Exercise 1 3 . Put “can, may, must, should, have to, be able to” (or the negative forms) and “needn’t” in the spaces.

1. “Oh, Nurse, ____________ I stay here?” “Stay here? Of course, you ___________.”

2. There are no buses or taxis, so we _______________walk.

3. No, Paula you _____________ have another potato. You’ve had two already.

4. We _____________ live without food and water. We ___________ eat and drink.

5. I _____________ get up early tomorrow, so I ______________ go to bed late tonight.

6. You _____________ walk all the way to the station. You ___________ take a bus round

  the corner.

7. You ___________ switch off the light if you’re afraid of the dark.

8. You ___________ sit there in your wet clothes; you will catch cold if you do.

9. They ____________ do all the exercises; it will be enough if they do four or five.

UNIT 10

Internet and lan TECHNOLOGY

 

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

1. application layer
2. aside
3. command-line interface
4. communications infrastructure
5. confusing
6. constitute
7. convenient
8. delegate
9. description
10. dial-up connection
11. efficient
12. embrace
13. establish
14. facilitate
15. fairly
16. fiber-optic line
17. free of charge
18. FTP
19. global
20. go on tour
21. Gopher
22. implementation
23. intermediate
24. Internet Engineering Task Force (IETF)
25. Internet Protocol Suite
26. knock out
27. lastly
28. layered system
29. make up
30. match
31. military
32. multi-lateral
33. Open Systems Interconnection (OSI)
34. owe
35. packet switching
36. participate
37. path
38. peering agreement
39. recipient
40. remote machine
41. Request for Comment (RFC)
42. retrieve
43. rigorous
44. scope
45. snail mail
46. socialize
47. standard-setting work group
48. stay in touch
49. subscribe
50. TCP/IP model
51. techno-jargon
52. Telnet
53. transfer
54. transport layer
55. USENET
56. vast

TEXT 10A. THE INTERNET

 

The Internet, a global computer network that embraces millions of users all over the world, began in the United States in 1969 as a military experiment. It was designed to survive a nuclear war. Information sent over the Internet takes the shortest path available from one computer to another. Because of this any two computers on the Internet will be able to stay in touch with each other as long as there is a single route between them. This technology is called packet switching. Owing to this technology, if some computers on the network are knocked out, information will just route around them. One such packet switching network that has already survived a war is the Iraqi computer network that was knocked out during the Gulf War.

Despite the confusing techno-jargon that surrounds it, the Internet is simple: computers talk to one another through a network that uses phone lines, cable, and fiber-optic lines.

At present more than 60 million people use the Internet and over five million computers worldwide are linked in. Most of the Internet host computers are in the United States, while the rest are located in more than 100 other countries. Although the number of host computers can be counted fairly accurately, nobody knows exactly how many people use the Internet, there are millions worldwide, and their number is growing by thousands each month. People use the Net for transferring data, playing games, socializing with other computer users, and sending e-mail.

The most popular Internet services are e-mail, reading USENET news, using the World Wide Web, telnet, FTP, information sites and Gopher.

 

The Internet can be divided into five broad areas:

Electronic mail

E-mail is much faster than traditional or snail mail because once the message is typed out, it arrives in the electronic mailbox of the recipient within minutes or seconds. Anything that can be digitized – pictures, sound, video –can be sent, retrieved and printed at the other end. This is efficient and convenient.

Information sites

This is perhaps the fastest growing area of the Internet as more and more people put their own information pages on line. One thing that computers do very well is processing vast amounts of data very fast, so, by specifying a key word or phrase, the computer can then search around the Net until it finds some matches. These information sites are usually stored on big computers that exist all over the world. The beauty of the Net is that you can access all of them from your home, using your own PC.

 

The World Wide Web

The World Wide Web usually referred to as WWW or 3W, is a vast network of information databases that feature text, visuals, sound, and video clips. On the WWW you can do such things as go on tour of a museum or art exhibition, see the latest images from outer space, go shopping, and get travel information on hotels and holidays.

 

USENET News

Usenet is a collection of newsgroups covering any topic. Newsgroups allow users to participate in dialogues and conversations by subscribing, free of charge. Each newsgroup consists of messages and information posted by other users. There are more than 10,000 newsgroups and they are popular with universities and businesses.

 

Telnet

Telnet programs allow you to use your personal computer to access a powerful mainframe computer. It is a network protocol used on the Internet or local area network connections (LANs). Telnet provides access to a command-line interface on a remote machine. Telnet clients are available for virtually all platforms.

 

Aside from the complex physical connections that make up its infrastructure, the Internet is facilitated by bi- or multi-lateral commercial contracts (peering agreements), and by technical specifications or protocols that describe how to exchange data over the network. Indeed, the Internet is defined by its interconnections and routing policies.

The complex communications infrastructure of the Internet consists of its hardware components and a system of software layers that control various aspects of the architecture. While the hardware can often be used to support other software systems, it is the design and the rigorous standardization process of the software architecture that characterizes the Internet.

The responsibility for the architectural design of the Internet software systems has been delegated to the Internet Engineering Task Force (IETF). The IETF conducts standard-setting work groups; open to any individual, about the various aspects of Internet architecture. Resulting discussions and final standards are published in Request for Comment (RFC), freely available on the IETF web site. The principal methods of networking that enable the Internet are contained in a series of RFC that constitute the Internet Standards. These standards describe a system known as the Internet Protocol Suite. This is a model architecture that divides methods into a layered system of protocols (e.g., RFC 1122, RFC 1123). The layers correspond to the environment or scope in which their services operate. At the top is the space (Application Layer) of the software application and just below it is the Transport Layer which connects applications on different host via the network (client-server model). The underlying network consists of two layers: the Internet Layer which enables computers to connect to one-another via intermediate (transit) networks and thus is the layer that establishes internetworking, and lastly, at the bottom, is a software layer that provides connectivity between hosts on the same local link, e.g., a local area network (LAN) or a dial-up connection. This model is also known as TCP/IP model of networking. While other models have been developed, such as the Open Systems Interconnection (OSI) model, they are not compatible in the details of description, nor implementation.

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