packet
** Sugar packet
* Network packet, a formatted unit of data carried by a packet-mode computer network
* Packet radio, a fo ...
format, and
routing methods provided by the
Internet Protocol
The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet.
...
.
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''.
Interconnection of 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 network
A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building. By contrast, a wide area network (WAN) not only covers a larger ...
s via some sort of
wide area network
A wide area network (WAN) is a telecommunications network that extends over a large geographic area. Wide area networks are often established with leased telecommunication circuits.
Businesses, as well as schools and government entities, u ...
.
The first international
resource sharing
In computing, a shared resource, or network share, is a computer resource made available from one host to other hosts on a computer network.
It is a device or piece of information on a computer that can be remotely accessed from another compu ...
network was the 1973 interconnection of the
ARPANET
The Advanced Research Projects Agency Network (ARPANET) was the first wide-area packet-switched network with distributed control and one of the first networks to implement the TCP/IP protocol suite. Both technologies became the technical fou ...
with early
British academic networks through the computer science department at
University College London
, mottoeng = Let all come who by merit deserve the most reward
, established =
, type = Public research university
, endowment = £143 million (2020)
, budget = ...
(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
The Cyclades (; el, Κυκλάδες, ) are an island group in the Aegean Sea, southeast of mainland Greece and a former administrative prefecture of Greece. They are one of the island groups which constitute the Aegean archipelago. The name ...
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
SATNET, also known as the Atlantic Packet Satellite Network, was an early satellite network that formed an initial segment of the Internet. It was implemented by BBN Technologies under the direction of the Advanced Research Projects Agency.
T ...
. In 1977, ARPA demonstrated a three-way internetworking experiment, which linked a mobile vehicle in
PRNET
The Packet Radio Network (PRNET) was a set of early, experimental mobile ad hoc networks whose technologies evolved over time. It was funded by the Advanced Research Projects Agency (ARPA). Major participants in the project included BBN Technol ...
with nodes in the ARPANET, and via SATNET, to nodes at UCL. The
X.25
X.25 is an ITU-T standard protocol suite for packet-switched data communication in wide area networks (WAN). It was originally defined by the International Telegraph and Telephone Consultative Committee (CCITT, now ITU-T) in a series of drafts ...
protocol, on which
public data networks were based in the 1970s and 1980s, was supplemented by the
X.75 X.75 is an International Telecommunication Union (ITU) (formerly CCITT) standard specifying the interface for interconnecting two X.25
X.25 is an ITU-T standard protocol suite for packet-switched data communication in wide area networks (WAN). ...
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 network
A personal area network (PAN) is a computer network for interconnecting electronic devices within an individual person's workspace. A PAN provides data transmission among devices such as computers, smartphones, tablets and personal digital ass ...
s.
To build an internetwork, the following are needed:
A standardized scheme to
address
An address is a collection of information, presented in a mostly fixed format, used to give the location of a building, apartment, or other structure or a plot of land, generally using political boundaries and street names as references, along ...
packets to any host on any participating network; a standardized
protocol
Protocol may refer to:
Sociology and politics
* Protocol (politics), a formal agreement between nation states
* Protocol (diplomacy), the etiquette of diplomacy and affairs of state
* Etiquette, a code of personal behavior
Science and technolog ...
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
A network bridge is a computer networking device that creates a single, aggregate network from multiple communication networks or network segments. This function is called network bridging. Bridging is distinct from routing. Routing allows ...
s and
network switch
A network switch (also called switching hub, bridging hub, and, by the IEEE, MAC bridge) is networking hardware that connects devices on a computer network by using packet switching to receive and forward data to the destination device.
A netw ...
es. This is sometimes incorrectly termed internetworking, but the resulting system is simply a larger, single
subnetwork, and no internetworking
protocol
Protocol may refer to:
Sociology and politics
* Protocol (politics), a formal agreement between nation states
* Protocol (diplomacy), the etiquette of diplomacy and affairs of state
* Etiquette, a code of personal behavior
Science and technolog ...
, such as
Internet Protocol
The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet.
...
