X. Fill in the gaps with the words from the box.

LAN and WAN were the original categories of area networks, while the others have gradually emerged over many years of technology evolution.

A LAN connects __1__ devices over a relatively short distance. A networked office building, school, or home usually contains a single LAN, though sometimes one building will contain a few small LANs. In __2__ networking, a LAN is often but not always implemented as a single IP__3__. In addition to __4__ in a limited space, LANs are also typically owned, controlled, and managed by a single person or __5__. They also tend to use certain connectivity __6__, primarily Ethernet and __7__.

As the term implies, a WAN spans a large physical __8__. The __9__ is the largest WAN, spanning the Earth. A WAN is a geographically-dispersed collection of LANs. A network device called a __10__ connects LANs to a WAN. In __11__ networking, the router maintains both a LAN address and a WAN address. A WAN differs from a LAN in several important ways. Most WANs (like the Internet) are not owned by any one organization but rather exist under collective or distributed __12__ and management. WANs tend to use __13__ like __14__, Frame Relay and X.25 for connectivity over the longer distances.

XI. While LAN and WAN are by far the most popular network types mentioned, you may also commonly see references to these others. Match other types of area networks with their definitions.

XII. Note that network types are a separate concept from network topologies such as bus, ring, star and tree. Match the topologies a) to the pictures and b) to the texts explaining how they function.

Text 1

It uses a common backbone to connect all devices. A single cable, the backbone functions as a shared communication medium that devices attach or tap into with an interface connector. A device wanting to communicate with another device on the network sends a broadcast message onto the wire that all other devices see, but only the intended recipient actually accepts and processes the message. They are relatively easy to install and don't require much cabling compared to the alternatives. However, these networks work best with a limited number of devices.

Text 2

In this network topology every device has exactly two neighbors for communication purposes. All messages travel in the same direction (either "clockwise" or "counterclockwise"). A failure in any cable or device breaks the loop and can take down the entire network. To implement it, one typically uses FDDI, SONET, or Token Ring technology. It may be found in some office buildings or school campuses.

Text 3

Many home networks use this topology type. It features a central connection point called a "hub node" that may be a network hub, switch or router. Devices typically connect to the hub with Unshielded Twisted Pair Ethernet. This network generally requires more cable, but a failure in any network cable will only take down one computer's network access and not the entire LAN.

Text 4

It integrates multiple star topologies together onto a bus. In its simplest form, only hub devices connect directly to the bus, and each hub functions as the root of a tree of devices. This bus/star hybrid approach supports future expandability of the network much better than a bus (limited in the number of devices due to the broadcast traffic it generates) or a star (limited by the number of hub connection points) alone.

XIII. Choose the correct word to complete the sentences.

1. The speed with which a modem can process data is measured in _____ .

a) bandwidth b) bits per second (bps) c) signal

2. Cables consisting of several copper wires each with a shield are known as ____ cables.

a) twisted pair b) optical fibre c) power cables

3. Computers that are connected together within one building form a ______ .

a) WAN b) ISP c) LAN

4. If you transfer a file from a remote computer to your computer, you _____ .

a) download b) upload c) run

5. To send out information is to _______ .

a) signal b) packet c) transmit

6. A document containing information and graphics that can be accessed on the Internet is ______ .

a) a website b) a web page c) the World Wide Web

XIV. How often do you shop online? Do you think e-commerce will ever replace traditional shopping?

Date: 2016-03-03; view: 2215