Text D. Types of networks

There are different types and sizes of networks.

A Local Area Network (LAN) is used to connect computers spread over a relatively small area. LANs are usually placed in the same building. They can be built with two main types of architecture: peer-to-peer, where the two computers have the same capabilities, or client-server, where one computer acts as the server containing the main hard disk and controlling the other workstations or nodes, all the devices linked in the network (e.g. printers, computers, etc.).

Computers in a LAN need to use the same protocol, or standard of communication. Ethernet is one of the most common protocols for LANs.

A router, a device that forwards data packets, is needed to link a LAN to another network, e.g. to the Net.

If your personal computer is connected to a network, it is called a network workstation. If your PC is not connected to a network, it is referred to as a standalone computer.

In order to connect to a network, your computer will need a network adapter. This circuitry and port could be built into the motherboard or it could be on a network interface card (NIC) in one of the computer’s expansion slots.

Typically in a LAN, hardware is connected by a cable but new Wi-Fi, wireless fidelity technologies allow the creation of WLANs, where cables or wires are replaced by radio waves.

A LAN which uses radio waves rather than cables to transmit the data from machine to machine is called a wireless local area network (WLAN).

To build a WLAN you need access points, radio-based receiver-transmitters that are connected to the wired LAN, and wireless adapters installed in your computer to link it to the network.

Hotspots are WLANs available for public use in places like airports and hotels, but sometimes the service is also available outdoors (e.g. university campuses, squares, etc.).

A wide area network (WAN) is a network which is spread over a large geographical area. WANs have no geographical limit and may connect computers or LANs on opposite sides of the world. They are usually linked through telephone lines, fiber-optic cables or satellites. The main transmission paths within a WAN are high-speed links called backbones.

Wireless WANs use mobile telephone networks. The largest WAN in existence is the Internet.

The ideas associated with LANs and WLANs of sharing data and making communications easier are still true with WANs. The difference is that because of the greater distances involved it is not possible to link the computers with cables or by radio.

A WAN normally uses communication media provided by a third party. An

example would be a telephone company providing links via telephone cables or via broadband facilities.

Often, several LANs are linked up by a WAN. For example, a firm that has offices in London, Lahore and Colombo would probably use LANs in each of the offices. The company would then use telecommunication media to link the individual LANs together as a WAN.

1) Define the terms LAN, WLAN and WAN.

2) What is the difference between a LAN and a WAN?

3) Is the Internet a LAN or a WAN?

3.9 Now read and memorize these definitions:

A bridge is a hardware and software combination used to connect the same type of networks. Bridges can also partition a large network into two smaller ones and connect two LANs that are nearby each other.

A router is a special computer that directs communicating messages when several networks are connected together. High-speed routers can serve as part of the Internet backbone.

A gateway is an interface that enables dissimilar networks to communicate, such as two LANs based on different topologies or network operating systems.

A backbone is the main transmission path, handling the major data traffic, connecting different LANs together.

A LAN is a network contained within a small area, for example a company department.

A modem is a device for converting digital signals to analogue signals and vice versa to enable a computer to transmit and receive data using an ordinary telephone line.

3.10 Complete these definitions with the correct participle given in brackets.

1. A gateway is an interface (enable) dissimilar networks to communicate.

2. A bridge is a hardware and software combination (use) to connect the same type of networks.

3. A backbone is a network transmission path (handle) major data traffic.

4. A router is a special computer (direct) messages when several networks are linked.

5. A network is a number of computers and peripherals (link) together.

6. A LAN is a network (connect) computers over a small distance such as within a company.

7. A server is a powerful computer (store) many programs (share) by all the clients in the network.

8. A client is a network computer (use) for accessing a service on a server.

9. A thin client is a simple computer (comprise) a processor and memory, display, keyboard, mouse and hard drives only.

10. A hub is an electronic device (connect) all the data cabling in a network.

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