A local area network (LAN) is a computer network A computer network, often simply referred to as a network, is a collection of computers and devices connected by communications channels that facilitates communications among users and allows users to share resources with other users. Networks may be classified according to a wide variety of characteristics. This article provides a general covering a small physical area, like a home, office, or small groups of buildings, such as a school, or an airport. The defining characteristics of LANs, in contrast to wide area networks (WANs) A wide area network is a computer network that covers a broad area (i.e., any network whose communications links cross metropolitan, regional, or national boundaries ). This is in contrast with personal area networks (PANs), local area networks (LANs), campus area networks (CANs), or metropolitan area networks (MANs) which are usually limited to a, include their usually higher data-transfer rates, smaller geographic area, and lack of a need for leased telecommunication lines A leased line is a symmetric telecommunications line connecting two locations. It is sometimes known as a 'Private Circuit' or 'Data Line' in the UK. Unlike traditional PSTN lines it does not have a telephone number, each side of the line being permanently connected to the other. Leased lines can be used for telephone, data or Internet services.
ARCNET ARCNET is a local area network (LAN) protocol, similar in purpose to Ethernet or Token Ring. ARCNET was the first widely available networking system for microcomputers and became popular in the 1980s for office automation tasks. It has since gained a following in the embedded systems market, where certain features of the protocol are especially, Token Ring Token ring local area network technology is a local area network protocol which resides at the data link layer (DLL) of the OSI model. It uses a special three-byte frame called a token that travels around the ring. Token ring frames travel completely around the loop. Token-possession grants the possessor permission to transmit on the medium and many other technologies have been used in the past, and G.hn G.hn is the common name for a home network technology standard being developed under the International Telecommunication Union and promoted by the HomeGrid Forum and several other organizations. and several other organizations. It supports networking over power lines, phone lines and coaxial cables with data rates up to 1 Gbit/s may be used in the future, but Ethernet Ethernet is a family of frame-based computer networking technologies for local area networks . The name came from the physical concept of the ether. It defines a number of wiring and signaling standards for the Physical Layer of the OSI networking model as well as a common addressing format and Media Access Control at the Data Link Layer over twisted pair Twisted pair cabling is a type of wiring in which two conductors are twisted together for the purposes of canceling out electromagnetic interference (EMI) from external sources; for instance, electromagnetic radiation from unshielded twisted pair (UTP) cables, and crosstalk between neighboring pairs. It was invented by Alexander Graham Bell and he cabling, and Wi-Fi Wi-Fi is a trademark of the Wi-Fi Alliance that manufacturers may use to brand certified products that belong to a class of wireless local area network (WLAN) devices based on the IEEE 802.11 standards, which is by far the most widespread WLAN class today. Because of the close relationship with its underlying standards, the term Wi-Fi is often are the two most common technologies currently in use.
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History
As larger universities and research labs obtained more computers during the late 1960s, there was an increasing pressure to provide high-speed interconnections. A report in 1970 from the Lawrence Radiation Laboratory The Ernest Orlando Lawrence Berkeley National Laboratory , is a U.S. Department of Energy (DOE) national laboratory conducting unclassified scientific research. It is located on the grounds of the University of California, Berkeley, in the Berkeley Hills above the central campus. It is managed and operated by the University of California. The detailing the growth of their "Octopus" network[1][2] gives a good indication of the situation.
Cambridge Ring The Cambridge Ring was an experimental local area network architecture developed at the Cambridge University Computer Laboratory in the mid-late 1970s and early 1980s. It used a ring topology with a theoretical limit of 255 nodes , around which cycled a fixed number of packets. Free packets would be "loaded" with data by a machine was developed at Cambridge University in 1974[3] but was never developed into a successful commercial product.
