What is a Network?

A network is a group of connected digital devices, such as a home computer network, the Internet, a mobile phone network or a landline phone network.

A network can be wired (using cables for connectivity) or wireless (using radio wave frequency for connectivity). Any device (smartphone, PDA, laptop, desktop) that is connected to a wireless network is called a station and must be equipped with a wireless network interface controller. A station contains the client and an access point (AP) which is usually a router which transmits and receives radio signals. A peer-to-peer (P2P) network refers to a device which communicates wirelessly with another device

without using a central access point. A Local Area Network (LAN) is used to connect computers within an office or building. A Wide Area Network (WAN) is used to connect computers across different sites and locations. Networking computers together enables users to share information, resources and printers.

A network is used to:

 Share information – social network sites, wikis, forums, chat rooms

 Mobile communication – between digital devices such as mobile phones and computers. This can range from calls and texts (SMS and MMS) to instant messaging and VoIP

 Share files – access to files stored on a networked drive enables collaborative working and means that files can be accessed on more than one computer

 Share printers – multiple computers can share one printer, making it a cheaper option with less space required

 Play games – ability to connect with other users to play online games

 Access to the Internet – via a home computer network sharing the same broadband connection using Wi-Fi or wired connections or via a mobile phone network

Networks are typically created in the following places:

 Home – multiple computers can share resources, such as broadband, files and printer; home entertainment systems can be connected together throughout a household via wireless or wired connections. This is called a LAN or local area network (or WLAN: wireless local area network).

 School and business – multiple workstations are connected to a mains server (a computer which holds the programs and other resources) over a LAN. Several LANs may be linked together over multiple sites creating a WAN (wide area network). A computer that is not connected to a network is called a stand-alone computer.

A network can give you the following advantages:

 A printer can be shared by more than one computer

 Files can be shared between more than one computer

 Applications can be shared between more than one computer

 An internet connection can be shared by more than one computer

 Cheap computers can access a powerful computer (e.g. a web server) which does all the work and then gives the results back to the cheap computer. An example of this working is the search engine Google.

Types of Network

There are many types of network available.

 Internet – an interconnected network of computers containing web pages (World Wide Web) which can be accessed globally. The Internet uses a WAN.

 Mobile phone network – 3G (third generation) and 4G (fourth generation which supersedes 3G) is the wireless network standard used in mobile phone technology and provides wireless mobile telephone and mobile Internet connectivity (sometimes referred to as mobile broadband).

 LAN and WLAN – a LAN (local area network) is a network which enables communication and sharing of files programs and printers within a single site or home. WLAN is a wireless local area network.

 WAN – a WAN (wide area network) is a network which enables the communication and sharing of files, programs and printers between different sites (e.g. different campuses of a college).

 Intranet – an intranet is an internal network which enables communication and

information/resource sharing with other departments within an organisation. An intranet is used only by the company and its staff and can usually be accessed remotely using a password to enable home working.

 Extranet – an extranet is similar to an Intranet with external access permitted to specified authorised users.

 PAN – a PAN or WPAN (personal area network and wireless personal area network) enables connectivity over a short distance, using a short-range radio frequency bandwidth, to mobile devices such as mobile phones, laptops and GPS among many others (both devices need to be compatible). Bluetooth (which uses a PAN) enables hands-free use of a mobile phone by a Bluetooth headset. Because Bluetooth uses connectivity over a short-range radio frequency bandwidth, it is vulnerable to security threats.

 Public – public networks are shared networks of computers providing access to a variety of public information, such as chat rooms, instant messaging and streaming video which are visible to external users. A public network connects devices via a public IP (Internet Protocol) address.

The IP address identifies a computer on a network. Because they are visible over the Internet, public networks are vulnerable to security threats.

 Unsecured networks – a wireless network with no security measures in place to prevent unauthorised access (hacking). Wi-Fi hotspots are public access points which operate over an unsecured network and are therefore vulnerable to security threats.

 VPN – (virtual private network) a private network that is used to communicate data over a public network system and enables access to users from remote sites. One of the advantages of using a VPN is that encryption is used as added security.

Types of Network Connections

Connections between computers on a network can be wired, such as cables (e.g. Ethernet, cat5 or a telephone line) or wireless (e.g. using radio waves) and run at different speeds, called the transfer rate. It is measured in bps (bits per second). Wireless networks are at risk from security threats, such as hacking, due to being more visible and accessible to other users. Devices, such as mobile phones and digital cameras, can be connected to other devices, such as a computer, in order to transfer data. This can be done using cables (wired) that insert into a USB port, or via wireless connection methods (using a card reader with a USB or FireWire interface means that the device does not have to be directly attached to the computer to transfer data). Internet-enabled devices can also connect wirelessly to the Internet using 3G and 4G (mobile broadband connectivity) and Wi-Fi. A device can also be connected wirelessly to

Types of wired and wireless connections are shown below:

 Infrared – high-speed network access for handheld devices such as mobile phones and PDAs within a local area (infrared devices need a direct line of sight communication path in order to communicate with other devices). Digital devices use infrared light to communicate with peripherals.

