UNIT 11

NETWORKS

Vocabulary Bank Unit 11

Task 1. Memorize the following words and word-combinations:

1. associated

2. accept

3. allow, enable

4. bridge

5. cohesive architecture

6. common

7. convert data

8. cover

9. dictate

10. establish

11. gateway

12. high-capacity storage device

13. implement

14. individual

15. interconnect

16. Internet backbone

17. introduce

18. local-area network

19. network

20. node

21. optical fibre

22. particular

23. seamless

24. search engine

25. searching software

26. share resources

27. sophisticated

28. tap into a network

29. transfer point

30. typically

31. variety

32. wide-area network

33. wiring technology

Text 11 A. COMPUTER NETWORKS

A computer network is a series of connections and associated devices through which computers can communicate with other computers. 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.

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. Open System Interconnection (OSI) and IBM's System Network Architecture are two popular architectures used at present.

Local-area networks and wide-area networks 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 square km. 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 access 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. 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 best example of a WAN is the Internet, a collection of networks and gateways linking millions of computer users on every continent. Networks within the Internet are linked by common communication programs and protocols. A protocol is a set of established standards that enable computers to communicate with each other. A number of network protocols such as TCP/IP,X.25, ATM and Frame relay can be used for WANs. By means of the Internet, users can obtain a variety of information browsing via buttons, highlighted text, or sophisticated searching software known as search engines.