Ethernet Ethernet is a family of frame-based computer networking technologies for local area networks . The name came from the physical concept of the ether. It defines a number of wiring and signaling standards for the Physical Layer of the OSI networking model as well as a common addressing format and Media Access Control at the Data Link Layer was developed at Xerox PARC PARC , formerly Xerox PARC, is a research and co-development company in Palo Alto, California with a distinguished reputation for its contributions to information technology and hardware systems in 1973–1975,[4] and filed as U.S. Patent 4,063,220. In 1976, after the system was deployed at PARC, Metcalfe and Boggs published their seminal paper, "Ethernet: Distributed Packet-Switching For Local Computer Networks."[5]
ARCNET ARCNET is a local area network (LAN) protocol, similar in purpose to Ethernet or Token Ring. ARCNET was the first widely available networking system for microcomputers and became popular in the 1980s for office automation tasks. It has since gained a following in the embedded systems market, where certain features of the protocol are especially was developed by Datapoint Datapoint Corporation, originally known as Computer Terminal Corporation , was a computer company based in San Antonio, Texas, United States. Founded in 1967 by Phil Ray, Gus Roche and Jerry Martin, its first products were, as the company's initial name suggests, computer terminals (intended to replace teletype units connected to time sharing Corporation in 1976 and announced in 1977.[6] It had the first commercial installation in December 1977 at Chase Manhattan Bank in New York.[7]
Standards evolution
The development and proliferation of CP/M CP/M is an operating system originally created for Intel 8080/85 based microcomputers by Gary Kildall of Digital Research, Inc. Initially confined to single-tasking on 8-bit processors and no more than 64 kilobytes of memory, later versions of CP/M added multi-user variations, and were migrated to 16-bit processors-based personal computers from the late 1970s and then DOS DOS, short for "Disk Operating System", is a shorthand term for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition-based personal computers A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end user, with no intervening computer operator. This is in contrast to the batch processing or time-sharing models which allowed large expensive mainframe from 1981 meant that a single site began to have dozens or even hundreds of computers. The initial attraction of networking these was generally to share disk space and laser printers, which were both very 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 proliferation of incompatible physical Layer The Physical Layer is the first and lowest layer in the seven-layer OSI model of computer networking. The implementation of this layer is often termed PHY and network protocol In computing and telecommunications, a protocol or communications protocol is a formal description of message formats and the rules for exchanging those messages. Protocols may include signaling, authentication and error detection and correction capabilities. In its simplest form, a protocol can be defined as the rules governing the syntax, 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 Some device operating systems, including Mac OS X and all versions of Microsoft Windows since Windows 2000, include NOS features. A NOS is an OS that has been specifically written to implement and maintain networks. A solution appeared with the advent of Novell NetWare NetWare is a network operating system developed by Novell, Inc. It initially used cooperative multitasking to run various services on a personal computer, and the network protocols were based on the archetypal Xerox Network Systems stack which provided even-handed support for dozens of competing card/cable types, and a much more sophisticated operating system than most of its competitors. Netware dominated[8] the personal computer LAN business from early after its introduction in 1983 until the mid 1990s when Microsoft introduced Windows NT Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. It was originally designed to be a powerful high-level-language-based, processor-independent, multiprocessing, multiuser operating system with features comparable to Unix. It was intended to complement consumer versions of Advanced Server and Windows for Workgroups Windows 3.1x is a series of 16-bit operating systems produced by Microsoft for use on personal computers. The series began with Windows 3.1, which was first sold during March 1992 as a successor to Windows 3.0. Further editions were released between 1992 and 1994 until the series was superseded by Windows 95.
Of the competitors to NetWare, only Banyan Vines Banyan VINES was a computer network operating system and the set of computer network protocols it used to talk to client machines on the network. The Banyan company based the VINES operating system on Unix, and the network protocols on the archetypical Xerox XNS stack. VINES formed one of a group of XNS-based systems which also included Novell had comparable technical strengths, but Banyan never gained a secure base. Microsoft Microsoft Corporation is a public multinational corporation based in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions. Established on April 4, 1975 to develop and sell BASIC interpreters for the Altair 8800, and 3Com 3Com was a digital electronics manufacturer best known for its computer network infrastructure products. The company was co-founded in 1979 by Robert Metcalfe, Howard Charney, Bruce Borden, and Greg Shaw, and is headquartered in Marlborough, Massachusetts. The name 3Com came from the company's focus on "Computers, Communication and worked together to create a simple network operating system which formed the base of 3Com's 3+Share, Microsoft's LAN Manager LAN Manager was a Network Operating System available from multiple vendors and developed by Microsoft in cooperation with 3Com Corporation. It was designed to succeed 3Com's 3+Share network server software which ran atop a heavily modified version of MS-DOS and IBM's LAN Server IBM LAN Server started as a close cousin of Microsoft LAN Manager and first shipped in early 1988. It was originally designed to run on top of Operating System/2 Extended Edition. The network client was called IBM LAN Requester and was included with OS/2 EE 1.1 by default. Here the short term LAN Server refers to the IBM OS/2 LAN Server product - but none of these were particularly successful.