, 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
unreliable (not guaranteed)
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
In computer networking, the transport layer is a conceptual division of methods in the layered architecture of protocols in the network stack in the Internet protocol suite and the OSI model. The protocols of this layer provide end-to-end ...
protocol, such as
Transmission Control Protocol
The Transmission Control Protocol (TCP) is one of the main protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, the entire suite is common ...
(TCP), which provides a
reliable stream. Some applications use a simpler, connection-less transport protocol,
User Datagram Protocol
In computer networking, the User Datagram Protocol (UDP) is one of the core communication protocols of the Internet protocol suite used to send messages (transported as datagrams in packets) to other hosts on an Internet Protocol (IP) network ...
(UDP), for tasks which do not require reliable delivery of data or that require real-time service, such as
video streaming
Video on demand (VOD) is a media distribution system that allows users to access videos without a traditional video playback device and the constraints of a typical static broadcasting schedule. In the 20th century, broadcasting in the form of o ...
[
] or voice chat.
Catenet
Catenet is an obsolete term for a system of
packet-switched communication networks interconnected via
gateways.
The term was coined by
Louis Pouzin
Louis Pouzin (April 20, 1931 in Chantenay-Saint-Imbert, Nièvre, France) is a French computer scientist. He designed an early packet communications network, CYCLADES.
This network was the first actual implementation of the pure datagram model, ...
in October 1973 in a note circulated to the
International Networking Working Group The International Networking Working Group (INWG) was a group of prominent computer science researchers in the 1970s who studied and developed standards and protocols for computer networking. Set up in 1972 as an informal group to consider the tec ...
,
later published in a 1974 paper "''A Proposal for Interconnecting Packet Switching Networks"''. Pouzin was a pioneer in packet-switching technology and founder of the
CYCLADES
The Cyclades (; el, Κυκλάδες, ) are an island group in the Aegean Sea, southeast of mainland Greece and a former administrative prefecture of Greece. They are one of the island groups which constitute the Aegean archipelago. The name ...
network, at a time when ''network'' meant what is now called a
local area network
A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building. By contrast, a wide area network (WAN) not only covers a larger ...
. Catenet was the concept of linking these networks into a ''network of networks'' with specifications for compatibility of addressing and routing. The term catenet was gradually displaced by the short-form of the term internetwork, ''internet'' (lower-case ''i''), when the
Internet Protocol
The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet.
...
replaced earlier protocols on the
ARPANET
The Advanced Research Projects Agency Network (ARPANET) was the first wide-area packet-switched network with distributed control and one of the first networks to implement the TCP/IP protocol suite. Both technologies became the technical fou ...
.
Networking models
Two architectural models are commonly used to describe the protocols and methods used in internetworking. The
Open System Interconnection
The Open Systems Interconnection model (OSI model) is a conceptual model that 'provides a common basis for the coordination of SOstandards development for the purpose of systems interconnection'. In the OSI reference model, the communications ...
(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
In the seven-layer OSI model of computer networking, the network layer is layer 3. The network layer is responsible for packet forwarding including routing through intermediate routers.
Functions
The network layer provides the means of tran ...
(Layer 3) of the model.
The
Internet Protocol Suite
The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the sui ...
, also known as the
TCP/IP
The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suit ...
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
A Request for Comments (RFC) is a publication in a series from the principal technical development and standards-setting bodies for the Internet, most prominently the Internet Engineering Task Force (IETF). An RFC is authored by individuals or g ...
and
Internet standard
In computer network engineering, an Internet Standard is a normative specification of a technology or methodology applicable to the Internet. Internet Standards are created and published by the Internet Engineering Task Force (IETF). They allow ...
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
A long-running debate in computer science known as the Protocol Wars occurred from the 1970s to the 1990s when engineers, organizations and nations became polarized over the issue of which communication protocol would result in the best and most ...
. 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
The history of the Internet has its origin in information theory and the efforts of scientists and engineers to build and interconnect computer networks. The Internet Protocol Suite, the set of rules used to communicate between networks and de ...
References
{{Authority control, state=collapsed
Network architecture