Network configurations

a

b

c

d

1 Star

In the star configuration, the central computer performs all processing and control functions. All access devices are linked directly to the central computer. The star 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 star network is very susceptible to failure, either in the central computer or the transmission links.

2 Switched

The central switch, which could be а 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 Ring

Each device is attached to а network shaped as а continuous loop. Data proceeds in only one direction and at а constant speed round the loop. Devices may send information only when they are in control of the 'token'. The token is а 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 Bus/Ethernet

А bus network consists of one piece of cable terminated at each end to which all devices are connected. In а bus-based 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 а sending device detects another's transmission, it aborts its own.

B These are answers to questions about the texts. Write the questions.

1. To connect different devices on the network directly.

2. No, it goes in only one direction round the loop.

3. No, only one device may send data at any given moment.

4. From the content of the massage.

5. It cancels its own transmission

CWhich of the network configurations does this flowchart refer to?

Exercise 5. The columns below describe characteristics of the bus and ring configurations. Which column refers to which configuration? How did you decide?

a b

varied time response calculable time response

easy expansion difficult reconfiguration

fault-tolerant fault-intolerant

simple more complex

Exercise 6. Speaking.

Work in pairs. А and В, using the information in the advertisement opposite. Prepare the role-play in advance and try not to refer to the advertisement during the activity.

Student А: You are а customer interested in the Netplan Eazy Kit. Before deciding whether to buy it ask questions to find out:

1. what you need in order to use the Netplan Eazy Kit.

2. the total number of PCs you can run on it.

3. the cost of adding additional PCs.

4. how difficult it is to install.

5. what software it runs.

6. the other features offered.

Student В: You represent the makers of the Netplan Eazy Kit. Make notes about the features of the product. Answer any questions and try to encourage the customer to buy it.

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