During the same period, Unix Unix is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna. Today's Unix systems are split into various branches, developed over time by AT&T as well as various commercial vendors and non-profit computer workstations A workstation is a high-end microcomputer designed for technical or scientific applications. Intended primarily to be used by one person at a time, they are commonly connected to a local area network and run multi-user operating systems. The term workstation has also been used to refer to a mainframe computer terminal or a PC connected to a from vendors such as Sun Microsystems Sun Microsystems, Inc. is a wholly owned subsidiary of Oracle Corporation, selling computers, computer components, computer software, and information technology services. Sun was founded on February 24, 1982. The company was headquartered in Santa Clara, California , on the former west campus of the Agnews Developmental Center, Hewlett-Packard Hewlett-Packard Company , commonly referred to as HP, is an American multinational information technology corporation headquartered in Palo Alto, California, USA. HP is one of the world's largest information technology companies and operates in nearly every country. HP specializes in developing and manufacturing computing, data storage, and, Silicon Graphics Silicon Graphics, Inc. was a manufacturer of high-performance computing solutions, including computer hardware and software, founded in 1981 by Jim Clark and Abbey Silverstone. Its initial market was 3D graphics display terminals, but its products, strategies and market positions evolved significantly over time, Intergraph Intergraph Corporation is an American software development and services company. It provides enterprise engineering and geospatially powered software to businesses, governments, and organizations around the world. Intergraph operates through two divisions: Process, Power & Marine and Security, Government & Infrastructure (SG&I). The, NeXT Next, Inc. was an American computer company headquartered in Redwood City, California, that developed and manufactured a series of computer workstations intended for the higher education and business markets. NeXT was founded in 1985 by Apple Computer co-founder Steve Jobs after his forced resignation from Apple. NeXT introduced the first NeXT and Apollo Apollo Computer, Inc., founded 1980 in Chelmsford, Massachusetts by William Poduska , developed and produced Apollo/Domain workstations in the 1980s. Along with Symbolics and Sun Microsystems, Apollo was one of the first vendors of graphical workstations in the 1980s were using TCP/IP The Internet Protocol Suite is the set of communications protocols used for the Internet and other similar networks. It is named from two of the most important protocols in it: the Transmission Control Protocol (TCP) and the Internet Protocol (IP), which were the first two networking protocols defined in this standard. Today's IP networking based 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 Linux refers to the family of Unix-like computer operating systems using the Linux kernel. Linux can be installed on a wide variety of computer hardware, ranging from mobile phones, tablet computers and video game consoles, to mainframes and supercomputers. Linux is predominantly known for its use in servers; in 2009 it held a server market share and Apple Mac OS X Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, Mac OS X has been included with all new Macintosh computer systems. It is the successor to Mac OS 9, the final release of the "classic" Mac OS, which had been Apple's primary operating system since 198 networking—and the TCP/IP protocol has now almost completely replaced IPX Internetwork Packet Exchange is the OSI-model Network layer protocol in the IPX/SPX protocol stack, AppleTalk AppleTalk is a proprietary suite of protocols developed by Apple Inc. for networking computers. It was included in the original Macintosh released in 1984, and is now unsupported with the release of Mac OS X v10.6 in 2009 in favor of TCP/IP networking. AppleTalk's Datagram Delivery Protocol corresponds closely to the Network layer of the Open, NBF NetBIOS Frames or NBF protocol is a non-routable network- and transport-level data protocol most commonly used as one of the layers of Microsoft Windows networking in the 1990s. NBF protocol or NetBIOS over IEEE 802.2 LLC is used by a number of network operating systems released in the 1990s, such as LAN Manager, LAN Server, Windows for Workgroups, and other protocols used by the early PC LANs.