 Wi-Fi – a wireless connection that enables connectivity to the Internet via a portable device, such as a laptop or mobile phone. Wi-Fi exists in hotspots in public places such as shopping centres, restaurants and airports and is a convenient way of gaining access to the Internet while on the move. Wi-Fi Direct enables easy communication and the transfer of data between devices.

 Bluetooth (referred to as a personal area network or PAN) enables connectivity over a short distance, using a short-range radio frequency bandwidth, to mobile devices such as mobile phones,

laptops and GPS among many others (both devices need to be compatible). Bluetooth enables hands-free use of a mobile phone by use of a Bluetooth headset. Because Bluetooth uses connectivity over a short-range radio frequency bandwidth, it is vulnerable to security threats.

 3G (third generation) is the wireless network standard used in mobile phone technology which provides wireless mobile telephone and mobile Internet connectivity. 4G is the next generation of faster mobile broadband.

 A dongle is a portable device (an adapter which looks similar to a USB memory stick) that connects to a USB port on a computer to enable connectivity with 3G networks (enabling access to wireless broadband).

 GPRS (general packet radio service) is used with 2G and 3G network services for mobile communication providing Internet access, a multimedia messaging service and IM (instant messaging). GPRS sends and receives data at higher speeds and at the same time as making a voice call.

 EDGE (Enhanced Data Rates for GSM Evolution) has been replaced by 3G although some networks will switch between 3G, EDGE and Wi-Fi if the 3G signal is weak (it provides slower data transfer rates but with a stronger signal than 3G).

 WAP enabled – Wireless Application Protocol supports most wireless networks and is used to connect digital devices to the Internet.

 Landline network – a landline telephone signal passes through a solid wire/cable (copper or optical fibre) unlike a mobile phone which operates via wireless radio signals. The PSTN (public switched telephone network) is a network of global telephone networks consisting of telephone lines, mobile phones, satellite transmission and underwater cables.

 ADSL – (asymmetric digital subscriber line) is a form of broadband Internet connection that sends data across a telephone line in the UK. Data using ADSL can be sent via both the phone line and broadband Internet communication, ensuring the user keeps permanent connection to the Internet without losing access to the phone line. ADSL requires a DSL filter or splitter to be plugged into your existing phone line socket to split the incoming signal so that it separates data and voice. ADSL users living in close proximity to a local exchange enjoy faster connection and download speeds than users who live further away. Download speeds of ADSL broadband are slower than cable and fibre optic networks (but ADSL currently has better coverage in the UK).

Latency: This is the time delay between sending and receiving data over a network. Transmission speed can be affected by the medium by which data is sent, such as wirelessly or via optical fibre. The data size will also contribute to latency.

This is required because

A network typically comprises the following:

 Modem – stands for modulator-demodulator and is required to connect devices to the Internet.

 Router – is often integrated with a modem and used to connect multiple devices. Should come with a built-in firewall for security. Use a wireless router to create a completely wireless network from scratch (otherwise you will need a wireless base station / access point to connect to an existing wired network). The router and all computers on the network must share the same name (called the SSID or Service Set Identifier).

A router or modem connects computers to a network or to the Internet. A router has a default password or network key which should be changed for security purposes. A router should also have a firewall to prevent unauthorised access (hacking).

 Ethernet Bridge - An Ethernet bridge enables connection between different types of network (wired and wireless). For example, a wireless Ethernet bridge enables the connection of devices on a wired Ethernet network to a wireless network.

In many cases one device fulfils multiple functions, such as a modem/router/switch. A wireless router also contains a built-in access point, which enables connection to a wired router, switch or hub.

 Switch/hub/splitter – creates a network by enabling connection between multiple devices (multiple inputs to one or more output devices). A splitter is required to connect multiple inputs to one output device.

 Wireless adapter – these are also referred to as network cards enabling wireless connection to a network.

 Wireless base station or access point – required for connecting multiple computers to a network or a wireless network to an existing wired network.

 Home server – the main computer on which shared resources are kept and backed up.

Examples of networks:

 A single PC to the Internet via a modem or wirelessly using Wi-Fi

 PC to PC via a router (peer-to-peer or P2P)

 Multiple PCs with built-in wireless adapters connected together using a switch and a modem/router to connect to the Internet

The example below shows a home network which comprises a hybrid wired and wireless network. The two PCs share a wireless connection with the printer, as well as a wired Internet broadband connection. A wireless access point is required because an existing wired broadband connection was present when the network was created.

A wireless router should be in a central position in the house. Computers that are nearer to the