Computer networks

1) A network is an intricately connected system of objects or people. Networks are all around us, even inside us. Your own nervous system and cardiovascular system are networks.

Computers and computer networks have changed the way we do almost everything – the way we teach, learn, do research, access or share information, communicate with each other, and even the way we entertain ourselves. A computer network consists of two or more computing devices (often called nodes) interconnected by means of some medium capable of transmitting data that allows the computers to communicate with each other in order to provide a variety of services to users.

2) In the very early days, computer networks were relatively small, and computer or modem vendors tended to develop proprietary protocols that allowed their machines to communicate with each other, but not necessarily with those made by others. This created the need to interconnect two or more compatible or incompatible networks together to create an Internet, or a network of networks. In the mid1970s, TCP/IP (Transmission Control Protocol/ Internet Protocol) was developed and became the main communication protocol. Today, TCP/IP is the defacto standard and is available for almost all computers. When sending a file from one machine to another, TCP breaks it into a number of data packets, which also include other information such as the type of packet, source, and destination addresses. IP then takes over, routing those packets from the source to the destination, where TCP takes over and reassembles them into the original file.

3) Networks that span a local area such as one or more neighboring buildings are called local-area networks, or LANs. Ethernet is by far the most widely used LAN technology today. LANs make it possible for businesses that use computer technology to share, efficiently, such items as files and printers, and to make possible communications such as e-mail.

As computer use in businesses grew, it soon became apparent that even LANs were not sufficient. In a LAN system, each department, or business was a kind of electronic island. What was needed was a way for information to move efficiently and quickly from one business to another. The solution was the creation of metropolitan-area networks (MANs) and wide-area networks (WANs). Generally, a MAN spans a larger geographic area than a LAN, but a smaller geographic area than a WAN. Because WANs connected user networks over a large geographical area, they made it possible for businesses to communicate with each other across great distances. As a result of being networked or connected, computers, printers, and other devices on a WAN could communicate with each other to share information and resources, as well as to access the Internet. Some common WAN technologies are: modems, ISDN (Integrated Services Digital Network), ADSL (Asymmetric Digital Subscriber Line), Frame Relay, ATM (Asynchronous Transfer Mode), The T (US) and E (Europe) Carrier Series: T1, E1, T3, E3, etc., SONET (Synchronous Optical Network)

LANs, MANs and WANs have always had one thing in common, though, and that is the use of the term bandwidth to describe their capabilities. Bandwidth is the measure of how much information can flow from one place to another in a given amount of time.

4) Client/server and peer-to-peer are phrases used to describe networks with different types of hierarchy and access control. Client/server computing describes distributed network systems in which transaction responsibilities are divided into two parts: client (front end) and server (back end). Peer-to-peer computing calls for each network device to run both client and server portions of an application.

During your study of networking, you will hear references to the word medium. (Note: The plural form of medium is media.) In networking, a medium is a material through which data packets travel. It could be any of the following materials:

• telephone wires

• Category 5 UTP (Unshielded Twisted Pair) (used for Ethernet)

• coaxial cables (used for cable TV)

• optical fibers (thin glass fibers that carry light)

• atmosphere (carries radio waves, microwaves, and light).

(From Cisco Networking Academy)

Task 4. Answer these questions about the text.

1. Using computers as stand-alone devices is ineffective for businesses, isn’t it? Why?

2. What does a data packet include?

3. What are LANs designed for?

4. What is the difference between client/server computing and peer-to-peer computing?

5. What are the media types used in networking?

Task 5. Decide if the statement is true, false or there is no information

in the text.

1. Computer networks appeared because people wanted something more quick and efficient than a conventional postal service.

2. TCP/IP was developed in 1980s.

3. A peer-to-peer network does not have any dedicated servers or hierarchy among its computers.

4. Routers make logical decisions regarding the best path for the delivery of data.

Task 6. Using the paragraph number references given, look back in the text and find words that have a similar meaning to.

1) environment (1)

2) sender address (2)

3) finding a path (2)

4) covers (3)

5) move (4)

Task 7. Choose the correct words.