Cabling
Early LAN cabling had always been based on various grades of coaxial cable Coaxial cable, or coax, is an electrical cable with an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis. Coaxial cable was invented by English engineer and mathematician Oliver Heaviside,, but IBM's Token Ring Token ring local area network technology is a local area network protocol which resides at the data link layer (DLL) of the OSI model. It uses a special three-byte frame called a token that travels around the ring. Token ring frames travel completely around the loop. Token-possession grants the possessor permission to transmit on the medium used shielded twisted pair Twisted pair cabling is a type of wiring in which two conductors are twisted together for the purposes of canceling out electromagnetic interference (EMI) from external sources; for instance, electromagnetic radiation from unshielded twisted pair (UTP) cables, and crosstalk between neighboring pairs. It was invented by Alexander Graham Bell and he cabling of their own design, and in 1984 StarLAN The standard known as 1BASE5 was developed in the mid 1980s by members of the IEEE 802.3. StarLAN ran at a speed of 1Mbit/s. Patented by AT&T, it was adopted by other networking vendors such as Hewlett-Packard and Ungermann-Bass. StarLAN provided the basis for the later standard 10BASE-T showed the potential of simple Cat3 Category 3 cable, commonly known as Cat 3, is an unshielded twisted pair cable designed to reliably carry data up to 10 Mbit/s, with a possible bandwidth of 16 MHz. It is part of a family of copper cabling standards defined jointly by the Electronic Industries Alliance and the Telecommunications Industry Association unshielded twisted pair Twisted pair cabling is a type of wiring in which two conductors are twisted together for the purposes of canceling out electromagnetic interference (EMI) from external sources; for instance, electromagnetic radiation from unshielded twisted pair (UTP) cables, and crosstalk between neighboring pairs. It was invented by Alexander Graham Bell and he—the same simple cable used for telephone systems. This led to the development of 10Base-T Ethernet over twisted pair refers to the use of cables that contain insulated copper wires twisted together in pairs for the physical layer of an Ethernet network—that is, a network in which the Ethernet protocol provides the data link layer. Other Ethernet cable standards use coaxial cable or optical fiber. There are several different standards (and its successors) and structured cabling which is still the basis of most LANs today. In addition, fiber-optic cabling is increasingly used.
Technical aspects
Switched Ethernet is the most common Data Link Layer implementation on local area networks. At the Network Layer, the Internet Protocol has become the standard. However, many different options have been used in the history of LAN development and some continue to be popular in niche applications. Smaller LANs generally consist of one or more switches linked to each other—often at least one is connected to a router, cable modem, or ADSL modem for Internet access.
Larger 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 to segregate traffic with VLANs. Larger LANS also contain a wide variety of network devices such as switches, firewalls, routers, load balancers, and sensors.[9]
LANs may have connections with other LANs via leased lines, leased services, or by tunneling across the Internet using virtual private network technologies. Depending on how the connections are established and secured in a LAN, and the distance involved, a LAN may also be classified as metropolitan area network (MAN) or wide area networks (WAN)
See also
- Ethernet physical layer
- LAN messenger
- LAN party
- Metropolitan area network
- Network card
- Wide area network
References
- ^ "OCTOPUS: THE LAWRENCE RADIATION LABORATORY NETWORK", Samuel F. Mendicino
- ^ "THE LAWRENCE RADIATION LABORATORY OCTOPUS", Courant symposium series on networks, 29 Nov 1970
- ^ A brief informal history of the Computer Laboratory
- ^ "Ethernet Prototype Circuit Board". Smithsonian National Museum of American History. http://americanhistory.si.edu/collections/object.cfm?key=35&objkey=96. Retrieved 2007-09-02.
- ^ Ethernet: Distributed Packet-Switching For Local Computer Networks
- ^ "History", ARCNET Trade Association
- ^ "The LAN turns 30, but will it reach 40?"
- ^ Has Microsoft Ever Read the History Books? - IT Channel - IT Channel News by CRN and VARBusiness
- ^ "A Review of the Basic Components of a Local Area Network (LAN)". NetworkBits.net. http://networkbits.net/lan-components/local-area-network-lan-basic-components/. Retrieved 2008-04-08.
External links
- LAN design and sizing
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