Lesson 12

Read the text: Computer networks

For most businesses in the United States, computers are an essential part of their daily operations. Many businesses have come to rely on their computers to store and track information, communicate with customers and suppliers, design and manufacture products, and more. It is not uncommon for businesses of all sizes to have multiple computers in an office. Often, these computers are connected through networks that allow information to be shared between computers.

A computer network, as defined in the Merriam-Webster dictionary, is "a system of computers, peripherals, terminals, and databases connected by communications lines." In other words, networks are used to connect computers to other computers, as well as to other devices such as printers, scanners, and fax machines. Networks can be used to connect devices in the same building or they can be used to connect devices that are miles apart. Perhaps the most well known network in use today is the Internet. Many individuals and businesses around the world connect to the Internet on a daily basis. Other examples of networks include library card catalogs, the displays of flight arrival and departure times used at airports, and credit card readers at retail stores.

Networks can be set up in a number of different ways depending on the number of devices, the distances between those devices, the transmission speed requirements, and other factors. The most popular configurations, or topologies, include the bus, token ring, star, and star bus topologies.

With a bus configuration, each node is connected sequentially along the network backbone. A node is any device connected to the network, such as a computer, printer, or scanner. Backbone is the term used to describe the main cables to which the network segments are connected. Resistors are placed at each end of the network to ensure that the signal is terminated when it reaches the end. When one node sends information to another node through the network, the information travels along the backbone until it reaches the desired receiving node.

With a ring configuration, each node is connected sequentially along the network backbone. However, unlike the bus configuration, the end of the network connects to the first node, forming a circuit. Nodes on a token ring take turns sending and receiving information. In the token ring topology, a token travels along the backbone with the information being sent. The node with the token sends information to the next node along the backbone. The receiving node reads the information addressed to it and then passes the token and any additional information to the next node. This continues until the token and data make it back to the first node in the network.

With a star configuration, each node is connected to a central hub via network segments. When one node sends information to another node, the information passes through the hub. The hub does not filter or route the information in any way; it simply serves as a connector between network segment.

With a star bus configuration, the hubs of multiple star networks are connected together via the backbone. This is the most common network configuration in use.

Exercise 1. Learn the following words and word-combinations:

set up, node, sequentially, backbone, terminate, take turns, token, hub, bus

Exercise 2. Answer the questions:

1) What is a computer network?

2) What are networks used for?

3) How can networks be set up?

4) Where are the resistors placed?

5) What is the most common network configuration in use?

Exercise 3. Match the left column with the right:

a) Network topology transmit when in possession of a sequence of bits (called token) which is passed to each node in turn	1) Network in which a node can only
b) Token ring systems, terminals and other equipment allowing information to be exchanged	2) A system of interconnected computer
c) Network	3) The arrangement of various elements (links, nodes, etc.) of a computer network

Exercise 4. Find synonyms in the text to the following words:

1) found; 2) depend on; 3) keep; 4) join; 5) describe; 6) demand; 7) guarantee; 8) achieve; 9) acquire; 10) extra; 11) speak

Exercise 5. Compose a story on one of the topics (up to 100 words):

1) Bus configuration.

2) Token ring configuration.

3) Star configuration.