1.3 Networks and Protocols

• Network

  A device connecting to another one
• Network

  • Allows device to share information and resources
• LAN (Local Area Network)


  Small geographical area
• LAN

  • Hardwares are owned by the organisation that uses it
  • Can be wired or wireless
  • Examples: businesses, schools
• WAN (Wide Area Network)


  Worldwide, different geographical locations
• WAN

  • Infrastructure owned by multiple entities
  • Easier to share files
  • Can share some hardware
  • Can install and update software on all computers at once
  • Examples: telephone lines, satellite links, internet
• Client-server

  Servers control the security and manage client requests, clients respond
• Client-server

  • Files and software are usually stored centrally
  • Can be upgraded to cope with high demand
  • Example: school dependent
• Peer-to-Peer (P2P)

  No central control, anyone can set up a server
• Peer-to-Peer (P2P)

  • All devices can be a client and a server
  • Has to be backed up individually
  • Example: home
• Star topology

  Devices are connected to a central switch or server
• Star topology

  • Easy to add new devices
  • Reliant on the central node
• Mesh topology

  Decentralised, devices are either directly or indirectly connected without the use of a switch or server
• Mesh topology

  • High performing, few collisions
  • Difficult to install
• Bus topology

  Devices are connected to a single backbone cable, data sent in both directions
• Ring topology

  Data moves in one direction
• WAP (Wireless Access Point)


  Provides access to a wireless network
• WAP

  • Often plugged into a router
• Router


  Forwards packets between networks, takes a message and routes it to the correct destination
• NIC (Network Interface Card)

  Every device connected to a network has one, enables connection to internet/ethernet cables
• MAC address

  Unique hardware address that enables pinpointing the correct device on a network
• Switches

  • Connects devices on a LAN, receives data frames from one device and transmits this data to the device on the network with the correct MAC address
• Bandwidth

  Amount of data that can be transferred over a given time
• More people using the network

  Can limit the bandwidth available to different users
• Factors affecting network performance

  • Bandwidth
  • Network congestion
  • Choice of hardware
  • Network topology
• Wired connections

  Ethernet cables are traditionally used to connect devices in LAN/WAN
• Wired connections

  • Limited flexibility/security, cheaper, higher reliability
  • Common types: CAT5e, CAT6
• Twisted pair cables

  Four pairs of copper wires twisted together, less interference
• Coaxial cables

  Single copper wire surrounded by plastic layer and metallic shielding, high flexibility
• Fibre optic cables

  Transmit data as light, high performance, no interference, very large distances
• Wireless connections

  Radio waves to transmit data packets, convenient, portable
• Wireless connections

  • Lower bandwidth, vulnerable to attack, health issues, lower reliability
• Bluetooth

  Direct connection, data can be shared, lower bandwidth
• Wi-Fi

  Allows multiple devices to connect at the same time, higher bandwidth
• Wi-Fi

  • Splits into channels, 2.4GHz and 5GHz frequencies
• Data packets

  Files are split into millions of data packets and sent over the internet
• IP address

  Used when sending data between TCP/IP networks, not linked to hardware, assigned manually or automatically
• MAC address

  Unique identifier assigned to all network-enabled devices, cannot be changed
• Network protocols

  Set of rules that devices use to communicate and transmit data across a network
• TCP/IP

  Protocols that dictate how devices connect on the network, in charge of splitting and reassembling data packets