Protocols and Layers

• A set of rules that allow devices on a network to communicate with each other.

• A protocol that allows packets to be sent and received between computer systems.

• Breaks the data into packets and reassembles them back into the original data at the destination.

• In charge of routing and addressing data packets. • This ensures data packets are sent across networks to the correct destination.

• It is an addressing system - every device on a network is given a unique IP address so data packets can be sent to the correct computer system.

• Used to transfer web pages over the Internet so that users can view them in a web browser.

• A more secure version of HTTP that works with another protocol called SSL (Secure Sockets Layer) to transfer encrypted data.

• Used to transfer files across a network. • Commonly used to upload or download files to/from a web server.

• Used to send emails to a mail server and between mail servers.

• Receiving and storing emails from a mail server. • Deletes an email once it has been downloaded to a device.

• Protocol for receiving and storing emails from a mail server. • Syncs the message with an email server so that can be accessed by different devices.

• IPv4 uses a 32-bit address that allows for over 4 billion unique addresses. • Uses a numerical dot-decimal notation: 212.58.244.66 • Can be changed.

• IPv6 was developed was a 128-bit address, represented in hexadecimal that allows for lots more unique addresses. • Can be changed.

• A unique hexadecimal dumber assigned to each NIC inside a networked device e.g a router or laptop. • CANNOT be changed.

• Rules that allow computer systems to communicate across networks. • Standards have been created to ensure devices can exchange data and work together.

• It simplifies design, making it easier to modify and use.

• Used to visualise the different parts of a network as each of the four layers has a specific role.

• Application. • Allows humans and software applications to use the network e.g browsers (HTTP/HTTPS) and email (SMTP) and file transfer (FTP).

• Transport • TCP breaks down the data into data packets. • This layer makes sure data is sent and received in the correct order and re-assembled at the destination without errors.

• Network/Internet Layer • IP is responsible for addressing and routing data packets. • The optimal route for the data to take is calculated in this layer.

• Data Link • Ethernet sets out the format of data packets. • This layer handles transmission errors and passes data to the physical layer.