| Computer network types|
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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 geographic distance, but also generally involves leased telecommunication circuits.
Ethernet and Wi-Fi are the two most common technologies in use for local area networks. Historical network technologies include ARCNET, Token Ring, and AppleTalk.
The increasing demand and usage of computers in universities and research labs in the late 1960s generated the need to provide high-speed interconnections between computer systems. A 1970 report from the Lawrence Radiation Laboratory detailing the growth of their "Octopus" network gave a good indication of the situation.
A number of experimental and early commercial LAN technologies were developed in the 1970s. Cambridge Ring was developed at Cambridge University starting in 1974.Ethernet was developed at Xerox PARC between 1973 and 1974. ARCNET was developed by Datapoint Corporation in 1976 and announced in 1977. It had the first commercial installation in December 1977 at Chase Manhattan Bank in New York.
In 1979, [ dubious ]the Electronic voting systems for the European Parliament was the first installation of a LAN connecting hundreds (420) of microprocessor-controlled voting terminals to a polling/selecting central unit with a multidrop bus with Master/slave (technology) arbitration.
The development and proliferation of personal computers using the CP/M operating system in the late 1970s, and later DOS-based systems starting in 1981, meant that many sites grew to dozens or even hundreds of computers. The initial driving force for networking was to share storage and printers, both of which were expensive at the time. There was much enthusiasm for the concept, and for several years, from about 1983 onward, computer industry pundits would regularly declare the coming year to be, "The year of the LAN".
In practice, the concept was marred by the proliferation of incompatible physical layer and network protocol implementations, and a plethora of methods of sharing resources. Typically, each vendor would have its own type of network card, cabling, protocol, and network operating system. A solution appeared with the advent of Novell NetWare which provided even-handed support for dozens of competing card and cable types, and a much more sophisticated operating system than most of its competitors. Netware dominated the personal computer LAN business from early after its introduction in 1983 until the mid-1990s when Microsoft introduced Windows NT.
Of the competitors to NetWare, only Banyan Vines had comparable technical strengths, but Banyan never gained a secure base. 3Com produced 3+Share and Microsoft produced MS-Net. These then formed the basis for collaboration between Microsoft and 3Com to create a simple network operating system LAN Manager and its cousin, IBM's LAN Server. None of these enjoyed any lasting success.
In 1983, TCP/IP was first shown capable of supporting actual defense department applications on a Defense Communication Agency LAN testbed located at Reston, Virginia.The TCP/IP-based LAN successfully supported Telnet, FTP, and a Defense Department teleconferencing application. This demonstrated the feasibility of employing TCP/IP LANs to interconnect Worldwide Military Command and Control System (WWMCCS) computers at command centers throughout the United States. However, WWMCCS was superseded by the Global Command and Control System (GCCS) before that could happen.
During the same period, Unix workstations were using TCP/IP networking. Although this market segment is now much reduced, the technologies developed in this area continue to be influential on the Internet and in both Linux and Apple Mac OS X networking—and the TCP/IP protocol has replaced IPX, AppleTalk, NBF, and other protocols used by the early PC LANs.
In 1979,the Electronic voting systems for the European Parliament was using 10 kilometers of simple unshielded twisted pair category 3 cable—the same cable used for telephone systems—installed inside the benches of the European Parliament Hemicycles in Strasbourg and Luxembourg.
Early Ethernet (10BASE-5 and 10BASE-2) used coaxial cable. Shielded twisted pair was used in IBM's Token Ring LAN implementation. In 1984, StarLAN showed the potential of simple unshielded twisted pair by using category 3 cable—the same cable used for telephone systems. This led to the development of 10BASE-T (and its twisted-pair successors) and structured cabling which is still the basis of most commercial LANs today.
While optical fiber cable is common for links between network switches, use of fiber to the desktop is rare.
In a wireless LAN, users have unrestricted movement within the coverage area. Wireless networks have become popular in residences and small businesses, because of their ease of installation. Most wireless LANs use Wi-Fi as it is built into smartphones, tablet computers and laptops. Guests are often offered Internet access via a hotspot service.
Network topology describes the layout of interconnections between devices and network segments. At the data link layer and physical layer, a wide variety of LAN topologies have been used, including ring, bus, mesh and star.
Simple LANs generally consist of cabling and one or more switches. A switch can be connected to a router, cable modem, or ADSL modem for Internet access. A LAN can include a wide variety of other network devices such as firewalls, load balancers, and network intrusion detection.Advanced LANs are characterized by their use of redundant links with switches using the spanning tree protocol to prevent loops, their ability to manage differing traffic types via quality of service (QoS), and their ability to segregate traffic with VLANs.
At the higher network layers, protocols such as NetBIOS, IPX/SPX, AppleTalk and others were once common, but the Internet protocol suite (TCP/IP) has prevailed as the standard of choice.
LANs can maintain connections with other LANs via leased lines, leased services, or across the Internet using virtual private network technologies. Depending on how the connections are established and secured, and the distance involved, such linked LANs may also be classified as a metropolitan area network (MAN) or a wide area network (WAN).
AppleTalk is a discontinued proprietary suite of networking protocols developed by Apple Inc. for their Macintosh computers. AppleTalk includes a number of features that allow local area networks to be connected with no prior setup or the need for a centralized router or server of any sort. Connected AppleTalk-equipped systems automatically assign addresses, update the distributed namespace, and configure any required inter-networking routing.
Ethernet is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 1983 as IEEE 802.3. Ethernet has since been refined to support higher bit rates, a greater number of nodes, and longer link distances, but retains much backward compatibility. Over time, Ethernet has largely replaced competing wired LAN technologies such as Token Ring, FDDI and ARCNET.