1. ADSL is more commonly known as __________.

A. longband B. broadband C. wideband

2. Broadband Internet connection is much faster than _________.

A. dial-in B. dial-through C. dial-up

3. Each time you want to connect to the network, you have to enter a log-in name and a __________.

A. security word B. safe word C. password

4. With dial-up, you can usually choose a ________ tariff.

A. pay-as-you-go B. pay-what-you-want C. pay-if-you-like

5. Some broadband contracts limit the amount of _________ you can have each month.

A. pages B. traffic C. use

6. Looking at web pages can be called "navigating the Web" but is more commonly called ________.

A. "surfing the net" B. "skiing the net" C. "swimming the net"

7. When your computer is not connected to the Internet, it is ________.

A. out of line B. offline C. off the line

8. An unexpected disconnection from the Internet is called a __________.

A. lost connection B. missed connection C. dropped connection

9. A file which is copied from the Internet onto your computer is called _____.

A. an upload B. a download C. a load

10. The word “blog” which means “online journal” originates from _______.

A. “block” B. “web log” C. “best log”

11. The word “spam” originates from _________.

A. “spice and ham” B. “spend and have” C. “spoiled ham”

Task 8. Match the network topologies with their descriptions.

Bus / Ethernet Star Switched Ring

1) In this configuration, the central computer performs all processing and control functions. All access devices are linked directly to the central computer. The configuration has two major limitations. First of all, the remote devices are unable to communicate directly. Instead, they must communicate via the central computer only. Secondly, the network is very susceptible to failure, either in the central computer or the transmission links.

2) The central device, which could be a telephone exchange, is used to connect different devices on the network directly. Once the link is established, the two devices communicate as though they were directly linked without interference from any other device. At the end of the session, the connection is closed, freeing capacity for other users and allowing access to other devices. Multiple switches can be used to create alternative transmission routes.

3) Each device is attached to a network shaped as a continuous loop. Data proceeds in only one direction and at a constant speed round the loop. Devices may send information only when they are in control of the 'token'. The token is a package of data which indicates which device has control. The receiving device picks up the token, then clears it for another's use once it has received the message. Only one device may send data at any given moment, and each device must be working for the network to function.

4) This network consists of one piece of cable terminated at each end to which all devices are connected. In such a network, each device is able to broadcast a message when it has detected silence for a fixed period of time. All devices receive the broadcast and determine from the content of the message whether it was intended for them. The only problem occurs when two devices try to send at the same time. When a sending device detects another's transmission, it aborts its own.

Task 9. Read the text and choose the correct words.

What's the difference between the Web and the Internet?

Some people think that the Internet and the Web are the same thing, but in fact they are different. The Internet (often called simply "the net") is a global (1) network/ net of interconnected computers. These computers communicate with each other (2) over / through existing telecommunications networks – principally, the telephone system. The Word Wide Web (usually known as just "the Web") is the billions of web pages that are stored on large computers called web (3) servers / services.

To (4) see / access the web, you may need a computer and a modem. You then connect over your telephone line to an Internet Service (5) Port / Provider (ISP), which sends your request to view a particular web page to the correct web server.

Websites are not the only service available on the Internet. It is also used for many other functions, including sending and receiving e-mail, and connecting to newsgroups and (6) discussion / talking groups.

You could say that the Internet is a system of roads, and web pages and e-mails are types of traffic that travel on those roads.

Task 10. Choose the correct word to complete each sentence. You may change some words slightly. Consult the Appendix for confusable words.

describe, proscribe, inscribe, prescribe

1. The name of the National hero was _______ on the memorial plaque.

2. The medicine was made as the doctor had _______.

3. The word alphanumeric is used to _______data that contains numbers and letters.

4. Bringing food and drinks into computer laboratories is strictly __________.

export, deport, report, import

5. Oil and gas are the main _______ of Russia.

6. The notorious spy was _______ from the country.

7. If there is an attempt of an unauthorised access, the security system ________ to an administrator.

8. DTP software can ________ text and graphics from another application.

express, oppress, impress, depress

9. He was really _______ by his failure in the exam.

10. I must _______ my thanks for your help.

11. I was hoping to _______ my new boss with my computer skills.

12. The rural poor were _______ by the land-owners.

Writing and Translation

Task 11. Make the written translation into Russian (3,000 characters).