Computer Networks
A computer network consists of two or more computers that are interconnected in order to share resources (such as printers), exchange files, or allow electronic communications. In a computer network the individual stations, called ‘nodes’, may be computers, terminals, or communication units of various kinds. The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams. So, a computer network is a group of computers and other devices connected together in order to share information.
In addition to physically connecting computers and communication devices, a network system has the function of establishing a cohesive architecture that allows almost seamless data transmission while using various equipment types. ISO Open Systems Interconnection (OSI) and IBM’s Systems Network Architecture (SNA) are two popular architectures used at present.
Local area network (LANs) and wide area network are two basic network types.
A local area network (LAN) is a computer network that covers a local area. It may be a home, office or small group of buildings such as a college or factory. The topology of a network dictates its physical structure. The generally accepted maximum size for a LAN is 1 km 2 . At present, there are two common wiring technologies for a LAN, Ethernet and Token Ring. A LAN typically includes two or more PCs, printers, CD-ROMs and high-capacity storage devices called file servers, which enable each computer on the network to have access to a common set of files. A LAN is controlled by LAN operating system software. LAN users may also have access to other LANs or tap into wide area networks. LANs with similar architectures are linked by transfer points, called ‘bridges’, and LANs with different architectures use ‘gateways’ to convert data as it passes between systems. A router is used to make the connection between LANs.
A wide area network (WAN) is a computer network that covers a wide geographical area, involving a large number of computers. Computer networks may link the computers by means of cables, optical fibres, or satellites and modems, devices that allow computers to communicate over telephone lines. The best example of a WAN is the Internet, a collection of networks and gateways linking millions of computer users on every continent.
Typically, WANs are used to connect LANs together. Many WANs are built for one particular organization and are private, others, built by Internet service providers, provide connections from an organization’s LAN to the Internet. WANs are most often built of leased lines. At each end of the leased line, a router is used to connect to the LAN on one side and a hub within the WAN on the other. The defining characteristics of LANs in contrast to WANs are: a) much higher data rates; b) smaller geographic range – at most a few kilometers – and c) they do not involve leased telecommunication lines.
A number of network protocols such as TCP/IP, X.25, ATM and Frame relay can be used for WANs. A protocol is a set of communication rules to regulate the cooperation of two devices, to make sure that everyone speaks the same language.
Exercise 3. Answer the following questions.
- What does a computer network consist of? 2. What may the individual stations in the computer network be? What are they called? 3. How are the computers on a network linked? 4. What is a computer network? 5. What are the functions of a network system? 6. What is an architecture of a network system and what data transmission does it allow? 7. What are two popular architectures used at present? 8. What two basic network types are there? 9. What is a local area network? (In size, wiring technology, the way of access to a common set of files and to other LANs). 10. What does a LAN include? 11. What is a wide area network? 12. What may computers on the network be linked by? 13. What are modems? 14. What is the Internet? 15. What are WANs used for? 16. What is a protocol?
- складатися з 2-х або більше комп’ютерів
- обмінюватися файлами
- робити можливим електронний зв’язок (обмін даними)
- окремі станції, що називаються «вузлами»
- пристрої зв’язку різних видів
- комп’ютери у мережі
- інфрачервоні світлові промені
- разом користуватися інформацією
- окрім фізичного з’єднання комп’ютерів і пристроїв зв’язку
- функція створення зв’язаної архітектури
- допускати майже непомітну для користувача передачу даних
- незважаючи на використання різноманітних типів обладнання
- еталонна модель OSI, затверджена Міжнародною організацією по стандартизації
- архітектура мережних систем, розроблена корпорацією IBM
- у теперішній час
- комп’ютерна мережа, що охоплює обмежену ділянку
- невелика група будівель таких, як коледж або фабрика
- загальноприйнятий максимальний розмір для ЛОМ
- загальноприйняті комутаційні технології для ЛОМ
- состоять из 2-х или более компьютеров
- обмениваться файлами
- делать возможной электронную связь (обмен данными)
- отдельные станции, называемые «узлами»
- устройства связи различных видов
- компьютеры в сети
- инфракрасные световые лучи
- совместно пользоваться информацией
- кроме физического соединения компьютеров и устройств связи
- функция создания связанной архитектуры
- допускать почти незаметную для пользователя передачу данных
- несмотря на использование различных типов оборудования
- эталонная модель OSI, утвержденная Международной организацией по стандартизации
- архитектура сетевых систем, разработанная корпорацией IBM
- в настоящее время
- компьютерная сеть, которая охватывает ограниченный участок
- небольшая группа зданий, таких как колледж или фабрика
- общепринятый максимальный размер для ЛВС
- общепринятые коммутационные технологии для ЛВС
computer network
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computer network, two or more computers that are connected with one another for the purpose of communicating data electronically. Besides physically connecting computer and communication devices, a network system serves the important function of establishing a cohesive architecture that allows a variety of equipment types to transfer information in a near-seamless fashion. Two popular architectures are ISO Open Systems Interconnection (OSI) and IBM’s Systems Network Architecture (SNA).
Two basic network types are local-area networks (LANs) and wide-area networks (WANs). LANs connect computers and peripheral devices in a limited physical area, such as a business office, laboratory, or college campus, by means of links (wires, Ethernet cables, fibre optics, Wi-Fi) that transmit data rapidly. A typical LAN consists of two or more personal computers, printers, and high-capacity disk-storage devices called file servers, which enable each computer on the network to access a common set of files. LAN operating system software, which interprets input and instructs networked devices, allows users to communicate with each other; share the printers and storage equipment; and simultaneously access centrally located processors, data, or programs (instruction sets). LAN users may also access other LANs or tap into WANs. LANs with similar architectures are linked by “bridges,” which act as transfer points. LANs with different architectures are linked by “gateways,” which convert data as it passes between systems.
WANs connect computers and smaller networks to larger networks over greater geographic areas, including different continents. They may link the computers by means of cables, optical fibres, or satellites, but their users commonly access the networks via a modem (a device that allows computers to communicate over telephone lines). The largest WAN is the Internet, a collection of networks and gateways linking billions of computer users on every continent.
This article was most recently revised and updated by Erik Gregersen.