Chapter 5: Networks

• Network


  Devices that are connected, either using cables or wireless technology, and are capable of sharing resources such as files and printers, and communicating with each other

  
• Network communication

  • Email sent from one person to another
  • Document sent to a networked printer
  • Web page viewed on a mobile phone
  • Smart-home lights responding to a command in an app to turn them on
  • Downloading a television programme to a set-top-box
  • Streaming a YouTube video on a tablet computer
  • Accessing a file on a school's virtual learning environment
• Local area network (LAN)

  A network usually found within a small geographic area such as a building or campus, often used in schools, hospitals, businesses and libraries, and in private homes
• LAN

  • Computers are within a small geographic area
  • Computer workstations with network interface cards (NICs), including wireless NICs
  • Connected using its own dedicated cables (or wireless devices) owned by the company, organisation or home
  • Often has shared peripherals, eg printers
• Devices in a typical home LAN

  • Desktop computer
  • Laptop computer
  • Tablet computer
  • Mobile phone
  • Printer
  • Network attached storage
• Switch

  Connects several devices together to enable communication between those devices
• Network Interface Card (NIC)


  Enables computers to connect to the network
• Wireless Access Point (WAP)

  Enables wireless devices to connect to the network using Wi-Fi

  
• Network cable

  Connects each ethernet network interface card to the switch
• Server

  A powerful computer that performs functions on behalf of devices connected to it, such as shared access to files, security, providing access to software, managing print jobs, providing mailboxes for email, and performing automated backups
• Larger local area networks will include one or more servers
• Wide area network (WAN)

  A network consisting of computers that are connected together but are geographically remote from each other, often connecting LANs in different locations
• WAN


  • Computers are not close together
  • External communications equipment such as a telephone line, leased line, satellite or 4G/5G are used as connections
  • A modem, router or other physical device is needed to connect to the WAN
• Examples of WANs


  • Universities with multiple campuses
  • Local education authorities connecting schools
  • Airline booking systems
  • National Lottery terminals
  • Automated Teller Machines (ATMs)
  • Train timetable systems
  • Large businesses with lots of offices or shops
• Internet

  The biggest example of a wide area network (WAN), with millions of devices connected through external communication links and information shared using the world wide web and email
• Internet Service Provider (ISP)

  Provides the connection to the Internet and offers services such as email, web hosting and file transfer
• Personal area network (PAN)


  A network centred around an individual person's use of digital equipment, usually wireless using Bluetooth

  
• Examples of using a PAN

  • Using a mobile phone hands-free in a car using a Bluetooth connection
  • Connecting a mobile phone to a Bluetooth speaker to play music
  • Tethering a mobile phone's Internet connection as a mobile Wi-Fi hot spot
  • Reading a text message on an Apple watch connected to an iPhone using Bluetooth
• Advantages of networking computers

  • Sharing peripherals such as printers
  • Sharing an Internet connection
  • Receiving updates to improve security
  • Sharing files and collaborating
  • Centralised backups
  • Accessing resources from any computer on the network
  • Controlling smart-home devices remotely
  • Automatic software deployment and updates
• Disadvantages of networking computers

  • Increased risk of hacking, viruses and spyware
  • Network could be hacked resulting in data loss
  • Viruses can spread throughout the network
  • Network resource failures can prevent access
  • Breaches of confidentiality with shared printers
  • Network performance issues
• Wired networks

  Use cables to connect devices together, usually using a switch
• Wired networks

  • Devices near the switch in a LAN (less than 100 metres) are connected using copper cable, often in the form of 4 twisted pairs of wires known as unshielded twisted pair (UTP) and often referred to as Ethernet cable
  • Fibre optic cable is an alternative cable that reflects light along the length of a thin glass tube
• Fibre optic cable

  Advantages over copper cable: they do not suffer from electromagnetic interference, data can travel much longer distances, data travels close to the speed of light which is much faster, higher bandwidths can be achieved
• Copper cable

  Advantages over fibre optic cable: it is cheaper per metre, it already exists within telephone networks
• Wireless networks

  Use radio signals to communicate between devices, commonly known as Wi-Fi

  
• Home Wi-Fi setup

  • Wireless access point (often part of a router), wireless devices such as laptops, printers, tablets, mobile phones, set-top boxes, televisions

  
• Public Wi-Fi hotspots

  Many local towns, cafés, restaurants, pubs, hotels, libraries, and other public buildings offer free Wi-Fi hotspots which enables any Wi-Fi device to connect to the Internet. Some places charge for Wi-Fi access. Most public Wi-Fi hotspots are unencrypted which means the data can be read by anybody with the right software connected to the same wireless network. Encrypted access points requiring an encryption key are better as they scramble the data.
• Larger Wi-Fi networks

  Wi-Fi access points are connected to the wired network around a building or site to enable coverage across the whole building or site. Wireless devices then connect to the wireless access point and the data is passed onto the main network.

  
• Advantages of wireless networks

  • Wireless devices can connect without a cable, users are not restricted to a specific location, mobile phones can connect at home and public hotspots saving 4G/5G data costs, bandwidth is big enough for Internet connectivity, any device conforming to Wi-Fi standard can connect, very easy to setup at home, relatively low cost to setup, employees may be able to bring their own device (BYOD)
• Disadvantages of wireless networks

  • If encryption is not used, hackers can see data, hackers don't need physical access to gain access, bandwidth is usually lower than wired networks, obstacles can interrupt signals causing lost data, range is limited requiring more access points, interference from electrical signals, microwaves and other wireless devices, bandwidth is shared if too many devices connected to one access point
• Network topology

  The way in which components in a local area network are arranged
• Star network topology

  • All devices connected directly back to a central switch, data cannot travel directly between devices but must go through the switch, switch receives all data and sends it to the recipient
• Star network topology diagram

  • C = Computer, P = Printer, S = Switch, with arrows showing bi-directional data flow
• Advantages of star network topology

  • If a cable is broken, only the connected device is affected, switch only sends data to the intended device improving security and speed, any device can be added without disrupting the network, data can be transmitted simultaneously by several devices
• Disadvantages of star network topology

  • If the switch fails, the whole network fails, a lot of cabling is required which is expensive to install
• Bus network topology

  • Includes a backbone cable, each device connects to the backbone, data travels in both directions along the backbone, only one device can send data at a time, data collisions can occur which slow down the network
• Advantages of bus network topology

  • Less cable required than star making it cheaper, works well for small networks, new nodes can be added anywhere on the bus
• Disadvantages of bus network topology

  • If the backbone breaks, the whole network goes down, problems with terminators can take down the network, collisions slow down performance, not good for larger networks, only one device can send data at a time
• Wireless Access Point

  Enables wireless devices to connect to a network

  
• Switch


  Receives data from devices and sends it to the intended recipient