![](http://image.absoluteastronomy.com/images//topicimages/noimage.gif)
Internetworking
Encyclopedia
Internetworking is the practice of connecting a computer network
with other networks through the use of gateways
that provide a common method of routing information packets between the networks. 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, but unified by an internetworking protocol
standard, the Internet Protocol Suite
, often also referred to as TCP/IP.
To avoid confusion, internetworking combines the word inter ("between") and networking; it is not internet-working.
The smallest amount of effort to create an internet (lowercase i, not talking about the Internet), is to have two LAN's of computers connected to each other via a router. Simply using either a switch or a hub to connect two local area networks together doesn't imply internetworking, it just expands the original LAN.
s via some sort of wide area network
. The original term for an internetwork was catenet
.
The definition of an internetwork today includes the connection of other types of computer networks such as personal area network
s.
The network elements used to connect individual networks in the ARPANET
, the predecessor of the Internet, were originally called gateways
, but the term has been deprecated in this context, because of possible confusion with functionally different devices. Today the interconnecting gateways are called Internet routers.
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 bridges and network switch
es. This is sometimes incorrectly termed internetworking, but the resulting system is simply a larger, single subnetwork
, and no internetworking 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.
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
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 or voice chat.
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 called the TCP/IP model of the Internet was not designed to conform to the OSI model and does not refer to it in any of the normative specifications in Requests for Comment and Internet standard
s. Despite similar appearance as a layered model, it uses a much less rigorous, loosely defined architecture that concerns itself only with the aspects of logical networking. It does not discuss hardware-specific low-level interfaces, and assumes availability of a Link Layer
interface to the local network link to which the host is connected. Internetworking is facilitated by the protocols of its Internet Layer
.
Computer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....
with other networks through the use of gateways
Gateway (telecommunications)
In telecommunications, the term gateway has the following meaning:*In a communications network, a network node equipped for interfacing with another network that uses different protocols....
that provide a common method of routing information packets between the networks. The resulting system of interconnected networks is called an internetwork, or simply an internet.
The most notable example of internetworking is the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
, a network of networks based on many underlying hardware technologies, but unified by an internetworking protocol
Communications protocol
A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications...
standard, the Internet Protocol Suite
Internet protocol suite
The Internet protocol suite is the set of communications protocols used for the Internet and other similar networks. It is commonly known as TCP/IP from its most important protocols: Transmission Control Protocol and Internet Protocol , which were the first networking protocols defined in this...
, often also referred to as TCP/IP.
To avoid confusion, internetworking combines the word inter ("between") and networking; it is not internet-working.
The smallest amount of effort to create an internet (lowercase i, not talking about the Internet), is to have two LAN's of computers connected to each other via a router. Simply using either a switch or a hub to connect two local area networks together doesn't imply internetworking, it just expands the original LAN.
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 networkLocal area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...
s via some sort of wide area network
Wide area network
A wide area network is a telecommunication network that covers a broad area . Business and government entities utilize WANs to relay data among employees, clients, buyers, and suppliers from various geographical locations...
. The original term for an internetwork was catenet
Catenet
Catenet is an obsolete term for a system of packet-switched communication networks interconnected via gateways.The term was coined by Louis Pouzin, a pioneer in packet-switching technology and founder of the CYCLADES network, at a time when network meant what is now called a local area network...
.
The definition of an internetwork today includes the connection of other types of computer networks such as personal area network
Personal area network
A personal area network is a computer network used for communication among computer devices, including telephones and personal digital assistants, in proximity to an individual's body. The devices may or may not belong to the person in question. The reach of a PAN is typically a few meters...
s.
The network elements used to connect individual networks in the ARPANET
ARPANET
The Advanced Research Projects Agency Network , was the world's first operational packet switching network and the core network of a set that came to compose the global Internet...
, the predecessor of the Internet, were originally called gateways
Gateway (telecommunications)
In telecommunications, the term gateway has the following meaning:*In a communications network, a network node equipped for interfacing with another network that uses different protocols....
, but the term has been deprecated in this context, because of possible confusion with functionally different devices. Today the interconnecting gateways are called Internet routers.
Another type of interconnection of networks often occurs within enterprises at the Link Layer
Link Layer
In computer networking, the link layer is the lowest layer in the Internet Protocol Suite , the networking architecture of the Internet . It is the group of methods or protocols that only operate on a host's link...
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 bridges and network switch
Network switch
A network switch or switching hub is a computer networking device that connects network segments.The term commonly refers to a multi-port network bridge that processes and routes data at the data link layer of the OSI model...
es. This is sometimes incorrectly termed internetworking, but the resulting system is simply a larger, single subnetwork
Subnetwork
A subnetwork, or subnet, is a logically visible subdivision of an IP network. The practice of dividing a network into subnetworks is called subnetting....
, and no internetworking protocol
Communications protocol
A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications...
, such as Internet Protocol
Internet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
, 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.
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
Transport layer
In computer networking, the transport layer or layer 4 provides end-to-end communication services for applications within a layered architecture of network components and protocols...
protocol, such as Transmission Control Protocol
Transmission Control Protocol
The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
(TCP), which provides a reliable stream. Some applications use a simpler, connection-less transport protocol, User Datagram Protocol
User Datagram Protocol
The User Datagram Protocol is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol network without requiring...
(UDP), for tasks which do not require reliable delivery of data or that require real-time service, such as video streaming 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
International Organization for Standardization
The International Organization for Standardization , widely known as ISO, is an international standard-setting body composed of representatives from various national standards organizations. Founded on February 23, 1947, the organization promulgates worldwide proprietary, industrial and commercial...
(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
Network Layer
The network layer is layer 3 of the seven-layer OSI model of computer networking.The network layer is responsible for packet forwarding including routing through intermediate routers, whereas the data link layer is responsible for media access control, flow control and error checking.The network...
(Layer 3) of the model.
The Internet Protocol Suite
Internet protocol suite
The Internet protocol suite is the set of communications protocols used for the Internet and other similar networks. It is commonly known as TCP/IP from its most important protocols: Transmission Control Protocol and Internet Protocol , which were the first networking protocols defined in this...
, also called the TCP/IP model of the Internet was not designed to conform to the OSI model and does not refer to it in any of the normative specifications in Requests for Comment and Internet standard
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 .-Overview:...
s. Despite similar appearance as a layered model, it uses a much less rigorous, loosely defined architecture that concerns itself only with the aspects of logical networking. It does not discuss hardware-specific low-level interfaces, and assumes availability of a Link Layer
Link Layer
In computer networking, the link layer is the lowest layer in the Internet Protocol Suite , the networking architecture of the Internet . It is the group of methods or protocols that only operate on a host's link...
interface to the local network link to which the host is connected. Internetworking is facilitated by the protocols of its Internet Layer
Internet layer
The internet layer or IP layer is a group of internetworking methods in the Internet protocol suite, commonly also called TCP/IP, which is the foundation of the Internet...
.