IGCSE ICT - Chapter 4: Computer Networks (basics)

Local Area Network (LAN)

A Local Area Network is a network confined to one building or site. Often a LAN is a private network belonging to an organisation or business. Because LANs are geographically small, they usually use cables or low-power radio (wireless) for the connections.

Network Interface Card (NIC)

A computer that is connected to the network needs a NIC and is usually built into the motherboard

Network Hub

A device that connects a number of computers together to make a LAN. If it receives a message, it sends it to every computer known as broadcasting data packets to every computer in a LAN.

Modem

A device that joins a digital computer to a analogue telephone-line connection (dial-up). It is an analogue to digital converter and vice versa

Bridge

A network device that typically links together two different parts of a LAN. It links independent parts of a LAN so they act as a single LAN

Wide Area Network (WAN)

A wide area network is a network that extends over a large area. A WAN is often created by joining several LANs together (businesses in different countries) by optical fibres, satellite or microwave radio links because of the large distance. E.g Internet

Wireless Local Area Network (WLAN)

A wireless LAN (WLAN) is a LAN that uses radio signals (WiFi) to connect computers instead of cables (like LAN). It has a wireless modem/switch at the centre that is used for sending and receiving data

Internet

A worldwide network that is accessible to anyone

Router

An electronic device used to connect two or more networks. and usually to the Internet, by radio signals or wire. This allows data to be transferred from one network to the other.

Clients (workstations)

Client computers, or workstations, are the normal computers that people sit at to get their work done.

Disadvantages of networks

The computer is vulnerable to hackers If the network breaks, many tasks become very difficult Your computer can more easily be attacked by a virus

Network

Two or more computers or electrical devices connected together to enable data exchange

Uses of routers

Used to connect LANs together and to connect them to the internet Might be a wireless router and connect WLANs. Might link a LAN to a WAN (the internet)

Network/ethernet cable

Used to connect devices in a network. They have faster data transfer speeds and are less open to hacking

What does a network allow you to do?

Easily share files and data Share resources such as printers and Internet connections Communicate with other network users (e-mail, instant messaging, video-conferencing, etc.) Store data centrally (using a file server) for ease of access and back-up Keep all of our settings centrally so we can use any workstation

What do the servers do?

Provide a central, common file storage area Share hardware such as printers Controlling who can or can't have access the network Sharing Internet connections

Servers

Servers are special, powerful computers that provide 'services' to the client computers on the network. They are more reliable and more expensive

Switch

Similar to a hub - connects a number of computers to make a LAN but is more smarter than a hub. When it receives a message, it checks who its addressed to and sends it to only that so they are more secure. Therefore, it directs data packets to computers in a LAN.