Wake-on-LAN (WoL) is an Ethernet or Token Ring computer networking standard that allows a computer to be turned on or awakened by a network message.
A wide area network (WAN) is a telecommunications network that extends over a large geographic area for the primary purpose of computer networking. Wide area networks are often established with leased telecommunication circuits.
A network operating system (NOS) is a specialized operating system for a network device such as a router, switch or firewall.
Network topology is the arrangement of the elements of a communication network. Network topology can be used to define or describe the arrangement of various types of telecommunication networks, including command and control radio networks, industrial fieldbusses and computer networks.
A metropolitan area network (MAN) is a computer network that interconnects users with computer resources in a geographic region of the size of a metropolitan area. The term MAN is applied to the interconnection of local area networks (LANs) in a city into a single larger network which may then also offer efficient connection to a wide area network. The term is also used to describe the interconnection of several local area networks in a metropolitan area through the use of point-to-point connections between them.
Attached Resource Computer NETwork is a communications protocol for local area networks. ARCNET was the first widely available networking system for microcomputers; it became popular in the 1980s for office automation tasks. It was later applied to embedded systems where certain features of the protocol are especially useful.
A virtual private network (VPN) extends a private network across a public network and enables users to send and receive data across shared or public networks as if their computing devices were directly connected to the private network. Applications running across a VPN may therefore benefit from the functionality, security, and management of the private network. It provides access to resources that may be inaccessible on the public network, and is typically used for telecommuting workers. Encryption is a common, although not an inherent, part of a VPN connection.
The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between nodes on a network segment across the physical layer. The data link layer provides the functional and procedural means to transfer data between network entities and may also provide the means to detect and possibly correct errors that can occur in the physical layer.
NetBIOS is an acronym for Network Basic Input/Output System. It provides services related to the session layer of the OSI model allowing applications on separate computers to communicate over a local area network. As strictly an API, NetBIOS is not a networking protocol. Older operating systems ran NetBIOS over IEEE 802.2 and IPX/SPX using the NetBIOS Frames (NBF) and NetBIOS over IPX/SPX (NBX) protocols, respectively. In modern networks, NetBIOS normally runs over TCP/IP via the NetBIOS over TCP/IP (NBT) protocol. This results in each computer in the network having both an IP address and a NetBIOS name corresponding to a host name. NetBIOS is also used for identifying system names in TCP/IP(Windows). Simply saying, it is a protocol that allows communication of files and printers through the Session Layer of the OSI Model in a LAN.
Ungermann-Bass, also known as UB and UB Networks, was a computer networking company in the 1980s to 1990s. Located in Santa Clara, California, in Silicon Valley, UB was the first large networking company independent of any computer manufacturer. UB was founded by Ralph Ungermann and Charlie Bass. John Davidson, vice president of engineering, was one of the creators of NCP, the transport protocol of the ARPANET before TCP.
A network interface controller is a computer hardware component that connects a computer to a computer network.
In telecommunications networks, a node is either a redistribution point or a communication endpoint. The definition of a node depends on the network and protocol layer referred to. A physical network node is an electronic device that is attached to a network, and is capable of creating, receiving, or transmitting information over a communication channel. A passive distribution point such as a distribution frame or patch panel is consequently not a node.
LattisNet was a family of computer networking hardware and software products built and sold by SynOptics Communications during the 1980s. Examples were the 1000, 2500 and 3000 series of LattisHub network hubs. LattisNet was the first implementation of 10 Megabits per second local area networking over unshielded twisted pair wiring in a star topology.
Local Area Transport (LAT) is a non-routable networking technology developed by Digital Equipment Corporation to provide connection between the DECserver terminal servers and Digital's VAX and Alpha and MIPS host computers via Ethernet, giving communication between those hosts and serial devices such as video terminals and printers. The protocol itself was designed in such a manner as to maximize packet efficiency over Ethernet by bundling multiple characters from multiple ports into a single packet for Ethernet transport. Over time, other host implementations of the LAT protocol appeared allowing communications to a wide range of Unix and other non-Digital operating systems using the LAT protocol.
Industrial Ethernet (IE) is the use of Ethernet in an industrial environment with protocols that provide determinism and real-time control. Protocols for industrial Ethernet include EtherCAT, EtherNet/IP, PROFINET, POWERLINK, SERCOS III, CC-Link IE, and Modbus TCP. Many industrial Ethernet protocols use a modified Media Access Control (MAC) layer to provide low latency and determinism. Some microcontrollers such as Sitara provide industrial Ethernet support.
A computer network is a group of computers that use a set of common communication protocols over digital interconnections for the purpose of sharing resources located on or provided by the network nodes. The interconnections between nodes are formed from a broad spectrum of telecommunication network technologies, based on physically wired, optical, and wireless radio-frequency methods that may be arranged in a variety of network topologies.
In audio and broadcast engineering, Audio over Ethernet is the use of an Ethernet-based network to distribute real-time digital audio. AoE replaces bulky snake cables or audio-specific installed low-voltage wiring with standard network structured cabling in a facility. AoE provides a reliable backbone for any audio application, such as for large-scale sound reinforcement in stadiums, airports and convention centers, multiple studios or stages.
'The Year of The LAN' is a long-standing joke, and I freely admit to being the comedian that first declared it in 1982...
...you will remember numerous computer magazines, over numerous years, announcing 'the year of the LAN.'
...a bit like the Year of the LAN which computer industry pundits predicted for the good part of a decade...
As alternatives were considered, fiber to the desk was evaluated, yet only briefly due to the added costs for fiber switches, cables and NICs. "Copper is still going to be a driving force to the desktop for the future, especially as long as the price for fiber components remains higher than for copper."
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