A set of rules that determine how data is transmitted between devices on a network.

• A family of protocols used to connect devices in a wired LAN.
• Define how data should be physically transmitted between different devices.
• Uses MAC addresses to determine which device the data should be sent to .
• Also define what should happen if collisions occur on the network.
• Can be used on copper or fibre-optic cables.

• A family of protocols that define how devices can communicate wirelessly using radio waves.
• The Wi-Fi standards determine:
  • the frequency band and channel that to be used,
  • data transmission rates,
  • how devices are authenticated when joining the network.

• Normally use two frequency bands, 2.4 GHz or 5 GHz.
• 2.4 GHz has longer range, but lower transmission rates.
• 5 GHz has shorter range, but high transmission rates.

• Splits data from applications into smaller data packets for transmission across a network.
• Each packet is made up of a header and a payload.
• The header contains the sequence number of the packet and a checksum to allow the recipient device to check that it has been sent correctly.
• The payload contains the actual data from the application that needs to be sent.
• When the data is correctly received, an acknowledgement message is sent back to the server.

• Used by applications to deliver data more quickly.
• It does not tell the server the data was correctly received - there are no checks at all, the data is just sent.
• Generally used for live broadcast or online gaming.
• If packets are lost the video or audio will continue to play but will be distorted for a moment.

• Defines how data packets should be sent between networks.
• Every device on a network has a unique IP address.
• Made up of four 8-bit numbers (e.g. 192.168.1.110).
• An IP header is added to each data packet contain both the source and destination IP addresses.
• The router then decides how to sent the data packet, either on the local network or to another network.
• Once received, the switch determines which device on the network should get the data packet.

• Secure version of HTTP.
• Adds Secure Socket Layer (SSL) encryption to the communication.
• Used originally for online banking and shopping, most web sites now uses HTTPS.

• Used to transfer computer files between a client and a server.
• Most commonly used for transferring web pages to web servers.

• Used for accessing email messages.
• Allows multiple devices to have synchronised access to the same inbox.
• The messages are retained on the email server.
• The most commonly used email protocol, due to the ability to keep email synchronised.