Section 3- Networks

• What is a LAN?

  Local Area Network
• What are the properties of a LAN?

  -covers a small geographical area

  -all hardware is owned by the organisation that uses it

  -either wired or wireless

  -often find them in businesses, schools and universities, homes
• Why use a LAN?

  -sharing files is easier because network users can access the same files and work collaboratively on them (same time)

  -can share the same hardware (printers)

  -internet connections can be shared between every device

  -can install and update software on devices at the same time

  -can communicate with LAN users easily and cheaply

  -user accounts are stored centrally so they can log in on any device
• What is a WAN?

  Wide Area Network- connects together all the LANs
• What are the properties of a WAN?

  -large geographical area as it connects together LANs

  -hardware is owned by companies (communication lines)

  -expensive to set up

  -can be connected using fibre or copper telephone lines, satellite links or radio links

  -the internet is a WAN
• What is a NIC

  Network interface controller- internal piece of hardware that allows a device to connect to a network
• What does a switch do?

  Connects devices on a LAN- receive data from one device and then transfers it to another device on the network
• What do routers do?

  Responsible for transmitting data between networks, directing data (traffic)- connect a LAN to the internet
• What is good about wired Ethernet connections?

  Fast and reliable
• What are the most common twisted pair cables?

  CAT 5e and CAT 6
• What are twisted pair cables?

  4 pairs of copper wires twisted together to reduce internal interference
• What are coaxial cables made of?

  Single copper wire surrounded by a plastic layer for insulation and metallic mesh to provide shielding from outside interference
• What are fibre optic cables?

  Cables that transmit data as light- high-performance as they don't suffer interference, can transmit data over a long distance but are very expensive
• How do wireless connections work?

  Transmit data using radio waves
• Why are wireless connections good?

  Convenient and cheaper
• What are the properties of a Bluetooth connection?

  -a direct connection between 2 devices

  -range is typically 10m

  -low bandwidth

  -often used in headphones and smartwatches
• What are the properties of Wi-Fi?

  -can be used by multiple devices to connect to a LAN

  -range between 40-100m

  -high bandwidth

  -often used in homes (laptops, phones)
• What are the 2 wireless connections?

  Wi-Fi, Bluetooth
• What do you need to set up Wi-Fi?

  Wireless Access Point (WAP)- a switch that allows devices to connect wirelessly (devices will need a wireless NIC)
• What is bandwidth?

  The amount of data that can be transferred in a given time
• What can affect the performance of a network?

  Bandwidth, number of devices, wired or wireless connection, choice of hardware
• What are client-server networks made up of?

  Clients and servers.
• What are the pros of the client-server model?

  -easier to keep track of files as they are stored centrally

  -easier to perform backups

  -easier to install and update software

  -easier to manage network security

  -servers are reliable and always on
• What are the cons of the client-server model?

  -expensive to set up

  -needs and IT specialist to maintain network and server

  -if server goes down then all clients lose access to network

  -server may become overloaded
• How are peer-to-peer networks set up?

  Each device connects directly to each other- no server
• What are the pros of a p2p network?

  -easy to maintain

  -cheaper

  -no dependence on server (if one device crashes then the other won't)
• What are the cons of p2p networks?

  -no centralised management (updates and security have to be done individually)

  -copying files between devices creates duplicates

  -less reliable (data could be lost if 1 device fails

  -machines are prone to slow down when other devices access them
• What are all devices connected to in a star topology?

  Central switch or server
• What are the pros of the star topology?

  -if 1 device fails then the others aren't affected

  -simple to add more devices

  -better performance than other topologies- few collisions of data
• What are the cons of the star topology?

  -if server fails then so does the entire network

  -in a wired network each device needs a cable to connect to the server with which is expensive
• What are the other 2 topologies?

  Bus and ring
• How are devices set up in a mesh topology?

  Each device is interconnected with the other
• What is the main advantage of the mesh topology?

  -no single point of failure

  -multiple routes data can take
• What is the main problem of mesh topologies?

  -very expensive if the network is wired

  -complicated
• What are network protocols?

  A set of rules for how devices communicate and how data is transmitted across a network
• What are communication protocols?

  Rules that specify how communication between 2 devices must start and end, how the data is organised and what the devices must do if the data goes missing
• What does communication on the same network use?

  MAC Addresses
• What are MAC addresses used by?

  Switches on LANs
• What are MAC addresses?

  48 or 64-bit binary numbers that are converted into hexadecimal
• What does communication between different networks use?

  IP addresses